17. Ray or Geometrical Optics II

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: Ray diagrams are used to investigate the behavior of light incident on mirrors and lenses. The principle of least time is used to show that all rays from an object in front of a concave mirror focus on the image point if they are not too far from the axis. The experiments describing the breakdown of geometric optics are discussed. 00:00 - Chapter 1. Parabolic and Spherical Mirrors 34:16 - Chapter 2. Lenses 43:34 - Chapter 3. Focal Point 63:56 - Chapter 4. Magnifying Lenses

uk: вхід без авторизації


18. Wave Theory of Light

Ramamurti Shankar

type: Person

de: Physik, Astronomie

fi: fysiikka, tähtitiede

uk: Фізика, Астрономія

en: Physics, Astronomy

fr: Physique, Astronomie

da: Fysik, Astronomi

es: Física, Astronomía

nl: Natuurkunde, Astronomie

de: Mathematik, Naturwissenschaften

uk: Математика, природничі науки

en: Mathematics, Natural Sciences

description: Young's double slit experiment shows clearly that light is a wave. (In order to observe the wave behavior of light, the slit size and separation should be comparable or smaller than the wavelength of light.) Interference is described using real and complex numbers (in anticipation of quantum mechanics). Grating and crystal diffraction are analyzed. 00:00 - Chapter 1. Revisions to Geometric Optics 08:20 - Chapter 2. Young's double slit experiment 50:52 - Chapter 3. Interference and Diffraction of Light

TIB AV-Portal

type: Service

type: WebContent

type: MediaObject

@language: en

cs: přihlášení není vyžadováno

de: keine Anmeldung erforderlich

uk: вхід без авторизації

en: no login required

nl: geen login vereist

YaleCourses, Yale University

addressCountry: US

addressLocality: New Haven

addressRegion: Connecticut

type: Organization

cs: Video

de: Video

fi: Video

uk: Відео

en: Video

fr: Vidéo

da: Video

nl: Video

es: Video


1. Electrostatics

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The course begins with a discussion of electricity. The concept of charge is introduced, and the properties of electrical forces are compared with those of other familiar forces, such as gravitation. Coulomb's Law, along with the principle of superposition, allows for the calculation of electrostatic forces from a given charge distribution. 00:00 - Chapter 1. Review of Forces and Introduction to Electrostatic Force 15:20 - Chapter 2. Coulomb's Law 21:09 - Chapter 3. Conservation and Quantization of Charge 26:15 - Chapter 4. Microscopic Understanding of Electrostatics 33:21 - Chapter 5. Charge Distributions and the Principle of Superposition

uk: вхід без авторизації


20. Quantum Mechanics II

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: Lecture begins with a detailed review of the double slit experiment with electrons. The fate of an electron traversing the double slit is determined by a wave putting an end to Newtonian mechanics. The momentum and position of an electron cannot both be totally known simultaneously. The wave function is used to describe a probability density function for an electron. Heuristic arguments are given for the wave function describing a particle of definite momentum. 00:00 - Chapter 1. Review of Double Slit Experiment using Electrons 20:28 - Chapter 2. Heisenberg's Uncertainty Principle 42:32 - Chapter 3. The Probability Density Function of an Electron

uk: вхід без авторизації


21. Quantum Mechanics III

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The fact that the wave function provides the complete description of a particle's location and momentum is emphasized. Measurement collapses the wave function into a spike located at the measured value. The quantization of momentum for a particle on a ring is deduced. 00:00 - Chapter 1. Review of the Particle Wave Function 11:21 - Chapter 2. Particle on a Ring 56:25 - Chapter 3. The Measurement Postulate

uk: вхід без авторизації


uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The time-dependent Schrödinger Equation is introduced as a powerful analog of Newton's second law of motion that describes quantum dynamics. It is shown how given an initial wave function, one can predict the future behavior using Schrödinger's Equation. The special role of stationary states (states of definite energy) is discussed. 00:00 - Chapter 1. The "Theory of Nearly Everything" 12:34 - Chapter 2. The time-dependent Schrodinger Equation 40:15 - Chapter 3. Stationary States

uk: вхід без авторизації

name: 24. Quantum Mechanics VI: Time-dependent Schrödinger Equation


2. Electric Fields

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The electric field is introduced as the mediator of electrostatic interactions: objects generate the field which permeates all of space, and charged objects in the field experience a force with magnitude proportional to their charge. Several instructive examples are given, including the field of an electric dipole and the notion of the electric dipole and dipole moment. The notion of field lines is introduced. 00:00 - Chapter 1. Review of Charges 16:34 - Chapter 2. Electric Fields 33:55 - Chapter 3. Electric Field Lines 40:18 - Chapter 4. Electric Dipoles

uk: вхід без авторизації


3. Gauss's Law I

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The electric field is discussed in greater detail and field due an infinite line charge is computed. The concepts of charge density and electric flux are introduced and Gauss's Law, which relates the two, is derived. It is applied to the study of the electric field generated by a spherical charge distribution. 00:00 - Chapter 1. Review of Electric field concepts 15:02 - Chapter 2. Electric field due to an infinite line of charge 28:41 - Chapter 3. The Infinite Sheet and Charge Density 44:29 - Chapter 4. Gauss' Law

uk: вхід без авторизації


10. Ampere's Law

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: Ampere's Law is used to find the magnetic field generated by currents in highly symmetric geometries like the infinitely long wire and the solenoid. It is shown how magnetism can be used to convert macroscopic mechanical energy to do microscopic electrical work. Lenz's and Faraday's Laws are introduced. The latter says that a changing magnetic field generates a non-conservative electric field. 00:00 - Chapter 1. Review of Ampere's Law 08:46 - Chapter 2. Magnetic field generated by current in a solenoid 49:51 - Chapter 3. Lenz's Law 67:07 - Chapter 4. Faraday's Law

uk: вхід без авторизації


11. Lenz's and Faraday's Laws

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The electric effect of a changing magnetic field is described using Faraday's Law. The direction of the current so generated is given by Lenz's Law. The operation and energy accounting of the generator are described. The concept of inductance is introduced. The Betatron is described as an example of Faraday's Law. Self and mutual inductance are introduced. The energy density in a magnetic field is derived. 00:00 - Chapter 1. Review of Lenz and Faraday's Law 25:37 - Chapter 2. The power generator 37:45 - Chapter 3. Mutual and self inductance 64:10 - Chapter 4. Energy density of a magnetic field

uk: вхід без авторизації


12. LCR Circuits—DC Voltage

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: Like capacitors, inductors act as energy storage devices in circuits. The relationship between voltage, inductance and current in a variety of circuits with DC voltages is described. 00:00 - Chapter 1. Review of Inductors 04:46 - Chapter 2. Inductive Circuits 54:18 - Chapter 3. LCR Circuits driven by an Alternating Source

uk: вхід без авторизації


13. LCR Circuits—AC Voltage

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The mathematics underlying LCR circuit theory for AC currents is discussed. Complex numbers are used to convert differential equations to algebraic equations. The notion of impedance is introduced. The radio is used to illustrate the concepts of resonance and variable capacitance. The body of classical electromagnetism treated so far is reviewed and summarized. The displacement current is introduced, leading to the complete Maxwell equations. 00:00 - Chapter 1. Review of LCR Circuits 08:48 - Chapter 2. Impedance 17:39 - Chapter 3. Resonance and Variable Capacitance 68:03 - Chapter 4. Displacement current

uk: вхід без авторизації


uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The physical meaning of the components of the wave equation and their applications are discussed. The power carried by the wave is derived. The fact that, unlike Newton's laws, Maxwell's equations are already consistent with relativity is discussed. The existence of magnetism is deduced from a thought experiment using relativity. 00:00 - Chapter 1. Recap—Solving Maxwell's Equations 18:18 - Chapter 2. Deriving the Energy and Intensity of an Electromagnetic Wave 30:40 - Chapter 3. The Origin of Electromagnetic Waves 37:03 - Chapter 4. Relativity and Maxwell's Equations 51:44 - Chapter 5. Deducing the Presence of Magnetism

uk: вхід без авторизації

name: 15. Maxwell's Equations and Electromagnetic Waves II


uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The double slit experiment, which implies the end of Newtonian Mechanics is described. The de Broglie relation between wavelength and momentum is deduced from experiment for photons and electrons. The photoelectric effect and Compton scattering, which provided experimental support for Einstein's photon theory of light are reviewed. The wave function is introduced along with the probability interpretation. The uncertainty principle is shown arise from the fact that the particle's location is determined by a wave and that waves diffract when passing a narrow opening. 00:00 - Chapter 1. Recap of Young's double slit experiment 09:10 - Chapter 2. The Particulate Nature of Light 23:15 - Chapter 3. The Photoelectric Effect 31:19 - Chapter 4. Compton's scattering 36:10 - Chapter 5. Particle-wave duality of matter 48:33 - Chapter 6. The Uncertainty Principle

uk: вхід без авторизації

name: 19. Quantum Mechanics I: The key experiments and wave-particle duality


uk: Фізика, Астрономія

uk: Математика, природничі науки

description: It is shown how to extract the odds for getting different values of momentum from a generic wave function by writing it as a sum over functions of definite momentum. A recipe is given for finding states of definite energy, which requires solving a differential equation that depends on what potential the particle is experiencing. The particle in a box is considered and the allowed energies derived. 00:00 - Chapter 1. Review of Wave Functions 40:13 - Chapter 2. The Schrodinger Equation 54:20 - Chapter 3. Quantization of Energy 63:43 - Chapter 4. Particle in a Box

uk: вхід без авторизації

name: 22. Quantum mechanics IV: Measurement theory, states of definite energy


uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The allowed energy states of a free particle on a ring and a particle in a box are revisited. A scattering problem is studied to expose more quantum wonders: a particle can tunnel into the classically forbidden regions where kinetic energy is negative and a particle incident on a barrier with enough kinetic energy to go over it has a nonzero probability to bounce back. 00:00 - Chapter 1. Review of Wave Functions 08:48 - Chapter 2. Particle on a ring 19:11 - Chapter 3. Particle in a Box 54:00 - Chapter 4. Scattering

uk: вхід без авторизації

name: 23. Quantum Mechanics V: Particle in a Box


uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The various postulates of quantum mechanics treated in previous lectures are reviewed and summarized. The uncertainty principle is again discussed and a new one between energy and time is introduced. The quantum mechanical behavior of an electron in a hydrogen atom is described. The principles of quantum mechanics are then generalized to describe two or more quantum particles. It is shown that identical particles have to be bosons or fermions, the latter obeying the Pauli exclusion principle, which in turn is key to explaining the periodic table. 00:00 - Chapter 1. Major Postulates of Quantum Mechanics 20:31 - Chapter 2. Applications of Quantum Mechanics 28:00 - Chapter 3. Energy-time uncertainty principle 41:21 - Chapter 4. Quantum Mechanics of more than one particle

uk: вхід без авторизації

name: 25. Quantum Mechanics VII: Summary of postulates and special topics


cs: Informatika

de: Informatik

fi: tietojenkäsittelytiede

uk: Комп'ютерні науки

en: Computer Science

fr: Informatique

da: Datalogi

es: Ciencias de la Computación

nl: Informatica

cs: Technické vědy

de: Ingenieurwissenschaften

fi: tekniikka

uk: Інженерія

en: Engineering Sciences

fr: Ingénierie

da: Ingeniørvidenskab

es: Ingeniería

nl: Engineering

description: How many different roles are there on engineering teams? Officially, there's probably just a manager and maybe a tech lead. Unofficially, you have technical specialists, company veterans, people focused on tools, and those who think deeply about the product. In this talk we'll steal the best ideas from operating rooms, wartime deployments, and courtroom litigation. We'll see how it's possible to train, reward, and empower your teammates by respecting their uniqueness while also making room for very junior developers to join fast-moving teams.

