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13:24 Joe Leys, Étienne Ghys, Aurélien Alvarez English 2012

Chaos | Chapter 2 : Vector fields - The lego race

  • Published: 2012
  • Publisher: Joe Leys, Étienne Ghys, Aurélien Alvarez
  • Language: English
13:21 Joe Leys, Étienne Ghys, Aurélien Alvarez English 2012

Chaos | Chapter 7 : Strange Attractors - The butterfly effect

  • Published: 2012
  • Publisher: Joe Leys, Étienne Ghys, Aurélien Alvarez
  • Language: English
13:21 Joe Leys, Étienne Ghys, Aurélien Alvarez English 2012

Chaos | Chapter 4 : Oscillations - The swing

  • Published: 2012
  • Publisher: Joe Leys, Étienne Ghys, Aurélien Alvarez
  • Language: English
13:15 Joe Leys, Étienne Ghys, Aurélien Alvarez English 2012

Chaos | Chapter 5 : Billiards - Duhem's bull

  • Published: 2012
  • Publisher: Joe Leys, Étienne Ghys, Aurélien Alvarez
  • Language: English
13:51 Joe Leys, Étienne Ghys, Aurélien Alvarez English 2008

Dimensions | Chapter 7

  • Published: 2008
  • Publisher: Joe Leys, Étienne Ghys, Aurélien Alvarez
  • Language: English
13:58 Joe Leys, Étienne Ghys, Aurélien Alvarez English 2008

Dimensions | Chapter 8

  • Published: 2008
  • Publisher: Joe Leys, Étienne Ghys, Aurélien Alvarez
  • Language: English
13:57 Joe Leys, Étienne Ghys, Aurélien Alvarez English 2008

Dimensions | Chapter 9

  • Published: 2008
  • Publisher: Joe Leys, Étienne Ghys, Aurélien Alvarez
  • Language: English
26:53 IWF (Göttingen) English 1985

The Planar Double Pendulum

Computer experiments made it possible to describe the complex dynamics of this classical exemple in mechanics. To begin with, the various types of motion of the double pendulum are presented. With the help of the method of Poincaré sections, a qualitative survey of the complex dynamics follows, with special emphasis on irrational winding numbers (golden ratio).
  • Published: 1985
  • Publisher: IWF (Göttingen)
  • Language: English
41:47 Open Science Training Initiative (OSTI) English 2013

3. Data, Code & Content Licensing

The following video is an original recording from the OSTI pilot initiative. Entitled "Data, Code & Content Licensing", the seminar introduces the theme of licensing, outlines the advantages of this approach, and takes students through the main steps of implementation.
  • Published: 2013
  • Publisher: Open Science Training Initiative (OSTI)
  • Language: English
24:23 FOSSGIS e.V. German 2014

Scientific 3D Printing with GRASS GIS

As the amount of scientific data continues to grow, researchers need new tools to help them visualize complex data. Immersive data-visualisations are helpful, yet fail to provide tactile feedback and sensory feedback on spatial orientation, as provided from tangible objects. The gap in sensory feedback from virtual objects leads to the development of tangible representations of geospatial information to solve real world problems. Examples are animated globes, interactive environments like tangible GIS, and on demand 3D prints. The production of a tangible representation of a scientific data set is one step in a line of scientific thinking, leading from the physical world into scientific reasoning and back: The process starts with a physical observation, or from a data stream generated by an environmental sensor. This data stream is turned into a geo-referenced data set. This data is turned into a volume representation which is converted into command sequences for the printing device, leading to the creation of a 3D printout. As a last, but crucial step, this new object has to be documented and linked to the associated metadata, and curated in long term repositories to preserve its scientific meaning and context. The workflow to produce tangible 3D data-prints from science data at the German Research Centre for Geosciences (GFZ) was implemented as a software based on the Free and Open Source Geoinformatics tools GRASS GIS and Paraview. The workflow was successfully validated in various application scenarios at GFZ using a RapMan printer to create 3D specimens of elevation models, geological underground models, ice penetrating radar soundings for planetology, and space time stacks for Tsunami model quality assessment. While these first pilot applications have demonstrated the feasibility of the overall approach, current research focuses on the provision of the workflow as Software as a Service (SAAS), thematic generalisation of information content and long term curation.
  • Published: 2014
  • Publisher: FOSSGIS e.V.
  • Language: German
41:32 droidcon Berlin English 2015

