The SEMPARIS seminar webserver hosts annoucements of all seminars taking place in Paris area, in all topics of physics, mathematics and computer science. It allows registered users to receive a selection of announcements by email on a daily or weekly basis, and offers the possibility to archive PDF or Powerpoint files, making it available to the scientific community.   [ More information ]

 Upcoming Seminars [Next 30 ] [ scheduler view ]

 Wednesday 29 January 2020, 11:30 at IJCLAB, 015 NUC-THEO (Séminaire de physique nucléaire théorique) nucl-th Lorenzo Contessi ( ESNT, IRFU, CEA, Université Paris-Saclay ) Single- and double-$\Lambda$ hypernuclei in pionless EFT Abstract: The extension of nuclear physics to the strange sector is a difficult challenge due to the shortage of experimental data, and the difficulty in solving QCD at low energies. With the forthcoming new facilities and new experiments dedicated to the study of single- and double-lambda hypernuclei we prospect new and important developments in this field in the very near future. Reliable theories are essential to support and analyze these experimental campaigns. In this talk, we present the first comprehensive application of pionless effective field theory to single and double $\Lambda$ hypernuclei composed of up to 6 baryons. The theory, fitted to reproduce available experimental data, solves the longstanding overbinding problem of the $^5_\Lambda$He hypernucleus and predicts the existence of a five-body double-$\Lambda$ Hypernuclear bound state yet to be found. Pionless effective field theory is revealed to be a very successful approach to hypernuclei due to the small number of free parameters, and the good theoretical accuracy, enhanced by the large breaking scale and the small momentum of the lambda particles.

 Wednesday 29 January 2020, 16:00 at LPENS, Conf IV LPENS-ACE (Astronomy and Cosmology at ENS) astro-ph Luiz Rodrigues ( Radboud University, Nijmegen ) Modelling the cosmic history of galactic magnetic fields Abstract: Do all spiral galaxies exhibit coherent magnetic fields? How are galactic magnetic fields amplified and maintained? What is the distribution of field strengths? How did this change with time? In this talk, I address these questions using a model which computes the magnetic properties of a statistical sample of evolving galaxies. It employs a semi-analytic model of galaxy formation to produce realistic time-varying galactic properties and numerically solves the dynamo equations from the early universe until the present. I will also discuss what are the prospects for observationally constraining this and similar models using a range of tracers.

 Wednesday 29 January 2020, 17:00 at LPENS, Conf IV LPENS-ACE (Astronomy and Cosmology at ENS) astro-ph Matthieu Bethermin ( Laboratoire d'Astrophysique de Marseille ) The evolution of dusty star-forming galaxy populations from the end of the reionization to nowadays Abstract: About half of the energy emitted by stars in galaxies was absorbed by dust and re-emitted in the far-infrared. This phenomenon is particularly dramatic for the UV radiation from young stars tracing the star formation. Estimating this intrinsic UV emission is key to understand the star formation across cosmic times. We thus need to know both the amount of UV and far-infrared emitted by the galaxies. During the last decade, Herschel and ALMA have pushed our knowledge of the dusty Universe up to the end of the reionization. It is now clear that very dusty objects exist very early in the Universe and a large fraction of the star formation budget at very high redshift (z~6) is still hidden by dust. I will review the main results from the last years and discuss the consequence on our understanding of galaxy formation. Finally, I will discuss how the SPICA mission can improve our knowledge of this dusty Universe. In particular, the B-BOP instrument will offer us the first opportunity to detect the polarized signal from high-redshift dusty galaxies.

 Thursday 30 January 2020, 11:00 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) hep-th|math.AG Alessandra Sarti ( Université de Poitiers ) On non-symplectic automorphisms of K3 surfaces Abstract: The K3 surfaces are complex algebraic surfaces with remarkable properties. A property that characterizes them, is the existence of a unique, up to scalar multiplication, global holomorphic two form which is never zero. In the last years their group of symmetry, the automorphisms of the K3 surfaces, aroused a lot of interest and it has been much studied. Depending on the action on the holomorphic two form, which can be trivial or not, an automorphism is called symplectic or non-symplectic. After an introduction on the subject, the aim of the talk is to show recent results in the study of non-symplectic automorphisms of 2-power order. In particular in the case of the order 16, I give a full description of the families of K3 surfaces carrying such automorphisms.

