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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 | ||
| [ scheduler view ] | ||
| Thursday 22 June 2017, 09:00 at
IPHT,
Amphi Claude Bloch, Bât. 774 ( https://indico.in2p3.fr/event/14442/ ) | WORK-CONF (Workshop or Conference) | physics |
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| Abstract: | \noindent ``In celebration of Nick Warner's 60th birthday''. \\ \\Details and Registration: https://indico.in2p3.fr/event/14442/ \\ (Iosif Bena, Mariana Grana, Monica Guica, David Turton and the other organizers.) | |
| Thursday 22 June 2017, 11:00 at IPN, Salle A201 | IPN-X (Séminaire commun de physique théorique des particules IPN-CPHT-X) | hep-ph |
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| Abstract: | In this talk, we begin by showing how it is possible to obtain full analytic results for the two-loop three distinct mass scale sunset diagrams that appear in the expressions for the masses and decay constants of the pion, kaon and eta particles in two-loop SU(3) chiral perturbation theory. We then talk about two applications of these results: a) how it allows one to obtain small quark mass ratios to arbitrarily high powers, and b) how it allows one to make fits to lattice data to extract greater information about low energy constants. We then change track and discuss in more detail the Mellin-Barnes method used in our calculations, and demonstrate how this method can be extended using analytic continuation to obtain results for Feynman diagrams whose mass value parameters are such that it is impossible to use a direct calculation. We show how such methods of analytic continuation can also be helpful in contexts where a direct calculation does yield results, and thus set the stage for more widespread application of this technique. | |
| Thursday 22 June 2017, 11:30 at
IPN,
IPNO, Salle des Conseils, Bat 100M RdC ( $$ ) | IPN-THEO (Séminaire du groupe de physique théorique de l'IPN Orsay) | nucl-th |
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| Abstract: | The Shell Model is about solving a Schrödinger equation with suitable interactions. So far, nuclear radii, binding energies and basic shell structure cannot be explained by the Shell Model. To "go beyond" means addressing the problem phenomenologically in ways to make it possible to discover basic mechanisms at play. Our starting point is the observation that nuclear radii and masses exhibit strong shell effects associated with "magic numbers" 6,14,28,50,82 and 126. Their origin is an open problem, difficult to pinpoint in the case of masses but subsumed by a single phenomenological term that brings down root mean square deviations with observed radii to 0.01 fermi. The origin of this term is unambiguously traced to the existence of huge "halo" orbits... | |
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| Thursday 22 June 2017, 14:00 at LPT, Salle cosmologie (110), bat 210, 1er etage | SEM-LPT (Séminaire de Physique des Particules du LPT) | hep-ph |
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| Thursday 22 June 2017, 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: | Much of the research in frustrated quantum magnets has focused on the elusive quest for magnetically disordered phases with highly entangled ground states - quantum spin liquids. Somewhat intermediate between these rare states and commonplace magnets are {\em nematic} phases which appear as a result of a two-magnon condensation and are characterized by the presence of a gap for excitations with spin one. As a result, nematic states exhibit no dipolar magnetic order. In my talk I describe two simple models supporting spin nematic phases. The first of them is provided by the two-magnon instability of the 1/3 magnetization plateau state of the quantum triangular antiferromagnet. I show that the two-magnon instability, which takes place near the end-point of the magnetization plateau, leads to a novel two-dimensional vector chiral phase with alternating spin currents. This interesting state spontaneously breaks inversion symmetry and can be thought of as appearing due to a fluctuation-generated Dzyaloshinskii-Moriya interaction. The second example involves an easy-axis spin-1 antiferromagnet in which transition into nematic state occurs via condensation of spin excitons. | |
| Friday 23 June 2017, 09:00 at
IPHT,
Amphi Claude Bloch, Bât. 774 ( https://indico.in2p3.fr/event/14442/ ) | WORK-CONF (Workshop or Conference) | physics |
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| Abstract: | \noindent ``In celebration of Nick Warner's 60th birthday''. \\ \\Details and Registration: https://indico.in2p3.fr/event/14442/ \\ (Iosif Bena, Mariana Grana, Monica Guica, David Turton and the other organizers.) | |
