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 ] 
Monday 5 December 2022, 15:00 at LPTHE, LPTHE LIbrary  SEMLPTHE (Séminaire du LPTHE)  condmat 



Abstract:  Quantum statistical mechanics and condensed matter physics traditionally deal with the collective behaviour of systems in thermal equilibrium. Here remarkable phenomena are known to emerge at low energy, as a result of strong interactions and quantum statistics. Whether genuine quantum effects can survive far away from thermal equilibrium is a question which has recently attracted broad interest and found several theoretical and experimental motivations. In this talk I will review the recent progress in understanding the dynamics of strongly interacting quantum systems far from equilibrium. Along the way I will discuss the paradox of quantum thermalisation and its breakdown due to quenched disorder or quantum measurements. 
Tuesday 6 December 2022, 11:00 at
LPTMS,
Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 ( Hybrid: onsite seminar + zoom. For zoom info, please write to valentina.ros@universiteparissaclay.fr or check LPTMS website http://lptms.upsud.fr/en/ )  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  condmat.statmech 



Abstract:  Disorder is ubiquitous in physical systems, and can radically alter their physical properties compared to their ‘pure’ counterparts. For instance, amorphous materials such as emulsions, foams, metallic glasses or biological tissues are all structurally disordered, and this has key implications for their rheological, mechanical or transport properties. Nevertheless, theoretical descriptions of such ‘driven’ amorphous materials remain challenging, despite decades of extensive analytical and computational studies. The difficulties pertain to the interplay of competing sources of stochasticity, and to the resulting outofequilibrium nature of these systems. A standard model for amorphous materials, which allows one to focus on the key role of their structural (positional) disorder, is provided by dense manybody systems of pairwise interacting particles. Here I will introduce an exact Dynamical MeanField Theory (DMFT) for these manybody systems, derived in the limit of infinite spatial dimension. In this framework, the manybody Langevin dynamics of the whole problem can be exactly reduced to a single scalar effective stochastic process, and dynamical observables such as pressure or shear stress can be computed for arbitrary driving protocols. Using this DMFT, we were in particular able to establish a direct equivalence between a global forcing (external shear) and a random local forcing (reminiscent of active matter), upon a simple rescaling of the control parameter (the accumulated strain). In this framework, global shear is thus simply a special case of a much broader family of local forcing that can be explored by tuning its spatial correlations. Our predictions were moreover found to be in remarkably good agreement with twodimensional numerical simulations. These results hint at a unifying framework for establishing rigorous analogies, at the meanfield level, between different families of driven disordered systems, such as sheared granular materials and active matter, or machinelearning algorithms. 
Tuesday 6 December 2022, 14:00 at LPENS, E239  LPTENSHE (Séminaire commun LPTENSLPTHE)  hepth 



Abstract:  Computing realtime SchwingerKeldysh (SK) correlation functions away from equilibrium stands out to be a theoretically outstanding as well as phenomenologically relevant problem in the holographic approach to the strongly interacting manybody systems. However, the realization of the bulk analogue of the SK contour away from equilibrium has remained elusive within the holographic framework for a long time. Lately, a promising (Horizon crosscap) prescription in this context has been put forward by CrossleyGloriossoLiu, which however mostly uses it in a static black hole background with slowlyvarying probe dynamics. This talk is based on an attempt to implement this prescription in a truly dynamical geometry that is dual to a Bjorken flow in the boundary a simple toy model describing the expansion and cooling of the hadronic matter produced in the heavy ion collision. We will explicitly compute the SK correlations of the scalar fluctuations of the Bjorken flow in a systematic latetime expansion, amenable to a Borel resummation. In this context, I will also discuss our newly developed matrix method which reproduces various known results and also gives an elegant way of computing the SK correlation functions beyond equilibrium. Finally, I will conclude with a set of open problems in this context. 
Tuesday 6 December 2022, 15:00 at
LPTHE,
library & Zoom link in comments ( Join Zoom Meeting https://cern.zoom.us/j/61239718813?pwd=ZjdmaDJ6c2h5eWpITk5yd0pDTDlTUT09 Meeting ID: 612 3971 8813 Passcode: 918259 )  LPTHEPPH (Particle Physics at LPTHE)  hepph 