 Friday 31 January 2020, 10:00 at IPHT, Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=en/node/246 ) COURS (Cours) hep-ph|hep-th Gregory Soyez ( IPhT ) Exploring High-Energy Physics with Jets (4/5) Abstract: This series of lectures is primarily associated with collider physics where one seeks to learn about fundamental interactions by colliding particles at high energy and by studying the products of these collisions. In this sense, talking about jets is essentially talking about the highly-energetic quarks and gluons produced in these collisions and their dynamics governed by the strong interaction. This is ubiquitous in all recent colliders and jets are (to varying degrees) present in almost all aspects of collider phenomenology. This set of lectures is mostly two-folded: on one side it will try to give a taste of the broad range of aspects and applications of jet physics, on the other side it will show how it is rooted in (perturbative) Quantum Chromodynamics (QCD). Lectures 4-5/5 - Jet substructure in QCD:I will cover several aspects of QCD calculations in the context of jet substructure with a specific focus on their conceptual interpretation. This will cover applications to quark/gluon separation, heavy-boson (W/Z/Higgs) tagging as well as a few curiosities that arise in the process of understanding jet substructure from first principles in perturbative QCD. Remarks:In terms of reference material, most of material covered in the lectures can be found in the set of Springer Lecture Notes "Looking Inside Jets: an introduction to jet substructure and boosted-object phenomenology" (arXiv:1901.10342).Some of the material covered in the first lecture can also be found in the review "Towards Jetography" (arXiv:0906.1833) as well as in standard QCD textbooks (e.g. "QCD and collider physics" by Keith Ellis, James Stirling and Brian Webber). The first and third lectures will be oriented towards concepts and phenomenological aspects. While keeping physics consequences as a target, lectures 2, 4 and 5 will focus more on calculations in the context of perturbative QCD. Note however that this is a tentative plan: I am happy to make adjustments if, in the course of the lectures, it appears that some aspects are worth exploring in more details or some different directions worth being introduced. Attachments: 2019-2020.pdf (4458798 bytes) jetsv2.pdf (4431234 bytes)

 Friday 31 January 2020, 11:00 at LPTHE, Bibliothèque SEM-LPTHE (Séminaire du LPTHE) cond-mat.stat-mech Ines Aniceto ( Southampton ) Unraveling the analytic structure of observables: from local asymptotics to phase transitions Abstract: The perturbative expansions of many physical quantities are divergent, and defined only as asymptotic series. It is well known that this divergence reflects the existence of nonperturbative, exponentially damped contributions, such as instanton effects, which are not captured by a perturbative analysis. This connection between perturbative and non-perturbative contributions of a given physical observable can be systematically studied using the theory of resurgence, allowing us to construct a full non-perturbative solution from perturbative asymptotic data. In this talk I will start by reviewing the essential role of resurgence theory in the description of the analytic solution behind an asymptotic series, and its relation to the so-called Stokes phenomena and phase transitions. I will then exemplify how these techniques can be applied to to the Lee-Yang zeros in the context of matrix models, a subject of great interest in both mathematics and physics.

 Friday 31 January 2020, 11:00 at APC, 454A APC-COLLOQUIUM (Colloquium de l'APC) astro-ph Albino Perego ( Trento University and TIFPA ) Modeling of binary neutron star mergers: from simulations to multimessenger observations Abstract: With the advent of ground-based gravitational waves detectors, such as Advanced Ligo and Advanced Virgo, the era of multimessenger astrophysics from compact binary merger has started. Such a kind of events represent bright sources of gravitational waves and electromagnetic radiation, as well as neutrinos and heavy nuclei. The detection and interpretation of multimessenger signals from the collision of two compact objects requires a fruitful interplay between the observational efforts and the theoretical modeling. The pivotal role of all fundamental interactions, as well as the multiscale, multiphysics nature of the process, represents a great challenge in the path towards a deeper understanding of the coalescence process and of its rich phenomenology. In this talk, I will review our present understanding of the major processes involved in the merger of two neutron stars and on their impact on some of the many observable we can presently detect. A special emphasis will be given to the role of neutrinos and weak interactions.