Android reactive programming with Rxjava

In a world where there is a smartphone in every pocket, designing and building applications that can run smoothly and provide the User Experience that users will like it’s the only way to go. Reactive Programming style with RxJava will help you to beat Android Platform limitations to create astonishing Android Apps. This talk will be a practical journey from basic Reactive Programming and Observer Pattern concepts to the main feature of RxJava, with practical code examples and a real-world app. I'll show the audience how to create an Observable "from scratch", from a list or from a function we already have in our code base. Our listeners will learn how to filter an Observable sequence to create a new sequence containing only the values we want; they will learn how to apply a function to an Observable, how to concatenate, merge or zip Observables. I'll show how to enjoy RxAndroid Schedulers to overcome the threading and concurrency hell in Android. I will close the talk with a practical example about RxJava + Retrofit, to easily communicate with a REST API.
  • Published: 2015
  • Publisher: droidcon Berlin
  • Language: English
1:02:05 Institut des Hautes Études Scientifiques (IHÉS) English 2014

2/4 Automorphic forms in higher rank

  • Published: 2014
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:15:07 Institut des Hautes Études Scientifiques (IHÉS) English 2015

Quantum Geometry and Strings

  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
49:58 Institut des Hautes Études Scientifiques (IHÉS) English 2013

Counterterms in gravity and N = 8 Supergravity

I will discuss counterterms in gravity using the light-cone frame formulation and show that also in this fully gauge fixed formulation we do need a local symmetry to find the correct counter terms.
  • Published: 2013
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:41:20 Institut des Hautes Études Scientifiques (IHÉS) English 2014

1/3 Mathematical Physics of Hurwitz numbers

Hurwitz numbers enumerate ramified coverings of a sphere. Equivalently, they can be expressed in terms of combinatorics of the symmetric group; they enumerate factorizations of permutations as products of transpositions. It turns out that these numbers obey a huge number of relations represented in the form of partial differential equations for their generating function. This includes equations of the KP hierarchy, Virasoro-type constraints, Chekhov-Eynard-Orantin-type recursion and others. Only a few of these relations can be derived from elementary combinatorics of permutations. All other relations follow from a deep relationship of Hurwitz numbers with moduli spaces of curves, Gromov-Witten invariants, matrix models, integrable systems and other domains of mathematics which are often referred to as `mathematical physics'. When discussing Hurwitz numbers in the talks, we consider them, thereby, as a sufficiently elementary but highly nontrivial model of all mentioned theories where all computations can be fulfilled completely, and all formulated relations can be checked explicitly in computer experiments.
  • Published: 2014
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:05:36 Institut des Hautes Études Scientifiques (IHÉS) English 2015

Approaches to quantum gravity

At this time, we do not have a theory of quantum gravity. In this talk I will first reiterate the reasons why such a theory is absolutely needed, and then review some of the proposals towards it, with special emphasis on `non-string' approaches. The presentation will be kept mostly at a general and introductory level.
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
2:25:34 Institut des Hautes Études Scientifiques (IHÉS) English 2015

3/3 Supersymmetric Vacua and Integrability

"I review the relationship between supersymmetric gauge theories and quantum integrable systems. From the quantum integrability side this relation includes various spin chains, as well as many well-known quantum many body systems like elliptic Calogero-Moser system and generalisations. From the gauge theory side one has supersymmetric gauge theories with four (and eight) supercharges in various space-time dimensions (compactified to two-dimensions, or in Omega-background). Gauge theory perspective provides the exact energy spectrum of corresponding quantum integrable system. Key elements, usually appearing in the topic of quantum integrability, such as Baxter equation, Yang-Yang function, Bethe equation, spectral curve, Yangian, quantum affine algebra, quantum elliptic algebra - all acquire meaning in the supersymmetric gauge theory." 29 avril 2015
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
2:03:38 Institut des Hautes Études Scientifiques (IHÉS) English 2014

