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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 ] | ||
| Wednesday 23 May 2018, 09:00 at
LPTM,
Maison internationale de la recherche, Neuville-sur-Oise. ( The aim of this conference is to contribute to the construction of new approaches to the study of complex problems in each of the involved disciplines. ) | WORK-CONF (Workshop or Conference) | cond-mat.dis-nn |
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| Abstract: | Sessions: Complex Dynamics I/II: Evolutionary Game Theory, Population Dynamics applied to economic and biological systems. Complexity in social systems; Physical and Mathematical models of complex systems See: https://web.u-cergy.fr/complexity2018/ | |
| Wednesday 23 May 2018, 11:30 at
IPN,
Bâtiment 100, Salle A015 ( $ $ ) | IPN-THEO (Séminaire du groupe de physique théorique de l'IPN Orsay) | nucl-th |
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| Abstract: | The unitary Fermi gas is a textbook model of strongly correlated fermions that accurately describes ultracold-atom experiments and is also relevant to neutron matter [1]. I will present our long-term project on reliable and accurate computation of equilibrium properties of the unitary Fermi gas by systematic summation of Feynman diagrams. Thanks to a diagrammatic Monte Carlo algorithm, we accurately sample all skeleton diagrams (built on dressed single-particle and pair propagators) up to order $\sim9$. The diagrammatic series is divergent and there is no small parameter so that a resummation method is needed. Previously we used Abelian resummation methods, which are applicable under the assumption that the diagrammatic series has a non-zero radius of convergence; this led to good agreement with experimental data for the equation of state [2] and Tan's contact [3]. In our more recent work [4], we compute analytically the large-order asymptotics of the diagrammatic series, and find that even though the radius of convergence is actually zero, the series is resummable by a generalised conformal-Borel transformation. Our new data for the equation of state and the contact are consistent with the old ones, but the resummation procedure is now mathematically justified and the error bars are significantly smaller. I will also discuss the computational complexity of diagrammatic Monte Carlo algorithms [5], including the new algorithm of [6]. 1] G. C. Strinati, P. Pieri, G. Roepke, P. Schuck, and M. Urban, Physics Reports 1, 738 (2018) [2] K. Van Houcke, F. Werner, E. Kozik, N. Prokof'ev, B. Svistunov, M. Ku, A. Sommer, L. Cheuk, A. Schirotzek, M. Zwierlein, Nature Phys. 8, 366 (2012) [3] K. Van Houcke, F. Werner, E. Kozik, N. Prokof'ev, B. Svistunov, arXiv:1303.6245 [4] R. Rossi, T. Ohgoe, K. Van Houcke, F. Werner, arXiv:1802.07717 [5] R. Rossi, N. Prokof'ev, B. Svistunov, K. Van Houcke, F. Werner, EPL 118, 10004 (2017) [6] R. Rossi, Phys. Rev. Lett. 119, 045701 (2017) | |
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| Thursday 24 May 2018, 11:00 at LPTHE, bibliothèque | SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) | math|math.MP |
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| Abstract: | We will first recall the general framework of cluster algebras and cluster varieties attached to arbitrary quivers. We will then explain what can be said about interesting differential forms on these varieties when the quiver is a tree, and how counting points over finite fields gives a first idea about their cohomology. This will be illustrated with examples, and involve an amusing set of Feynman rules with 3 colors. | |
| Thursday 24 May 2018, 14:00 at LPTHE, Library | LPTHE-PPH (Particle Physics at LPTHE) | hep-ph |
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| Abstract: | There are some discrepancies with respect to Standard Model predictions in measurements of $b-$meson decays. After reviewing the discrepancies and effective field theory fits, we examine simplified models of new physics that may explain a subset of them: in particular, $B \rightarrow K^{(\ast)} \mu^+ \mu^-$. There are two such classes of model that explain the discrepancies at tree-level: leptoquarks or $Z^\prime$ models. We then examine the prospects of detecting these two explanations at future colliders: the future circular collider and the high luminosity or high energy versions of the LHC. | |
| Thursday 24 May 2018, 14:00 at LPTM, 4.13 St Martin II | SEM-LPTM-UCP (Seminaires du LPTM , Universite de Cergy Pontoise) | cond-mat |
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| Abstract: | The goal of this seminar is to present how spin models are relevant in the physics of quantum simulators through two examples. In the first one, we show that the strong interacting limit of a topological Bose-Hubbard model with two species maps onto a 2D XY spin model with frustrated couplings on the honeycomb lattice. This model displays an exotic phase thats breaks both parity and time reversal symmetry through the stabilization of a chiral order parameter. While the ground-state remains gapped and the original bosonic model is topological, we find a zero Chern number for the groundstate. In the second example, we discuss how spin models are realized in Rydberg based quantum simulators. We discuss a proposal envisionned by colleagues at College de France and perspectives on some relevant information that could be extracted from the Loschmidt echo. | |