 Monday 3 February 2020, 10:45 at LPTMC, Jussieu tower 13-12 5th floor room 5-23 SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée) cond-mat.mes-hall Alvaro L. M. A. Nogueira ( CEFET, Rio de Janeiro, Brasil ) Extended-supersymmetric framework and graphene-like fermionic degrees of freedom: an example of worthiness Abstract: We present an N=2-supersymmetric extension [1] of Jackiw-Pi´s chiral gauge theory (CGT) [2] originally designed to describe Dirac electrons in graphene. The augmented framework allows for the identification of non-perturbative solutions, as vortex-like configurations that saturate a topologically non-trivial (BPS- )bound are proven to be. Remarkably, that regime reveals to be free from extra scalar degrees of freedom brought about to the model as needed partners to fermions in such a linear realisation of supersymmetry, but lacking a phenomenological interpretation. Furthermore, inherent R-Parity provides the room for incorporating a global phase-fermion number symmetry already manifest in the CGT, but now regarded as an external (superspace) invariance. Comments on the fermionic mass-matrix and perspectives shall compose our conclusions. [1] E.M.C. Abreu, M.A. De Andrade, L.P.G. De Assis, J.A. Helayël-Neto, A.L.M.A. Nogueira, R.C. Paschoal, Annals of Physics 354 (2015) 618–636. [2] R. Jackiw, S.-Y. Pi, Phys. Rev. Lett. 98 (2007) 266402.

 Monday 3 February 2020, 14:30 at IHES, Amphithéâtre Léon Motchane ( Séminaire Géométrie et groupes discrets ) MATH-IHES (TBA) hep-th Peter Haissinsky ( Aix-Marseille Université ) Characterizations of Kleinian Groups Abstract: In low dimension, it is expected that topological properties determine a natural geometry. In this spirit, several characterizations are conjectured for Kleinian groups, i.e. discrete subgroups of PSL(2,C). We will survey different methods that lead to their topological and dynamical characterizations, and point out their limits and the difficulties encountered in obtaining a complete answer.

 Monday 3 February 2020, 16:30 at IHES, Amphithéâtre Léon Motchane ( Séminaire Géométrie et groupes discrets ) MATH-IHES (TBA) hep-th Timothée Marquis ( Université Catholique de Louvain ) Cyclically Reduced Elements in Coxeter Groups Abstract: Let W be a Coxeter group. We provide a precise description of the conjugacy classes in W, yielding an analogue of Matsumoto's theorem for the conjugacy problem in arbitrary Coxeter groups. This extends to all Coxeter groups an important result on finite Coxeter groups by M. Geck and G. Pfeiffer from 1993. In particular, we describe the cyclically reduced elements of W, thereby proving a conjecture of A. Cohen from 1994.

 Tuesday 4 February 2020, 11:00 at LPTHE, Library, tour 13-14, 4th floor P^3 (Particle Physics in Paris) hep-ph|hep-th Francesco Riva ( Geneva University ) Microscopic Bounds on Macroscopic Theories Abstract: Effective Field Theories (EFTs) appear everywhere there is a mass scale. They serve to simplify complex multiscale problems (e.g. the theory of fermions below the electroweak scale), and they serve as general tools to parametrise the unknown or incalculable (e.g. the pion chiral Lagrangian, gravity, or physics beyond the standard model). In this sense, they are perhaps even too general (everything which is not forbidden is compulsory). In this talk I will present a tool to distinguish EFTs that can originate from microscopic unitary theories and I will show that this strongly limits the (classic and quantum) running of EFTs scattering amplitudes. In particular, Massive gravity, theories with isolated massive higher-spin particles, and theories with very irrelevant interactions, cannot originate from unitary theories.

