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Séminaires à venir  [30 suivants]  
[ vue agenda ] 
Lundi 24 Septembre 2018, 10:45 à LPTMC, Jussieu tower 1213 room 523  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat.meshall 



Abstract:  In Nature exceptional permeability and selectivity properties are reached, for example ion channels are able to distinguish with high throughput very similar ions like Sodium and Potassium. The paradigm change as compared to nanoscale technology is that these biological filters are outofequilibrium, submitted to either thermal or active fluctuations – for example of the pore constriction. Here we investigate how outofequilibrium fluctuations of a pore may affect the translocation dynamics, in particular dispersion coefficients. Our findings demonstrate a complex interplay between transport and surface wiggling and elucidate the impact of pore agitation in a broad range of artificial and biological porins, but also, at larger scales, in vascular motion in fungi, intestinal contractions and microfluidic surface waves. These results open up the possibility that transport across membranes can be actively tuned by external stimuli, with potential applications to nanoscale pumping, osmosis and dynamical ultrafiltration.  
Fichiers attachés: 
Lundi 24 Septembre 2018, 11:00 à IPHT, Salle Claude Itzykson, Bât. 774  IPHTPHM (Séminaire de physique mathématique)  mathph 



Abstract:  Recently, there has been observed several connections of integrable models to supersymmetric gauge theories and special functions of hypergeometric type. One of such connections is a correspondence between supersymmetric quiver gauge theories and integrable lattice models such that the integrability emerges as a manifestation of supersymmetric dualities. Particularly, partition functions of supersymmetric quiver gauge theories with four supercharge on different manifolds can be identified with partition functions of twodimensional exactly solvable statistical models. This relationship has led to the construction of new exactly solvable models of statistical mechanics, namely the YangBaxter equation was solved in terms of new special functions. In the talk, I will review this progress and present some new solutions of the YangBaxter equation. 
Lundi 24 Septembre 2018, 11:00 à IAP, Salle des séminaires  SEMGRECO (Séminaire du GReCO : groupe de GRavitation et COsmologie à l'IAP)  hepth 



Abstract:  Ultralight bosons exist in various proposed extensions to the Standard Model, which can form condensates around rapidly rotating black holes through a process called superradiance. These boson clouds have many interesting observational consequences, such as the continuous emission of monochromatic gravitational waves. In this talk, I will describe the dynamics of the system when it is part of a binary black hole. I will show that the presence of a binary companion greatly enriches the evolution of the boson clouds, most remarkably through the existence of resonant transitions between growing and decaying modes of the clouds. Finally, I will sketch some phenomenological consequences, both for the gravitational waves emitted by the clouds and the finitesize effects imprinted in the waveforms of the binary signal. (basé sur 1804.03208 ) 
Lundi 24 Septembre 2018, 13:30 à LPA, Conf IV E244  LPA (Séminaire du laboratoire Pierre Aigrain)  condmat 



Abstract:  Collective phenomena originating from interactions between light and matter have become a major focus of interest spanning different fields of research. Quantum materials represent ideal test beds for the investigation of novel phenomena induced by the lightmatter interaction. By allowing the creation of entangled quantum states of light and collective matter excitations, cavity quantum electrodynamics offers a fascinating platform in this context. In this talk I will discuss how a cooperative effect between longrange correlations induced by the lightmatter interaction and strong electron interactions intrinsic to quantum materials can lead to the stabilization of coherent phases of light and matter. By studying a simple model of interacting electrons coupled to a single mode cavity field I will show that a phase characterized by the simultaneous condensation of excitons and photon superradiance, the “superradiant excitonic insulator" (SXI) can be realized. Superradiance cannot be reached in the absence of electronic interactions. At the same time coupling with the cavity field promotes excitonic condensation in regimes of temperature and interaction where it cannot be stabilized in the absence of lightmatter coupling. Therefore the SXI intertwines excitonic condensation and superradiance in conditions where the two phases cannot be individually stabilized in the absence of such cooperative effect. I will discuss probes as photon spectra and optical conductivity of the hybrid lightmatter system. 
Mardi 25 Septembre 2018, 11:00 à LPTMS, LPTMS, salle 201, 2ème étage, Bât 100, Campus d'Orsay  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  physics 