uk: вхід без авторизації

name: Designing an engineering team: Making room for everyone


uk: Фізика, Астрономія

uk: Математика, природничі науки

description: Lecture begins with a recap of Gauss's Law, its derivation, its limitation and its applications in deriving the electric field of several symmetric geometries—like the infinitely long wire. The electrical properties of conductors and insulators are discussed. Multiple integrals are briefly reviewed. 00:00 - Chapter 1. Derivation of Gauss' Law 21:12 - Chapter 2. The Electric Field due to a Spherical Distribution of Charge 44:47 - Chapter 3. Electric Field due to an Infinitely Long Wire 51:39 - Chapter 4. Electric Conductors and Insulators

uk: вхід без авторизації

name: 4. Gauss's Law and Application to Conductors and Insulators


uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The law of conservation of energy is reviewed using examples drawn from Newtonian mechanics. The work-energy theorem is derived from first principles and used to initiate a discussion of the vector calculus underlying the law of conservation of energy. 00:00 - Chapter 1. Review of Electrostatics 03:49 - Chapter 2. Review of Law of Conservation of Energy 08:13 - Chapter 3. Deriving the Work-Energy Theorem and the Law of Conservation of Energy 59:33 - Chapter 4. Electric Potential

uk: вхід без авторизації

name: 5. The Electric Potential and Conservation of Energy


6. Capacitors

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The electric potential is defined for the electric field. It is introduced as an integral of the electric field making the field the derivative of the potential. After discussing the ideas of electric potential and field as presented in the previous lecture, the concept of capacitance is introduced as a means of storing charge and energy. 00:00 - Chapter 1. Review of Electric Potential 15:52 - Chapter 2. Advantages of Electric Potential, V 43:31 - Chapter 3. Conductors as Equipotentials 61:46 - Chapter 4. Capacitors

uk: вхід без авторизації


7. Resistance

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: Lecture begins with a discussion of electric potential distribution in conductors. Image charges are introduced and exploited. Capacitance is explained in greater detail and illustrated using the parallel plate capacitor. The energy stored in the electric field is derived. The forces acting on an electric current flowing through a conducting wire are examined. The RC circuits and its energetics are discussed. The EMF due to a battery is explained. 00:00 - Chapter 1. Review of Image Charges 28:45 - Chapter 2. The Parellel Plate Capacitor 42:46 - Chapter 3. The Concept of Resistance

uk: вхід без авторизації


8. Circuits and Magnetism I

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: After a description of more complicated electric circuits, the basic ideas underlying magnetism are discussed and the relationship between electrical charges and magnetic fields is explored. Magnetism is caused and experienced only by moving charges. The Lorentz force on a charge is described and used to deduce the force on a current carrying wire. The cyclotron and velocity selector are described. 00:00 - Chapter 1. Review of Electric Circuits 34:32 - Chapter 2. Introduction to Magnetism 45:29 - Chapter 3. Fundamental Equations of Magnetostatics 62:42 - Chapter 4. Force on a Current Carrying Wire

uk: вхід без авторизації


9. Magnetism II

uk: Фізика, Астрономія

uk: Математика, природничі науки

description: The mechanism by which electric currents produce a magnetic field (Law of Biot-Savart) is discussed in greater detail. The field due to a single loop and an infinite wire are computed. Ampere's Law is derived. The operation of the DC electric motor is used to illustrate the torque generated on moving charges in a magnetic field. 00:00 - Chapter 1. Review of Magnetic Fields 14:00 - Chapter 2. Torque on Charge moving in Magnetic Field 20:56 - Chapter 3. Magnetic effects produced by electric currents 51:26 - Chapter 4. Ampere's Law

uk: вхід без авторизації


Topos and Information

cs: Matematika

de: Mathematik

fi: matematiikka

uk: Математика

en: Mathematics

fr: Mathématiques

da: Matematik

es: Matemáticas

nl: Wiskunde

uk: Математика, природничі науки

description: As part of the IHES-Huawei partnership, this one-day workshop is organised by the Huawei's Mathematical and Algorithmic Sciences Lab jointly with IHES and aims at creating scientific exchanges around mathematical topics that are essential for the development and innovation of the ICT. The topic of this year is on the potential of the mathematics of Artificial Intelligence for breakthrough results in the ICT field

uk: вхід без авторизації

name: Institut des Hautes Études Scientifiques (IHÉS)

addressCountry: FR

addressLocality: Bures-sur-Yvette

addressRegion: Île-de-France


uk: Математика, природничі науки

uk: вхід без авторизації

name: Huawei's Mathematical and Algorithmic Sciences Lab

name: Discussion - Panel: What is the role of Topos in Information and Communication Technologies?


uk: Математика, природничі науки

uk: вхід без авторизації

name: Toposes for Wireless Networks: An idea whose time has come


4th Huawei-IHES Workshop - Introduction

uk: Математика, природничі науки

uk: вхід без авторизації


uk: Математика, природничі науки

uk: вхід без авторизації

name: Grothendieck toposes and their role in Mathematics


uk: Математика, природничі науки

uk: вхід без авторизації

name: Computational Interpretation of Topos Theory


uk: Математика, природничі науки

description: Liouville conformal field theory (LCFT hereafter), introduced by Polyakov in his 1981 seminal work "Quantum geometry of bosonic strings", can be seen as a random version of the theory of Riemann surfaces. LCFT appears in Polyakov's work as a 2d version of the Feynman path integral with an exponential interaction term. Since then, LCFT has emerged in a wide variety of contexts in the physics literature and in particular recently in relation with 4d supersymmetric gauge theories (via the AGT conjecture). cA major issue in theoretical physics was to solve the theory, namely compute the correlation functions. In this direction, an intriguing formula for the three point correlations of LCFT was proposed in the middle of the 90's by Dorn-Otto and Zamolodchikov-Zamolodchikov, the celebrated DOZZ formula. The purpose of the course is twofold (based on joint works with F. David, A. Kupiainen and R. Rhodes). First, I will present a rigorous probabilistic construction of Polyakov's path integral formulation of LCFT. The construction is based on the Gaussian Free Field. Second, I will show that the three point correlation functions of the probabilistic construction indeed satisfy the DOZZ formula. This establishes an explicit link between probability theory (or statistical physics) and the so-called conformal bootstrap approach of LCFT. Mercredi 22 novembre

uk: вхід без авторизації

name: 1/4 Liouville conformal field theory and the DOZZ formula


uk: Математика, природничі науки

description: Liouville conformal field theory (LCFT hereafter), introduced by Polyakov in his 1981 seminal work "Quantum geometry of bosonic strings", can be seen as a random version of the theory of Riemann surfaces. LCFT appears in Polyakov's work as a 2d version of the Feynman path integral with an exponential interaction term. Since then, LCFT has emerged in a wide variety of contexts in the physics literature and in particular recently in relation with 4d supersymmetric gauge theories (via the AGT conjecture). cA major issue in theoretical physics was to solve the theory, namely compute the correlation functions. In this direction, an intriguing formula for the three point correlations of LCFT was proposed in the middle of the 90's by Dorn-Otto and Zamolodchikov-Zamolodchikov, the celebrated DOZZ formula. The purpose of the course is twofold (based on joint works with F. David, A. Kupiainen and R. Rhodes). First, I will present a rigorous probabilistic construction of Polyakov's path integral formulation of LCFT. The construction is based on the Gaussian Free Field. Second, I will show that the three point correlation functions of the probabilistic construction indeed satisfy the DOZZ formula. This establishes an explicit link between probability theory (or statistical physics) and the so-called conformal bootstrap approach of LCFT. Vendredi 24 novembre

uk: вхід без авторизації

name: 2/4 Liouville conformal field theory and the DOZZ formula


uk: Математика, природничі науки

description: Liouville conformal field theory (LCFT hereafter), introduced by Polyakov in his 1981 seminal work "Quantum geometry of bosonic strings", can be seen as a random version of the theory of Riemann surfaces. LCFT appears in Polyakov's work as a 2d version of the Feynman path integral with an exponential interaction term. Since then, LCFT has emerged in a wide variety of contexts in the physics literature and in particular recently in relation with 4d supersymmetric gauge theories (via the AGT conjecture). cA major issue in theoretical physics was to solve the theory, namely compute the correlation functions. In this direction, an intriguing formula for the three point correlations of LCFT was proposed in the middle of the 90's by Dorn-Otto and Zamolodchikov-Zamolodchikov, the celebrated DOZZ formula. The purpose of the course is twofold (based on joint works with F. David, A. Kupiainen and R. Rhodes). First, I will present a rigorous probabilistic construction of Polyakov's path integral formulation of LCFT. The construction is based on the Gaussian Free Field. Second, I will show that the three point correlation functions of the probabilistic construction indeed satisfy the DOZZ formula. This establishes an explicit link between probability theory (or statistical physics) and the so-called conformal bootstrap approach of LCFT. Mercredi 29 novembre

