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Upcoming Seminars [Next 30 ]
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Thursday 19 September 2019, 10:00 at LPTHE, Bibliotheque RENC-THEO (Rencontres Théoriciennes) hep-th
Ning Su ( EPFL ) Recent progress on bootstrapping Ising, O(N) and related models
Abstract: [NOTICE UNUSUAL PLACE] Numerical bootstrap is proven to be an effective method to study scale invariant critical points. In particular, most precise critical exponent of 3D Ising model can be obtained. Typical method used in the past was that we exploit conformal constrains from four-point correlators involving one or two operators. To further improve the numerical results and to target more complicated critical points, we have to consider a larger set of correlators. Doing so raises many challenges in numerical implementation. In this talk, I will discuss a set of new techniques we developed to address those challenges. With the new tool, we obtained a series of results on Ising, O(N) and related models.

Thursday 19 September 2019, 11:00 at IHES, Amphithéâtre Léon Motchane MATH-IHES (TBA) math
Albert Schwarz ( UC Davis & IHES ) Geometric Approach to Quantum Theory and Inclusive Scattering Matrix
Abstract: One can formulate the quantum theory taking as the starting point the cone of states. The probabilities can be derived from the first principles in this approach. The formulation in terms of states is useful, in particular, in statistical physics. It leads to the notion of inclusive scattering matrix related to inclusive cross-sections. This notion can be applied to the scattering of quasiparticles, where the usual notion of scattering matrix does not make sense.

Thursday 19 September 2019, 11:40 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage RENC-THEO (Rencontres Théoriciennes) hep-th
Joan Elias Miro ( CERN ) Flux Tube S-matrix Bootstrap
Abstract: I will discuss the theory of long string-like objects (or flux tubes) in 3 and 4 spacetime dimensions. On top of the vacuum configuration of this string, we will scatter oscilations (or phonons) and study its S-matrix elements. We are going to constraint the space of consistent flux tube theories by bounding this S-matrix. Finally we will see that these bounds on the S- matrix have precise implications for the finite volume energy levels and its associated phenomenology, that are well measured on the lattice MC simulations. (based on 1906.08098 )
Attachments:
  • talkEliasMiro.pdf (4592176 bytes) OPEN

Thursday 19 September 2019, 13:30 at LPS/ENS, L369
( Séminaire exceptionnel )
CONDMAT-ENS (Séminaire théorie de la matière condensée de l'ENS) cond-mat
Synge Todo ( U Tokyo ) Geometric allocation approaches in Markov chain Monte Carlo
Abstract: The Markov chain Monte Carlo (MCMC) method is a versatile tool in statistical physics to evaluate multi-dimensional integrals numerically. For the method to work effectively, one must consider the following key issues: representation of problems in the MCMC framework, choice of ensemble, selection of candidate states, optimization of transition kernel, algorithm for choosing a configuration according to the transition probabilities, and parallelization/optimization for target computer architecture [1-3]. We show that the unconventional approaches based on the geometric allocation of probabilities or weights can improve the dynamics and scaling of the Monte Carlo simulation in several aspects [4]. Particularly, the approach using the irreversible kernel can reduce or sometimes completely eliminate the rejection of trial move in the Markov chain [4,5]. We also discuss how the space-time interchange trick can reduce the computational time especially for the case where the number of candidates is large, such as models with long-range interactions [4,6] and random-bit generation problems [7]. References: [1] S. Todo, in Strongly Correlated Systems: Numerical Methods (Springer Series in Solid-State Sciences), ed. A. Avella, F. Mancini, p. 153 (Springer-Verlag, Berlin, 2013). [2] S. Todo, H. Matsuo, H. Shitara, Comp. Phys. Comm. 239, 84 (2019). [3] B. Bauer, et al, J. Stat. Mech. P05001 (2011). [4] S. Todo and H. Suwa, J. Phys.: Conf. Ser. 473, 012013 (2013). [5] H. Suwa and S. Todo, Phys. Rev. Lett. 105, 120603 (2010). [6] K. Fukui and S. Todo, J. Comp. Phys. 228, 2629 (2009). [7] H. Watanabe, S. Morita, S. Todo, and N. Kawashima, J. Phys. Soc. Jpn. 88, 024004 (2019).

