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 ] 
Friday 1 March 2024, 10:00 at IPHT, Salle Claude Itzykson, Bât. 774  COURS (Cours)  physics 



Abstract:  Abstract: In this course, we review twodimensional CFT in the bootstrap approach, and sketch the known exactly solvable CFTs with no extended chiral symmetry: Liouville theory, (generalized) minimal models, limits thereof, and loop models, including the O(n), Potts and U(n) models. Exact solvability relies on local conformal symmetry, and on the existence of degenerate fields: we explain how these assumptions constrain the spectrum and correlation functions. We discuss the crossing symmetry equations, and how they can be solved analytically or numerically, leading to analytic formulas for structure constants. \\ \\ In the case of loop models, we review the combinatorial description of correlation functions, inspired by the lattice construction of statistical models. We sketch what remains to be done for solving the models. \\ \\ The plan is: \\ 1. The Virasoro algebra and its representations. Fields and operator product expansions.\\ 2. Fusion rules and fusion products. Correlation functions and Ward identities. Crossing symmetry and conformal blocks.\\ 3. Defining a CFT. Diagonal and nondiagonal fields, degenerate fields. Exactly solvable CFTs and their spectrums.\\ 4. Degenerate 4point functions. Analytic formulas for 2point and 3point structure constants.\_ 5. Computing conformal blocks. Numerical bootstrap.\\ 6. Correlation functions in loop models.\\ \\ Livestream on youtube.com/IPhTTV: no subscription required.\\ Videoconference: subscribe to the course newsletter to receive links 
Monday 4 March 2024, 10:45 at LPTMC, On Zoom  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat 



Abstract:  Nonstationary processes are special types of nonmixing dynamics characterised by longtime deterministic dynamics. They are ubiquitous in the real world around us  from biological to social phenomena. Likewise, on the quantum level, any successful long circuit depth calculation on a quantum computer is, by definition, nonstationary. Therefore, understanding how nonstationarity emerges from the microscopic quantum laws is of fundamental scientific and technological importance. I will discuss fully general algebraic theory that describes the longtime dynamics of a quantum manybody system, including nonstationary cases. The theory is full general and allows for exact solutions even in nonintegrable systems provided that the relevant algebraic dynamical symmetries of the model can be identified. I give several physically relevant examples in both closed and open quantum manybody systems, including various quantum manybody scarred systems, a spin1/2 Creutz ladder with oscillating outoftimeorder correlators, a spindephased FermiHubbard model, and a twocomponent BEC in a lossy optical cavity which was recently experimentally studied and Hilbert space fragmented models. [1] B Buca, J Tindall, D Jaksch. Nat. Comms. 10 (1), 1730 (2019) [2] B Buca, D Jaksch. Phys. Rev. Lett. 123, 260401 (2019) [3] N Dogra, et al. Science, 366, 1496 (2019) [4] B Buca. Phys. Rev. Lett. 128, 100601 (2022). [5] B Buca. Phys. Rev. X 13, 031013 (2023) 
Monday 4 March 2024, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTPHM (Séminaire de physique mathématique)  mathph 



Abstract:  Andreas Kluemper, Mouhcine Azhari We present recent results for the computational treatment of the spectra of the integrable staggered sixvertex model and the integrable $3\bar 3$ superspin chain. The staggered sixvertex model has attracted the interest of several groups of authors who derived a wealth of results (e.g.~Ikhlef, Jacobsen, Saleur 08, 12 
Tuesday 5 March 2024, 10:30 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES )  MATHIHES (TBA)  math 



Abstract:  The ZilberPink conjecture is a diophantine finiteness conjecture. It unifies and gives a farreaching generalization of the classical MordellLang and AndreOort conjectures, and is wide open in general. Pointcounting results for definable sets in ominimal structures provide a strategy for proving suitable cases which has had some success, in particular in its use in proving the AndreOort conjecture. The course will describe the ZilberPink conjecture and the pointcounting approach to proving cases of it, eventually concentrating on the case of a curve in a power of the modular curve. We will describe the modeltheoretic contexts of the conjectures and techniques, and the essential arithmetic ingredients. 
Tuesday 5 March 2024, 11:00 at IPHT, Amphi Claude Bloch, Bât. 774  IPHTGEN (Séminaire général du SPhT)  physics 