uk: вхід без авторизації

name: 3/4 Liouville conformal field theory and the DOZZ formula


uk: Математика, природничі науки

description: Liouville conformal field theory (LCFT hereafter), introduced by Polyakov in his 1981 seminal work "Quantum geometry of bosonic strings", can be seen as a random version of the theory of Riemann surfaces. LCFT appears in Polyakov's work as a 2d version of the Feynman path integral with an exponential interaction term. Since then, LCFT has emerged in a wide variety of contexts in the physics literature and in particular recently in relation with 4d supersymmetric gauge theories (via the AGT conjecture). cA major issue in theoretical physics was to solve the theory, namely compute the correlation functions. In this direction, an intriguing formula for the three point correlations of LCFT was proposed in the middle of the 90's by Dorn-Otto and Zamolodchikov-Zamolodchikov, the celebrated DOZZ formula. The purpose of the course is twofold (based on joint works with F. David, A. Kupiainen and R. Rhodes). First, I will present a rigorous probabilistic construction of Polyakov's path integral formulation of LCFT. The construction is based on the Gaussian Free Field. Second, I will show that the three point correlation functions of the probabilistic construction indeed satisfy the DOZZ formula. This establishes an explicit link between probability theory (or statistical physics) and the so-called conformal bootstrap approach of LCFT. Vendredi 1er décembre

uk: вхід без авторизації

name: 4/4 Liouville conformal field theory and the DOZZ formula


Sinh-Gordon model and its duality

uk: Математика, природничі науки

description: Many interesting strongly interacting Quantum Field Theories are not amenable to analytical treatment. This workshop will focus on systematic numerical approaches to such theories relying on the quantum Hamiltonian, including Truncated Spectrum Approach, Light Front Quantization, Matrix Product States and Tensor Networks. Such methods provide a viable alternative to Lattice Monte Carlo simulations. Their advantage is the ability to access real-time observables, and to study Renormalization Group flows originating from strongly-interacting fixed points.

uk: вхід без авторизації


uk: Математика, природничі науки

uk: вхід без авторизації

name: Conformal data from critical spin chains using periodic MPS and the Koo-Saleur formula


uk: Математика, природничі науки

uk: вхід без авторизації

name: Precise calculations with the Renormalized Hamiltonian Truncation approach


Nonperturbative light-front methods

uk: Математика, природничі науки

uk: вхід без авторизації


Tensor networks and the Schwinger model

uk: Математика, природничі науки

uk: вхід без авторизації


uk: Математика, природничі науки

uk: вхід без авторизації

name: A look at \phi^4_2 using perturbation theory


uk: Математика, природничі науки

uk: вхід без авторизації

name: Tensor network applications to (1+1)d gauge theories


uk: Математика, природничі науки

uk: вхід без авторизації

name: Studying RG Flows with Lightcone Conformal Truncation


uk: Математика, природничі науки

uk: вхід без авторизації

name: Rare non-thermal states in the non-integrable Ising field theory


uk: Математика, природничі науки

uk: вхід без авторизації

name: Simulation of 2D strongly correlated systems with infinite projected entangled-pair states


uk: Математика, природничі науки

uk: вхід без авторизації

name: Application of Light-Front methods to model theories

name: Institut des Hautes Études Scientifiques (IHÉS)


uk: Математика, природничі науки

uk: вхід без авторизації

name: Numerical Hamiltonian truncation approach to the \phi^4 theory in 1+1d and beyond


uk: Математика, природничі науки

uk: вхід без авторизації

name: Truncated spectrum approaches for 2D many-body quantum systems


Free field states and conformal bases

uk: Математика, природничі науки

uk: вхід без авторизації


uk: Математика, природничі науки

uk: вхід без авторизації

name: Investigation of the chiral antiferromagnetic Heisenberg model using PEPS


uk: Математика, природничі науки

uk: вхід без авторизації

name: Finding purifications with minimal entanglement


Applications of TCSA to quenches

uk: Математика, природничі науки

uk: вхід без авторизації


Neural-network quantum states

uk: Математика, природничі науки

uk: вхід без авторизації


de: Architektur, Innenarchitektur

uk: Архітектура, дизайн інтер'єру

en: Architecture, Interior Architecture

description: Im ersten Semester wird eine Einführung in die Methodik der Disziplin gegeben und die Stadtbaugeschichte im Zeitraum von den Anfängen bis in die Mitte des 19. Jahrhunderts thematisch präsentiert.

@language: de

uk: вхід без авторизації

name: Auf dem Weg zur Aufklärung: geometrische Stadtexperimente, die europäische kolonialisierung Amerikas und der Wiederaufbau Lissabons

name: Eidgenössische Technische Hochschule Zürich (ETH Zürich)

addressCountry: CH

addressLocality: Zurich

addressRegion: Zurich


keywords:
Richelieu
Versailles
Königliche Plätze
Boulevards

uk: Архітектура, дизайн інтер'єру

uk: вхід без авторизації

name: Barocke Strategien: Die Neuordnung Roms unter Sixtus V., die Inszenierung von Versailles und die Erfindung von St. Petersburg


uk: Архітектура, дизайн інтер'єру

uk: вхід без авторизації

name: Stadtideale, Stadtstaaten und Stadtgrüdungen: Planungen des Mittelalters und der Renaissance


uk: Архітектура, дизайн інтер'єру

uk: вхід без авторизації

name: Vom Geist der Gleichheit zum kolonialen Baustein: Griechische und römische Stadtgründungen


uk: Архітектура, дизайн інтер'єру

uk: вхід без авторизації

name: Athen und Rom in der Antike: Mythos, Selbstdarstellung und Spekulation


uk: Архітектура, дизайн інтер'єру

uk: вхід без авторизації

name: Einführung zu Gegenstand, Methode und Strategien: Geschichte des Städtebaus als historisches Projekt


uk: Архітектура, дизайн інтер'єру

description: Von der Wohnzelle zur Stadt Anwendungsgegenstände Radikalisierungen und Präzisierungen Von der vertikalen zur linearen Stadt, von der geradenen zur geschwungenen Linie Theoretische Synthese und Umsetzungsversuche

uk: вхід без авторизації

name: Le Corbusier: Theorien, Visionen und Kahlschläge im Namen der autorité


uk: Архітектура, дизайн інтер'єру

description: Voraussetzungen und Experimente Siedlungen des Neuen Frankfurt Epilog

uk: вхід без авторизації

name: Trabantensiedlungen versus Superblöcke: Das Neue Frankfurt und das Rote Wien


uk: Архітектура, дизайн інтер'єру

description: Die Lebensreformbewegung Bruno Tauts Stadttheorien Die Siedlungen der Neuen Sachlichkeit

uk: вхід без авторизації

name: Von der Lebensreform-Bewegung über die Stadtkrone zur Siedlung der Neuen Sachlichkeit: Deutschland zwischen 1900 und 1930


uk: Архітектура, дизайн інтер'єру

description: Der Wettbewer Gross-Berlin (1910) Der reformierte Block Die Germanisierung des Wolkenkratzers Grossstadttheorien: KArl Scheffler, Ludwig Hilbersheimer Weltstadtplätze der Moderne: Drei Berliner Wettbewerbe

uk: вхід без авторизації

name: "Ganglinien" der Fussgänger und "Fliesslinien" des Verkehrs: Die Modernisierung der Grossstadt Berlin


uk: Архітектура, дизайн інтер'єру

description: Es werden die grossen städtebaulichen Veränderungen des 19. Jahrhunderts und ihre Auswirkungen bis zur Zwischenkriegszeit präsentiert. Die Architektur der Stadt von der Industriellen Revolution zur Moderne

uk: вхід без авторизації

name: Stadtideen der radikalen Avantgarde: Futurismus in Italien und Konstruktivismus in der postrevolutionären Sowjetunion


uk: Архітектура, дизайн інтер'єру

description: Städtebau an der école des Beaux-Arts (1850-1900) Das Centre Mondial de Communication von Tony Garniers Cité Industrielle (1899-1917) Les grands travaux de la ville de Lyon (1906-1933) Der Gratte-ciel von Villeurbanne (1928-34)

uk: вхід без авторизації

name: Beaux-Arts-Städtebau, moderne Klassik und ein sozialistischer Wolkenkratzerkomplex: Die Cité Industrielle von Tony Garnier und der Gratte-ciel von Villeurbanne


uk: Архітектура, дизайн інтер'єру

description: Otto Wagner Camillo Sitte Die Ausstrahlung von Sittes Theorie Von der gekrümmten Strasse zur urbanistischen Akupunktur: der Fall Ljubljana

uk: вхід без авторизації

name: Antagonisten im Schatten des Rings: Otto Wagners "unbegrenzte Grossstadt", Camillo Sittes künstlerischer Städtebau und Adolf Loos' "rückwärtsgewandte Utopie"


keywords:
Park Movement
City Beautiful

uk: Архітектура, дизайн інтер'єру

uk: вхід без авторизації

name: Zivilisierte Wildnis und schöne Grossstadt: Vom Park Movement zur City Beautiful-Bewegung in den USA


keywords:
Voraussetzungen
Sozialutopien
die englischen Company Towns

uk: Архітектура, дизайн інтер'єру

uk: вхід без авторизації

name: Zwischen Sozialutopie und Paternalismus: Robert Owen, Charles Fourier und die englischen Company Towns


uk: Архітектура, дизайн інтер'єру

description: Von der büergerlichen Landflucht zu "Nowhere", Ebenezer Howard und das Modell der Gartenstadt, Verwirklichte Garten(vor)städte in England, Verwirklichte Garten(vor)städte in Europa, Die lineare, durchgrünte Stadt, Die Adaption für das Automobil

uk: вхід без авторизації

name: Gartenstädte für morgen: Ebenezer Howard und die grüne Alternative zur Grossstadt


uk: Архітектура, дизайн інтер'єру

description: Impressionistische Baukunst Stadterweiterungspläne für Amsterdam Amsterdamer Schule Variationen des Blocks Vom Block zur Siedlung

uk: вхід без авторизації

name: "Impressionistische" Stadtarchitektur: Hendrik Perus Berlage und die Amsterdamer Schule


uk: Математика, природничі науки

uk: вхід без авторизації

name: Two equivalent versions of the Riemann Hypothesis

name: Institut des Hautes Études Scientifiques (IHÉS)