| Thursday 24 May 2018, 16:00 at LPT, 114 | LPT-PTH (Particle Theory Seminar of LPT Orsay) | hep-ph |
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| Abstract: | The observed abundance of dark matter can be explained by a thermal relic that annihilates with a weak scale cross section. This so-called “WIMP miracle” points to dark matter masses near the TeV scale. However, dramatic improvements in the sensitivity of direct detection experiments targeting TeV scale dark matter, and the lack of a discovery so far, motivates exploration beyond the WIMP. I will review three well-known “exceptions” to the WIMP miracle argument: (1) annihilations near a pole, (2) annihilations among multiple channels (“coannihilations”), and (3) annihilations into heavier states (“forbidden channels”). I will argue that forbidden channels and coannihilations are both mechanisms for producing dark matter that is exponentially lighter than the weak scale. I will also introduce a fourth exception, “coscattering,” where the dark matter abundance is produced by inelastic scattering against the thermal bath, instead of annihilations. | |
| Friday 25 May 2018, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=fr/node/197 ) | COURS (Cours) | cond-mat|q-bio |
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| Abstract: | Artificial neural networks, introduced decades ago, are now key tools for automatic learning from data. This series of six lectures will focus on a few neural network architectures used in the context of unsupervised learning, that is, of unlabeled data. \par In particular we will focus on dimensional reduction, feature extraction, and representation building. We will see how statistical physics, in particular the techniques and concepts of random matrix theory and disordered systems, can be used to understand the properties of these algorithms and the phase transitions taking place in their operation. \par Special attention will be devoted to the so-called high-dimensional inference setting, where the numbers of data samples and of defining parameters of the neural nets are comparable. The general principles will be illustrated on recent applications to data coming from neuroscience and genomics, highlighting the potentialities of unsupervised learning for biology. \par Some issues: \\ - What is unsupervised learning? \\ - Hebbian learning for principal component analysis: retarded-learning phase transition and prior information. \\ - Bipartite neural nets and representations: auto-encoders, restricted Boltzmann machines, Boltzmann machines. \\ - Recurrent neural nets: from point to finite-dimensional attractors, temporal sequences. | |
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| Friday 25 May 2018, 11:00 at LPTHE, Bibliothèque | SEM-LPTHE (Séminaire du LPTHE) | cond-mat.stat-mech |
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| Abstract: | In this talk, I will discuss a theoretical framework for understanding materials that are fragile. These are marginal solids or highly viscous liquids that emerge out of thermal equilibrium in response to external stresses. Granular materials and non-Brownian colloidal suspensions are well-known examples, however, reconfigurable pathways of force transmission also play an important role in biological systems. In granular materials, external forces such as gravity create rigid and flowing states. The mechanical integrity of these marginal solids is reliant on a filamentary network of stress-bearing structures. An outstanding question in the field has been how the constraints of vectorial force balance influence the response of granular assemblies to stress, and create localized stress pathways. I will present results of recent work showing that the localized response is a consequence of the disorder in the underlying contact network, and can be mapped on to a ``localization'' problem. I will also discuss an interpretive theory, based on statistical ensembles, of two transitions driven by frictional contacts: shear jamming and discontinuous shear thickening. | |
| Monday 28 May 2018, 10:45 at LPTMC, Jussieu, tower 13-12, 5th floor, room 5-23 | SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée) | cond-mat.mes-hall |