Abstract:  The Galactic Bulge Time Domain Survey of the NASA Nancy Grace Roman Space Telescope (launch in 2026/2027, formerly called WFIRST) will use the gravitational microlensing method to detect more than 1000 planets with masses as low as Mars mass around G, K and M stars. The high resolution capability and high precision photometry of the telescope will also yield the mass measurements of ~700 such planets and their host stars during its prime mission. In this talk, I will present the physical concepts and observational techniques behind this space survey, using results already obtained from ground observations, including from followup observations that enable a mass measurement of cold exoplanets on wide orbits (~0.510 AU). Past microlensing surveys have measured the planettohost star massratio function of the cold exoplanets in the Milky Way. When compared to predictions from planet population synthesis models, these observational results question some stages of the models of giant planet formation. After discussing these results, I will present an ongoing program aiming at converting the aforementioned "massratio function" into a "mass function" which is expected to provide new insights on the abundance of cold exoplanets, its dependence to the hoststar mass and location in the galaxy. 
Tuesday 5 March 2024, 11:00 at LPTMS, Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  condmat.statmech 



Abstract:  We analyze flows generated by iterative dynamics of reflections of triangles. We interpret these flows as the probe particle adiabatic dynamics in the fundamental domain of the modular group. We consider two specific cases of lattices: (a) generated by reflections of equilateral triangles, and (b) generated by reflections of rectangular isosceles triangles. We show that stationary points of the flows for equilateral and isosceles triangles are correspondingly the « Golden » and the « Silver » ratios. We speculate about the manifestation of the difference between the Golden and the Silver ratios in cultural traditions of the « Western » and the « Eastern » world. 
Tuesday 5 March 2024, 14:00 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTHEP (Séminaire de physique des particules et de cosmologie)  hepph 



Abstract:  The discovery of Gravitational Waves (GWs) has propelled us into a new age of astronomy. However, possibly even more interesting than the waves themselves, are their sources. In this talk we will first examine the scenarios predicting GWs in the radio band above kHz. We will see that such highfrequency GWs could provide a unique window into new physics. We will then demonstrate how existing and upcoming experiments targeting other signals can be recycled to search for Radio Gravity. 
Tuesday 5 March 2024, 14:00 at LPENS, Conf IVE244, 24 Rue Lhomond  LPTENSHE (Séminaire commun LPTENSLPTHE)  hepth 



Abstract:  I give an overview of the SachdevYeKitaev model. Despite the simplicity of its Hamiltonian, it displays very rich physics with applications in both statistical mechanics and quantum gravity. And the end of my talk I will argue that a variant of this model also shares a lot of properties with de Sitter spacetime. 
Tuesday 5 March 2024, 14:00 at IJCLAB, A018  NUCTHEO (Séminaire de physique nucléaire théorique)  nuclth 



Abstract:  Recently, new measurements of the fission fragments’ spin showed no correlations between the fragments’ spin. These results have stimulated extensive theoretical discussion about the generation, orientation, and correlation of the fission fragments spin. In this contribution, I will discuss several approaches microscopical and collective to describe the mechanisms responsible for the angular momentum at scission. Although we currently have experimental data about the correlation between the magnitude of the angular momenta of the fragments, the presence of correlation between their direction described by the opening angle distribution is subject to different predictions from various theories. I will show how quantal effects and geometry of the scission configuration can change the opening angle distribution.  
Attachments: 
Tuesday 5 March 2024, 14:00 at LPTHE, Library and Zoom (link in the comments)  LPTHEPPH (Particle Physics at LPTHE)  hepph 



Abstract:  Thanks to the Higgs boson's close connection with many unsolved problems of Particle Physics, precision studies of Higgs properties constitute a crucial probe of BeyondtheStandard Model (BSM) Physics. Among these properties, the trilinear Higgs coupling provides a unique opportunity to access the structure of the Higgs sector, investigate the nature of the electroweak phase transition and the origin of the baryon asymmetry of the Universe, and search for indirect signs of BSM Physics. I will show that the trilinear Higgs coupling can, in models with extended scalar sectors, be significantly enhanced with respect to its SM prediction. Consequently, the current experimental bounds on this coupling are already sufficient to rule out significant parts of the BSM parameter space that would otherwise be unconstrained by stateoftheart theoretical and experimental constraints. Next, I will present the new public tool anyH3, which provides complete oneloop predictions for the trilinear Higgs coupling in arbitrary renormalisable theories. I will review the main features of anyH3 and present examples of new results obtained with it, as well as ongoing developments. 
Wednesday 6 March 2024, 11:00 at CPHT, Louis Michel  SEMCPHT (Séminaire du CPHT)  hepth 