Facets of Probabilistic Databases

uk: Комп'ютерні науки

description: Probabilistic databases are commonly known in the form of the tuple-independent model, where the validity of every tuple is an independent random event. Conceptually, the notion is more general, as a probabilistic database refers to any probability distribution over ordinary databases. A central computational problem is that of marginal inference for database queries: what is the probability that a given tuple is a query answer? In this talk, I will discuss recent developments in several research directions that, collectively, position probabilistic databases as the common and natural foundation of various challenges at the core of data analytics. Examples include reasoning about uncertain preferences from conventional distributions such as the Mallows model, data cleaning and repairing in probabilistic paradigms such as the HoloClean system, and the explanation of query answers through concepts from cooperative game theory such as the Shapley value and the Banzhaf Power Index. While these challenges manifest different facets of probabilistic databases, I will show how they interrelate and, moreover, how they relate to the basic theory of inference over tuple-independent databases.

uk: вхід без авторизації

name: International Conference on Database Theory (ICDT)


uk: Математика, природничі науки

uk: вхід без авторизації

name: 2/3 Universality and quantum unique ergodicity in random matrix theory


uk: Математика, природничі науки

uk: вхід без авторизації

name: 3/3 Universality and quantum unique ergodicity in random matrix theory


1/3 Topics in random operator theory

uk: Математика, природничі науки

uk: вхід без авторизації


2/3 Topics in random operator theory

uk: Математика, природничі науки

uk: вхід без авторизації


3/3 Topics in random operator theory

uk: Математика, природничі науки

uk: вхід без авторизації


uk: Математика, природничі науки

uk: вхід без авторизації

name: 1/3 The cutoff phenomenon and rate of escape for Markov chains


uk: Математика, природничі науки

uk: вхід без авторизації

name: 2/3 The cutoff phenomenon and rate of escape for Markov chains


uk: Математика, природничі науки

uk: вхід без авторизації

name: 3/3 The cutoff phenomenon and rate of escape for Markov chains


1/3 Operator limits of random matrices

uk: Математика, природничі науки

uk: вхід без авторизації


2/3 Operator limits of random matrices

uk: Математика, природничі науки

uk: вхід без авторизації


3/3 Operator limits of random matrices

uk: Математика, природничі науки

uk: вхід без авторизації


uk: Математика, природничі науки

uk: вхід без авторизації

name: Distributional symmetry of random matrices and the non commutative notions of independence


1/3 Spectrum of random graphs

uk: Математика, природничі науки

uk: вхід без авторизації


2/3 Spectrum of random graphs

uk: Математика, природничі науки

uk: вхід без авторизації


3/3 Spectrum of random graphs

uk: Математика, природничі науки

uk: вхід без авторизації


uk: Математика, природничі науки

uk: вхід без авторизації

name: 1/3 Self-interacting processes and random Schrödinger operators


uk: Математика, природничі науки

uk: вхід без авторизації

name: 2/3 Self-interacting processes and random Schrödinger operators


uk: Математика, природничі науки

uk: вхід без авторизації

name: 3/3 Self-interacting processes and random Schrödinger operators


uk: Математика, природничі науки

uk: вхід без авторизації

name: 1/3 Spectral vs. geometric approaches to random walks on random graphs


uk: Математика, природничі науки

uk: вхід без авторизації

name: 2/3 Spectral vs. geometric approaches to random walks on random graphs


uk: Математика, природничі науки

uk: вхід без авторизації

name: 3/3 Spectral vs. geometric approaches to random walks on random graphs


uk: Математика, природничі науки

uk: вхід без авторизації

name: 1/3 Large systems of interacting quantum particles in a random field


uk: Математика, природничі науки

uk: вхід без авторизації

name: 2/3 Large systems of interacting quantum particles in a random field


uk: Математика, природничі науки

uk: вхід без авторизації

name: 3/3 Large systems of interacting quantum particles in a random field


uk: Математика, природничі науки

description: Studying spectral properties of large random objects has been a very active playground in probability theory, mathematical physics and computer science during the last decades. The motivations are manifold: viewing random matrices as a model for complicated quantum Hamiltonians, studying random Schrödinger operators to understand the Anderson localization phenomenon, viewing eigenvectors of random matrices as models for eigenmodes of quantized chaotic systems, or understanding the geometry of large (random) graphs such as expanders via the spectral properties of their adjacency matrices. In those studies the emphasis is generally put either on the eigenvalues or the eigenvectors of the object.

uk: вхід без авторизації

name: Spectral theory of unimodular random trees: a few results and many questions

name: Institut des Hautes Études Scientifiques (IHÉS)


1/6 Resurgence and Quantization

uk: Математика, природничі науки

uk: вхід без авторизації


uk: Математика, природничі науки

uk: вхід без авторизації

name: 1/3 Universality and quantum unique ergodicity in random matrix theory


keywords:
Chaux
frabzösische Revolution bis zum Empire
Napoléon I.
jakobinischer Platz für Mailand

uk: Архітектура, дизайн інтер'єру

uk: вхід без авторизації

name: Zwischen Modernisierung, Grandeur und Repression: Embellissement in Paris 1750-1830

name: Eidgenössische Technische Hochschule Zürich (ETH Zürich)


keywords:
Wiederaufbau London
Stadtumbau
Stadterweiterung
Bath
Edinburgh
John Nash

uk: Архітектура, дизайн інтер'єру

uk: вхід без авторизації

name: Squares, Circuses, Crescents and Improvements: Städtebau der Kontinuität in Grossbritannien 1630-1870


uk: Комп'ютерні науки

uk: вхід без авторизації

name: Foundations of SPARQL Query Optimization

name: International Conference on Database Theory (ICDT)


uk: Комп'ютерні науки

description: As graph databases grow in popularity, decades of work in graph query languages and models are materialising in industry standards and in the construction of new graph database systems. However, this surge in graph systems has in turn opened up a series of new, interesting research problems related to graph databases. Our first set of problems has to do with more efficient ways of computing the answers of graph queries, specifically graph patterns, path queries, and combinations between them. Traditionally, researchers in graph databases have pointed out that relational systems are ill-equipped to process these types of queries, and if one looks at the performance of native graph database systems, there is clearly a lot of room for improvement. The talk focuses on two possible directions for improving the state of the art in graph query processing. The first is implementing worst-case optimal algorithms for processing graph patterns that traduce in relational queries with several joins. Some advances are already in development (see e.g. Nguyen, Dung, et al. "Join processing for graph patterns: An old dog with new tricks." GRADES'15. or Hogan, Aidan, et al. "A Worst-Case Optimal Join Algorithm for SPARQL." ISWC’19.), but we are still far from a full fledged solution: most algorithms require complex data structures, or need further support in terms of heuristics to select an order in which joins are processed. Second, we need to understand what is the best way of evaluating path queries (that is, finding all pairs of nodes connected by a path), in such a way that these results can be further integrated with other query results in a graph system pipeline. We already have complexity results regarding path computation and enumeration for different semantics of path queries (see e.g. Martens, Wim, and Tina Trautner. "Evaluation and enumeration problems for regular path queries." ICDT'18. or Bagan, Guillaume, Angela Bonifati, and Benoit Groz. "A trichotomy for regular simple path queries on graphs." PODS'13.), but still very little is known in terms of optimal processing of path queries when inside a tractable fragment. Our second set of problems is related to graph analytics, one of the current selling points of graph databases. Systems should be able to run more complex analytical queries involving tasks such as more complex path finding, centrality or clustering. It is also important to be able to run these algorithms not over native graphs, but perhaps over a certain set of nodes or edges previously selected by a graph query, and one may also want to pose further queries over the result of the analytics task. Finally, all of this should be done in an efficient way, specially in the prospect that graph databases may contain a huge amount of nodes. In this talk I will discuss possible approaches to perform these operations, covering aspects from the design of languages for graph analytics to efficient ways of processing them, and also comparing the expressive power of graph analytics solutions with other forms of graph computation.

uk: вхід без авторизації

name: Current Challenges in Graph Databases (Invited Talk)


uk: Комп'ютерні науки

description: We present the theoretical foundations of a new approach in centrality measures for graph data. The main principle of our approach is very simple: the more relevant subgraphs around a vertex, the more central it is in the network. We formalize the notion of "relevant subgraphs" by choosing a family of subgraphs that, give a graph G and a vertex v in G, it assigns a subset of connected subgraphs of G that contains v. Any of such families defines a measure of centrality by counting the number of subgraphs assigned to the vertex, i.e., a vertex will be more important for the network if it belongs to more subgraphs in the family. We show many examples of this approach and, in particular, we propose the all-subgraphs centrality, a centrality measure that takes every subgraph into account. We study fundamental properties over families of subgraphs that guarantee desirable properties over the corresponding centrality measure. Interestingly, all-subgraphs centrality satisfies all these properties, showing its robustness as a notion for centrality. Finally, we study the computational complexity of counting certain families of subgraphs and show a polynomial time algorithm to compute the all-subgraphs centrality for graphs with bounded tree width.

uk: вхід без авторизації

name: A Family of Centrality Measures for Graph Data Based on Subgraphs


uk: Комп'ютерні науки

description: Worst-case optimal join algorithms have gained a lot of attention in the database literature. We now count with several algorithms that are optimal in the worst case, and many of them have been implemented and validated in practice. However, the implementation of these algorithms often requires an enhanced indexing structure: to achieve optimality we either need to build completely new indexes, or we must populate the database with several instantiations of indexes such as B+-trees. Either way, this means spending an extra amount of storage space that may be non-negligible. We show that optimal algorithms can be obtained directly from a representation that regards the relations as point sets in variable-dimensional grids, without the need of extra storage. Our representation is a compact quadtree for the static indexes, and a dynamic quadtree sharing subtrees (which we dub a qdag) for intermediate results. We develop a compositional algorithm to process full join queries under this representation, and show that the running time of this algorithm is worst-case optimal in data complexity. Remarkably, we can extend our framework to evaluate more expressive queries from relational algebra by introducing a lazy version of qdags (lqdags). Once again, we can show that the running time of our algorithms is worst-case optimal.

uk: вхід без авторизації

name: Optimal Joins Using Compact Data Structures


uk: Комп'ютерні науки

description: We investigate when two graphs, represented by their adjacency matrices, can be distinguished by means of sentences formed in MATLANG, a matrix query language which supports a number of elementary linear algebra operators. When undirected graphs are concerned, and hence the adjacency matrices are real and symmetric, precise characterisations are in place when two graphs (i.e., their adjacency matrices) can be distinguished. Turning to directed graphs, one has to deal with asymmetric adjacency matrices. This complicates matters. Indeed, it requires to understand the more general problem of when two arbitrary matrices can be distinguished in MATLANG. We provide characterisations of the distinguishing power of MATLANG on real and complex matrices, and on adjacency matrices of directed graphs in particular. The proof techniques are a combination of insights from the symmetric matrix case and results from linear algebra and linear control theory.