Thursday 19 September 2019, 14:00 at LPTM, 4.13 St Martin II SEM-LPTM-UCP (Seminaires du LPTM , Universite de Cergy Pontoise) cond-mat
Jean Decamp ( Center for Quantum Technologies, NUS, Singapore ) "Symmetry, Tan Contact and Spectral Gap in One-dimensional Fermions: A Graph Theory Treatment"
Abstract: "In the limit of strong repulsion, one-dimensional atomic mixtures of fermions realize an effective spin chain, and are thus a clean and controllable platform for the study of quantum magnetism or in the context of quantum computation. In the work I will present you, we interpret this model in terms of spectral graph theory. This well-studied mathematical framework allows us to completely characterize the symmetry properties of the system and to develop a powerful method to compute the Tan contacts associated with certain symmetry classes. In particular, compared to brute force diagonalization, our technique enables us to obtain much more efficiently the energy gap of complex spin mixtures, which is of central importance for the design of adiabatic control of correlated quantum systems."

Monday 23 September 2019, 10:45 at LPTMC, Jussieu, tower 13-12, room 5-23 SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée) cond-mat.mes-hall
Juliette Mignot ( IPSL-LOCEAN Jussieu ) De la recherche sur le climat aux pratiques de la recherche pour le climat
Abstract: Le changement climatique est un sujet de recherche en soit, et nous en évoquerons les bases scientifiques. C'est aussi devenu une réalité sociétale et un enjeu pour notre futur. Comment les climatologues se positionnent-ils par rapport à cette évolution de leur objet scientifique? Plus généralement, quelle réflexion peuvent avoir les scientifiques par rapport à leurs pratiques de recherche. Des initiatives émergent dans toute la France et dans tous les domaines. Quelles sont-elles, comment s'organisent elles, où vont-elles?

Monday 23 September 2019, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774 IPHT-PHM (Séminaire de physique mathématique) math-ph
Sylvain Ribault ( IPhT ) The non-rational limit of D-series minimal models
Abstract: We study the limit of D-series minimal models when the central charge tends to an irrational value $c \leq 1$. We find that the limit theory's diagonal three-point structure constant differs from that of Liouville theory by a distribution factor, which is given by a divergent Verlinde formula. Nevertheless, in the limit theory, correlation functions that involve both non-diagonal and diagonal fields are smooth functions of the fields' conformal dimensions. The limit theory is a non-trivial example of a non-diagonal, non-rational, solved two-dimensional conformal field theory.

Monday 23 September 2019, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774 IPHT-PHM (Séminaire de physique mathématique) math-ph
Yuan Miao ( Amsterdam ) From quantum integrability to classical one and back: taming classicalness of XXZ spin chain
Abstract: I will discuss about the recent work on the classical limit of anisotropic spin-half XXZ chain. From asymptotic Bethe ansatz technique in XXZ spin chain, the Bethe equation can be formulated as a Riemann-Hilbert problem, hinting a connection to finite-gap solution of classical Landau-Lifshitz field theory. By solving the classical corresponding problem, and using the functional technique developed by Kostov, Gromov et al, an exact quantum-classical correspondence of the solution to quantum integrable chain and classical integrable field theory is implied.

Tuesday 24 September 2019, 11:00 at LPTMS, Salle de séminaire, LPTMS LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) physics
Marco Schirò ( IPHT and Collège de France ) Defying Quantum Thermalization through Interactions and Disorder: From Many Body Localization to Quantum Glassiness
Abstract: Generic interacting quantum many body systems are expected to reach thermal equilibrium when isolated from their environment and let evolve under their own quantum dynamics. Exceptions to this paradigm can emerge in presence of quenched random disorder, due to many body localization (MBL) or quantum glassiness. Those two robust scenarios for ergodicity breaking have recently attracted considerable interest both from a purely theoretical viewpoint and for their implications on the robustness of future quantum technologies. In this talk I will study the quantum dynamics of two prototype models for MBL and quantum glassy systems. I will first introduce a theoretical framework based on flow equations to study the properties MBL systems, in particular the emergence of localised integral of motions, and their dynamics. Then I will consider a mean field model of a quantum glass and I will study its isolated dynamics after a quantum quench. I will show that, contrary to the conventional wisdom based on thermodynamics, quantum fluctuations and non equilibrium effects result in an enhanced glassiness and ageing behavior.