Abstract:  The classical limit of scattering amplitudes offers a convenient strategy to calculate gravitationalwave observables for binary processes in the post Minkowskian (PM) regime, in which the two objects are far apart and interact weakly. In this talk I will discuss how the eikonal exponentiation offers a simple and conceptually transparent framework to exploit this connection and calculate key gravitational observables from amplitudes: the deflection angle for twobody encounters, energy and angular momentum losses, as well as the emitted gravitational waveform itself. The latter emerges in particular from the 2to3 amplitude for the scattering of two massive scalars and the emission of a graviton. I will briefly illustrate the calculation of its oneloop contribution, which is the key ingredient to obtain the first PM correction to the classic result obtained by Kovacs and Thorne in the 70s. Moreover, I will show how the choice of asymptotic BMS frame is crucial in order to compare the resulting amplitudebased waveform with the multipolar postNewtonian (PN) one, in the smallvelocity and soft limits, finding agreement up to 3PN order. 
Wednesday 6 March 2024, 12:45 at LPENS, 3 rue dUlm  FORUMENS (Forum de Physique Statistique @ ENS)  condmat.statmech 



Abstract:  This talk will be based on the two recent works: https://arxiv.org/abs/2402.10732, and https://arxiv.org/abs/2311.01529 (based on 2402.10732 ) 
Wednesday 6 March 2024, 13:30 at DPTPHYSENS, ConfIV (E244)  Dépt de Physique de l'ENS  24 rue Lhomond 75005 PARIS  COLLOQUIUMENS (Colloquium of the Physics Department of ENS)  physics 



Abstract:  TBA 
Wednesday 6 March 2024, 14:00 at IJCLAB, Room 114 (Salle des Séminaires), Bat. 210, 1st floor  IJCLABCOSM (Seminar of the Gravity and cosmology group of IJCLAB)  grqc 



Abstract:  Both Einstein's equations and the field equations of a modified theory of gravity can be derived as equations of state from purely thermodynamical considerations, leading to the identification of GR with an equilibrium state of gravity and modified gravity with a nonequilibrium one. This breakthrough made the relationship between gravity and thermodynamics even more intriguing. I will present a new approach to the thermodynamics of modified gravity which is inspired by these results, but follows a starkly different path. A precise description of the approach to equilibrium naturally emerges from using Eckart’s firstorder irreversible thermodynamics on the effective imperfect fluid describing scalartensor gravity. Applications of this framework to cosmology, extensions to different classes of modified theories, and the formulation of two complementary descriptions based on the notions of temperature and chemical potential all contribute to a new and unifying picture of the landscape of gravity theories GR is embedded in. 
Wednesday 6 March 2024, 14:00 at IJCLAB, A018  NUCTHEO (Séminaire de physique nucléaire théorique)  nuclth 



Abstract:  The origin of elements as well as their abundance in the Universe and among stars is at the heart of astrophysics today. Since the Big Bang, chemicals abundances are continuously evolving due to the nucleosynthesis involving different processes with mainly nuclear fusion or particle capture and the subsequent reactions. These processes are taking place in a variety of astrophysical sites, from stars to supernovae and merging events. Stellar evolution codes have been developed to describe the evolution and structure of stars using different physical input ingredients. In particular, the precise determination of the nuclear reaction rates, that drive the stellar evolution, is a crucial ingredient in understanding chemical evolution. Recently, new nuclear reaction rates have been determined for the different stellar evolution phases by nuclear experiments, potentially leading to significant changes in the nucleosynthesis predictions, with consequences on light and sprocess elements abundances. In order to improve stellar modeling, we now need to take into account these new results that can bring one of the key to better constrain stellar evolution and better understand the chemically peculiar stars. Especially I focus on the C12+C12 nuclear reaction that takes place during the Cburning phase of massive stars (> 8Msol) and for which new measurements have been obtained recently by the IPHCSTELLA team of Strasbourg.  
Attachments: 
Wednesday 6 March 2024, 16:00 at IJCLAB, A243  NUCTHEO (Séminaire de physique nucléaire théorique)  nuclth 



Abstract:  I will present my recent work developing connections between precision quantum experiments and quantum many body physics. I will present lattice field theory calculations informing atomic gas experiments, then speculate a way to take a literal continuum limit in the lab. I will then present a numerical framework for qubit design.  
Attachments: 
Thursday 7 March 2024, 11:00 at LPTHE, bibliothèque du LPTHE, tour 1314, 4eme étage  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  hepthmath.AG 