 Tuesday 4 February 2020, 11:00 at IPHT, Amphi Hermite IPHT-HEP (Séminaire de physique des particules et de cosmologie) hep-ph Francesco Riva ( University of Geneva ) Microscopic Bounds on Macroscopic Theories Abstract: Effective Field Theories (EFTs) appear everywhere there is a mass scale. They serve to simplify complex multiscale problems (e.g. the theory of fermions below the electroweak scale), and they serve as general tools to parametrise the unknown or incalculable (e.g. the pion chiral Lagrangian, gravity, or physics beyond the standard model). In this sense, they are perhaps even too general Â (everything which is not forbidden is compulsory). In this talk I will present a tool to distinguish EFTs that can originate from microscopic unitary theories and I will show that this strongly limits the (classic and quantum) running of EFTs scattering amplitudes. In particular, Massive gravity, theories with isolated massive higher-spin particles, and theories with very irrelevant interactions, cannot originate from unitary theories. Â

 Tuesday 4 February 2020, 17:15 at DPT-PHYS-ENS, Conf IV (E244) - Département de Physique de l'ENS 24 rue Lhomond 75005 PARIS COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS) physics Michael Lebars ( Institut de recherche sur les phénomènes hors équilibre (IRPHE), Marseille ) Dynamics of mixed turbulent / stably-stratified fluids: from nuclear safety to atmospheric and stellar circulation Abstract: The organization of fluid systems into a turbulent layer adjacent to a stably stratified one is common both in Nature (atmospheres, stellar interiors, ...) and in the industry (e.g. nuclear power plant in accidental configurations). Understanding the exchanges of mass and momentum at the interface and the coupled dynamics of such systems is challenging, because of the large range of involved time- and length-scales, from the rapid small-scale turbulence associated to the excitation of propagating waves, to their longterm non-linear interactions associated to large-scale circulations. I will present the results of various experimental investigations of idealised configurations, complemented by numerical simulations: a turbulent jet impinging a density interface, the convection in water around 4 degree Celsius, etc. Applications in meteorology, stellar evolution, and nuclear safety, will be addressed.

 Wednesday 5 February 2020, 12:00 at LPENS, Conf. IV FORUM-ENS (Forum de Physique Statistique @ ENS) cond-mat.stat-mech Bruno Bertini ( University of Ljubljana ) Non-equilibrium dynamics in dual-unitary quantum circuits Abstract: Abstract: I will consider the non-equilibrium dynamics of a recently introduced class of "statistically solvable” many-body quantum systems: the dual-unitary circuits. These systems furnish a minimal modelling of generic locally interacting many-body quantum systems: they are generically non-integrable and include a quantum chaotic subclass. I will first discuss the dynamics of initial-state dependent quantities, such as the entanglement entropies and local correlators, showing that it is possible to find (and classify) a family of initial states in MPS form that allow for an exact solution of the dynamics (also in the presence of quantum chaos). Then I will discuss the dynamics of an initial-state independent quantity, the so called “operator entanglement”, that measures the growth of entanglement that the Heisenberg evolution induces in operator space. I will show that one can identify different subclasses of dual- unitary circuits. In particular I will describe a “maximally chaotic” subclass, where the entanglement of local operators grows linearly, and a “dynamically constrained” one, where the entanglement of local operators is bounded.