| Friday 23 June 2017, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=fr/node/168 ) | COURS (Cours) | cond-mat|quant-ph |
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| Abstract: | Closed systems (classical or quantum) are always an idealization of reality. A number of techniques of various accuracy and complexity are in use to take into account interactions of the system with its environment. In the crudest non trivial approximation, the effect of the environment is assumed to depend only on the immediate past of the state of the system (i.e. the density matrix in the quantum case), leading to the notion of Markovian open systems. \par In these lectures we motivate the relevance and consistence of the Markovian approximation for open quantum systems. We also show a very deep connection between effects of an environment and effects of repeated indirect measurements. \par We introduce non-demolition measurements and draw some broad conclusions on measurement in quantum mechanics. More generally we use indirect measurements as a tool to scrutinize the evolution of open quantum systems and analyze some properties of quantum trajectories. \par We also introduce the basics of quantum noises. \par Our focus is on properties that are related, or analogous to classical probability theory. We use the discrete time case to introduce the basic concepts, but also make the connection with continuous time systems. \\ \\ Lecture 1: Quick overview of open quantum systems; Brief review of quantum mechanics; Indirect measurements \\ Lecture 2: Discrete quantum Markovian evolution; Non demolition measurements and progressive wave function collapse \\ Lecture 3: From discrete to continuous time: Lindbladian evolution and its stochastic counterpart \\ Lecture 4: Quantum trajectories, quantum jumps \\ Lecture 5: A brief introduction to quantum noises | |
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| Friday 23 June 2017, 10:30 at LPTENS, Conf IV | LPTENS-HE (Séminaire commun LPTENS-LPTHE) | cond-mat.str-el|hep-th |
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| Abstract: | A wide array of phenomena occurring in quantum Hall fluid can be explained by postulating a new quasiparticle - the composite fermion. The previous field theory of the composite fermion, the Halperin-Lee-Read theory, suffers from the lack of particle-hole symmetry. I will describe a new theory, known as the "Dirac composite fermion theory," which solves the problem of particle-hole symmetry and reveals deep connections to novel dualities between field theories in 2+1 dimensions. I will also describe physical consequences of the Dirac composite fermion theory. | |
| Friday 23 June 2017, 11:30 at LPT, Amphi 1, 2eme etage, bldg 210, LPT Orsay | SOUTEN-TH (Soutenance de thèse) | hep-ph |
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| Abstract: | This thesis was devoted to the study of quantum fields in curved space-times in Lorentz-violating theories. While theories breaking Lorentz invariance at a fundamental level typically do so near the Planck scale, making their predictions out of reach of foreseeable experiments, low-energy models with an effective Lorentz invariance can be used to study, both theoretically and experimentally, the physical effects of the symmetry breaking. In this thesis we studied several aspects of these "analogue" models. I will present our main results concerning the relations between the properties of the (analogue) horizons and those of Hawking radiation, transitions between resonances and instabilities, and the nonlinear dynamics of (analogue) horizons. | |
| Tuesday 27 June 2017, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774 | SEM-INFOR (Séminaire informel) | physics |
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| Abstract: | La physique statistique a été développée pour comprendre comment les phénomènes macroscopiques émergent à partir des interactions entre un grand nombre de constituants élémentaires (particules, molécules, spins, etc). Ce problème est maintenant commun à d'autres disciplines comme la biologie, l'économie, ou l'intelligence artificielle. Je montrerai de quelle façon la physique statistique est au centre de ce défi, et je présenterai des avancées récentes. | |
| Tuesday 27 June 2017, 14:00 at IPHT, Salle Claude Itzykson, Bât. 774 | SOUTEN-TH (Soutenance de thèse) | physics |
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| Tuesday 27 June 2017, 14:00 at APC, 483A - Malevitch | APC-TH (Seminar of the theory group of APC) | hep-th |