2/3 Mathematical Physics of Hurwitz numbers

Hurwitz numbers enumerate ramified coverings of a sphere. Equivalently, they can be expressed in terms of combinatorics of the symmetric group; they enumerate factorizations of permutations as products of transpositions. It turns out that these numbers obey a huge number of relations represented in the form of partial differential equations for their generating function. This includes equations of the KP hierarchy, Virasoro-type constraints, Chekhov-Eynard-Orantin-type recursion and others. Only a few of these relations can be derived from elementary combinatorics of permutations. All other relations follow from a deep relationship of Hurwitz numbers with moduli spaces of curves, Gromov-Witten invariants, matrix models, integrable systems and other domains of mathematics which are often referred to as `mathematical physics'. When discussing Hurwitz numbers in the talks, we consider them, thereby, as a sufficiently elementary but highly nontrivial model of all mentioned theories where all computations can be fulfilled completely, and all formulated relations can be checked explicitly in computer experiments.
  • Published: 2014
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:01:45 Institut des Hautes Études Scientifiques (IHÉS) English 2014

4/4 Analytic number theory around torsion homology

  • Published: 2014
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
45:19 Institut des Hautes Études Scientifiques (IHÉS) English 2013

Equations for stability­

  • Published: 2013
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:06:29 Institut des Hautes Études Scientifiques (IHÉS) English 2013

Spectral networks and harmonic maps to buildings

This is joint work with L. Katzarkov, A. Noll, and P. Pandit in Vienna. A boundary point of the character variety gives rise to a spectral curve, and a harmonic map to a building. The differential of the harmonic map is the real part of the multivalued tuple of differentials defined over the spectral curve. Gaiotto-Moore-Neitzke have introduced the notion of "spectral network" associated with such a multivalued differential, determining the WKB approximation of the nonabelian Hodge or Riemann-Hilbert correspondences. We have tried to gain some insight into the relationship between the spectral network and the harmonic map to the building: basically, the spectral network lines are located where the curve intersects the codimension 1 faces of the building.
  • Published: 2013
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:54:58 Institut des Hautes Études Scientifiques (IHÉS) English 2013

3/4 Mathematical Structures arising from Genetics and Molecular Biology

  • Published: 2013
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:50:24 Institut des Hautes Études Scientifiques (IHÉS) English 2015

2/4 Singular support of coherent sheaves

Singular support is an invariant that can be attached to a coherent sheaf on a derived scheme which is quasi-smooth (a.k.a. derived locally complete intersection). This invariant measures how far a given coherent sheaf is from being perfect. We will explain how the subtle difference between "coherent" and "perfect" is responsible for the appearance of Arthur parameters in the context of geometric Langlands correspondence.
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
2:06:56 Institut des Hautes Études Scientifiques (IHÉS) English 2015

2/4 Motivic periods and the cosmic Galois group

In the 1990's Broadhurst and Kreimer observed that many Feynman amplitudes in quantum field theory are expressible in terms of multiple zeta values. Out of this has grown a body of research seeking to apply methods from algebraic geometry and number theory to problems in high energy physics. This talk will be an introduction to this nascent area and survey some recent highlights. Most strikingly, ideas due to Grothendieck (developed by Y. André) suggest that there should be a Galois theory of certain transcendental numbers defined by the periods of algebraic varieties. Many Feynman amplitudes in quantum field theories are of this type. P. Cartier suggested several years ago applying these ideas to amplitudes in perturbative physics, and coined the term `cosmic Galois group'. One of my goals will be to describe how to set up such a theory rigorously, define a cosmic Galois group, and explore its consequences and unexpected predictive power. Topics to be addressed will include: 1) A Galois theory of periods, multiple zeta values. 2) Parametric representation of Feyman integrals and their mixed Hodge structures. 3) Operads and the principle of small graphs. 4) The cosmic Galois group: results, counterexamples and conjectures.
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:54:26 Institut des Hautes Études Scientifiques (IHÉS) English 2015