Abstract:  BPS invariants and cohomology are central objects in the study of (Kontsevich Soibelman) Hall algebras or in enumerative geometry of CalabiYau 3folds. In joint work with Yukinobu Toda, we introduce a categorical version of BPS cohomology for local K3 surfaces, called quasiBPS categories. When the weight and the Mukai vector are coprime, the quasiBPS category is smooth, proper, and with trivial Serre functor etale locally on the good moduli space. Thus quasiBPS categories provide (twisted) categorical (etale locally) crepant resolutions of the moduli space of semistable sheaves on a K3 surface for generic stability condition and a general Mukai vector. Time permitting, I will also discuss a categorical version of the \chiindependence phenomenon for BPS invariants. 
Thursday 7 March 2024, 14:00 at
LPTMC,
zoom: https://us06web.zoom.us/j/82091932293?pwd=zeSTGU68EkQWbN4z29E7alV9qf4o8C.1 ( Join Zoom Meeting https://us06web.zoom.us/j/82091932293?pwd=zeSTGU68EkQWbN4z29E7alV9qf4o8C.1 Meeting ID: 820 9193 2293 Passcode: 798606 )  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat 



Abstract:  Entanglement is the unique property that sharply distinguishes quantum from classical physics. Quantum entanglement is the hallmark of quantum phases and transitions without symmetry breaking. Beyond the conceptual level, quantum entanglement is essential in quantum computing devices. By instilling entanglement into unentangled product states, physicists have realized topologically ordered phases with anyons and noisy intermediatescale quantum (NISQ) devices in experiments. In this talk, I discuss two examples exhibiting an inseparable connection between entanglement and phases of matter. The first is the topologically ordered time crystal phase, which has been realized experimentally on quantum processors; the second is spin ladders with specific discrete symmetries, emulating 2D spinful bosons with longrange entanglement. I conclude with an outlook on how quantum entanglement reshapes science and technology in manybody physics. 
Thursday 7 March 2024, 14:30 at IHES, Amphithéâtre Léon Motchane  MATHIHES (TBA)  math 



Abstract:  Quantizing the mirror curve of a toric CalabiYau threefold gives rise to quantummechanical operators. Their fermionic spectral traces produce factorially divergent power series in the Planck constant and its inverse, which are conjecturally captured by the NekrasovShatashvili and standard topological strings via the TS/ST correspondence. In this talk, I will discuss a general conjecture on the resurgence of these dual asymptotic series, and I will present a proven exact solution in the case of the first spectral trace of local P^2. A remarkable numbertheoretic structure underpins the resurgent properties of the weak and strong coupling expansions and paves the way for new insights relating them to quantum modular forms. Finally, I will mention how these results fit into a broader paradigm linking resurgence and quantum modularity. This talk is based on arXiv:2212.10606 and further work with V. Fantini (available soon). 
Friday 8 March 2024, 10:00 at IPHT, Salle Claude Itzykson, Bât. 774  COURS (Cours)  physics 



Abstract:  Abstract: In this course, we review twodimensional CFT in the bootstrap approach, and sketch the known exactly solvable CFTs with no extended chiral symmetry: Liouville theory, (generalized) minimal models, limits thereof, and loop models, including the O(n), Potts and U(n) models. Exact solvability relies on local conformal symmetry, and on the existence of degenerate fields: we explain how these assumptions constrain the spectrum and correlation functions. We discuss the crossing symmetry equations, and how they can be solved analytically or numerically, leading to analytic formulas for structure constants. \\ \\ In the case of loop models, we review the combinatorial description of correlation functions, inspired by the lattice construction of statistical models. We sketch what remains to be done for solving the models. \\ \\ The plan is: \\ 1. The Virasoro algebra and its representations. Fields and operator product expansions.\\ 2. Fusion rules and fusion products. Correlation functions and Ward identities. Crossing symmetry and conformal blocks.\\ 3. Defining a CFT. Diagonal and nondiagonal fields, degenerate fields. Exactly solvable CFTs and their spectrums.\\ 4. Degenerate 4point functions. Analytic formulas for 2point and 3point structure constants.\_ 5. Computing conformal blocks. Numerical bootstrap.\\ 6. Correlation functions in loop models.\\ \\ Livestream on youtube.com/IPhTTV: no subscription required.\\ Videoconference: subscribe to the course newsletter to receive links 
Friday 8 March 2024, 14:00 at LPTHE, library  LPTHEPPH (Particle Physics at LPTHE)  hepph 