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| Abstract: | The electric double layer is generally viewed as simply the boundary that interpolates between an electrolyte solution and a metal surface. Contrary to that view, recent studies have shown that the interface between ionic liquids and metallic electrodes can exhibit structures and fluctuations that are not simple reflections of surrounding bulk materials [1]. The charge of the electrode is screened by the interfacial fluid and induces subtle changes in its structure, which cannot be captured by the conventional Gouy-Chapman theory. In recent years, this topic has been more intensively addressed in order to develop more efficient supercapacitors [2]. The latter are electrochemical devices that store the charge at the electrode/electrolyte interface through reversible ion adsorption. In order to understand the molecular mechanisms at play, we have performed molecular dynamics simulations on a variety of systems made of ionic liquids and electrodes of different geometries ranging from planar to nanoporous. A key aspect of our simulations is to use a realistic model for the electrodes, by allowing the local charges on the atoms to vary dynamically in response to the electrical potential caused by the ions and molecules in the electrolyte [3]. These simulations have allowed us to gain strong insight on the structure and dynamics of ionic liquids at electrified interfaces. From the comparison between graphite and nanoporous carbide-derived carbon (CDC) electrodes, we have elucidated the microscopic mechanism at the origin of the increase of the capacitance enhancement in nanoporous carbons [4]. We have also studied the impact of the carbon texture, by comparing CDC with perforated graphene materials [5]. References: 1. Fedorov, M.V., Kornyshev, A.A., Chem. Rev., 114 (2014), 2978-3036 2. Salanne, M., Rotenberg, B., Naoi, K., Kaneko, K., Taberna, P.L., Grey, C.P., Dunn, B., Simon, P., Nature Energy, 1 (2016), 16070 3. Merlet, C., Pean, C., Rotenberg, B., Madden, P.A., Simon, P., Salanne, M., J. Phys. Chem. Lett., 4 (2013), 264-268 4. Merlet, C., Rotenberg, B., Madden, P.A., Taberna, P.L., Simon, P., Gogotsi, Y., Salanne, M., Nature Materials, 11 (2012), 306-310 5. Mendez-Morales, T., Burbano, M., Haefele, M., Rotenberg, B., Salanne M., J. Chem. Phys., 148 (2018), 193812 | |
| Monday 28 May 2018, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-PHM (Séminaire de physique mathématique) | math-ph |
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| Abstract: | In this talk I will discuss recent developments in the study of scattering amplitudes in Einstein-Yang-Mills Theory. I will present novel relations between tree-level amplitudes in this theory and YM theory. Finally, I will discuss unitarity based observations regarding rational one-loop amplitudes involving gluons and gravitons. | |
| Monday 28 May 2018, 14:00 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-STA (Séminaire de Physique Statistique, CEA/Saclay) | cond-mat |
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| Abstract: | Much much work has been recently devoted to the study of the dynamics of quantum isolated systems after a sudden change in the Hamiltonian. In this talk I will describe the evolution of a family of isolated classical many-body disordered systems after instantaneous quenches of the same kind. The aim of these studies was to disentangle effects due to the quantum/classical nature of the systems from those intimately linked to the isolation and internal interactions (integrability vs. Non-integrability). I will emphasise the discussion of the dynamic phase diagram and the possible measures reached asymptotically (comparing Gibbs-Boltzmann equilibrium to Generalised Gibbs Ensemble probabilities). | |
| Tuesday 29 May 2018, 11:00 at LPTMS, LPTMS, salle 201, 2ème étage, Bât 100, Campus d'Orsay | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | physics |
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| Abstract: | The realization of two-dimensional electronic gases (2DEGs) in oxide-based heterostructures (e.g. LaAlO3/SrTiO3) has led to important discoveries about superconductivity in low dimensions. There have been reports of the observation of pairing interactions without superconductivity (Cheng et al., Nature 521, 196 (2015)) and density-of-states features resembling the pseudogap in cuprates (Richter et al., Nature 502, 528 (2013)). Consequently, this 2DEG has emerged as a model system to study the physics of Cooper pair formation in two dimensions and to gain useful insights about complex problems, e.g., the phase diagram of high temperature superconductors. In this talk, we will discuss about a new method developed in our group for realizing such superconducting systems in oxide heterostructures, and the results of experiments to characterize their properties. Due to the low carrier density, it is possible to change it using a gate voltage following the principle of a field-effect transistor. The superconducting critical parameters (temperature and field) are tunable as a function of the gate voltage, leading to a ‘superconducting dome’ in the phase diagram. The possibility of continuously varying the carrier density allows us to study different equilibrium and non-equilibrium features characterizing the electronic phases. Results of some recent experiments will be presented. | |