1/4 Motivic periods and the cosmic Galois group

In the 1990's Broadhurst and Kreimer observed that many Feynman amplitudes in quantum field theory are expressible in terms of multiple zeta values. Out of this has grown a body of research seeking to apply methods from algebraic geometry and number theory to problems in high energy physics. This talk will be an introduction to this nascent area and survey some recent highlights. Most strikingly, ideas due to Grothendieck (developed by Y. André) suggest that there should be a Galois theory of certain transcendental numbers defined by the periods of algebraic varieties. Many Feynman amplitudes in quantum field theories are of this type. P. Cartier suggested several years ago applying these ideas to amplitudes in perturbative physics, and coined the term `cosmic Galois group'. One of my goals will be to describe how to set up such a theory rigorously, define a cosmic Galois group, and explore its consequences and unexpected predictive power. Topics to be addressed will include: 1) A Galois theory of periods, multiple zeta values. 2) Parametric representation of Feyman integrals and their mixed Hodge structures. 3) Operads and the principle of small graphs. 4) The cosmic Galois group: results, counterexamples and conjectures.
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:03:48 Institut des Hautes Études Scientifiques (IHÉS) English 2015

2/3 Classical transversality methods in SFT

In this talk I will discuss two transversality results that are standard but perhaps not so widely understood: (1) Dragnev's theorem that somewhere injective curves in symplectizations are regular for generic translation-invariant J, and (2) my theorem on automatic transversality in 4-dimensional symplectic cobordisms (which generalizes earlier results for closed curves by Gromov, Hofer-Lizan-Sikorav and Ivashkovich-Shevchishin). The common feature of these two theorems is that both can be proved by considering the restriction of the usual linearized Cauchy-Riemann operator to the "generalized normal bundle" of a (not necessarily immersed) holomorphic curve.
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
55:49 Vanschoren, Joaquin English 2014

Meta-Learning on QSAR data

Can we learn how to design drugs? Topics include: Automating drug discovery with the Robot Scientist. Using chemoinformatic databases and in-house datasets to systematically run extensive comparative QSAR experiments. Learning how to better apply existing QSAR methods. Decreasing the time and cost to develop new drugs. Prof. Dr. Ross D. King is Professor of Machine Intelligence in the School of Computer Science at the University of Manchester. King's research interests are in the automation of science, drug design, AI, machine learning and synthetic biology. He is probably best known for the Robot Scientist.
  • Published: 2014
  • Publisher: Vanschoren, Joaquin
  • Language: English
2:20:05 Institut des Hautes Études Scientifiques (IHÉS) English 2015

2/3 Supersymmetric Vacua and Integrability

"I review the relationship between supersymmetric gauge theories and quantum integrable systems. From the quantum integrability side this relation includes various spin chains, as well as many well-known quantum many body systems like elliptic Calogero-Moser system and generalisations. From the gauge theory side one has supersymmetric gauge theories with four (and eight) supercharges in various space-time dimensions (compactified to two-dimensions, or in Omega-background). Gauge theory perspective provides the exact energy spectrum of corresponding quantum integrable system. Key elements, usually appearing in the topic of quantum integrability, such as Baxter equation, Yang-Yang function, Bethe equation, spectral curve, Yangian, quantum affine algebra, quantum elliptic algebra - all acquire meaning in the supersymmetric gauge theory." 22 avril 2015
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
2:22:26 Institut des Hautes Études Scientifiques (IHÉS) English 2015

1/3 Supersymmetric Vacua and Integrability

"I review the relationship between supersymmetric gauge theories and quantum integrable systems. From the quantum integrability side this relation includes various spin chains, as well as many well-known quantum many body systems like elliptic Calogero-Moser system and generalisations. From the gauge theory side one has supersymmetric gauge theories with four (and eight) supercharges in various space-time dimensions (compactified to two-dimensions, or in Omega-background). Gauge theory perspective provides the exact energy spectrum of corresponding quantum integrable system. Key elements, usually appearing in the topic of quantum integrability, such as Baxter equation, Yang-Yang function, Bethe equation, spectral curve, Yangian, quantum affine algebra, quantum elliptic algebra - all acquire meaning in the supersymmetric gauge theory."
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:10:44 Institut des Hautes Études Scientifiques (IHÉS) English 2015

1/2 Introduction to Polyfold Regularization

This lecture will discuss the overall ideas and challenges in regularizing moduli spaces, and introduce the two basic ideas behind polyfold theory: Making reparametrization actions "smooth" and making pregluing a "chart map". [related literature: Sections 2.1 and 3.3 of Polyfolds: A First and Second Look. Related videos: Lecture 8 and Lecture 20 from Wehrheim's special topics course.]
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:10:54 Institut des Hautes Études Scientifiques (IHÉS) English 2015

