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 ] 
Friday 20 July 2018, 14:00 at LPTHE, Library 4th Floor  LPTHEPPH (Particle Physics at LPTHE)  hepph 


Monday 23 July 2018, 11:00 at IHES, Amphithéâtre Léon Motchane  MATHIHES (TBA)  hepth 



Abstract:  We introduce Feynman categories and show that they naturally define bialgebras. In good circumstances these bialgebras have Hopf quotients. Corresponding to several levels of sophistication and decoration (both terms have technical definitions), we recover the Hopf algebras of Goncharov and Brown from number theory, a Hopf algebra of Baues used in the analysis of double loop spaces and the various Hopf algebras of ConnesKreimer used in QFT as examples of the general theory. Coactions also appear naturally in this context as we will explain. 
Thursday 26 July 2018, 11:30 at
IPN,
Bâtiment 100, Salle A015 ( $ $ )  IPNTHEO (Séminaire du groupe de physique théorique de l'IPN Orsay)  nuclth 



Abstract:  Recent developments in nuclear structure approaches offer a great mean to improve various aspects of nuclear reaction modeling and to further understand reaction mechanisms from a microscopic point of view. Recently, direct and precompound nucleon emission, for nucleon induced reaction on spherical and axially deformed nuclei, have been successfully modeled [1] using a description of target states provided by fully consistent axiallysymmetric deformed quasiparticle randomphase approximation (QRPA) calculations [2]. Direct inelastic scattering to target excitations built from onephonon QRPA states accounted simultaneously for direct inelastic scattering to discrete states, and preequilibrium emission as far as second order processes, that involve more complex excitations such as twophonon states, and multiple emission remain negligible. The QRPA nuclear structure approach has also been applied recently to determine, for a large pannel of eveneven nuclei, E1 and M1 photon strength functions [3], that play a keyrole in the modeling of statistical reactions.\\ We will review the status on the ongoing work on direct/precompound neutron emission for neutron induced reaction below 20~MeV for eveneven actinides. Target states are described as rotational bands built from each state in the target intrinsic frame, described as QRPA onephonon excitation of the intrinsic correlated ground state. QRPA excitations which display a collective character can thus be viewed as vibrational band heads. Couplings between states of the GS band and states belonging to an excited band are accounted for within a coupled channel framework. Our approach in then applied to the modeling of (n,n'$\gamma$) reactions and for both intra and interband gamma transitions [4]. For these reactions, the role played by the present microscopic approach for direct/preequilibrium emission is discussed. We finally focus on the impact on the determination of (n,n'$\gamma$) cross sections of newly calculated QRPA E1 and M1photon strength functions, that enter the description of statistical decay from compound nucleus states in the continuum.\\ [1] M. Dupuis, E. Bauge, S. Hilaire, F. Lechaftois, S. Péru, N. Pillet and C. Robin, Eur. Phys. J. A, 51 12 (2015) 168.\\[.1cm] [2] S. Péru,G. Gosselin, M. Martini, M. Dupuis, S. Hilaire, and J.C. Devaux, Phys. Rev. C 014314 (2011).\\[.1cm] [3] S. Goriely, S. Hilaire, S. Péru, M. Martini, I. Deloncle, and F. Lechaftois Phys. Rev. C 94, 044306 (2016); M. Martini, S. Péru, S. Hilaire, S. Goriely, and F. Lechaftois, Phys. Rev. C 94, 014304 (2016).\\[.1cm] [4] M. Dupuis, S. Hilaire, S. Péru, E. Bauge, M. Kerveno, P. Dessagne and G. Henning EPJ Web Conf., 146 (2017) 12002.  
Attachments: 
Monday 3 September 2018, 14:00 at IPHT, Amphi Claude Bloch, Bât. 774  SCOPI (Séminaire SCOPI ParisSaclay)  physics 


Monday 10 September 2018, 13:30 at IPHT, Amphi Claude Bloch, Bât. 774  SOUTENTH (Soutenance de thèse)  physics 


Tuesday 11 September 2018, 14:00 at APC, 483 A  Malevitch  APCTH (Seminar of the theory group of APC)  hepth 


Tuesday 18 September 2018, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTSEM (Séminaire du IPHT)  physics 



Abstract:  La force de gravitÃ© est la seule force universelle. Elle agit sur toutes les formes de matiÃ¨re et dâ€™Ã©nergie. Elle conditionne la structure et la dynamique de notre Univers, dont notre comprÃ©hension est intimement liÃ©e au modÃ¨le thÃ©orique de la gravitÃ©. La dÃ©tection des ondes gravitationnelles ouvre une nouvelle fenÃªtre dâ€™observation sur la nature de la gravitÃ©. La thÃ©orie des cordes nous enseigne sur des aspects fondamentaux de cette force et sa relation avec les autres forces fondamentales. \par Dans cet exposÃ©, nous expliquerons les difficultÃ©s Ã penser la gravitÃ© et ce que lâ€™on peut espÃ©rer dÃ©couvrir sur la nature fondamentale de cette force mystÃ©rieuse. 
Tuesday 18 September 2018, 14:00 at APC, 483 A  Malevitch  APCTH (Seminar of the theory group of APC)  hepth 



Abstract:  The inflationary paradigm is the most successful model for the generation of primordial perturbations. These perturbations have a purely quantum origin, while the inhomogeneities and anisotropies observed today exhibit a classical behavior. The model called Continuous Spontaneous Localization (CSL) is a proposed mechanism to solve the measurement problem in quantum mechanics. In this presentation, we will analyze the theoretical predictions resulting from incorporating the CSL model into the inflationary Universe. In particular, the predictions for the scalar spectral index and the tensortoscalar ratio are different from the standard ones. Based on these predictions, we will show that the inflationary potentials allowed by recent observational data are different from the traditional approach. 
Tuesday 25 September 2018, 14:00 at APC, 483 A  Malevitch  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. 
Tuesday 2 October 2018, 14:00 at APC, 483 A  Malevitch  APCTH (Seminar of the theory group of APC)  hepth 


Friday 5 October 2018, 10:00 at
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.  
Attachments: 
Wednesday 10 October 2018, 14:00 at IPHT, Amphi Claude Bloch, Bât. 774  SOUTENTH (Soutenance de thèse)  physics 


Friday 12 October 2018, 10:00 at
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.  
Attachments: 
Friday 19 October 2018, 10:00 at
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.  
Attachments: 
Friday 19 October 2018, 14:15 at
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.  
Attachments: 
Wednesday 24 October 2018, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 


Friday 28 December 2018, 16:00 at LPT, 114  LPTPTH (Particle Theory Seminar of LPT Orsay)  hepph 



Abstract:  Weakly Interacting Massive Particles (WIMPs) are among the best motivated dark matter candidates. However, in light of non conclusive detection signals and strong constraints from collider, direct and indirect detection experiments, I will start by giving an overview of the WIMP paradigm in the context of simplified dark matter models. I will then discuss models considering extended gauge structures such as constructions involving generalized Chern Simons couplings and a specific WIMP scenario motivated by flavor anomalies. In a second part, I will discuss an alternative dark matter thermal production mechanism by showing an explicit realization of the Strongly Interacting Massive Particles (SIMPs) paradigm in the context of a nonabelian hidden gauge structure. In a last part I will discuss the strong impact of the reheating stage of the universe on the dark matter density production in the context of nonthermal scenarios. 

[ English version ] 