uk: вхід без авторизації

name: When Can Matrix Query Languages Discern Matrices?


uk: Комп'ютерні науки

description: Data exchange heavily relies on the notion of incomplete database instances. Several semantics for such instances have been proposed and include open (OWA), closed (CWA), and open-closed (OCWA) world. For all these semantics important questions are: whether one incomplete instance semantically implies another; when two are semantically equivalent; and whether a smaller or smallest semantically equivalent instance exists. For OWA and CWA these questions are fully answered. For several variants of OCWA, however, they remain open. In this work we adress these questions for Closed Powerset semantics and the OCWA semantics of [Leonid Libkin and Cristina Sirangelo, 2011]. We define a new OCWA semantics, called OCWA*, in terms of homomorphic covers that subsumes both semantics, and characterize semantic implication and equivalence in terms of such covers. This characterization yields a guess-and-check algorithm to decide equivalence, and shows that the problem is NP-complete. For the minimization problem we show that for several common notions of minimality there is in general no unique minimal equivalent instance for Closed Powerset semantics, and consequently not for the more expressive OCWA* either. However, for Closed Powerset semantics we show that one can find, for any incomplete database, a unique finite set of its subinstances which are subinstances (up to renaming of nulls) of all instances semantically equivalent to the original incomplete one. We study properties of this set, and extend the analysis to OCWA*.

uk: вхід без авторизації

name: On Equivalence and Cores for Incomplete Databases in Open and Closed Worlds


uk: Комп'ютерні науки

description: In PODS'17, Ketsman and Suciu gave an algorithm in the MPC model for computing the result of any natural join where every input relation has two attributes. Achieving an optimal load O(m/p^{1/ρ}) - where m is the total size of the input relations, p the number of machines, and ρ the fractional edge covering number of the join - their algorithm requires 7 rounds to finish. This paper presents a simpler algorithm that ensures the same load with 3 rounds (in fact, the second round incurs only a load of O(p²) to transmit certain statistics to assist machine allocation in the last round). Our algorithm is made possible by a new theorem that provides fresh insight on the structure of the problem, and brings us closer to understanding the intrinsic reason why joins on binary relations can be settled with load O(m/p^{1/ρ}).

uk: вхід без авторизації

name: A Simple Parallel Algorithm for Natural Joins on Binary Relations


uk: Комп'ютерні науки

description: In this work, we consider misinformation propagating through a social network and study the problem of its prevention. In this problem, a "bad" campaign starts propagating from a set of seed nodes in the network and we use the notion of a limiting (or "good") campaign to counteract the effect of misinformation. The goal is to identify a set of k users that need to be convinced to adopt the limiting campaign so as to minimize the number of people that adopt the "bad" campaign at the end of both propagation processes. This work presents RPS (Reverse Prevention Sampling), an algorithm that provides a scalable solution to the misinformation prevention problem. Our theoretical analysis shows that RPS runs in O((k + l)(n + m)(1/(1 - γ)) log n / ε²) expected time and returns a (1 - 1/e - ε)-approximate solution with at least 1 - n^{-l} probability (where γ is a typically small network parameter and l is a confidence parameter). The time complexity of RPS substantially improves upon the previously best-known algorithms that run in time Ω(m n k ⋅ POLY(ε^{-1})). We experimentally evaluate RPS on large datasets and show that it outperforms the state-of-the-art solution by several orders of magnitude in terms of running time. This demonstrates that misinformation prevention can be made practical while still offering strong theoretical guarantees.

uk: вхід без авторизації

name: Reverse Prevention Sampling for Misinformation Mitigation in Social Networks


uk: Комп'ютерні науки

description: Integrity constraints such as functional dependencies (FD), and multi-valued dependencies (MVD) are fundamental in database schema design. Likewise, probabilistic conditional independences (CI) are crucial for reasoning about multivariate probability distributions. The implication problem studies whether a set of constraints (antecedents) implies another constraint (consequent), and has been investigated in both the database and the AI literature, under the assumption that all constraints hold exactly. However, many applications today consider constraints that hold only approximately. In this paper we define an approximate implication as a linear inequality between the degree of satisfaction of the antecedents and consequent, and we study the relaxation problem: when does an exact implication relax to an approximate implication? We use information theory to define the degree of satisfaction, and prove several results. First, we show that any implication from a set of data dependencies (MVDs+FDs) can be relaxed to a simple linear inequality with a factor at most quadratic in the number of variables; when the consequent is an FD, the factor can be reduced to 1. Second, we prove that there exists an implication between CIs that does not admit any relaxation; however, we prove that every implication between CIs relaxes "in the limit". Finally, we show that the implication problem for differential constraints in market basket analysis also admits a relaxation with a factor equal to 1. Our results recover, and sometimes extend, several previously known results about the implication problem: implication of MVDs can be checked by considering only 2-tuple relations, and the implication of differential constraints for frequent item sets can be checked by considering only databases containing a single transaction.

uk: вхід без авторизації

name: Integrity Constraints Revisited: From Exact to Approximate Implication


uk: Комп'ютерні науки

description: We study the expressive power of the Lara language - a recently proposed unified model for expressing relational and linear algebra operations - both in terms of traditional database query languages and some analytic tasks often performed in machine learning pipelines. We start by showing Lara to be expressive complete with respect to first-order logic with aggregation. Since Lara is parameterized by a set of user-defined functions which allow to transform values in tables, the exact expressive power of the language depends on how these functions are defined. We distinguish two main cases depending on the level of genericity queries are enforced to satisfy. Under strong genericity assumptions the language cannot express matrix convolution, a very important operation in current machine learning operations. This language is also local, and thus cannot express operations such as matrix inverse that exhibit a recursive behavior. For expressing convolution, one can relax the genericity requirement by adding an underlying linear order on the domain. This, however, destroys locality and turns the expressive power of the language much more difficult to understand. In particular, although under complexity assumptions the resulting language can still not express matrix inverse, a proof of this fact without such assumptions seems challenging to obtain.

uk: вхід без авторизації

name: On the Expressiveness of LARA: A Unified Language for Linear and Relational Algebra


uk: Комп'ютерні науки

description: Complex Event Recognition (CER for short) has recently gained attention as a mechanism for detecting patterns in streams of continuously arriving event data. Numerous CER systems and languages have been proposed in the literature, commonly based on combining operations from regular expressions (sequencing, iteration, and disjunction) and relational algebra (e.g., joins and filters). While these languages are naturally first-order, meaning that variables can only bind single elements, they also provide capabilities for filtering sets of events that occur inside iterative patterns; for example requiring sequences of numbers to be increasing. Unfortunately, these type of filters usually present ad-hoc syntax and under-defined semantics, precisely because variables cannot bind sets of events. As a result, CER languages that provide filtering of sequences commonly lack rigorous semantics and their expressive power is not understood. In this paper we embark on two tasks: First, to define a denotational semantics for CER that naturally allows to bind and filter sets of events; and second, to compare the expressive power of this semantics with that of CER languages that only allow for binding single events. Concretely, we introduce Set-Oriented Complex Event Logic (SO-CEL for short), a variation of the CER language introduced in [Grez et al., 2019] in which all variables bind to sets of matched events. We then compare SO-CEL with CEL, the CER language of [Grez et al., 2019] where variables bind single events. We show that they are equivalent in expressive power when restricted to unary predicates but, surprisingly, incomparable in general. Nevertheless, we show that if we restrict to sets of binary predicates, then SO-CEL is strictly more expressive than CEL. To get a better understanding of the expressive power, computational capabilities, and limitations of SO-CEL, we also investigate the relationship between SO-CEL and Complex Event Automata (CEA), a natural computational model for CER languages. We define a property on CEA called the *-property and show that, under unary predicates, SO-CEL captures precisely the subclass of CEA that satisfy this property. Finally, we identify the operations that SO-CEL is lacking to characterize CEA and introduce a natural extension of the language that captures the complete class of CEA under unary predicates.

uk: вхід без авторизації

name: On the Expressiveness of Languages for Complex Event Recognition


Dynamic Complexity of Document Spanners

uk: Комп'ютерні науки

description: The present paper investigates the dynamic complexity of document spanners, a formal framework for information extraction introduced by Fagin, Kimelfeld, Reiss, and Vansummeren (JACM 2015). We first look at the class of regular spanners and prove that any regular spanner can be maintained in the dynamic complexity class DynPROP. This result follows from work done previously on the dynamic complexity of formal languages by Gelade, Marquardt, and Schwentick (TOCL 2012). To investigate core spanners we use SpLog, a concatenation logic that exactly captures core spanners. We show that the dynamic complexity class DynCQ is more expressive than SpLog and therefore can maintain any core spanner. This result is then extended to show that DynFO can maintain any generalized core spanner and that DynFO is more powerful than SpLog with negation.

uk: вхід без авторизації


uk: Комп'ютерні науки

description: We study the containment problem for UC2RPQ, that is, two-way Regular Path Queries, closed under conjunction, projection and union. We show a dichotomy property between PSpace-c and ExpSpace-c based on a property on the underlying graph of queries. We show that for any class C of graphs, the containment problem for queries whose underlying graph is in C is in PSpace if and only if C has bounded bridgewidth. Bridgewidth is a graph measure we introduce to this end, defined as the maximum size of a minimal edge separator of a graph.

uk: вхід без авторизації

name: Containment of UC2RPQ: The Hard and Easy Cases


uk: Комп'ютерні науки

description: Computing joins is expensive, and often unnecessary when the output size is large. In 1999, Chaudhuri et al. [Surajit Chaudhuri et al., 1999] posed the problem of random sampling over joins as a potentially effective approach to avoiding computing the join in full, while obtaining important statistical information about the join results. Unfortunately, no significant progress has been made in the last 20 years, except for the case of acyclic joins. In this paper, we present the first non-trivial result on sampling over cyclic joins. We show that after a linear-time preprocessing step, a join result can be drawn uniformly at random in expected time O(IN^ρ/OUT), where IN^ρ is known as the AGM bound of the join and OUT is its output size. This result holds for all joins on binary relations, as well as certain joins on relations of higher arity. We further show how this algorithm immediately leads to a join size estimation algorithm with the same running time.