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| Abstract: | Conserved charges associated with large gauge symmetries and Bondi-Metzer-Sachs symmetries of asymptotically Minkowski spacetime have been recently shown to give new "soft hair" for black holes -- beyond mass, charge and angular momentum. In this talk, I will outline a study of the constraint on dynamics due to these new symmetries. I will prove that they only constrain long-time, infrared dynamics, in a way that is completely factorizable. Factorization implies in particular that soft hair does not constrain the ``hard" physical processes that account for black hole microstates. | |
| Tuesday 27 June 2017, 14:30 at IHES, Amphithéâtre Léon Motchane | MATH-IHES (TBA) | hep-th |
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| Abstract: | In their paper, "On the motivic class of the stack of bundles", Behrend and Dhillon were able to derive a formula for the class of a stack of vector bundles on a curve in a completion of the K-ring of varieties. Later, Mozgovoy and Schiffmann performed a similar computation in order to obtain the number of points over a finite field in the moduli space of twisted Higgs bundles. We will briefly introduce motivic classes. Then, following Mozgovoy and Schiffmann's argument, we will outline an approach for computing motivic classes for the moduli stack of vector bundles with connections on a curve. This is joint work with Roman Fedorov and Yan Soibelman. | |
| Tuesday 27 June 2017, 16:00 at LPT, salle des seminaires 114 bat 210 1er etage | SEM-LPT (Séminaire de Physique des Particules du LPT) | hep-ph |
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| Abstract: | Warning :unusual day | |
| Wednesday 28 June 2017, 11:30 at
IPN,
IPN, Bâtiment 100, salle des conseils ( $$ ) | IPN-THEO (Séminaire du groupe de physique théorique de l'IPN Orsay) | nucl-th |
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| Abstract: | In recent years, chiral effective field theory (EFT) has reshaped our approach to the modelling of nuclear interactions, both conceptually and practically. At present several EFT-inspired nuclear Hamiltonians, derived more or less rigorously according to EFT principles, are on the market and are successful in describing numerous properties of light and medium-mass nuclei. Nevertheless, there is increasing debate on whether such calculations truly fulfil EFT potentialities, with alternative EFT schemes also being pursued. I this seminar I will discuss how these developments and issues at the level of the nuclear Hamiltonian impact many-body methods and calculations. I will do so by first examining a few successful results in medium-mass nuclei obtained with chiral-EFT potentials. Next, I will present a preliminary study of extended neutron matter where a pionless-EFT interaction, devoid of the issues alluded to above, is employed. | |
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| Wednesday 28 June 2017, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-HEP (Séminaire de physique des particules et de cosmologie) | hep-ph |
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| Abstract: | I will present a combinatorial operation on one-loop Feynman diagrams, described by cutting and pinching edges, that corresponds to the Hopf-algebraic coaction on the multiple polylogarithms resulting from their integration. A generalization of this operation, expressed simply in terms of master integrands paired with master contours, can be applied directly to larger classes of functions including hypergeometric functions. I will discuss applications to analyses of discontinuities of and differential equations for Feynman diagrams. | |
| Wednesday 28 June 2017, 14:30 at IHES, Amphithéâtre Léon Motchane | PT-IHES (Séminaire de physique théorique de l'IHES) | hep-th |
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| Thursday 29 June 2017, 13:30 at DPT-PHYS-ENS, room Conf. IV, 24 Rue Lhomond, ENS Paris | SEM-PHYS-ENS (Colloquium du Département de Physique de l'ENS) | hep-th |
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| Abstract: | Hydrodynamics, the theory describing collective behaviors of fluids and gases, is usually considered as a classical theory. In recent years, it has been found that hydrodynamics can be influenced by quantum anomalies. We will see how this interplay between quantum and classical physics has been discovered, unexpectedly, using the method of gauge/gravity duality. I will mention the possible relevance of the new findings to the physics of the quark gluon plasma. | |
| Friday 30 June 2017, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=fr/node/168 ) | COURS (Cours) | cond-mat|quant-ph |