Tuesday 24 September 2019, 11:30 at LPTENS, LPTENS library STR-LPT-ENS-HE (Séminaire commun LPTENS/LPTHE) hep-th
Chiara Toldo ( CPHT ) TBA

Thursday 26 September 2019, 10:00 at CPHT, Salle Louis Michel
( From 10 am to 6 pm, Ecole Polytechnique, Salle Louis Michel )
SEM-CPHT (Séminaire du CPHT) hep-th
Conference On Various Topics In Gravity And Strings Conference on Various Topics in Gravity and Strings
Abstract: Speakers: Carlo Angelantonj, Stephane Detournay, Rodrigo Olea, Anastasios Petkou, Marios Petropoulos, Celine Zwikel

Thursday 26 September 2019, 11:00 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) math.AG
Bertrand Eynard ( IPHT Saclay, IHES Bures sur Yvette, CRM Montreal ) Topological recursion: from spectral curve to conformal blocks
Abstract: Topological recursion, takes as inpout data a "spectral curve" S (ex: an algebraic equation P(x,y)=0 with P a polynomial, but can be more general), and associates to it an infinite sequence of differential n-forms W_{g,n}(S), called the invariants of the spectral curve. The scalar invariants n=0 are often denoted F_g(S)=W_{g,0}(S). Many invariants of enumerative geometry are special cases of these, like Gromov-Witten invariants, Hurwitz numbers,... The formal series of scalar invariants is formally like a Tau-function $\Tau(S)=exp{\sum_g F_g(S)}$, and has OPE and Ward indentities that enables to interpret them as heavy limit asymptotic expansion of conformal blocks in a 2dCFT on a surface. We shall make a short presentation of the topological recursion, and its application to Mirzakhani's recursion, and to Liouville 2dCFT.

Thursday 26 September 2019, 14:30 at IHES, Amphithéâtre Léon Motchane PT-IHES (Séminaire de physique théorique de l'IHES) hep-th
Dmitri Bykov ( MPI für Physik, München & Steklov Math. Inst., Moscow & IHES ) Flag Manifold Sigma-Models
Abstract: The talk is dedicated to flag manifold sigma-models, which are theories of generalized harmonic maps from a Riemann surface to a manifold of flags in $C^N$. These theories feature interesting geometric properties and are in certain cases examples of the so-called ‘integrable’ models. I will review some of these facts.

Friday 27 September 2019, 10:00 at IPHT, Salle Claude Itzykson, Bât. 774
( https://courses.ipht.cnrs.fr/?q=en/node/226 )
COURS (Cours) hep-th|math-ph|quant-ph
Slava Rychkov ( IHES, ENS ) Lorentzian methods in conformal field theory (1/4)
Abstract: Paraphrasing Alexander Polyakov, ``Conformal Field Theory is a way to learn about elementary particles by studying boiling water''. There is a technical statement behind this joke: Euclidean Conformal Field Theory, under certain conditions, can be rotated to the Lorentzian signature, and vice versa. This means that even statistical physicists studying finite-temperature phase transitions on a lattice should learn about the Minkowski space! The goal of this course will be to explain various classical and recent results pertaining to this somewhat surprising conclusion. \\ \\ Plan of the course: \\ - Elementary introduction to Euclidean CFT in $d>2$ dimensions; \\ - The Osterwalder--Schrader theorem about the Wick rotation of general reflection-positive Euclidean Quantum Field Theories, and its limitations; \\ - The Luescher--Mack theorem about continuation of CFT correlation functions to the Lorentzian cylinder, and its limitations; \\ - Recent results about the analytic structure of Lorentzian CFT correlators.
Attachments:
  • 2019_Rychkov.pdf ( bytes) OPEN
  • 2019-2020.pdf (4458798 bytes) OPEN

Friday 27 September 2019, 11:00 at LPTMC, LPTHE library, Jussieu, 4th floor, tower 13-14
( séminaire commun LPTHE-LPTMC )
SEM-EXCEP (Séminaire exceptionel) cond-mat.mes-hall
Nicolás Wschebor ( Universidad de la República, Montevideo, Uruguay ) Convergence of Non-Perturbative Approximations to the Renormalization Group
Abstract: We provide analytical arguments showing that a non-perturbative approximation scheme known as the derivative expansion is controlled by a small parameter for very generic model at thermodynanical equilibrium. This approximation must be implemented within the Non-Perturbative Renormalisation Group (a modern version of Wilson's renormalisation group) with a regulator profile properly chosen. We employ the Ising model in three dimensions as a testing ground of the general analysis. In this case the derivative expansion has been recently pushed at order fourth order. We find fast convergence of critical exponents to their exact values, in full agreement with our general arguments. We also analyze preliminary results by employing the same techniques for O(N) models.