 Wednesday 5 February 2020, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774 IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires) hep-th Krzysztof Pilch ( University of Southern California ) AdS Vacua of Maximal Gauged Supergravities

 Thursday 6 February 2020, 10:00 at LPTHE, LPTHE Library RENC-THEO (Rencontres Théoriciennes) hep-th Oliver Schlotterer ( Uppsala University ) Double-copy structures and universality in string tree-level interactions Abstract: > This talk is dedicated to recent double-copy constructions that unify massless tree-level amplitudes in a variety of perturbative string theories. All the polarization dependence in gauge- and gravity amplitudes of type-I, type-II, bosonic and heterotic string theories is proposed to enter via field-theory building blocks with a known Lagrangian origin. The second double-copy component of massless string amplitudes involves moduli-space integrals over punctured sphere and disk worldsheets whose low-energy expansion introduces multiple zeta values. At each order in the inverse string tension alpha’, the coefficients of highest transcendental weight turn out to be universal across the above perturbative string theories. These phenomena have not been explained by the known string dualities and are hoped to reflect a deeper principle in the theory of quantum gravity.

 Thursday 6 February 2020, 11:40 at LPTHE, LPTHE Library RENC-THEO (Rencontres Théoriciennes) hep-th Jerome Gauntlett ( Imperial College, London ) Geometric Extremization for AdS-CFT and Black Hole Entropy

 Thursday 6 February 2020, 14:00 at LPTM, 4.13 St Martin II SEM-LPTM-UCP (Seminaires du LPTM , Universite de Cergy Pontoise) math-ph Ben Craps ( Theoretical Physics (TENA), Vrije Universiteit Brussel, Belgique ) Quantum chaos, thermalization and holography Abstract: Classical chaos refers to exponential sensitivity of phase-space trajectories to small changes in initial conditions. It is not straightforward to extend this notion to quantum systems, which undergo linear evolution and moreover do not exhibit precise phase space trajectories. One possible way to define quantum chaos is via statistical properties of energy levels, which have been related to those of random matrices. Recently, motivated by studies of black holes, exponential growth of out-of-time-order correlators has received a lot of attention as another possible diagnostic of quantum chaos, and an upper bound on the corresponding “Lyapunov exponent” has been obtained. Chaos is closely related to the thermalization of isolated quantum systems. Via holography, quantum chaos is reflected in the physics of black holes, which are dual to thermal states. In the same way, the study of black hole formation has given a new handle on the thermalization of strongly correlated systems. This talk contains a review of these ideas as well as brief discussions of some recent projects in our group.

 Friday 7 February 2020, 10:00 at IPHT, Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=en/node/246 ) COURS (Cours) hep-ph|hep-th Gregory Soyez ( IPhT ) Exploring High-Energy Physics with Jets (5/5) Abstract: This series of lectures is primarily associated with collider physics where one seeks to learn about fundamental interactions by colliding particles at high energy and by studying the products of these collisions. In this sense, talking about jets is essentially talking about the highly-energetic quarks and gluons produced in these collisions and their dynamics governed by the strong interaction. This is ubiquitous in all recent colliders and jets are (to varying degrees) present in almost all aspects of collider phenomenology. This set of lectures is mostly two-folded: on one side it will try to give a taste of the broad range of aspects and applications of jet physics, on the other side it will show how it is rooted in (perturbative) Quantum Chromodynamics (QCD). Lectures 4-5/5 - Jet substructure in QCD:I will cover several aspects of QCD calculations in the context of jet substructure with a specific focus on their conceptual interpretation. This will cover applications to quark/gluon separation, heavy-boson (W/Z/Higgs) tagging as well as a few curiosities that arise in the process of understanding jet substructure from first principles in perturbative QCD. Remarks:In terms of reference material, most of material covered in the lectures can be found in the set of Springer Lecture Notes "Looking Inside Jets: an introduction to jet substructure and boosted-object phenomenology" (arXiv:1901.10342). Some of the material covered in the first lecture can also be found in the review "Towards Jetography" (arXiv:0906.1833) as well as in standard QCD textbooks (e.g. "QCD and collider physics" by Keith Ellis, James Stirling and Brian Webber). The first and third lectures will be oriented towards concepts and phenomenological aspects. While keeping physics consequences as a target, lectures 2, 4 and 5 will focus more on calculations in the context of perturbative QCD. Note however that this is a tentative plan: I am happy to make adjustments if, in the course of the lectures, it appears that some aspects are worth exploring in more details or some different directions worth being introduced. Attachments: 2019-2020.pdf (4458798 bytes) jetsv2.pdf (4431234 bytes)