Abstract:  We present a formalism that resums both threshold enhanced logarithms and their subleading contributions to all orders in perturbative Quantum Chromodynamics for the rapidity distribution of any colorless particle produced in hadron colliders. We achieve this by exploiting the factorization properties and K+G equations satisfied by the soft and virtual parts of the cross section. We compute for the first time, the resummed result in two dimensional Mellin space up to N3LL accuracy. Using various stateof theart multiloop and multileg results, we demonstrate the numerical impact of the resummed results up to nexttonextto leading order for the rapidity distributions of DrellYan and of the Higgs boson at the Large Hadron Collider. We find that these threshold logs in the resummed result stabilise the predictions against renormalization and factorization scale variations. 
Wednesday 7 December 2022, 11:00 at LKB, Amphi Charpak – Sorbonne université – 4 place Jussieu – 75005 Paris  SEMLKB (Séminaire du Laboratoire Kastler Brossel)  quantph 


Wednesday 7 December 2022, 14:00 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES )  MATHIHES (TBA)  math 



Abstract:  The Loewner energy for Jordan curves first arises from the large deviations of SchrammLoewner evolution (SLE), a family of random fractal curves modeling interfaces in 2D statistical mechanics. In a certain way, this energy measures the roundness of a Jordan curve, and we show that it is finite if and only if the curve is a WeilPetersson quasicircle and connect it to determinants of Laplacians. Furthermore, the Loewner energy is a Kahler potential on the WeilPetersson Teichmueller space identified with the space of WeilPetersson quasicircles. Intriguingly, this class of finite energy curves has more than 20 equivalent definitions arising in very different contexts, including Teichmueller theory, geometric function theory, hyperbolic geometry, spectral theory, and has been studied since the eighties with motivations from string theory. The myriad of perspectives on this class of curves is both luxurious and mysterious. I will overview the links between Loewner energy and SLE, WeilPetersson quasicircles, and other branches of mathematics it touches on. I will highlight how ideas from random conformal geometry inspire new results on WeilPetersson quasicircles and discuss further directions. 
Thursday 8 December 2022, 10:00 at IHP, Grisvard (314)  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  Field theories in AdS give rise to CFTs through their boundary correlators. Conversely, only special CFTs correspond to local bulk theories. We study the constraints imposed by bulk locality and the reconstruction of bulk fields as a bootstrap problem. By constructing a complete basis of functionals, we recast the locality constraint as a list of sum rules on the Boundary Operator Expansion and boundary OPE data. These sum rules are "dual" to the Generalized Free Field spectrum, and we also engineer a large family of "interacting" bases of functionals that naturally bootstrap interacting solutions. We discuss the flat space limit, when the locality problem becomes that of constructing local form factors from an Smatrix. 
Thursday 8 December 2022, 11:45 at IHP, Grisvard (314)  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  I will show that the space of EFT couplings and the space of 2D CFT partition functions can be described by identical geometries known as "moment problems" in the mathematics literature. Using Minkowski sums one can bootstrap both geometries analytically, including constraints which so far have been less explored. These include the unitarity upper bound and low spin dominance (for EFT) and degeneracy integrality (for CFT), leading to interesting reductions in allowed theory space. 
Thursday 8 December 2022, 14:00 at LPTHE, INSP Jussieu towers 2223 room 317  TQM (Theory of quantum matter)  condmat 



Abstract:  In a onedimensional Bose fluid, disorder can induce a quantum phase transition between a superfluid phase (Luttinger liquid) and a localized phase (Bose glass). Using bosonization, the replica method and a nonperturbative functional renormalizationgroup approach, we find that the Boseglass phase is described by a fully attractive strongdisorder fixed point characterized by a singular disorder correlator whose functional dependence assumes a cuspy form. This reveals the glassy properties (pinning, "shocks" and "avalanches") due to the existence of metastable states, as well as the crucial role of quantum tunneling between different metastable configurations. We also show that longrange interactions can stabilize a Mott glass, i.e. a state intermediate between a Mott insulator and a Bose glass, and characterized by a vanishing compressibility and a gapless optical conductivity. 
Thursday 8 December 2022, 14:00 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES )  MATHIHES (TBA)  math 



Abstract:  The Loewner energy for Jordan curves first arises from the large deviations of SchrammLoewner evolution (SLE), a family of random fractal curves modeling interfaces in 2D statistical mechanics. In a certain way, this energy measures the roundness of a Jordan curve, and we show that it is finite if and only if the curve is a WeilPetersson quasicircle and connect it to determinants of Laplacians. Furthermore, the Loewner energy is a Kahler potential on the WeilPetersson Teichmueller space identified with the space of WeilPetersson quasicircles. Intriguingly, this class of finite energy curves has more than 20 equivalent definitions arising in very different contexts, including Teichmueller theory, geometric function theory, hyperbolic geometry, spectral theory, and has been studied since the eighties with motivations from string theory. The myriad of perspectives on this class of curves is both luxurious and mysterious. I will overview the links between Loewner energy and SLE, WeilPetersson quasicircles, and other branches of mathematics it touches on. I will highlight how ideas from random conformal geometry inspire new results on WeilPetersson quasicircles and discuss further directions. 
Monday 12 December 2022, 14:00 at
IHES,
Amphithéâtre Léon Motchane ( Séminaire Géométrie et groupes discrets )  MATHIHES (TBA)  math 