Friday 27 September 2019, 14:00 at CPHT, Salle Louis Michel
( PhD defense of Luca Ciambelli )
SEM-CPHT (Séminaire du CPHT) hep-th
Luca Ciambelli Paving the Fluid Road to Flat Holography

Monday 30 September 2019, 10:45 at LPTMC, Jussieu, tower 13-12, room 5-23 SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée) cond-mat.mes-hall
Claude Loverdo ( Laboratoire Jean Perrin, Paris ) Interactions of antibodies and bacteria in the digestive tract
Abstract: Inside the organism, the immune system can fight generically against any bacteria. However, the lumen of the gut is home to a very important microbiota, so the host has to find alternative ways to fight dangerous bacteria while sparing beneficial ones. While many studies have focused on the complex molecular and cellular pathways that trigger an immune response, little is known about how the produced antibodies act once secreted into the intestinal lumen. Our modeling work is along 3 axes. First, using stochastic models of bacterial population dynamics and branching processes, we infer relevant biological parameters of the dynamics of the bacterial population in the in vivo experiments of our collaborator, Emma Slack (ETH Zurich). We contributed to show that the main physical effect of these antibodies is to cross-link bacteria into clusters as they divide, preventing them from interacting with epithelial cells, thus protecting the host. We then developed a simple ordinary differential equations model of these bacterial clusters, and studied how the interplay of the time scales of bacterial growth and of link breaking could enable the immune system to target the most problematic bacteria. Last, we studied how such immune-mediated bacterial clustering could impact the evolution of drug resistance by using a hybrid cross-scale model (with deterministic within-host bacterial growth, and stochastic transmission).

Tuesday 1 October 2019, 11:00 at CPHT, Salle Louis Michel, CPHT, Ecole Polytechnique SEM-CPHT (Séminaire du CPHT) hep-th
Francesco Galvagno ( University of Turin ) 1/2 BPS Wilson loops in N=2 SuperConformal Field theories
Abstract: The partition function of a four dimensional N=2 Super Yang-Mills theory can be mapped to a matrix model on a sphere using supersymmetric localization. We write it in a superconformal case, in particular playing with the matter content in different representation of the SU(N) gauge group, one obtains various conformal theories with interesting properties. In this set-up we compute the vacuum expectation value a 1/2 BPS Maldacena-Wilson loop and we mention possible holographic consequences of this achievement. Finally, we check our result against a perturbative computation up to a four-loops order, introducing new techniques to deal with superspace variables.

Tuesday 1 October 2019, 14:00 at APC, 646A - Mondrian APC-TH (Seminar of the theory group of APC) gr-qc
B Bellazini TBA

Wednesday 2 October 2019, 12:00 at LPENS, Conf IV FORUM-ENS (Forum de Physique Statistique @ ENS) cond-mat.stat-mech
Zala Lenarcic ( UC Berkeley ) TBA

Wednesday 2 October 2019, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774 IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires) hep-th
Elias Kiritsis ( APC ) (TBA)

Thursday 3 October 2019, 11:40 at IHP, 314 RENC-THEO (Rencontres Théoriciennes) hep-th
Daniel Arean ( IFT Madrid ) TBA
Abstract: TBA

Friday 4 October 2019, 10:00 at IPHT, Salle Claude Itzykson, Bât. 774
( https://courses.ipht.cnrs.fr/?q=en/node/226 )
COURS (Cours) hep-th|math-ph|quant-ph
Slava Rychkov ( IHES, ENS ) Lorentzian methods in conformal field theory (2/4)
Abstract: Paraphrasing Alexander Polyakov, ``Conformal Field Theory is a way to learn about elementary particles by studying boiling water''. There is a technical statement behind this joke: Euclidean Conformal Field Theory, under certain conditions, can be rotated to the Lorentzian signature, and vice versa. This means that even statistical physicists studying finite-temperature phase transitions on a lattice should learn about the Minkowski space! The goal of this course will be to explain various classical and recent results pertaining to this somewhat surprising conclusion. \\ \\ Plan of the course: \\ - Elementary introduction to Euclidean CFT in $d>2$ dimensions; \\ - The Osterwalder--Schrader theorem about the Wick rotation of general reflection-positive Euclidean Quantum Field Theories, and its limitations; \\ - The Luescher--Mack theorem about continuation of CFT correlation functions to the Lorentzian cylinder, and its limitations; \\ - Recent results about the analytic structure of Lorentzian CFT correlators.
Attachments:
  • 2019_Rychkov.pdf (4580711 bytes) OPEN
  • 2019-2020.pdf (4458798 bytes) OPEN