uk: вхід без авторизації

name: Random Sampling and Size Estimation Over Cyclic Joins


uk: Комп'ютерні науки

description: State-of-the-art fault-tolerant and federated data management systems rely on fully-replicated designs in which all participants have equivalent roles. Consequently, these systems have only limited scalability and are ill-suited for high-performance data management. As an alternative, we propose a hierarchical design in which a Byzantine cluster manages data, while an arbitrary number of learners can reliable learn these updates and use the corresponding data. To realize our design, we propose the delayed-replication algorithm, an efficient solution to the Byzantine learner problem that is central to our design. The delayed-replication algorithm is coordination-free, scalable, and has minimal communication cost for all participants involved. In doing so, the delayed-broadcast algorithm opens the door to new high-performance fault-tolerant and federated data management systems. To illustrate this, we show that the delayed-replication algorithm is not only useful to support specialized learners, but can also be used to reduce the overall communication cost of permissioned blockchains and to improve their storage scalability.

uk: вхід без авторизації

name: Coordination-Free Byzantine Replication with Minimal Communication Costs


uk: Комп'ютерні науки

description: Motivated by the problem of filtering candidate pairs in inner product similarity joins we study the following inner product estimation problem: Given parameters d∈ℕ, α>β≥0 and unit vectors x,y∈ ℝ^d consider the task of distinguishing between the cases ⟨x,y⟩≤β and ⟨x,y⟩≥α where ⟨x,y⟩ = ∑_{i=1}^d x_i y_i is the inner product of vectors x and y. The goal is to distinguish these cases based on information on each vector encoded independently in a bit string of the shortest length possible. In contrast to much work on compressing vectors using randomized dimensionality reduction, we seek to solve the problem deterministically, with no probability of error. Inner product estimation can be solved in general via estimating ⟨x,y⟩ with an additive error bounded by ε = α - β. We show that d log₂ (√{1-β}/ε) ± Θ(d) bits of information about each vector is necessary and sufficient. Our upper bound is constructive and improves a known upper bound of d log₂(1/ε) + O(d) by up to a factor of 2 when β is close to 1. The lower bound holds even in a stronger model where one of the vectors is known exactly, and an arbitrary estimation function is allowed.

uk: вхід без авторизації

name: The Space Complexity of Inner Product Filters


uk: Комп'ютерні науки

description: Complex event processing (CEP) has gained a lot of attention for evaluating complex patterns over high-throughput data streams. Recently, new algorithms for the evaluation of CEP patterns have emerged with strong guarantees of efficiency, i.e. constant update-time per tuple and constant-delay enumeration. Unfortunately, these techniques are restricted for patterns with local filters, limiting the possibility of using joins for correlating the data of events that are far apart. In this paper, we embark on the search for efficient evaluation algorithms of CEP patterns with joins. We start by formalizing the so-called partition-by operator, a standard operator in data stream management systems to correlate contiguous events on streams. Although this operator is a restricted version of a join query, we show that partition-by (without iteration) is equally expressive as hierarchical queries, the biggest class of full conjunctive queries that can be evaluated with constant update-time and constant-delay enumeration over streams. To evaluate queries with partition-by we introduce an automata model, called chain complex event automata (chain-CEA), an extension of complex event automata that can compare data values by using equalities and disequalities. We show that this model admits determinization and is expressive enough to capture queries with partition-by. More importantly, we provide an algorithm with constant update time and constant delay enumeration for evaluating any query definable by chain-CEA, showing that all CEP queries with partition-by can be evaluated with these strong guarantees of efficiency.

uk: вхід без авторизації

name: Towards Streaming Evaluation of Queries with Correlation in Complex Event Processing


Datalog with Negation and Monotonicity

uk: Комп'ютерні науки

description: Positive Datalog has several nice properties that are lost when the language is extended with negation. One example is that fixpoints of positive Datalog programs are robust w.r.t. the order in which facts are inserted, which facilitates efficient evaluation of such programs in distributed environments. A natural question to ask, given a (stratified) Datalog program with negation, is whether an equivalent positive Datalog program exists. In this context, it is known that positive Datalog can express only a strict subset of the monotone queries, yet the exact relationship between the positive and monotone fragments of semi-positive and stratified Datalog was previously left open. In this paper, we complete the picture by showing that monotone queries expressible in semi-positive Datalog exist which are not expressible in positive Datalog. To provide additional insight into this gap, we also characterize a large class of semi-positive Datalog programs for which the dichotomy `monotone if and only if rewritable to positive Datalog' holds. Finally, we give best-effort techniques to reduce the amount of negation that is exhibited by a program, even if the program is not monotone.

uk: вхід без авторизації


uk: Комп'ютерні науки

description: The framework of document spanners abstracts the task of information extraction from text as a function that maps every document (a string) into a relation over the document’s spans (intervals identified by their start and end indices). For instance, the regular spanners are the closure under the Relational Algebra (RA) of the regular expressions with capture variables, and the expressive power of the regular spanners is precisely captured by the class of vset-automata - a restricted class of transducers that mark the endpoints of selected spans. In this work, we embark on the investigation of document spanners that can annotate extractions with auxiliary information such as confidence, support, and confidentiality measures. To this end, we adopt the abstraction of provenance semirings by Green et al., where tuples of a relation are annotated with the elements of a commutative semiring, and where the annotation propagates through the (positive) RA operators via the semiring operators. Hence, the proposed spanner extension, referred to as an annotator, maps every string into an annotated relation over the spans. As a specific instantiation, we explore weighted vset-automata that, similarly to weighted automata and transducers, attach semiring elements to transitions. We investigate key aspects of expressiveness, such as the closure under the positive RA, and key aspects of computational complexity, such as the enumeration of annotated answers and their ranked enumeration in the case of numeric semirings. For a number of these problems, fundamental properties of the underlying semiring, such as positivity, are crucial for establishing tractability.

uk: вхід без авторизації

name: Weight Annotation in Information Extraction


uk: Комп'ютерні науки

description: The logic of information flows (LIF) has recently been proposed as a general framework in the field of knowledge representation. In this framework, tasks of a procedural nature can still be modeled in a declarative, logic-based fashion. In this paper, we focus on the task of query processing under limited access patterns, a well-studied problem in the database literature. We show that LIF is well-suited for modeling this task. Toward this goal, we introduce a variant of LIF called "forward" LIF, in a first-order setting. We define FLIF^io, a syntactical fragment of forward LIF, and show that it corresponds exactly to the "executable" fragment of first-order logic defined by Nash and Ludäscher. The definition of FLIF^io involves a classification of the free variables of an expression into "input" and "output" variables. Our result hinges on inertia and determinacy laws for forward LIF expressions, which are interesting in their own right. These laws are formulated in terms of the input and output variables.

uk: вхід без авторизації

name: Executable First-order Queries in the Logic of Information Flows

name: International Conference on Database Theory (ICDT)


Infinite Probabilistic Databases

uk: Комп'ютерні науки

description: Probabilistic databases (PDBs) are used to model uncertainty in data in a quantitative way. In the standard formal framework, PDBs are finite probability spaces over relational database instances. It has been argued convincingly that this is not compatible with an open-world semantics (Ceylan et al., KR 2016) and with application scenarios that are modeled by continuous probability distributions (Dalvi et al., CACM 2009). We recently introduced a model of PDBs as infinite probability spaces that addresses these issues (Grohe and Lindner, PODS 2019). While that work was mainly concerned with countably infinite probability spaces, our focus here is on uncountable spaces. Such an extension is necessary to model typical continuous probability distributions that appear in many applications. However, an extension beyond countable probability spaces raises nontrivial foundational issues concerned with the measurability of events and queries and ultimately with the question whether queries have a well-defined semantics. It turns out that so-called finite point processes are the appropriate model from probability theory for dealing with probabilistic databases. This model allows us to construct suitable (uncountable) probability spaces of database instances in a systematic way. Our main technical results are measurability statements for relational algebra queries as well as aggregate queries and Datalog queries.

uk: вхід без авторизації


The Shapley Value of Database Tuples

uk: Комп'ютерні науки

description: We investigate the application of the Shapley value to quantifying the contribution of a tuple to a query answer. The Shapley value is a widely known numerical measure in cooperative game theory and in many applications of game theory for assessing the contribution of a player to a coalition game. It has been established already in the 1950s, and is theoretically justified by being the very single wealth-distribution measure that satisfies some natural axioms. While this value has been investigated in several areas, it received little attention in data management. We study this measure in the context of conjunctive and aggregate queries by defining corresponding coalition games. We provide algorithmic and complexity-theoretic results on the computation of Shapley-based contributions to query answers; and for the hard cases we present approximation algorithms.

uk: вхід без авторизації


uk: Комп'ютерні науки

description: This paper introduces a declarative framework to specify and reason about distributions of data over computing nodes in a distributed setting. More specifically, it proposes distribution constraints which are tuple and equality generating dependencies (tgds and egds) extended with node variables ranging over computing nodes. In particular, they can express co-partitioning constraints and constraints about range-based data distributions by using comparison atoms. The main technical contribution is the study of the implication problem of distribution constraints. While implication is undecidable in general, relevant fragments of so-called data-full constraints are exhibited for which the corresponding implication problems are complete for EXPTIME, PSPACE and NP. These results yield bounds on deciding parallel-correctness for conjunctive queries in the presence of distribution constraints.

uk: вхід без авторизації

name: Distribution Constraints: The Chase for Distributed Data


uk: Комп'ютерні науки

description: We study the problem of probabilistic query evaluation (PQE) over probabilistic graphs, namely, tuple-independent probabilistic databases (TIDs) on signatures of arity two. Our focus is the class of queries that is closed under homomorphisms, or equivalently, the infinite unions of conjunctive queries, denoted UCQ∞. Our main result states that all unbounded queries in UCQ∞ are #P-hard for PQE. As bounded queries in UCQ∞ are already classified by the dichotomy of Dalvi and Suciu [Dalvi and Suciu, 2012], our results and theirs imply a complete dichotomy on PQE for UCQ∞ queries over probabilistic graphs. This dichotomy covers in particular all fragments in UCQ∞ such as negation-free (disjunctive) Datalog, regular path queries, and a large class of ontology-mediated queries on arity-two signatures. Our result is shown by reducing from counting the valuations of positive partitioned 2-DNF formulae (#PP2DNF) for some queries, or from the source-to-target reliability problem in an undirected graph (#U-ST-CON) for other queries, depending on properties of minimal models.