Abstract:  The wellknown collar or Margulis lemma describes the structure of negatively curved manifolds at mesoscopic scale, in particular it allows to describe these manifolds globally through the "thickthin decomposition". This is not sufficient, however, to completely understand the homotopy type of the manifold, even roughly. In this talk I will describe an "arithmetic Margulis lemma" (essentially a consequence of work of E. Breuillard) which allows to describe thin parts at a macroscopic scale in certain circumstances, and how to use it to obtain sharp bounds on the volume of thin parts of arithmetic locally symmetric spaces. This is joint work with M. Frączyk and S. Hurtado. 
Monday 12 December 2022, 16:00 at
IHES,
Amphithéâtre Léon Motchane ( Séminaire Géométrie et groupes discrets )  MATHIHES (TBA)  math 



Abstract:  If a finite set S densely generates a compact, semisimple Lie group G, then how well does the set of words of length ℓ in S (and S1) approximate G? We could ask for them words to be an εnet of G; or, beyond an εnet, we could ask for the words to be evenly distributed down to a scale of ε; or we could ask for an efficient algorithm to produce a word that lies within ε of any given g in G. An optimal statistical result, with ℓ = O(log 1/ε), was first established by Lubotzky, Phillips, and Sarnak when G = SU(2) for special choices of S; and later generalized by others, but still with some restrictions on S. Not long afterwards, in the context of quantum computing, Solovay and Kitaev independently established an algorithm to find a word with ℓ = O((log 1/ε)a) for any S and (initially) also G = SU(2). I will discuss the current status of different versions of this question, including versions when G might not be compact or S1 might not be used. I will also discuss my own result, in which I improve the exponent in the (algorithmic) SolovayKitaev theorem from the previous best value of a = 3+δ to a = (logφ 2) + 1 + δ < 2.4405. 
Tuesday 13 December 2022, 11:00 at IPHT, Amphi Claude Bloch, Bât. 774  IPHTGEN (Séminaire général du SPhT)  physics 



Abstract:  The PoissonBoltzmann theory stems from the pioneering works of Debye and Onsager and is considered even today as the benchmark of ionic solutions and electrified interfaces. It has been instrumental during the last century in predicting charge distributions and interactions between charged surfaces, membranes, electrodes, macromolecules, and colloids. The electrostatic model of charged fluids, on which the PoissonBoltzmann description rests and its statistical mechanical consequences have been scrutinized in great detail. Much less, however, is understood about its probable shortcomings when dealing with various aspects of real physical, chemical, and biological systems. After reviewing the PoissonBoltzmann theory, I will discuss several extensions and modifications to the seminal works of Debye and Onsager as applied to ions and macromolecules in confined geometries. These novel ideas include the effect of dipolar solvent molecules, finite size of ions, ionic specificity, surface tension, and conductivity of concentrated ionic solutions. 
Tuesday 13 December 2022, 11:00 at
LPTMS,
Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 ( Hybrid: onsite seminar + zoom. For zoom info, please write to valentina.ros@universiteparissaclay.fr or check LPTMS website http://lptms.upsud.fr/en/ )  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  condmat.statmech 



Abstract:  Ultracold alkalineearth atoms offer the possibility to study the effect of a large spin degree of freedom in interacting fermionic ensembles. I will present the recent developments of our experiment, on which we produce degenerate Fermi gases of strontium 87, held in optical lattices to realize the FermiHubbard model generalized to largespin atoms (F = 9/2). In this seminar, I will focus on our capabilities for measurement and control of the spins, and connect this to our intended approach for the study of the antiferromagnetic Heisenberg model of magnetism. For our atomic species, the spins are of nuclear nature, which is both a strength and a complication as standard spin measurement or manipulation schemes based on magnetic gradients are ineffective. I will show nevertheless that a narrow line with large hyperfine structure offers us very powerful tools, associated with the engineering of effective spinorbit coupling, that we will use on several central aspects of our studies. First, we applied adiabatically a threelevel coupling involving a dark atomic state, reminiscent of EIT or STIRAP, to transfer momentum in a spinselective manner [1]. This, we now use for spin measurements, and could provide information through spinmomentum noise correlations. Second, we have demonstrated controlled coherent adiabatic operations in the 10component spinmanifold, on degenerate gases prepared deterministically in a single spin state. I will connect this to our present effort at using microstructured optical fields to adiabatically reach lowenergy states of the Heisenberg Hamiltonian, by the controlled breaking of its symmetries [2]. [1] P. Bataille et. al., Phys. Rev. A 102, 013317 (2020). [2] Comparin et.al., Phys. Rev. Lett. 129, 113201 (2022) 
Tuesday 13 December 2022, 14:00 at LPENS, L357/L359 (24 Rue Lhomond)  LPTENSHE (Séminaire commun LPTENSLPTHE)  hepth 