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| Abstract: | Closed systems (classical or quantum) are always an idealization of reality. A number of techniques of various accuracy and complexity are in use to take into account interactions of the system with its environment. In the crudest non trivial approximation, the effect of the environment is assumed to depend only on the immediate past of the state of the system (i.e. the density matrix in the quantum case), leading to the notion of Markovian open systems. \par In these lectures we motivate the relevance and consistence of the Markovian approximation for open quantum systems. We also show a very deep connection between effects of an environment and effects of repeated indirect measurements. \par We introduce non-demolition measurements and draw some broad conclusions on measurement in quantum mechanics. More generally we use indirect measurements as a tool to scrutinize the evolution of open quantum systems and analyze some properties of quantum trajectories. \par We also introduce the basics of quantum noises. \par Our focus is on properties that are related, or analogous to classical probability theory. We use the discrete time case to introduce the basic concepts, but also make the connection with continuous time systems. \\ \\ Lecture 1: Quick overview of open quantum systems; Brief review of quantum mechanics; Indirect measurements \\ Lecture 2: Discrete quantum Markovian evolution; Non demolition measurements and progressive wave function collapse \\ Lecture 3: From discrete to continuous time: Lindbladian evolution and its stochastic counterpart \\ Lecture 4: Quantum trajectories, quantum jumps \\ Lecture 5: A brief introduction to quantum noises | |
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| Wednesday 5 July 2017, 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: | T-branes are bound states of ordinary D-branes, characterized by non-commuting expectation values for the worldvolume scalars. They defy usual geometric intuition and feature a variety of unconventional brane-model-building phenomena. In this talk I will discuss some general global properties of the vacuum solutions corresponding to T-branes, and show how supersymmetry puts strong constraints on the manifolds supporting them. Moreover, I will consider stability issues of such bound states at large volume, and give conditions to prevent their decay. | |
| Thursday 6 July 2017, 11:30 at
IPN,
IPN, Bâtiment 100, salle A015 ( $$ ) | IPN-THEO (Séminaire du groupe de physique théorique de l'IPN Orsay) | nucl-th |
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| Abstract: | Effective field theories (EFTs) are broadly recognized as a modern tool to construct nuclear interactions that are compatible with quantum chromodynamics (QCD) as the underlying theory of the strong interaction. While a lot of progress has been made in the development and application of such methods, there remain many important questions to be studied. In this talk, I will present recent calculations that apply perturbation theory to the nuclear few-body problem. I will emphasize the consistent treatment of electromagnetic interactions within an EFT framework, and in particular focus on a new approach that describes light nuclei as emerging from a very simple leading order (the unitarity limit), where -- much like the fine structure of atomic spectra -- observables are moved to their physical values by small perturbative corrections. | |
| Tuesday 11 July 2017, 14:00 at APC, 483 A - Malevitch | APC-TH (Seminar of the theory group of APC) | hep-th |
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| Wednesday 6 September 2017, 14:00 at IPHT, Amphi Claude Bloch, Bât. 774 | SOUTEN-TH (Soutenance de thèse) | physics |
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| Tuesday 12 September 2017, 09:00 at IPHT, Amphi Claude Bloch, Bât. 774 | SOUTEN-TH (Soutenance de thèse) | physics |
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| Friday 15 September 2017, 14:00 at IPHT, Amphi Claude Bloch, Bât. 774 | SOUTEN-TH (Soutenance de thèse) | physics |
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| Thursday 21 September 2017, 14:00 at IPHT, Amphi Claude Bloch, Bât. 774 | SOUTEN-TH (Soutenance de thèse) | physics |
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| Wednesday 27 September 2017, 14:00 at LPT, Amphi 1, bat 210, 2eme etage, LPT-Orsay | SOUTEN-TH (Soutenance de thèse) | hep-ph |
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| Monday 9 October 2017, 09:00 at IPHT, Salle Claude Itzykson, Bât. 774 | SOUTEN-TH (Soutenance de thèse) | physics |
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