uk: вхід без авторизації

name: A Dichotomy for Homomorphism_Closed Queries on Probalistic Graphs


keywords:
Airborne Wind Energy
Kite Power
Kite Launch
Airfield Valkenburg

description: The video recording shows an attempted launch of the TU Delft V3 kite from an upside-down hanging position on 2 August 2012 at the former airfield Valkenburg, Leiden, Netherlands. The GoPro camera is taped to the rear side of the leading edge tube of the wing, between the two center struts, looking at the kite control unit. During the upswing of the kite, the kite control unit remains in the line of sight between video camera and mast head. At 11 s into the video, the ground station appears at the top of the field of view. Also clearly visible is the tether running from the mast head to the ground station. At 15 s into the video, the tether suddenly disengages from the mast head, which leads to a strong dynamic perturbation of the tensile system. Playing the video in slow motion reveals that the disengaged tether moves within 1 s towards a new equilibrium shape, which is the straight line connecting ground station and kite. This rapid straigthening of the tether yanks the kite control unit upwards, into the line of sight between video camera and ground station. The tensile system stays in this new equilibrium state for only 0.1-0.2 s, after which the weak link, just below the kite control unit, breaks due to overload. The shock force of this event yanks the video camera by about 90 degrees in its mount, now looking in the direction of the heading, along the leading edge tube. Between 20-22 s into the video, a loose bridle line connected to the leading edge tube can be seen flying by. Around 23 s into the video, fabric debris from the progressive-tearing energy absorber, that is integrated into the safety line, passes the field of view. The wing impacts the ground at 27 s into the video. This launch attempt was also covered by data recording, by a regular photo camera and by a second GoPro video camera that was positioned on the ground, next to the launch mast. The remaining course of events can be reconstructed from the photo footage: with the break of the weak link, the pulling force of the detached kite immediately shifts to the safety line, which at this point in time remains the only physical connection between the kite and the tether. The sudden force increase in this line activates the integrated progressive-tearing energy absorber. The kite control unit, on the other hand, is catapulted in radial direction towards the wing and eventually caught by the bridle line system. This ballistic event leads to an irreversible collapse of the wing. Secured by the safety line, the parachute-like assembly of curled-up wing and kite control unit slowly descends and hits the ground at about 27 s into the video. Because the time setting of the GoPro video camera was incorrect, the time information in the metadata was synchronized with the absolute time available from the data recording. The creation date of the video was set to the launch time 18:27:18 such that the weak link ruptures about 16 s later, at 18:27:34.

uk: вхід без авторизації

name: Rupture of the weak link during a mast-based launch attempt of the V3 kite: Video recorded on 2 August 2012 with a GoPro camera mounted on the leading edge tube

Delft University of Technology

addressCountry: NL

addressLocality: Delft

addressRegion: South Holland


description: The animated photo sequence shows an attempted launch of the TU Delft V3 kite from an upside-down hanging position on 2 August 2012 at the former airfield Valkenburg, Leiden, Netherlands. While the upswing of the kite towards the upright position proceeds well, the tether suddenly disengages from the mast head, at 15 s into the video. Within only 1 s, the kite accelerates in downwind direction, pulling the disengaged tether into a new tensioned state, which is the straight line connecting the kite with the ground station placed upwind of the launch mast. During this rapid straigthening of the tether, the entire kite, consisting of wing bridle line system and kite control unit, is pitching up, yanking the relatively heavy control unit upwards. Once the tether is tensioned, it takes only a fraction of a second until the weak link breaks due to overload. As a result, the pulling force of the detached kite immediately shifts to the safety line, which at this point in time remains the only physical connection between the kite and the tether. The sudden force increase in this line activates the integrated progressive-tearing energy absorber, which is visible from the scattering fabric debris (starting at 16 s into the video) and the kite again accelerating in downwind direction. With the breaking of the weak link, the kite control unit is catapulted in radial direction towards the wing and eventually caught by the bridle line system. This ballistic event leads to an irreversible collapse of the wing. Secured by the safety line, the parachute-like assembly of curled-up wing and kite control unit slowly descends and hits the ground about 27 s into the video. This launch attempt was also covered by data recording, and by two different GoPro video cameras, of which one was positioned on the ground, next to the launch mast, and the other one taped to the leading edge tube of the kite, looking down at the kite control unit. The 39 photos capturing this launch attempt were shot with a Nikon D40X in irregular intervals. The photos were assembled into a video using the precise time information available for each photo from its metadata. Because the time duration between the first and the second photo of the sequence is about 10 s, the animation does not resolve the first 10 s of the upswing. Also, the absolute time setting of the camera was incorrect, which is why the time information of the generated video file was synchronized with the absolute time available from the data recording. The creation date of the video was set to the launch time 18:27:18 such that the weak link ruptures about 16 s into the video, at 18:27:34.

uk: вхід без авторизації

name: Rupture of the weak link during a mast-based launch attempt of the V3 kite: Animated sequence of photos taken on 2 August 2012 from the ground


keywords:
Airborne Wind Energy
Kite Power
Tether Rupture
Airfield Valkenburg

description: This video footage is from a test flight conducted on 11 March 2010 at the former naval airfield Valkenburg, Leiden, Netherlands. It was recorded by a GoPro video camera mounted on the swivel head of the ground station, looking along the tether at the kite. The kite power system was equipped with a Mutiny V1 kite of 25 m2 wing surface area and a radio-controlled improvised kite control unit. At 24:10 min after lauch (29 s into this video excerpt) the tether ruptured at the kite end, while the kite was flying downwards during a figure-of- eight maneuver. Because the system was not yet equipped with safety line and ripcord shock absorber, the detached, highly-tensioned Dyneema® line lashed back towards the swivel head, deforming into a wave-like shape before falling to the ground. This sudden contraction of the tether happened within a fraction of a second. The sudden drop of the tether force also jolted the ground station significantly. The detached kite first continued on its downwards trajectory, but was eventually redirected into a gentle gliding decent and landed at some distance from the ground station.

uk: вхід без авторизації

name: Tether backlash after rupture at kite end on 11 March 2010: Video recorded from the ground station, looking along the tether at the kite


keywords:
Airborne Wind Energy
Kite Power
Kite Collapse
Jirnsum

description: This video footage is from a test flight conducted on 9 September 2010 at Jirnsum, Province of Friesland, Netherlands. It was recorded by a GoPro video camera mounted on the swivel head of the ground station, looking along the tether at the kite. The kite power system was equipped with a Mutiny V1 kite of 25 m2 wing surface area and a radio-controlled improvised kite control unit. In this flight the wing collapsed 9:34 min after launch (60 s into this video excerpt), during the reel-in phase, subsequently sinking to the ground, in a spiraling motion. The start of the reel in phase can be recognized by the audible increase of the reeling speed starting at 40 s into this video excerpt. Shortly after the wing collapsed, the reeling of the tether is stopped. The entire decent, from wing collapse until ground impact, took about 40 s. The event was video recorded simultaneously by a GoPro video camera taped to the leading edge tube at the wing tip, looking towards the other wing tip.

uk: вхід без авторизації

name: Kite collapse during reel in on 9 September 2010: Video recorded from the ground station, looking along the tether at the kite


description: This video footage is from a test flight conducted on 9 September 2010 at Jirnsum, Province of Friesland, Netherlands. It was recorded by a GoPro video camera mounted on the left tip of the inflatable wing, looking at the right wing tip. The kite power system was equipped with a Mutiny V1 kite of 25 m2 wing surface area and a radio-controlled improvised kite control unit. In this flight the wing collapsed 9:34 min after launch (60 s into this video excerpt), during the reel in phase, subsequently descending to the ground, in a collapsed state. The reel in phase starts at 40 s into this video excerpt. Between 40 and 50 s, the indentations in the center of the wing become more and more prominent, indicating that the relative flow is impining on the suction side of the wing as a result of a negative angle of attack. Between 50 and 60 s into the video the indentations intensify and the wing increasingly flattens. At 60 s, the entire wind buckles and decends in a spiraling motion. The entire decent, from wing collapse until ground impact, took about 40 s. The event was video recorded simultaneously by a GoPro video camera mounted on the swivel head of the ground station.

uk: вхід без авторизації

name: Kite collapse during reel in above Friesland on 9 September 2010: Video recorded from the wing tip, looking at the other tip


description: The video recording shows an attempted launch of the TU Delft V3 kite from an upside-down hanging position on 2 August 2012 at the former airfield Valkenburg, Leiden, Netherlands. While the upswing of the kite towards the upright position proceeds well, the tether suddenly disengages from the mast head (15 s into the video) and the resulting lash leads to an overloading and breaking of the weak link, located just below the kite control unit. As a result, the pulling force of the detached kite immediately shifts to the safety line, which at this point in time remains the only physical connection between the kite and the tether. The sudden force increase in this line activates the integrated progressive-tearing energy absorber, which is visible from the scattering fabric debris (starting at 16 s into the video) and the kite rapidly drifting out of the field of view. This launch attempt was also covered by data recording, by a regular photo camera and by a second GoPro video camera that was taped to the leading edge tube of the kite, looking down at the kite control unit. The remaining course of events can be reconstructed from the additional photo footage: with the sudden break of the weak link, the kite control unit is catapulted in radial direction towards the wing and eventually caught by the bridle line system. This ballistic event leads to an irreversible collapse of the wing. Secured by the safety line, the parachute-like assembly of curled-up wing and kite control unit slowly descends and hits the ground about 27 s into the video. Because the time setting of the GoPro video camera was incorrect, the time information in the metadata was synchronized with the absolute time available from the data recording. The creation date of the video was set to the launch time 18:27:18 such that the weak link ruptures about 16 s later, at 18:27:34.

uk: вхід без авторизації

name: Rupture of the weak link during a mast-based launch attempt of the V3 kite: Video recorded on 2 August 2012 with a GoPro camera on the ground next to the launch mast


UI/UX Tips & Tricks for developers

uk: Комп'ютерні науки

description: I will present some general UI/UX tips & tricks that will help you design better. Everyone should know the basic principles and patterns of design, and once you understand them you will naturally integrate them in your work. UI/UX is a craft. The more you practice it, the better you are at it. Some people argue that you need to have 'good taste' in order to be a designer, to be the 'artsy type'. While this might be true for Graphic Design, Branding and Visual Arts in general, when it comes to Interface, Interaction and Product Design, the focus is more on practicality and 'common sense'.