Abstract:  The production of W+c at the LHC features very interesting physics but also poses several problems. With the current experimental precision, precise theoretical predictions are therefore crucial to fully explore the physics content of the process. In this presentation, I will present stateoftheart theoretical predictions and discuss theoretical aspects relevant for the precise measurement of the process. 
Monday 11 March 2024, 10:45 at LPTMC, campus Jussieu, couloir 1213, 5ème étage, salle 523  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat 


Monday 11 March 2024, 13:30 at LPENS, U209 (29 rue d'Ulm)  LPENSMDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS)  condmat 


Tuesday 12 March 2024, 10:30 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES )  MATHIHES (TBA)  math 



Abstract:  The ZilberPink conjecture is a diophantine finiteness conjecture. It unifies and gives a farreaching generalization of the classical MordellLang and AndreOort conjectures, and is wide open in general. Pointcounting results for definable sets in ominimal structures provide a strategy for proving suitable cases which has had some success, in particular in its use in proving the AndreOort conjecture. The course will describe the ZilberPink conjecture and the pointcounting approach to proving cases of it, eventually concentrating on the case of a curve in a power of the modular curve. We will describe the modeltheoretic contexts of the conjectures and techniques, and the essential arithmetic ingredients. 
Tuesday 12 March 2024, 11:00 at LPTMS, Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  condmat.statmech 


Tuesday 12 March 2024, 11:00 at
IHES,
Centre de conférences Marilyn et James Simons ( Séminaire Laurent Schwartz )  MATHIHES (TBA)  math 


Tuesday 12 March 2024, 14:00 at IMO, Onlineonly. Zoom link by subscribing at https://seedseminar.apps.math.cnrs.fr/  SEED (Seed Seminar of Mathematics and Physics)  mathph 


Tuesday 12 March 2024, 14:00 at
IHES,
Centre de conférences Marilyn et James Simons ( Cours de l'IHES )  MATHIHES (TBA)  math 



Abstract:  Lecture 1 : Energy super critical singularity formation. Abstract : The description of singularity formation for non linear PDE’s is a classical problem with deep physical roots. Immense progress have been done in the last thirty on the understanding of “bubbling” phenomenon for focusing problems. But recently, new mecanisms have been discovered for “defocusing” problems with a deep connection to fluid mechanics. This series of 4 lectures is intended as a graduate class and will propose an introduction to the key results and open problems in the field, as well as a self contained description of the essential steps of the proofs. 
Tuesday 12 March 2024, 14:00 at LPTHE, Library and Zoom (link in the comments)  LPTHEPPH (Particle Physics at LPTHE)  hepph 



Abstract:  Since its appearance almost a decade ago, the Hubble Tension received a great deal of proposals to solve it, with none being completely successful. However, new state of the art data improve our assessment of these models and better constrain their parameters. In this talk, which is based on the work in arXiv: 2312.09814, an evaluation of eleven cosmological models is presented. These models consist of five classical extensions of ΛCDM, Early Dark Energy, the Majoron and the varying electron mass models, along with three of the latter’s extensions. This evaluation, previously performed using Planck, ACT and SDSS data (up to DR12), is now updated with recent SPT3G, SDSSDR16 and SH0ES data. Using a set of novel tension metrics, these models are ranked based on which one is able to reduce the tension, and which requires further study before potentially becoming the new concordance model of Cosmology. 
Thursday 14 March 2024, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  The conformal bootstrap is a robust tool for the nonperturbative study of conformal field theories (CFTs) making use unitarity and crossing of simple fourpoint correlation functions. However, not all observables are accessible in this setup and it is not clear whether a theory can be determined uniquely through these constraints. Higherpoint correlation functions of simple operators contain information about an infinite number of fourpoint correlators with complicated operators, and can potentially address the aforementioned problems. In this talk, I will discuss recent progress in generalizing the bootstrap program to higherpoint functions, with emphasis on a positive semidefinite numerical setup for the sixpoint crossing equation in one dimension. Despite the drastic simplifications with respect to higher dimensions, the problem retains its infinite nature, which we are able to address, obtaining nontrivial bounds on scaling dimensions and fourpoint functions at fixed kinematics. 

[ English version ] 