Abstract:  Correlation functions of the SL(2,$\R$)WZW model involving spectrally flowed vertex operators are notoriously difficult to compute. An explicit integral expression for the corresponding threepoint functions was recently conjectured in [2105.12130]. Here we provide the proof for this conjecture. For this we extend the methods of [2208.00978] based on the socalled SL(2,$\R$) series identifications, which relate vertex operators belonging to "adjacent" spectral flow sectors. 
Wednesday 14 December 2022, 14:00 at LPENS, L357  FORUMENS (Forum de Physique Statistique @ ENS)  condmat.statmech 


Thursday 15 December 2022, 11:00 at LPTHE, bibliothèque du LPTHE, tour 1314, 4eme étage  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  hepth 


Thursday 5 January 2023, 14:00 at LPTHE, Bibliothèque LPTHE 1314 4th floor  TQM (Theory of quantum matter)  mathph 



Abstract:  TBA 
Monday 9 January 2023, 13:30 at LPENS, L357  LPENSMDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS)  condmat 


Tuesday 10 January 2023, 11:00 at
LPTMS,
Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 ( Hybrid: onsite seminar + zoom. For zoom info, please write to valentina.ros@universiteparissaclay.fr or check LPTMS website http://lptms.upsud.fr/en/ )  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  condmat.statmech 


Wednesday 11 January 2023, 13:30 at DPTPHYSENS, ConfIV (E244)  24 rue Lhomond 75005 PARIS  COLLOQUIUMENS (Colloquium of the Physics Department of ENS)  physics 


Tuesday 17 January 2023, 11:00 at
LPTMS,
Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 ( Hybrid: onsite seminar + zoom. For zoom info, please write to valentina.ros@universiteparissaclay.fr or check LPTMS website http://lptms.upsud.fr/en/ )  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  condmat.statmech 


Thursday 19 January 2023, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 19 January 2023, 11:00 at IHES, Amphithéâtre Léon Motchane  MATHIHES (TBA)  math 



Abstract:  Brylynski defined and studied the topological analogue of the Radon transform on Grassmannians over Complex numbers. Using techniques from the theory of Dmodules he characterized the image of these Radon transforms in terms of their singular supports. In this talk, we shall discuss a characteristic p > 0 analogues of Brylynski’s work on the characterization of the image of the Radon transform and obtain a precise description in terms of BeilinsonSaito's theory of singular support. This is joint work with Deepam Patel. 
Thursday 19 January 2023, 14:00 at LPTHE, INSP Jussieu towers 2223 room 317  TQM (Theory of quantum matter)  hepth 



Abstract:  TBA 
Wednesday 25 January 2023, 13:30 at DPTPHYSENS, ConfIV (E244)  24 rue Lhomond 75005 PARIS  COLLOQUIUMENS (Colloquium of the Physics Department of ENS)  physics 


Thursday 26 January 2023, 11:00 at LPTHE, bibliothèque du LPTHE, tour 1314, 4eme étage  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  hepth 


Tuesday 31 January 2023, 11:00 at
LPTMS,
Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 ( Hybrid: onsite seminar + zoom. For zoom info, please write to valentina.ros@universiteparissaclay.fr or check LPTMS website http://lptms.upsud.fr/en/ )  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  condmat.statmech 


Thursday 2 February 2023, 14:00 at LPTHE, INSP Jussieu towers 2223 room 317  TQM (Theory of quantum matter)  condmat.meshall 


Tuesday 7 February 2023, 11:00 at
LPTMS,
Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 ( Hybrid: onsite + zoom. For zoom please write to valentina.ros@universiteparissaclay.fr or check LPTMS website http://lptms.upsud.fr/en/activites/seminaires/ )  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  condmat.statmech 



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