Friday 4 October 2019, 11:00 at APC, Amphithéatre Buffon APC-COLLOQUIUM (Colloquium de l'APC) astro-ph
Thibault Damour ( IHES ) Analytical Approaches to the General Relativistic Two-Body Problem
Abstract: The observation of gravitational wave signals from inspiralling and coalescing binary black holes has been significantly helped, from the theoretical side, by the availability of analytical results on the motion and gravitational radiation of binary systems, and notably the Effective One-Body (EOB) theory of the motion and radiation of binary systems. We shall review the structure of perturbative calculations in classical gravity from various points of view: post- Minkowskian, post-Newtonian, self-force, reduced action, effective one-body. We shall also discuss the (two-way) maps between classical dynamics and quantum scattering amplitudes.

Monday 7 October 2019, 10:45 at LPTMC, campus Jussieu, tower 13-12, 5th floor, room 523 SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée) cond-mat.mes-hall
Hervé Mohrbach ( LPCT Metz ) La confotronique des biofilaments

Monday 7 October 2019, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774 IPHT-PHM (Séminaire de physique mathématique) math-ph
Alexander M. Povolotsky ( Joint Institute for Nuclear Research, Dubna ) Statistics of Avalanche Currents in the Raise and Peel model
Abstract: The Raise and Peel model is a stochastic model of fluctuating interface with non-local avalanche dynamics. Its dynamical rules stem from the structure of a specific representation of the Temperley-Lieb algebra, and its stochastic generator can be represented by the Hamiltonian of the XXZ Heisenberg quantum spin chain with twisted boundary conditions. We describe the recent progress in description of the statistics of the avalanches in the model. We focus on the large deviations of two avalanche currents in the thermodynamic limit, which reveal a phase transition in the behaviour of one current conditioned to atypical values of another one. We also describe a proof of the laws of large numbers for the two currents at arbitrary finite lattices, which in addition proves two earlier conjectures on the structure of the stationary state of the model. The technique is based on the analysis of the largest eigenvalue of the deformed stochastic generator using the Bethe ansatz and Baxter's T-Q relation.

Monday 7 October 2019, 14:30 at IHES, Amphithéâtre Léon Motchane
( Séminaire Géométrie et groupes discrets )
MATH-IHES (TBA) math
Romain Dujardin ( LPMA, Sorbonne Université ) Degenerations of SL(2,C) Representations and Lyapunov Exponents
Abstract: Let G be a finitely generated group endowed with some probability measure $\mu$ and $(\rho_{\lambda})$ be a non-compact algebraic family of representations of G into SL(2,C). This gives rise to a random product of matrices depending on the parameter $\lambda$, so the upper Lyapunov exponent defines a function on the parameter space. Using techniques from non-Archimedean analysis and algebraic geometry, we study the asymptotics of the Lyapunov exponent when $\lambda$ goes to infinity. This is joint work with Charles Favre.

Monday 7 October 2019, 16:30 at IHES, Amphithéâtre Léon Motchane
( Séminaire Géométrie et groupes discrets )
MATH-IHES (TBA) math
Jérémy Toulisse ( Université de Nice-Sophia Antipolis ) Quasi-circles and Maximal Surfaces in the Pseudo-hyperbolic Space
Abstract: Quasi-circles in the complex plane are fundamental objects in complex analysis; they were used by Bers to define an infinite-dimensional analogue of the usual Teichmüller space. After introducing the notion of quasi-circles in the boundary of the pseudo-hyperbolic space H^2,n, I will explain how to construct a unique complete maximal surface in H^2,n bounded by a given quasi-circle. This construction relies on Gromov's theory of pseudo-holomorphic curves and provides a generalization of maximal representations of surface groups into rank 2 Lie groups. This joint work with François Labourie and Mike Wolf.

Tuesday 8 October 2019, 11:00 at CPHT, Salle Louis Michel SEM-CPHT (Séminaire du CPHT) hep-th
Elias Kiritsis ( APC ) Emergent gravity and hidden sectors

Tuesday 8 October 2019, 14:00 at APC, 646A - Mondrian APC-TH (Seminar of the theory group of APC) gr-qc
Marc Geiller TBA

seminars from series at institute
in subject with field matching

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