Abstract:  When a wave such as light propagates through a disordered system, it is scattered many times in various directions before escaping. At first sight, this process is well described by diffusion. However, diffusion neglects interferences, making us believe that the information content of a wave is progressively lost through spreading. This picture is incorrect. In fact, multiple scattering is a linear process that redistributes information among many degrees of freedom which can nowadays be resolved and manipulated. In this talk, we will give an overview of different strategies to achieve original light transport properties in open disordered systems that deviate both from the diffusive picture and the Gaussian field model. First, we will characterize the statistical properties of the transmission matrix to demonstrate large energy transfer or focusing through nominally opaque media [1, 2]. Then, we will discuss how to achieve similar performance in transmission by means of the reflection matrix only [3, 4]. Finally, we will characterize the distribution of scattering times, in order to generate excitations with particularly short or long dwell times. References: [1] A. Goetschy and A. D. Stone, Filtering Random Matrices: The Effect of Incomplete Channel Control in Multiple Scattering, Phys. Rev. Lett. 111, 063901 (2013) [2] C. W. Hsu, S. F. Liew, A. Goetschy, H. Cao, and A. D. Stone, Correlationenhanced control of wave focusing in disordered media, Nature Phys. 13, 497 (2017) [3] N. Fayard, A. Goetschy, R. Pierrat and R. Carminati, Mutual Information between Reflected and Transmitted Speckle Images, Phys. Rev. Lett. 120, 073901 (2018) [4] I. Starshynov, A. M. PaniaguaDiaz, N. Fayard, A. Goetschy, R. Pierrat, R. Carminati and J. Bertolotti, NonGaussian Correlations between Reflected and Transmitted Intensity Patterns Emerging from Opaque Disordered Media, Phys. Rev. X 8, 021041 (2018) 
Mardi 25 Septembre 2018, 11:30 à LPTENS, LPTENS library  STRLPTENSHE (Séminaire commun LPTENS/LPTHE)  hepth 


Mardi 25 Septembre 2018, 14:00 à APC, 646 A  Mondrian  APCTH (Seminar of the theory group of APC)  hepth 



Abstract:  Higgs Inflation is no doubt one of the most favoured models of inflation in present time. But the huge non minimal coupling of the Higgs field with gravity required for the model to work often raises concern which is dubbed as the 'unitarity problem' of Higgs inflation. We will show that CSLlike collapse dynamics, otherwise applied to inflationary dynamics in order to explain the quantumtoclassical transition of primordial quantum modes, can bring down the value of nonminimal coupling considerably. 
Mardi 25 Septembre 2018, 14:00 à LPTHE, Library  LPTHEPPH (Particle Physics at LPTHE)  hepph 



Abstract:  I will discuss different frameworks addressing the strong CP problem in the Standard Model. First, I will discuss axion solutions which are testable at colliders and a broad physics program to hunt for them. Second, I will explain how the strong CP problem can be solved without an axion at high scale and connected to flavor physics. 
Mardi 25 Septembre 2018, 16:00 à IPHT, Salle Claude Itzykson, Bât. 774  IPHTHEP (Séminaire de physique des particules et de cosmologie)  hepph 



Abstract:  It is generally believed that modification of general relativity inevitably introduce extra physical degree(s) of freedom. In this talk I argue that this is not the case by constructing modified gravity theories with two local physical degrees of freedom. After classifying such theories into two types, I show explicit examples and discuss their cosmology and phenomenology. 
Mercredi 26 Septembre 2018, 10:00 à
LPTM,
MIR Neuville 1 rue Descartes, 95000 NeuvillesurOise. ( https://www.ucergy.fr/fr/laboratoires/labolptm/actualitesdulaboratoire/quant2018.html )  WORKCONF (Workshop or Conference)  mathph 



Abstract:  The Laboratoire de Physique Théorique et Modélisation (LPTM) organises a threeday workshop aiming at bringing together specialists in quantum technologies and the members of the computer sciences, mathematics and physics laboratories of the University of CergyPontoise. This event is associated with the activities of the Institut d'études avancées (IEA) and the foreseen curriculum development on the subject. 
Mercredi 26 Septembre 2018, 11:30 à LPTENS, LPTENS Library  STRINT (Strings, integrability and beyond)  hepth 



Abstract:  We construct Roperators, the general solution of the YangBaxter equation, in a uniform way for three symmetry algebras: SL(2,C)symmetry, Faddeev modular double symmetry (qdeformation) and Sklyanin's algebra symmetry (elliptic deformation). 
Mercredi 26 Septembre 2018, 13:45 à DPTPHYSENS, Jussieu  Tour 1323  2e étage, salle 210.  SEMPHYSENS (Colloquium du Département de Physique de l'ENS)  quantph 