 Friday 7 February 2020, 11:00 at LPTHE, Bibliothèque SEM-LPTHE (Séminaire du LPTHE) cond-mat.stat-mech|hep-th|math-ph Stefano Negro ( Stony Brook ) On irrelevant deformations of integrable field theories: CDD factors and generalized Gibbs ensemble Abstract: The study of irrelevant perturbations has profound implications on our understanding of the space of QFTs and possesses important applications in Statistical and Condensed Matter Physics -- e.g. the control on sub-leading corrections to the scaling limits of lattice models. In 1+1 D a partial map of the above mentioned space can be traced out thanks to the existence of integrable systems, which grant us a high degree of control on certain renormalization flows trajectories. In this talk I will present some results from a recent work concerning a large class of irrelevant perturbations that, in the framework of factorized scattering, can be described by generic deformations of the S-matrix by a CDD factor. I will show how these deformations can be described as certain field-dependent twists in the boundary conditions of the fields -- a natural generalization of the geometric interpretation of the $T\bar{T}$ deformation -- and that there exists a relation amongst CDD deformations and the thermodynamics of the Generalized Gibbs Ensemble. Exploiting the integrability of the models, I will derive a general flow equation for the finite size spectrum and, for the particular case of the sinh-Gordon model, will present a connection with the fermionic basis description of finite-size one-point functions.

 Friday 7 February 2020, 11:00 at APC, Amphithéatre Pierre Gilles de Gennes APC-COLLOQUIUM (Colloquium de l'APC) astro-ph Andrzej Szelc ( University of Manchester ) TBA

 Friday 7 February 2020, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774 IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires) hep-th Cumrun Vafa (TBA) Abstract: (TBA)

 Tuesday 11 February 2020, 11:00 at CPHT, Salle Louis Michel SEM-CPHT (Séminaire du CPHT) hep-th Keun-Young Kim ( GIST ) TBA

 Wednesday 12 February 2020, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774 IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires) hep-th Evgeny Skvortsov Quantum Higher Spin Gravity and three-dimensional bosonization duality Abstract: Higher Spin Gravities are supposed to be minimalistic extensions of gravity that embed it into a quantum consistent theory. However, such minimality turns out to be in tension with the field theory approach, as well as with the numerous no-go theorems. We report on the recent progress in constructing Higher Spin Gravities and testing quantum effects therein. The same time, via AdS/CFT Higher Spin Gravities should be related to a variety of interesting three-dimensional CFT

 Tuesday 18 February 2020, 11:00 at CPHT, Salle Louis Michel, CPHT, Ecole Polytechnique SEM-CPHT (Séminaire du CPHT) hep-th Blagoje Oblak ( LPTHE ) Virasoro Berry Phases in the KdV Equation Abstract: I consider a model of fluid particle motion given by the reconstructed KdV equation on a circle. For travelling waves that are "uniformizable" in a suitable sense, the map that governs stroboscopic motion can be derived analytically. The particle's drift velocity, then, is essentially the Poincaré rotation number of that map, and has a geometric origin: it is the sum of a dynamical phase, a geometric/Berry phase, and an "anomalous phase". The last two phases are universal, as they follow entirely from the underlying Virasoro group structure. The Berry phase, in particular, is produced by a sequence of adiabatic conformal transformations due to the moving wave profile, and was previously found in two-dimensional conformal field theories.