| Tuesday 29 May 2018, 11:30 at LPTENS, LPTENS library | STR-LPT-ENS-HE (Séminaire commun LPTENS/LPTHE) | hep-th |
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| Abstract: | Nekrasov and Shatashvili have found a large class of gauge theories in the Omega background, which are dual to some quantum integrable models. Later, the string dual was constructed by Hellerman, Orlando and Reffert in a series of papers. Alternatively, one can also construct the gravity dual of these theories using the gauge/gravity correspondence. In this talk, we will discuss the simplest example, the gravity dual of the 2d N=(2,2)* supersymmetric Yang-Mills (SYM) theory, which can be viewed as the mass deformation of the 2d N=(4,4) SYM theory and is dual to the simplest integrable model, the nonlinear Schrödinger equation. The technique is similar to the construction of the 4d N=2* SYM theory. Eventually, we will identify the mass deformation parameter with the twisted mass and find its counterpart on the gravity side, and we will also see the correspondence between solitons in the integrable model and D-branes. Possible generalizations to the full Nekrasov-Shatashvili duality will also be discussed. This talk is based on the paper arXiv:1706.09016 and some work in progress. | |
| Tuesday 29 May 2018, 14:00 at APC, 483 A - Malevitch | APC-TH (Seminar of the theory group of APC) | hep-th |
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| Abstract: | I will discuss the generalization to p-forms of the Galileon idea: to construct the most general theory of an (abelian gauge invariant) p-form with (strictly) second order field equations. Such theory have recently be fully classified for space-time dimension strictly smaller than 12. The covariantization of these theories will also be discussed. | |
| Tuesday 29 May 2018, 17:15 at DPT-PHYS-ENS, Jean Jaures (29 rue d'Ulm) | SEM-PHYS-ENS (Colloquium du Département de Physique de l'ENS) | physics.bio-ph |
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| Abstract: | TBA | |
| Thursday 31 May 2018, 10:00 at IHP, 314 | RENC-THEO (Rencontres Théoriciennes) | hep-th |
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| Thursday 31 May 2018, 11:45 at IHP, 314 | RENC-THEO (Rencontres Théoriciennes) | hep-th |
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| Friday 1 June 2018, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=fr/node/197 ) | COURS (Cours) | cond-mat|q-bio |
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| Abstract: | Artificial neural networks, introduced decades ago, are now key tools for automatic learning from data. This series of six lectures will focus on a few neural network architectures used in the context of unsupervised learning, that is, of unlabeled data. \par In particular we will focus on dimensional reduction, feature extraction, and representation building. We will see how statistical physics, in particular the techniques and concepts of random matrix theory and disordered systems, can be used to understand the properties of these algorithms and the phase transitions taking place in their operation. \par Special attention will be devoted to the so-called high-dimensional inference setting, where the numbers of data samples and of defining parameters of the neural nets are comparable. The general principles will be illustrated on recent applications to data coming from neuroscience and genomics, highlighting the potentialities of unsupervised learning for biology. \par Some issues: \\ - What is unsupervised learning? \\ - Hebbian learning for principal component analysis: retarded-learning phase transition and prior information. \\ - Bipartite neural nets and representations: auto-encoders, restricted Boltzmann machines, Boltzmann machines. \\ - Recurrent neural nets: from point to finite-dimensional attractors, temporal sequences. | |
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| Monday 4 June 2018, 09:00 at
IPHT,
Amphi Claude Bloch, Bât. 774 ( https://indico.in2p3.fr/event/17044/ ) | WORK-CONF (Workshop or Conference) | physics |
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| Abstract: | The 23rd Claude Itzykson Conference, which will take place in the Bloch Amphitheater from June 4 to 6, 2018, is dedicated to our colleague and friend Cirano De Dominicis who was the head and a prominent member of our laboratory for many years. \\ \par The themes of the conference will cover the scientific interests of Cirano: \\ Quantum Systems, \\ Out of Equilibrium Statistical Physics, \\ Disordered Systems and Spin Glasses, \\ Interdisciplinary Systems. \\ \\ \\ The website of the conference is: https://indico.in2p3.fr/event/17044/ \\ \\ Organizing committee: Giulio Biroli, Edouard Brézin, Henri Orland and Laure Sauboy (secretary). \\ \\ Sponsors and benefactors: IPhT (CEA and CNRS), DRF, LabEx LMH. | |
| Monday 4 June 2018, 10:45 at LPTMC, Jussieu, room 5-23, 5th floor, tower 13-12 | SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée) | cond-mat.mes-hall |