Abstract:  Measurements of the finestructure constant are powerful tests of the consistency of theory and experiment in physics. Using the recoil frequency of cesium133 atoms in a matterwave interferometer, we recorded a measurement of the finestructure constant α = 1/137.035999046(27) at 0.20 parts per billion accuracy using multiphoton interactions such as Bragg diffraction and Bloch oscillations. Comparison with Penning trap measurements of the electron gyromagnetic anomaly via the Standard Model of particle physics has implications for darksector candidates and electron substructure. We will close with an outlook on future applications of matterwave interferometry. 
Mercredi 26 Septembre 2018, 14:15 à IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 


Mercredi 26 Septembre 2018, 14:30 à LPTENS, LPTENS Library  STRINT (Strings, integrability and beyond)  hepth 



Abstract:  The talk will present the derivation of a class of planar 4point Feynman diagrams for 2D Fishnet conformal theory. These graphs are the 2D analogue of what has been computed by Basso and Dixon in the paper titled “Gluing ladders into Fishnets” for 4dimensional spacetime. Our computation of diagrams is based on Separation of Variables for the SL(2,C) spin chain, and is valid for different choices of bare propagators in the graph. 
Jeudi 27 Septembre 2018, 10:00 à IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Jeudi 27 Septembre 2018, 11:40 à IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  The minimal D = 5, N = 2 gauged supergravity will be discussed in relation to the recently proposed clockwork mechanism. The minimal embedding requires one vector multiplet in addition to the supergravity multiplet and the clockwork scalar is identified with the scalar in the vector multiplet. The scalar has a twoparameter potential and it can accommodate the clockwork, the RandallSundrum and a noscale model with a flat potential, depending on the values of the parameters. The continuous clockwork background breaks half of the original supersymmetries, leaving a D = 4, N = 1 theory on the boundaries.generating powerlaw hierarchies. 
Jeudi 27 Septembre 2018, 16:00 à LPT, 114  LPTPTH (Particle Theory Seminar of LPT Orsay)  hepph 



Abstract:  I will discuss an approach to the scalar hierarchy problem that draws on concepts that have so far been primarily applied to certain dynamical systems. These are systems that are naturally driven to critical points and are maintained there by dynamical internal adjustment (i.e. by avalanche phenomena, slippage, etc). Motivated in part by conjecture and experimental hints that some such systems exhibit log periodic scaling associated with complex valued scaling dimensions, I will discuss a 5 dimensional dual to a renormalization group trajectory that runs towards a regime of approximate discrete scale invariance. Such behavior is forbidden as a "healthy" trajectory, and is dual to an emergent BreitenlohnerFreedman tachyon instability for scalar fields in AdS space. We explore how bulk 5D physics responds to this instability, and how this model might simultaneously relate to the lightness of the Higgs and issues of cosmology through a mechanism akin to frustration in condensed matter systems. 
Vendredi 28 Septembre 2018, 11:00 à LPTHE, Bibliothèque  SEMLPTHE (Séminaire du LPTHE)  condmat.statmech 



Abstract:  Topological phases exist beyond the standard GinzburgLandau paradigm that dominated the understanding of phases and phase transitions in condensed matter systems. Paradigmatic examples have been derived to establish a new theoretical basis that takes into consideration these topological aspects. The spin 1 Haldane phase is one of them for the unidimensional case. The seminar presents a way to implement this phase as well as its suggested generalizations by focusing using ultracold fermionic alkalineearth atoms, that involve an internal SU(N) symmetry. The model describing the experiment is called the doublewell model and depicts a lattice of two interacting chains. The model is analysed at weak coupling, strong coupling and using a numerical tool : DMRG. 
Vendredi 28 Septembre 2018, 14:15 à IPHT, Itzykson  SEMEXCEP (Séminaire exceptionel)  hepth 


Lundi 1 Octobre 2018, 10:45 à LPTMC, Jussieu tower 1213 room 523  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat.meshall 