uk: вхід без авторизації


uk: Комп'ютерні науки

description: Keeping track caring about web performance is hard with constantly changing standards, improving browsers, frameworks and devices. It gets even harder when you develop a tool meeting these changing requirements. Eight years ago, as an IT service provider, we were faced with the task of permanently monitoring the performance of one of the largest e-commerce platforms. After the initial use of WebPagetest, we quickly needed to develop our own features. What started as minor extensions became a separate project over time. In this talk, we would like to take you on the journey we have taken developing OpenSpeedMonitor. You will hear about some unexpected challenges, what we learned the hard way and why we would have failed years ago, if we didn't decide to develop FLOSS.

uk: вхід без авторизації

name: The journey of building OpenSpeedMonitor: Learnings from unexpectedly finding ourselves developing a FLOSS project


uk: Комп'ютерні науки

description: A tour of the internals of Weave Net, one of the most popular container networks: design challenges and lessons learned from five years in the wild. Including Kubernetes integration and how CNI was born. Weave Net is written in Go, using many Linux kernel features such as veths, bridges and iptables. Aimed at developers rather than network engineers, Weave Net tries to be self-configuring and find the best available transport between nodes. The control plane operates via gossip, with no central point of control.

uk: вхід без авторизації

name: Weave Net, an Open Source Container Network: Five years with no central point of control


uk: Комп'ютерні науки

description: Boomerang is an open-source Real User Monitoring (RUM) JavaScript library used by thousands of websites to measure their visitor's experiences. The developers behind Boomerang take pride in building a reliable and performant third-party library that everyone can use without being concerned about its measurements affecting their site. We recently performed and shared an audit of Boomerang's performance, to help communicate its "cost of doing business", and in doing so we found several areas of code that we wanted to improve. We'll discuss how we performed the audit, some of the improvements we've made, how we're testing and validating our changes, and the real-time telemetry we capture for our library to ensure we're having as little of an impact as possible on the sites we're included on. Boomerang is an open-source Real User Monitoring (RUM) JavaScript library used by thousands of websites to measure their visitor's experiences. Boomerang runs on billions of page loads a day, either via the open-source library or as part of Akamai's mPulse RUM service. The developers behind Boomerang take pride in building a reliable and performant third-party library that everyone can use without being concerned about its measurements affecting their site. Recently, we performed and shared an audit of Boomerang's performance, to help communicate the "cost of doing business" of including Boomerang on a page while it takes its measurements. In doing the audit, we found several areas of code that we wanted to improve and have been making continuous improvements ever since. We've taken ideas and contributions from the OSS community, and have built a Performance Lab that helps "lock in" our improvements by continuously measuring the metrics that are important to us. We'll discuss how we performed the audit, some of the improvements we've made, how we're testing and validating our changes, and the real-time telemetry we capture on our library to ensure we're having as little of an impact as possible on the sites we're included on.

uk: вхід без авторизації

name: Check Yourself Before You Wreck Yourself: Auditing and Improving the Performance of Boomerang


uk: Комп'ютерні науки

description: The connection between Web and MIDI seems as likely as the joining of Garlic with Bread! Yet, we now have the power to create music from the web browser! Either by generating MIDI files for later manipulation, or as live instruments, WebMIDI provides us with the power to build some amazing online music applications. In this short form talk, Steven will cover the internal details of the MIDI protocol, and its related file format, to show how music is represented by computers. This details both the recording and playback of music within the browser, and external application. It comes complete with live demos, synthesized sounds, and occasional music jokes!

uk: вхід без авторизації

name: WebMIDI: The garlic bread of the music industry


uk: Комп'ютерні науки

description: You will learn how to localize your project easily with little effort, open-source way. No repetitive work, no manual work with translation files anymore. Weblate is unique for its tight integration to VCS. Set it up once and start engaging the community of translators. More languages translated means more happy users of your software. Be like openSUSE, Fedora, and many more, and speak your users' language now thanks to Weblate! I will show you the main perks of Weblate and the setup of the project. If you have a project with open repo and you want to start translating it, take your git:// link, and we will set it up right on the spot. FOSDEM is a great time and place to found your translating community.

uk: вхід без авторизації

name: Localize your project wirh ease: WEBLATE


Web 3 - A New Web For A New World

uk: Комп'ютерні науки

description: For as long as human society has existed, humans have been unable to trust each other. For millennia, we relied on middlemen to establish business or legal relationships. With the advent of Web2.0, we also relayed the establishment of personal connections, and the system has turned against us. The middlemen abuse our needs and their power and we find ourselves chained to convenience at the expense of our own thoughts, our own privacy. Web3 is a radical new frontier ready to turn the status quo on its head, and these are the technologies we're using to make it happen.

uk: вхід без авторизації


uk: Комп'ютерні науки

description: Vita is a high-performance IPsec VPN gateway designed with medium and large network operators in mind. It is written in a high-level language (Lua) using the Snabb networking toolkit and achieves high performance via networking in userspace, i.e. bypassing the kernel network stack. This talk will discuss Vita and how it was developed using Snabb. Topics include: fast software networking using a dynamic, high-level language; cryptographic ciphers implemented in software software accelerated by x86 extensions; modern cryptography; limiting complexity; multi-core scaling; YANG enabled control planes; minimalist NIC drivers.

uk: вхід без авторизації

name: High-speed traffic encryption on x86_64 with Snabb: Coming to your cloud with XDP, AVF, and Kubernetes integration


uk: Комп'ютерні науки

description: Virtualization brings many advantages, but what about the overhead it introduces? What about performance? This talk will show how great virtualization performance can be achieved, if proper tuning is applied to all the components of the system: hypervisor, host and guests, for both Xen and KVM. As a case study, we will describe how we tuned our OS in order to be able to reach, inside VMs, close to baremetal performance, on a server powered by a CPU from the AMD EPYC 7002 (codename "Rome") series. We will, of course, show the benchmarks proving that (run on KVM), even when memory encryption is used. Virtualization is great because it decouples the software from the hardware on top of which it runs, and this brings benefits in terms of flexibility, security, reliability and cost savings. But what about the overhead that this, unavoidably, introduces? Well, often enough, a virtualized system is really able to fulfill its goals with an acceptable quality of service, efficient exploitation of HW resources, satisfactory user experience, etc., only if all the components are configured properly. This is not entirely new, as baremetal systems need tuning too, but in a virtualized environment one has to take care of tuning both the the host and the guests. And beware that the interactions between all the different components may not always be straightforward, especially on a large server with complex CPU architecture, such anything based on the AMD EPYC 7002 (codename "Rome") series of processors. This talk will go over some of the typical virtualization “tuning tricks” (for both Xen and KVM). Then, as a case study, we will illustrate how we managed to reach, inside Virtual Machines, a performance level that almost matches the one of the host, on a server powered by a CPU from the AMD EPYC 7002 series. In fact, we will show the results of running CPU and memory intensive benchmarks (on KVM) with and without the suggested tuning. Last (but not least :-D), we will show the impact that the Secure Encrypted Virtualization (SEV) technology has on performance.

uk: вхід без авторизації

name: Reaching "EPYC" Virtualization Performance: Case Study: Tuning VMs for Best Performance on AMD EPYC 7002 /7004 Processor Series Based Servers


uk: Комп'ютерні науки

description: How to run virtual machines in oVirt without copying their disks. Have you ever wanted to run your virtual machine in oVirt without copying its hugh disks? Tired of checking the slow transfer progress? We did, and we have a good plan to avoid the wait! In this talk we show how oVirt can start virtual machine without copying the disks, using external disk via NBD or other protocols supported by qemu. Once the virtual machine is running, copy the disks in the background to oVirt storage. This minimizes downtime to seconds instead of minutes, and can be used in many scenarios such as importing virtual machines from other systems (even from foreign systems via virt-v2v), previewing backups before restore, and provisioning a virtual machines. Audience: Virtualization administrators or developers interested in oVirt architecture and would like a peek into future development.

uk: вхід без авторизації

name: Running virtual machines out of thin air


Edge Clouds with OpenNebula

uk: Комп'ютерні науки

description: Edge computing is currently getting a lot of traction thanks to the growing availability of rented computing resources around the world. The idea is based on moving the core computational logic and storage to distant locations that are closer to the entities they interact with (e.g. users or sensors). The benefits come from improving network latencies, increasing user experience with the provided service, and lowering the transfers to the central locations. Edge clouds bring the flexibility and proven workflows of cloud computing to the edge. OpenNebula is an open source framework to build private and hybrid clouds based on KVM, LXD, and/or VMware vCenter. While the main domain is the corporate private on-premises cloud, it comes with simple and extensible tooling ("oneprovision") for automated deployment of edge clouds. When provided with a deployment descriptor, it allocates the physical hosts on the public bare-metal cloud provider, configures all necessary services (e.g. install libvirt/KVM or LXD), and enables them for use in OpenNebula. The process is as simple as running a command-line tool and the cloud administrator gets a fully usable configured edge cluster in a few minutes. As part of a usability validation exercise, we successfully deployed public gaming servers from scratch to running services on 17 different locations worldwide in just 25 minutes: https://opennebula.org/opennebula-a-lightning-fast-video-gaming-edge-use-case-2 . This talk introduces the OpenNebula "edge" concept and shows the current state, capabilities, and limitations of edge cloud deployment tooling. It explores the difficulties of running the IaaS-in-IaaS cloud and demonstrates with practical examples the use of tooling and management of edge deployments.

uk: вхід без авторизації


uk: Комп'ютерні науки

description: A whole bunch of CPU vulnerabilities were revealed in the past few years: Meltdown and Spectre, SSB, L1TF and MDS -- and there's little hope that we've seen them all. Every time there is a new vulnerability released, big cloud provides on day 1 claim that their hosts were updated and that their users are secure. Is this so or do we also need to do something inside our Linux guests to mitigate these vulnerabilities? And, do we have the required tools to actually do the mitigations? Are all of them enabled by default or not? And, if not, why? In the talk I'll try to answer these questions. The talk will cover recently discovered CPU vulnerabilities starting with Meltdown and Spectre. I will go through them and try to highlight 'public cloud specifics': what has/can to be done in the infrastructure of the cloud and what has/can be done inside Linux guests depending on the desired level of security and usage patterns.

uk: вхід без авторизації

name: Public clouds and vulnerable CPUs: are we secure?