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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
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Monday 25 January 2021, 10:45 at LPTMC, on-line zoom seminar
( ID de réunion : 952 5691 0532 Code secret : 141152 )
SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée) cond-mat.mes-hall
Francesca Pietracaprina ( Trinity College Dublin ) Many-Body Localization in 2D and constrained models
Abstract: Many-body localization is a way to break ergodicity, thermalization and transport in disordered interacting quantum systems.The existence of a many-body localization transition in 2D systems is an open question that is being addressed experimentally, theoretically and numerically. In this talk, I will show some recent numerical results for a model whose features make it especially accessible to exact diagonalization. We numerically study the possibility of many-body localization transition in a constrained system: a disordered quantum dimer model on the honeycomb lattice. By using the peculiar constraints of this model and state-of-the-art exact diagonalization and time evolution methods, we probe large two-dimensional systems of up to N=108 sites. F Pietracaprina and F Alet, Arxiv Preprint arXiv:2005.10233 [cond-mat.dis-nn] (2020)

Monday 25 January 2021, 11:00 at IPHT, (voir dans annonce) IPHT-PHM (Séminaire de physique mathématique) math-ph
Monica Guica ( IPhT ) Infinite pseudo-conformal symmetry in classical TTbar, JTbar and JTa-deformed CFTs
Abstract: I will start with a brief review of the irrelevant current-current deformations of two-dimensional QFTs introduced by Smirnov and Zamolodchikov, concentrating on the $T\bar T, J\bar T $ and $ JT_a$ ones. I will then show that classical $T\bar T, J\bar T $ and $ JT_a$ -deformed CFTs possess an infinite set of symmetries that take the form of a field- dependent generalization of two-dimensional conformal and, if applicable, $U(1)$ transformations. The Poisson bracket algebra of the associated conserved charges consists of two commuting copies of a functional Witt - (Ka\v{c}-Moody) algebra. One notes, however, that at semi-classical level on a cylinder, the equal spacing of the descendants' energies predicted by such a symmetry algebra is inconsistent with the known finite-size spectrum of the deformed CFTs. I will show how to resolve this tension in the specific case of $J\bar T$ - deformed CFTs, by exhibiting a new set of (classical) conserved charges, which are related to the previous symmetry generators by a type of energy-dependent spectral flow. The above results suggest then that $T\bar T, J\bar T $ and $ JT_a$ -deformed CFTs correspond to non-local versions of usual two-dimensional conformal field theories, a structure that would be interesting to explore further. \\ \\ The seminar is online only. \\ Internet link to be collected from the Organizer: Vincent Pasquier (

Monday 25 January 2021, 16:00 at LPNHE, Online
( Contact for Zoom link )
LPNHE (Séminaires du LPNHE) hep-ex
Andrea De Gouvêa ( Northwestern University ) TBD

Tuesday 26 January 2021, 14:00 at APC, APC-TH (Seminar of the theory group of APC) gr-qc
Eemeli Tomberg ( NICPB ) A numerical approach to stochastic inflation and primordial black holes
Abstract: Primordial black holes are a dark matter candidate, which may originate from strong perturbations created during inflation. These perturbations can be studied using the formalism of stochastic inflation. I present a numerical approach to this problem, where the stochastic dynamics is solved by generating a large number of random realizations. This makes it possible to go beyond analytical approximations and take into account additional effects such as backreaction between the perturbations and the background. I show that in an example model with an inflection point potential and ultra-slow-roll inflation, compatible with CMB measurements, stochastic effects produce a highly non-Gaussian tail for the perturbations, which changes the predictions for black hole production significantly.

Tuesday 26 January 2021, 16:00 at IHP, Seminar via zoom P^3 (Particle Physics in Paris) astro-ph|hep-ph
Pedro Machado ( Fermilab ) New ideas and opportunities at future liquid argon neutrino experiment
Abstract: In this talk I will highlight some special experimental capabilities of future liquid argon time projection chamber (LArTPCs) neutrino experiments like the Fermilab’s Short Baseline Neutrino Program and DUNE. I will give a broad overview of what could be gained with these capabilities. Then, I will provide concrete physics opportunities that are enabled by LArTPCs, including measuring the CP violation phase with atmospheric neutrinos, searching for light dark matter, and performing precision electroweak physics measurements.

Thursday 28 January 2021, 11:00 at LPTHE, Zoom and bibliothèque du LPTHE, tour 13-14, 4eme étage
( This seminar will be given in hybrid mode. People who wish to attend in person should contact Ander Retolaza. Zoom: (pwd= 1234 ) )
RENC-THEO (Rencontres Théoriciennes) hep-th
Eric Perlmutter ( Caltech & IPhT ) A CFT Distance Conjecture
Abstract: We formulate a series of conjectures relating the geometry of conformal manifolds to the spectrum of local operators in conformal field theories in d>2 spacetime dimensions. We focus on conformal manifolds with limiting points at infinite distance with respect to the Zamolodchikov metric. Our central conjecture is that all theories at infinite distance possess an emergent higher-spin symmetry, generated by an infinite tower of currents whose anomalous dimensions vanish exponentially in the distance. Stated geometrically, the diameter of a non-compact conformal manifold must diverge logarithmically in the higher-spin gap. Our conjectures are related to the Distance Conjecture in the swampland program. We discuss the supporting evidence, their holographic interpretation, and implications for superconformal field theories.

