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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 | [Next 30 ] | |
| [ scheduler view ] | ||
| Monday 11 December 2023, 10:45 at LPTMC, LPTMC seminar room, Jussieu, towers 12-13, 5th floor, room 523 | SEM-EXCEP (Seminaire exceptionnel) | cond-mat |
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| Abstract: | Metals, commonly found in various quantum materials, are characterized by the presence of Fermi surfaces, where all zero-energy modes contribute to the low-energy dynamics. In this talk, I will present our recent work on the simplest metallic state, the Fermi liquid phase, from the RG perspective. The novel functional framework enables us to capture the non-trivial RG flow around the Fermi liquid fixed-point and uncovers the collective modes and Fermi liquid instabilities. I will also discuss our study on the Fermi liquid with non- circular fermi surface, especially on the collective modes associated with the inflection points. | |
| Tuesday 12 December 2023, 11:00 at
LPTMS,
Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 ( This seminar will be on zoom also: for the link, please check abstract or LPTMS website ) | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Abstract: | A goal of unsupervised machine learning is to build representations of complex high-dimensional data, with simple relations to their properties. Such disentangled representations make it easier to interpret the significant latent factors of variation in the data, as well as to generate new data with desirable features. The methods for disentangling representations often rely on an adversarial scheme, in which representations are tuned to avoid discriminators from being able to reconstruct information about the data properties (labels). Unfortunately, adversarial training is generally difficult to implement in practice. Here we propose a simple, effective way of disentangling representations without any need to train adversarial discriminators and apply our approach to Restricted Boltzmann Machines, one of the simplest representation-based generative models. Our approach relies on the introduction of adequate constraints on the weights during training, which allows us to concentrate information about labels on a small subset of latent variables. The effectiveness of the approach is illustrated with four examples: the CelebA dataset of facial images, the two-dimensional Ising model, the MNIST dataset of handwritten digits, and the taxonomy of protein families. In addition, we show how our framework allows for analytically computing the cost, in terms of the log-likelihood of the data, associated with the disentanglement of their representations. Paper link: https://journals.aps.org/prx/abstract/10.1103/PhysRevX.13.021003 —— This seminar will be on zoom also: https://universite-paris-saclay-fr.zoom.us/j/93026726739?pwd=TFhIdHMrSy8vRkNMdzZMT3ptSFRxQT09 Meeting ID: 930 2672 6739 Passcode: 244859 | |
| Tuesday 12 December 2023, 14:00 at IMO, Online-only. Zoom link by subscribing at https://seedseminar.apps.math.cnrs.fr/ | SEED (Seed Seminar of Mathematics and Physics) | math-ph |
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| Abstract: | Toda conformal field theories form a family of two-dimensional quantum field theories initially introduced in the physics literature. They are natural generalizations of Liouville theory that enjoy, in addition to conformal invariance, an enhanced level of symmetry encoded by W-algebras. In this presentation we will explain how one can study these theories from a mathematically rigorous perspective. For this purpose we will describe a probabilistic framework designed to make sense of these models and provide some insight on how the introduction of this framework can help to understand the model. To be more specific, we will prove ---we will not enter into much details but rather try to convey the main ideas--- that one can compute some basic correlation functions of the theory based on probabilistic tools. Along the proof of this statement we will shed light on some unexpected interplays between probability theory and conformal field theory such as a generalized Brownian path decomposition. | |
| Tuesday 12 December 2023, 14:00 at LPENS, L382/L384 | LPTENS-HE (Séminaire commun LPTENS-LPTHE) | hep-th |
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| Abstract: | Type IIB string theory on AdS_5 x S^5 is integrable, which allows us to compute the spectrum of the dual CFT to extreme accuracy, even for non-BPS states. The arguably simplest deformation of this model is an orbifold projection, which generically breaks supersymmetry but retains integrability. This allows us to study AdS/CFT in systems with reduced supersymmetry. If we break supersymmetry completely, as for example in type 0B theory, tachyons come to haunt us, and their matching across AdS/CFT is quite puzzling. If we retain N=2 supersymmetry, the gauge theory is well behaved and extensively studied. However, the string theory side is lagging behind, so I raise the question whether recent localisation results can help us understand it better. | |
| Wednesday 13 December 2023, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Wednesday 13 December 2023, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-SEM (Séminaire du IPHT) | physics |
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| Abstract: | Résoudre un problème physique dans toute sa complexité est en général impossible : la physique est trop compliquée ! Une façon de simplifier le problème est de supposer qu'il possède des symétries, qui peuvent être exactes, ou seulement approximatives. Dans cet exposé, je vais définir ce qu'on appelle une symétrie, et donner de nombreux exemples concrets. On verra que dans certains cas, les symétries peuvent être explicitement ou spontanément brisées, ce qui joue un rôle fondamental dans la dynamique des systèmes. De façon surprenante, tous ces concepts, bien connus des physiciens depuis des décennies, semblent encore receler des mystères, qu'ils commencent à peine à comprendre. | |