Abstract:  Consider a statistical system evolving on a state space of graphical structures, such as e.g. a social network system. Given a set of transitions on such a system, where each transition consists of a local transformation pattern applied at random to the system's state (e.g. adding a new edge, deleting an edge,...), one may define a continuoustime Markov chain in order to study the stochastic evolution of the system. Our novel approach to this problem involves an extension of Doi's description of chemical reaction systems in terms of boson creation and annihilation operators (which later evolved into the DoiPeliti formalism) to a general stochastic mechanics framework based on the idea of socalled rule algebras. Assuming no prior familiarity with the underlying concept of graph rewriting and related mathematics, I will give an introduction to the formalism and present a number of application examples. 
Lundi 1 Octobre 2018, 11:00 à IPHT, Salle Claude Itzykson, Bât. 774  IPHTPHM (Séminaire de physique mathématique)  mathph 



Abstract:  We identify theÂ persistence probability for the spin located at the origin of a halfspace magnetized GlauberIsing chain as a Fredholm Pfaffian gap probability generating function with a sechkernel. This is then recast asÂ a taufunction for a certain Painlevé VI transcendent  a sort of exact Kramers' formulaÂ for the associated explicitelyÂ timedependent Hamiltonian Â where the persistence exponent emerges as an asymptotic decay rate. By aÂ known yet remarkable correspondence that relates Painlevé equations to Bonnet surfaces, the persistence probability has also a geometric meaning Ã la GaussBonnet in terms of the intrinsic curvature of the underlying surface. Since the sameÂ sechkernel with an underlying Pfaffian structure shows up in a variety of Gaussian firstpassage problems, our Painlevé VI characterization appears as aÂ universal probability distribution akin to the famous Painlevé II TracyWidom laws. Its tail behaviorÂ in the magnetizationsymmetric case allows in particular to recover the exact value 3/16 for the persistence exponent of a 2d diffusing random field, as found very recently by Poplavskyi and Schehr (arXiv:1806.11275). Due to its topological origin, this value should constitute the superuniversal persistence exponent for the coarsening of a nonconserved scalar order parameter in two space dimensions. 
Lundi 1 Octobre 2018, 11:00 à IAP, Salle des séminaires  SEMGRECO (Séminaire du GReCO : groupe de GRavitation et COsmologie à l'IAP)  astroph 



Abstract:  We present the results of a new fieldtheoretic simulation of cosmological axion strings, which are eight times longer than previous ones. We have upgraded our previous simulation of physical strings in terms of the number of grids as well as the suite of analysis methods. These improvements enable us to monitor a variety of quantities characterizing the dynamics of the physical string network for the longest term ever. Our extended simulations have revealed that global strings do not evolve according to the scaling solution, but that its scaling parameter, or the number of long strings per horizon, increases logarithmically in time. In addition, we have also found that the scaling parameter shows nontrivial dependence on the breaking scale of the PecceiQuinn symmetry. 
Lundi 1 Octobre 2018, 14:15 à IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 



Abstract:  (TBA) 
Mardi 2 Octobre 2018, 11:30 à LPTENS, LPTENS library  STRLPTENSHE (Séminaire commun LPTENS/LPTHE)  hepth 


Mardi 2 Octobre 2018, 14:00 à APC, 412 B  Rothko  APCTH (Seminar of the theory group of APC)  hepth 


Vendredi 5 Octobre 2018, 10:00 à
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=en/node/220 )  COURS (Cours)  astrophgrqc 



Abstract:  The recent observation of gravitational wave signals from inspiralling and coalescing binary black holes has been significantly helped, from the theoretical side, by the availability of analytical results on the motion and gravitational radiation of binary systems. \par The course will deal with the Effective OneBody (EOB) theory of the motion and radiation of binary systems, and explain the links between this formalism and various classical and quantum approaches to gravitationally interacting twobody systems, from traditional postNewtonian computations of the effective twobody action to quantum gravitational scattering amplitudes. \par The following analytical techniques will be reviewed ab initio: \\ 1  Matched Asymptotic Expansions approach to the motion of black holes and neutron stars; \\ 2  postNewtonian theory of the motion of point particles; \\ 3  Multipolar postMinkowskian theory of the gravitational radiation of general sources; \\ 4  Effective OneBody (EOB) theory of the motion and radiation of binary systems. \par The EOB formalism was initially based on a resummation of postNewtonianexpanded results. The postNewtonian approach assumes small gravitational potentials and small velocities, and loses its validity during the last orbits before the merger of black holes. The resummed EOB approach was able to extend the validity of the postNewtonian description of the motion and radiation of binary black holes to the strongfield, highvelocity regime reached during the last orbits, and the merger. EOB theory initially used a dictionary to translate postNewtonianexpanded results on (slowmotion) bound states of gravitationally interacting binary systems into the (resummed) Hamiltonian of a particle moving in an effective external gravitational field. \par The second part of the course will present the recent extension of EOB theory to the description of (classical) scattering states within the postMinkowskian approach which does not assume that velocities are small. This led to new insights in the highenergy limit of gravitational scattering and opened the way to transcribe quantum gravitational scattering amplitudes into their EOB Hamiltonian description. For instance, some twoloop ultra highenergy quantum scattering results of Amati, Ciafaloni and Veneziano could be transcribed into an improved knowledge of the highenergy limit of the classical gravitational interaction of two black holes. This leads also to interesting predictions about a linearReggetrajectory behavior of highangularmomenta, highenergy circular orbits.  
Fichiers attachés: 
Vendredi 5 Octobre 2018, 11:00 à APC, TBA  APCCOLLOQUIUM (Colloquium de l'APC)  astroph 