Monday 1 February 2021, 10:45 at LPTMC, on-line zoom seminar
( ID de réunion : 950 1508 7598 Code secret : 599922 )
SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée) cond-mat.mes-hall
Riccardo Ben Ali Zinati ( LPTMC Paris ) A bird's eye view on discrete universalities
Abstract: Our modern understanding of universality, namely the independence of the critical properties of a system from its microscopic details, is based on the ideas put forward by K. Wilson and formalised within the framework of the renormalization group (RG). Despite the centrality of the subject in modern days theoretical Physics and the many decades passed since Wilson's original works, the classification of universality classes is to date largely unsolved. In recent years, however, the functional reformulation of the perturbative RG provided a simple tool to approach such a classification, extending significantly our knowledge of universality classes entailed by discrete symmetry groups in scalar field theories. In this talk, I will first introduce the technique, elucidate its key-point features and explain why it is so effective in charting the theory space. In passing, I briefly review the theory of invariant polynomials paying particular attention to the so-called Hilbert (or Molien) series. I will then focus on three particular cases: the scalar field theories endowed with the symmetry group of regular polytopes, the randomly diluted Ising models and the more general hyper-cubic scalar field theories. For each of these three cases, I review the main results and suggest possible lines of future investigations. References:

Tuesday 2 February 2021, 14:00 at APC, APC-TH (Seminar of the theory group of APC) gr-qc
Suddhasattwa Brahma ( McGill University ) Detecting quantum entanglement in the sky
Abstract: Although inflation is broadly accepted to be the standard paradigm for early universe cosmology, many of its quantum properties remain unknown. For instance, the crowning glory of inflation lies in explaining late-time macroscopic inhomogeneities as arising from tiny quantum fluctuations; however, most of the established literature ignores the crucial role that entanglement between the modes of the fluctuating field plays in its observable predictions. In this talk, I shall discuss how treating observable long-wavelength modes as part of an open quantum system can significantly affect the dynamics (and detectable consequences) of inflation, even when considering the nonlinearities arising solely from gravity. Since these dissipative effects are at the heart of decoherence (and how quantum fluctuations turn classical), such primordial entanglement is inescapable and provides universal upper bounds on the duration of inflation.

Tuesday 2 February 2021, 14:00 at LPTHE, Seminar via zoom LPTHE-PPH (Particle Physics at LPTHE) astro-ph|hep-ph|hep-th
Mathias Pierre ( IFT Madrid ) TBA

Tuesday 2 February 2021, 17:00 at LPTENS, GoToMeeting STR-LPT-ENS-HE (Séminaire commun LPTENS/LPTHE) hep-th
Gustavo Joaquin Turiaci ( UCSB ) TBA

Thursday 4 February 2021, 11:00 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) cond-mat|hep-th|math.MP
Johannes Kellendonk ( Institut Camille Jordan, Université Claude Bernard Lyon 1 ) The non-commutative topological approach to topological phases with protecting symmetry
Abstract: In this talk we review the K-theoretic description of topological phases of insulators and superconductors in the effective one particle approximation. In that approximation, an insulator (or superconductor) is described by a Hamiltonian whose spectrum has a gap at the Fermi energy. Two Hamiltonians belong to the same topological phase if they can be deformed into each other without closing the gap. For this to be well-defined, it is important to specify the space of possible Hamiltonians with its topology. When this space is taken to be a C*-algebra equipped with a real structure and a grading, one can use real graded K-theory and its dual (K-homology or cyclic cohomology) to describe the topological phases and their numerical topological invariants.

Friday 5 February 2021, 14:00 at LPTENS, GoToMeeting STR-LPT-ENS-HE (Séminaire commun LPTENS/LPTHE) hep-th
Karim Noui ( APC and Tours University ) TBA

Monday 8 February 2021, 10:45 at LPTMC, on-line zoom seminar
( ID de réunion : 386 319 3200 Code secret : 044816 )
SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée) cond-mat.mes-hall
Adriano Angelone ( Sissa and ICTP Trieste ) Strongly Correlated Systems of Bosons and Fermions: Many-body phenomena and Numerical Methods (provisoire)
Abstract: TBA

Tuesday 9 February 2021, 16:00 at IHP, Seminar via zoom
( This seminar will be followed by the one of Constantinos Skordis (University of Cyprus and Czech Academy of Sciences) at 16:30 )
P^3 (Particle Physics in Paris) astro-ph|hep-ph|hep-th
David Spergel ( Princeton University ) MOND day - TBA

Tuesday 9 February 2021, 16:30 at IHP, Seminar via zoom
( This seminar follows the one at 16:00 by David Spergel (Princeton University) )
P^3 (Particle Physics in Paris) astro-ph|hep-ph|hep-th
Constantinos Skordis ( University of Cyprus and Czech Academy of Sciences ) MOND day - TBA

Friday 19 February 2021, 14:00 at LPTENS, GoToMeeting STR-LPT-ENS-HE (Séminaire commun LPTENS/LPTHE) hep-th
Andrea Wulzer ( CERN and EPFL and Padua ) TBA

Tuesday 23 February 2021, 16:00 at IHP, Seminar via zoom P^3 (Particle Physics in Paris) hep-ph|hep-th
Jesse Thaler ( MIT ) TBA

Friday 5 March 2021, 11:00 at APC, APC-COLLOQUIUM (Colloquium de l'APC) hep-th
Mikhail Shaposhnikov ( EPFL Lausanne ) TBA
Abstract: TBA

seminars from series at institute
in subject with field matching

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