| Wednesday 13 December 2023, 12:45 at LPENS, College de France, 3 rue d Ulm | FORUM-ENS (Forum de Physique Statistique @ ENS) | cond-mat.stat-mech |
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| Wednesday 13 December 2023, 14:00 at IHES, Amphithéâtre Léon Motchane | PT-IHES (Séminaire de physique théorique de l'IHES) | hep-th |
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| Abstract: | Metals, commonly found in various quantum materials, are characterized by the presence of Fermi surfaces, where all zero-energy modes contribute to the low-energy dynamics. In this talk, I will present our recent work on the simplest metallic state, the Fermi liquid phase, from the RG perspective. The novel functional framework enables us to capture the non-trivial RG flow around the Fermi liquid fixed-point and uncovers the collective modes and Fermi liquid instabilities. I will also discuss our study on the Fermi liquid with non-circular fermi surface, especially on the collective modes associated with the inflection points. | |
| Wednesday 13 December 2023, 14:00 at LPTHE, library | LPTHE-PPH (Particle Physics at LPTHE) | hep-ph |
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| Abstract: | Quantum entanglement has been probed in several low-energy experiments with electrons and photons. Which is then the motivation to study it with heavy particles, such as top quarks and W/Z bosons? Not only to extend tests to the energy frontier, but also to perform tests that could not be done elsewhere: those involving entanglement and particle decay. Entanglement tests also provide several useful by-products that I will discuss. | |
| Wednesday 13 December 2023, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires) | hep-th |
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| Abstract: | I will discuss some features of ALE partition functions of 6d theories. For M-strings and M-string orbifold theories, we can compute these quantities explicitly exploiting a chain of string dualities. Time permitting, I will also comment on a relation of these observables with higher DT invariants. Based on joint works with Guglielmo Lockhart. | |
| Thursday 14 December 2023, 10:00 at IHP, Amphithéatre Darboux | RENC-THEO (Rencontres Théoriciennes) | hep-th |
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| Abstract: | In this talk I will discuss the structure of higher-twist Regge trajectories in conformal field theories. I will first describe a general mechanism that reconciles analyticity in spin with the growing number local operators at large spin. I will then demonstrate how this mechanism works in the case of one-loop phi^4 Wilson-Fisher theory in epsilon-expansion. This example will also clarify the properties of double-twist trajectories and light-cone bootstrap at higher-twist. Finally, I will briefly discuss a work in progress on going beyond the double-twist limit. | |
| Thursday 14 December 2023, 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)) | cond-mat.stat-mech |
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| Abstract: | Chaotic-to-non-chaotic transitions play a prominent role in our understanding of the dynamical phase diagram of both quantum and classical systems. In quantum many-body systems, a certain kind of chaotic- non-chaotic transitions, dubbed ‘measurement-induced phase transitions’ (MIPT), have led to a new paradigm for dynamical phase transitions in recent years. On the other hand, prominent examples of transition in chaos in classical dynamical systems are the stochastic synchronization transitions (ST). In this case, classical trajectories starting from different initial conditions synchronize when subjected to sufficiently strong common random stochastic noise. In this talk, I will establish a possible link between MIPT and ST by considering models of interacting quantum particles whose positions are measured continuously, albeit weakly. In the semiclassical limit, the dynamics of the system is described by a stochastic Langevin equation where the noise and the dissipation terms are both controlled by the small quantum parameter and measurement strength. I will show the existence of a chaotic-to-non-chaotic transition in the Langevin evolution as a function of either interaction or noise/dissipation strength. | |
| Thursday 14 December 2023, 11:45 at IHP, Amphithéatre Darboux | RENC-THEO (Rencontres Théoriciennes) | hep-th |
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| Thursday 14 December 2023, 15:00 at LPTM, 4.13b + Teams distanciel | SEM-LPTM-UCP (Seminaires du LPTM , Universite de Cergy Pontoise) | cond-mat |
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| Abstract: | I will discuss effects of non-local fluctuations on correlated electronic systems and in particular on the physics of the Hubbard model. In the first part of the talk I will present results of a recent work, where using non-perturbative many-body techniques that are able to interpolate between the spin-fluctuation-dominated Slater regime at weak coupling and the Mott insulator at strong-coupling, we disentangle the effects of antiferromagnetic fluctuations and local electronic correlations in the formation of an insulating state. This allows us to identify the Slater and Heisenberg regimes in the phase diagram, which are separated by a crossover region of competing spatial and local electronic correlations. This bridging of the two limits had been a key missing ingredient to our understanding of metal-insulator transitions in real materials. In the second part of the talk I will present a non-local description of Hubbard bands and Green’s function zeros of Mott insulators. Their momentum dispersion has been found to be crucial in order to address the topological classification of strongly interacting insulators, a very intensively debated subject. Our analytical result offers a general and accurate description of the Hubbard bands and Green’s function zeros, establishing a one-to-one connection between their respective momentum dispersions. | |