 Tuesday 18 February 2020, 17:15 at DPT-PHYS-ENS, Amphi Jaurès - Département de Physique de l'ENS 24 rue Lhomond 75005 PARIS COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS) physics Frédéric Restagno ( Laboratoire de Physique des Solides, CNRS, Université Paris-Saclay ) Slip of polymer fluids Abstract: Modeling fluid flows in channels is a general problem in science and engineering. For ideal liquids, the situation is simple: there is no dissipation due to fluid movement. For real liquids, some energy is lost. Navier, in his pioneering work on fluid mechanics identified two possible sources of dissipation: bulk dissipation, associated to the viscosity and the friction of the last layer of liquid molecules sliding on the solid surface. For surface dissipation, a classical assumption of fluid dynamics is that a liquid element adjacent to the surface is equal to the velocity of the surface, i.e. a non-slip boundary condition, which leads to no surface dissipation. This is not the only possibility. Navier, postulating the existence of a slip velocity at the surface, introduced the possibility of surface dissipation. He proposed a linear relation between the shear stress at the solid-liquid interface and the slip velocity: σ=kV, where k is the interfacial friction coefficient. Indeed, it is also possible to define the slip length b as the distance from the solid surface where the fluid velocity profile extrapolates linearly to zero. During this presentation, I will briefly review what we know on the boundary condition for simple Newtonian liquids and show that polymers, due to their entanglements present a unique tool to study and understand the Navier condition. Based on a setup using the photobleaching of fluorescent polymers, I will present our last results on the slip of polymer melts and polymer solutions.

 Wednesday 19 February 2020, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774 IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires) hep-th Geoffrey Compère ( Université Libre de Bruxelles ) Some physics behind supertranslations and superrotations Abstract: I will first provide a bird-eye view upon the infrared structure of gravity. I will shortly describe the relationship between BMS symmetry, soft theorems and memory effects at leading and subleading orders in the large radius expansion, while emphasizing the specificities of super-Lorentz symmetries. Secondly, I will present a no-go result on the soft hair conjecture: supertranslations induced by matter creating and falling inside black holes do not affect Hawking radiation, though they do affect scattering amplitudes. I will start by proving that Unruh radiation is unaffected by supertranslations induced by a shockwave and then show that Hawking radiation is mathematically related to this system, as a consequence of the principle of equivalence. Third, I will explain how BMS symmetry is associated to flux-balance laws that provide constraints upon the motion of binary compact mergers. Finally, I will present the extension of the BMS group to asymptotically de Sitter spacetimes.

 Monday 24 February 2020, 10:30 at LPTMC, Jussieu tower 13-12 5th floor room 5-23 ( Mini-lecture: three times 1.5 hours ) SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée) cond-mat.mes-hall Janos Asboth ( Wigner Research Centre for Physics, Budapest, Hongrie ) Kitaev's toric code and its use in quantum computation (part 1) Abstract: TBA

 Tuesday 25 February 2020, 10:30 at IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES ) MATH-IHES (TBA) hep-th Bruno Klingler ( Humboldt Universität, Berlin ) Tame Geometry and Hodge Theory (1/4) Abstract: Hodge theory, as developed by Deligne and Griffiths, is the main tool for analyzing the geometry and arithmetic of complex algebraic varieties. It is an essential fact that at heart, Hodge theory is NOT algebraic. On the other hand, according to both the Hodge conjecture and the Grothendieck period conjecture, this transcendence is severely constrained. Tame geometry, whose idea was introduced by Grothendieck in the 80s, seems a natural setting for understanding these constraints. Tame geometry, developed by model theorists as o-minimal geometry, has for prototype real semi-algebraic geometry, but is much richer. It studies structures where every definable set has a finite geometric complexity. The aim of this course is to present a number of recent applications of tame geometry to several problems related to Hodge theory and periods. After recalling basics on o-minimal structures and their tameness properties, I will discuss: - the use of tame geometry in proving algebraization results (Pila-Wilkie theorem; o-minimal Chow and GAGA theorems in definable complex analytic geometry); - the tameness of period maps; algebraicity of images of period maps; - functional transcendence results: Ax-Schanuel conjecture from abelian varieties to Shimura varieties and variations of Hodge structures. Applications to atypical intersections (André-Oort conjecture and Zilber-Pink conjecture); - the geometry of Hodge loci and their closures.

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