2/3 The rise of sc-retracts

In this talk, we discuss the second of two fundamental analysis concepts polyfold theory is built on: sc-retracts. In particular, we discuss how they arise naturally as a means of using pre-gluing maps to parametrize a neighborhood of nodal and non-nodal (or broken and unbroken) maps near a nodal (or broken) map. Despite locally varying dimensions, such retracts support a version of the sc-calculus on which the chain rule holds, and we define M-polyfolds (manifold-like polyfolds) to be those topological spaces locally modeled on such retracts. [Related literature: Sections 2.3 and 5.1 of Polyfolds: A First and Second Look.]
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:12:02 Institut des Hautes Études Scientifiques (IHÉS) English 2015

Fredholm theory and Deligne-Mumford spaces for witch balls

In work-in-progress with Katrin Wehrheim, we aim to bind together the Fukaya categories of many different symplectic manifolds into a single algebraic object. This object is the "symplectic A-infinity-2-category", whose objects are symplectic manifolds, and where hom(M,N):=Fuk(M-xN). At the core of our project are witch balls - certain pseudoholomorphic quilts with figure eight singularity. I will discuss recent progress: toward the construction of the moduli space of domains on one hand, and toward establishing the Fredholm property on the other.
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:07:23 Institut des Hautes Études Scientifiques (IHÉS) English 2015

2/3 Knot contact homology and string topology

We show how to relate knot contact homology to a version of string topology. More precisely we express knot contact homology in terms of strings in the singular space which is the union of the three sphere and the Lagrangian conormal of the knot that split in a certain way when they hit the knot.
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
2:20:00 Institut des Hautes Études Scientifiques (IHÉS) English 2015

4/4 Motivic periods and the cosmic Galois group

In the 1990's Broadhurst and Kreimer observed that many Feynman amplitudes in quantum field theory are expressible in terms of multiple zeta values. Out of this has grown a body of research seeking to apply methods from algebraic geometry and number theory to problems in high energy physics. This talk will be an introduction to this nascent area and survey some recent highlights. Most strikingly, ideas due to Grothendieck (developed by Y. André) suggest that there should be a Galois theory of certain transcendental numbers defined by the periods of algebraic varieties. Many Feynman amplitudes in quantum field theories are of this type. P. Cartier suggested several years ago applying these ideas to amplitudes in perturbative physics, and coined the term `cosmic Galois group'. One of my goals will be to describe how to set up such a theory rigorously, define a cosmic Galois group, and explore its consequences and unexpected predictive power. Topics to be addressed will include: 1) A Galois theory of periods, multiple zeta values. 2) Parametric representation of Feyman integrals and their mixed Hodge structures. 3) Operads and the principle of small graphs. 4) The cosmic Galois group: results, counterexamples and conjectures.
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:07:38 Institut des Hautes Études Scientifiques (IHÉS) English 2015

2/4 Polyfolds and the construction of Symplectic Field Theory

Topics: 1 Polyfold structures. 2 Consequences of polyfold structures. 3 Weighted categories and their smooth versions. 4 The polyfold of stable maps. 5 Bundle category
  • Published: 2015
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
1:16:48 Institut des Hautes Études Scientifiques (IHÉS) English 2013

Wall-crossing and geometry at infinity of Betti moduli spaces

Linear algebraic differential equation (in one variable) depending on a small parameter produces a spectral curve, which is a point in the base of a Hitchin integrable system. Gaiotto, Moore and Neitzke discovered a remarkable structure on the Hitchin base, consisting in certain integer numbers (BPS counting) associated with cycles on the spectral curves, and satisfying universal wall-crossing constraint at hypersurfaces of discontinuity. For a generic spectral curve the wall-crossing structure leads to a preferred coordinate system on the Betti moduli space (a.k.a. the character variety, or the moduli space of monodromy data). I'll speak about interpretation of BPS counting as trees on the Hitchin base, about generalized Strebel differentials and associated quivers, and how one can effectively calculate BPS counting using algebraic curves in Betti moduli spaces.
  • Published: 2013
  • Publisher: Institut des Hautes Études Scientifiques (IHÉS)
  • Language: English
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