| Friday 15 December 2023, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Friday 15 December 2023, 13:45 at
LPTMS,
Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 ( https://cnrs.zoom.us/j/99619966409?pwd=Z25nUDBhaDBuMm42a2MxaDcvREswZz09 Meeting ID: 996 1996 6409 Passcode: 4kbEd6 ) | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Abstract: | Metals, commonly found in various quantum materials, are characterized by the presence of Fermi surfaces, where all zero-energy modes contribute to the low-energy dynamics. In this talk, I will present our recent work on the simplest metallic state, the Fermi liquid phase, from the RG perspective. The novel functional framework enables us to capture the non-trivial RG flow around the Fermi liquid fixed-point and uncovers the collective modes and Fermi liquid instabilities. I will also discuss our study on the Fermi liquid with non- circular Fermi surface, especially on the collective modes associated with the inflection points. | |
| Monday 18 December 2023, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-PHM (Séminaire de physique mathématique) | math-ph |
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| Abstract: | We thoroughly revisit the ferromagnetic Ising chain under Glauber dynamics in the case where temperature depends on time according to an arbitrary protocol. We show how the Glauber theory simplifies in the low-temperature scaling regime where the typical size of the ferromagnetic domains is much larger than the lattice spacing. We analyse in depth various classes of protocols, including slow quenches over a large but finite quenching time, everlasting slow quenches, periodic temperature protocols, and the Kovacs effect. The key observables are the density of domain walls, the susceptibility, and their dimensionless product referred to as the form factor. Our quantitative results are compared to the phenomenological Kibble-Zurek scaling theory whenever such a comparison is possible. Based on a recent work in collaboration with Claude Godrèche. | |
| Tuesday 19 December 2023, 11:00 at LPTMS, Salle des séminaires du FAST et du LPTMS | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Abstract: | Within strongly correlated systems, frustrated magnetism is the field that study magnetic insulators when different microscopic magnetic interactions favor incompatible orders and no classical spin configuration can fulfill all of them. This realm offers a fertile ground for experimental and fundamental exploration, giving rise to unconventional phenomena such as order by disorder or the enigmatic quantum spin liquid phase. Nevertheless, its study poses challenges due to the presence of competing interactions of comparable magnitude, confounding perturbation theory. On the numerical side, frustration usually prevents the use of quantum Monte Carlo algorithms. Over the last decades, tensor network methods have emerged as the one of the most powerful numerical approach to tackle the many-body problem in both classical and quantum physics. In this talk, we will review the core principles of tensor network and their applications in condensed matter physics. We will focus on strongly correlated systems in two dimensions and discuss the simulation of frustrated quantum magnets at thermal equilibrium using Projected Entangled Pair States (PEPS). To illustrate this approach, we will address the spin-1/2 Heisenberg model on the square lattice with nearest- neighbor coupling J1 and next-nearest coupling J2 (J1-J2 model) at finite temperature [1]. We will consider both antiferromagnetic (J1 > 0) and ferromagnetic (J1 < 0) cases. We will expose the first unambiguous and direct evidence of an Ising transition associated with the spontaneous breaking of the C_4v symmetry within the collinear antiferromagnet region of the phase diagram. [1] O. Gauthé & F. Mila, PRL, 128, 227202 (2022) | |
| Tuesday 19 December 2023, 14:00 at IMO, Online-only. Zoom link by subscribing at https://seedseminar.apps.math.cnrs.fr/ | SEED (Seed Seminar of Mathematics and Physics) | math-ph |
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| Wednesday 20 December 2023, 10:00 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-SEM (Séminaire du IPHT) | physics |
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| Abstract: | To be announced. | |
| Wednesday 20 December 2023, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Wednesday 20 December 2023, 12:45 at LPENS, 3 rue d Ulm, College de France | FORUM-ENS (Forum de Physique Statistique @ ENS) | cond-mat.stat-mech |
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| Abstract: | TBA | |
| Friday 22 December 2023, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Monday 8 January 2024, 13:30 at LPENS, U209 (29 rue d'Ulm) | LPENS-MDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS) | cond-mat |
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| Tuesday 9 January 2024, 14:00 at LPTMS, LPTMS seminar room | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Wednesday 10 January 2024, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Thursday 11 January 2024, 10:00 at IHP, 314 (Grisvard) | RENC-THEO (Rencontres Théoriciennes) | hep-th |
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| Friday 12 January 2024, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Friday 12 January 2024, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-STA (Séminaire de Physique Statistique, CEA/Saclay) | cond-mat |
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| Tuesday 16 January 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)) | cond-mat.stat-mech |
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