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| Tuesday 5 June 2018, 11:30 at LPTENS, LPTENS library | STR-LPT-ENS-HE (Séminaire commun LPTENS/LPTHE) | hep-th |
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| Abstract: | TBA | |
| Tuesday 5 June 2018, 14:00 at APC, 483 A - Malevitch | APC-TH (Seminar of the theory group of APC) | hep-th |
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| Tuesday 5 June 2018, 16:00 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-HEP (Séminaire de physique des particules et de cosmologie) | hep-ph |
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| Wednesday 6 June 2018, 10:30 at
IHES,
Centre de conférences Marilyn et James Simons ( Séminaire de Géométrie Arithmétique Paris-Pékin-Tokyo ) | MATH-IHES (TBA) | hep-th |
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| Abstract: | Let G be a reductive group over a function field of large enough characteristic. We prove the temperedness at unramified places of automorphic representations of G, subject to a local assumption at one place, stronger than supercuspidality. Such an assumption is necessary, as was first shown by Saito-Kurokawa and Howe-Piatetskii-Shapiro in the 70's. Our method relies on the l-adic geometry of Bun_G, and on trace formulas. Work with Will Sawin. | |
| Wednesday 6 June 2018, 11:30 at
IPN,
Bâtiment 100, Salle A015 ( $ $ ) | IPN-THEO (Séminaire du groupe de physique théorique de l'IPN Orsay) | nucl-th |
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| Abstract: | Since the pioneering work of Robledo [1], the Pfaffian has been extensively studied in nuclear physics. With the use of the Grassmann integrals, his work gives an excellent answer to the sign-problem in the overlap between HFB wave functions (Onishi formula [2] proposed in half a century ago). After Robledo's work, I have also studied some extensions [3] and applications. Here I will talk about the following topics: \begin{enumerate} \item Basics of Pfaffian and matrix elements of quantum many-body system \item Pfaffian and sign-problem of Onishi formula \begin{itemize} \item Pfaffian formula for overlap of HFB wave functions \item Origin of the sign-problem and liked cluster theorem \end{itemize} \item Pfaffian and Wick's theorem \end{enumerate} I will show some examples of Pfaffian in other fields of quantum many-body physics.\\ \newline [1] L.M. Robledo, Phys. Rev. C 79 (2009), 021302(R).\newline [2] N. Onishi, S. Yoshida, Nucl. Phys. 80 (1966) 367.\newline [3] M. Oi, T. Mizusaki, Phys. Lett. B 707 (2012) 305, T. Mizusaki, M. Oi, Phys. Lett. B 715 (2012) 219,T. Mizusaki, M. Oi, F. Chen, Y. Sun, Phys. Lett. B 725 (2013) 175, T.Mizusaki, M.Oi, N.Shimizu, Phys. Lett. B779 (2018) 237. | |
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| Wednesday 6 June 2018, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires) | hep-th |
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| Friday 8 June 2018, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=fr/node/197 ) | COURS (Cours) | cond-mat|q-bio |
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| Abstract: | Artificial neural networks, introduced decades ago, are now key tools for automatic learning from data. This series of six lectures will focus on a few neural network architectures used in the context of unsupervised learning, that is, of unlabeled data. \par In particular we will focus on dimensional reduction, feature extraction, and representation building. We will see how statistical physics, in particular the techniques and concepts of random matrix theory and disordered systems, can be used to understand the properties of these algorithms and the phase transitions taking place in their operation. \par Special attention will be devoted to the so-called high-dimensional inference setting, where the numbers of data samples and of defining parameters of the neural nets are comparable. The general principles will be illustrated on recent applications to data coming from neuroscience and genomics, highlighting the potentialities of unsupervised learning for biology. \par Some issues: \\ - What is unsupervised learning? \\ - Hebbian learning for principal component analysis: retarded-learning phase transition and prior information. \\ - Bipartite neural nets and representations: auto-encoders, restricted Boltzmann machines, Boltzmann machines. \\ - Recurrent neural nets: from point to finite-dimensional attractors, temporal sequences. | |
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| Friday 8 June 2018, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires) | hep-th |
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| Monday 11 June 2018, 10:55 at LPTMC, Jussieu, room 5-23, 5th floor, tower 13-12 | SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée) | cond-mat.mes-hall |
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| Monday 11 June 2018, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-PHM (Séminaire de physique mathématique) | math-ph |
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