Abstract:  Disséquée par la lunette de Galilée, la Voie Lactée perdait, avec son mystère, son identité d’objet céleste, elle n’était plus qu’un « tas d’étoiles ». Au fil d’une relecture de quelques contributions qui jalonnent les quatre siècles écoulés, on voudrait montrer le cheminement d’idées et d'observations par où l’objet physique « Voie Lactée » a réémergé lentement, de l’intérieur. Non seulement comme concept, mais comme système mesurable, lié par la gravitation, avant qu’on y reconnaisse l'écosystème premier, la matrice des matrices, la mère des mondes planétaires, l'unité de production de la complexité, et qu’on lui cherche des géniteurs dans l'avant incertain des fluctuations primordiales, tout près du commencement. 
Lundi 8 Octobre 2018, 14:00 à IPHT, Salle Claude Itzykson, Bât. 774  IPHTSTA (Séminaire de Physique Statistique, CEA/Saclay)  condmat 



Abstract:  We study the statistics of the kinetic (or equivalently potential) energy for $N$ noninteracting fermions in a 1d harmonic trap of frequency $\omega$, at finite temperature $T$. Remarkably, we find an exact solution for the full distribution of the kinetic energy, at any temperature $T$ and for any $N$. As a function of temperature $T$, and for large $N$, we identify: (i) a quantum regime, for $T \sim \hbar\omega$, where quantum fluctuations dominate and (ii) a thermal regime, for $T \sim N \hbar \omega$, governed by thermal fluctuations. We show how the mean, the variance, as well as the large deviation function associated with the distribution of the kinetic energy cross over from the quantum to the thermal regime as $T$ increases. \\ \\ J. Grela, S.N. Majumdar, G. Schehr, Phys. Rev. Lett., 119, 130601 (2017) \\ A. Grabsch, S.N. Majumdar, G. Schehr, C. Texier, SciPost Phys. 4, 014 (2018) 
Mardi 9 Octobre 2018, 11:00 à LPTMS, LPTMS, salle 201, 2ème étage, Bât 100, Campus d'Orsay  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  physics 



Abstract:  From nanometerscale proteins to micronscale colloidal particles, particles in biological and soft matter systems undergo Brownian dynamics: their deterministic motion due to external forces and interactions competes with the random diffusion due to thermal noise. In the absence of forces, all trajectories look alike: the key information characterizing the system’s dynamics thus lies in its force field. However, reconstructing the force field by inspecting microscopy observations of the system’s trajectory is a hard problem, for two reasons. First, there needs to be enough information about the force available in the trajectory: the effect of the force field becomes apparent only after a long enough observation time. Second, one needs a practical method to extract that information and reconstruct the force field, which is challenging for force fields with a spatial structure, in particular in the presence of measurement noise. Here we address these two problems for steadystate Brownian trajectories. We first give a quantitative meaning to the information contained in a trajectory, and show how it limits force inference. We then propose a practical procedure to optimally use this information to reconstruct the force field by decomposing it into moments. Using simple model stochastic processes, we demonstrate that our method permits a quantitative evaluation of phase space forces and currents, circulation, and entropy production with a minimal amount of data. 
Mardi 9 Octobre 2018, 15:00 à
LPTENS,
LPTENS library ( Unusual time. )  STRLPTENSHE (Séminaire commun LPTENS/LPTHE)  hepth 


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