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Le serveur de séminaires SEMPARIS accueille toutes les annonces de séminaires de la région parisienne, dans tous les domaines de la physique et des mathématiques. Il vous permet aussi de recevoir par courrier électronique la sélection de votre choix. Enfin, il permet l'archivage des présentations au format PDF ou Powerpoint.   [ Plus d'informations ]


Séminaires à venir
[ vue agenda ]

Lundi 23 Juillet 2018, 11:00 à IHES, Amphithéâtre Léon Motchane MATH-IHES (TBA) hep-th
Ralph Kaufmann ( Purdue University & IHES ) Hopf algebras from Feynman categories
Abstract: We introduce Feynman categories and show that they naturally define bi-algebras. In good circumstances these bi-algebras 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 Connes-Kreimer used in QFT as examples of the general theory. Co-actions also appear naturally in this context as we will explain.

Jeudi 26 Juillet 2018, 11:30 à IPN, Bâtiment 100, Salle A015
( $ $ )
IPN-THEO (Séminaire du groupe de physique théorique de l'IPN Orsay) nucl-th
Marc Dupuis ( CEA, DAM, DIF ) Advances in microscopic modeling of (n,$x$n$\gamma$) reactions for actinides
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 pre-compound 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 axially-symmetric deformed quasi-particle random-phase approximation (QRPA) calculations [2]. Direct inelastic scattering to target excitations built from one-phonon QRPA states accounted simultaneously for direct inelastic scattering to discrete states, and pre-equilibrium emission as far as second order processes, that involve more complex excitations such as two-phonon states, and multiple emission remain negligible. The QRPA nuclear structure approach has also been applied recently to determine, for a large pannel of even-even nuclei, E1 and M1 photon strength functions [3], that play a key-role in the modeling of statistical reactions.\\ We will review the status on the ongoing work on direct/pre-compound neutron emission for neutron induced reaction below 20~MeV for even-even actinides. Target states are described as rotational bands built from each state in the target intrinsic frame, described as QRPA one-phonon 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 inter-band gamma transitions [4]. For these reactions, the role played by the present microscopic approach for direct/pre-equilibrium emission is discussed. We finally focus on the impact on the determination of (n,n'$\gamma$) cross sections of newly calculated QRPA E1- and M1-photon 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.
Fichiers attachés:
  • 2018_07_26_M_Dupuis.pdf (301044 bytes) OPEN

Lundi 3 Septembre 2018, 14:00 à IPHT, Amphi Claude Bloch, Bât. 774 SCOPI (Séminaire SCOPI Paris-Saclay) physics
(tba) (TBA)

Lundi 10 Septembre 2018, 13:30 à IPHT, Amphi Claude Bloch, Bât. 774 SOUTEN-TH (Soutenance de thèse) physics
Séverin Charbonnier ( IPhT ) (TBA)

Mardi 11 Septembre 2018, 14:00 à APC, 483 A - Malevitch APC-TH (Seminar of the theory group of APC) hep-th
Rodrigo Olea TBA

Mardi 18 Septembre 2018, 11:00 à IPHT, Salle Claude Itzykson, Bât. 774 IPHT-SEM (Séminaire du IPHT) physics
Pierre Vanhove ( IPhT ) L?attraction de la gravitation
Abstract: La force de gravité est la seule force universelle. Elle agit sur toutes les formes de matière et d’énergie. Elle conditionne la structure et la dynamique de notre Univers, dont notre compréhension est intimement liée au modèle théorique de la gravité. La détection des ondes gravitationnelles ouvre une nouvelle fenêtre d’observation sur la nature de la gravité. La théorie des cordes nous enseigne sur des aspects fondamentaux de cette force et sa relation avec les autres forces fondamentales. \par Dans cet exposé, nous expliquerons les difficultés à penser la gravité et ce que l’on peut espérer découvrir sur la nature fondamentale de cette force mystérieuse.

Mardi 18 Septembre 2018, 14:00 à APC, 483 A - Malevitch APC-TH (Seminar of the theory group of APC) hep-th
Gabriel Leon ( National University of La Plata, Argentina ) Observational constraints on inflationary potentials within the quantum collapse framework
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 tensor-to-scalar 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.

Mardi 25 Septembre 2018, 14:00 à APC, 483 A - Malevitch APC-TH (Seminar of the theory group of APC) hep-th
Suratna Das ( IIT Kanpur ) The `unitarity problem' of Higgs inflation in the light of collapse dynamics
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 CSL-like collapse dynamics, otherwise applied to inflationary dynamics in order to explain the quantum-to-classical transition of primordial quantum modes, can bring down the value of non-minimal coupling considerably.

Mardi 2 Octobre 2018, 14:00 à APC, 483 A - Malevitch APC-TH (Seminar of the theory group of APC) hep-th
Emilian Dudas ( CPHT - Ecole Polytechnique ) TBA

Vendredi 5 Octobre 2018, 10:00 à IPHT, Salle Claude Itzykson, Bât. 774
( https://courses.ipht.cnrs.fr/?q=en/node/220 )
COURS (Cours) astro-ph|gr-qc
Thibault Damour ( IHES ) From Classical Gravity to Quantum Amplitudes (1/4)
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 One-Body (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 two-body systems, from traditional post-Newtonian computations of the effective two-body 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 - post-Newtonian theory of the motion of point particles; \\ 3 - Multipolar post-Minkowskian theory of the gravitational radiation of general sources; \\ 4 - Effective One-Body (EOB) theory of the motion and radiation of binary systems. \par The EOB formalism was initially based on a resummation of post-Newtonian-expanded results. The post-Newtonian 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 post-Newtonian description of the motion and radiation of binary black holes to the strong-field, high-velocity regime reached during the last orbits, and the merger. EOB theory initially used a dictionary to translate post-Newtonian-expanded results on (slow-motion) 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 post-Minkowskian approach which does not assume that velocities are small. This led to new insights in the high-energy limit of gravitational scattering and opened the way to transcribe quantum gravitational scattering amplitudes into their EOB Hamiltonian description. For instance, some two-loop ultra high-energy quantum scattering results of Amati, Ciafaloni and Veneziano could be transcribed into an improved knowledge of the high-energy limit of the classical gravitational interaction of two black holes. This leads also to interesting predictions about a linear-Regge-trajectory behavior of high-angular-momenta, high-energy circular orbits.
Fichiers attachés:
  • 2018_Damour.pdf (4806153 bytes) OPEN

Mercredi 10 Octobre 2018, 14:00 à IPHT, Amphi Claude Bloch, Bât. 774 SOUTEN-TH (Soutenance de thèse) physics
Santiago Migliaccio ( IPhT ) (TBA)

Vendredi 12 Octobre 2018, 10:00 à IPHT, Salle Claude Itzykson, Bât. 774
( https://courses.ipht.cnrs.fr/?q=en/node/220 )
COURS (Cours) astro-ph|gr-qc
Thibault Damour ( IHES ) From Classical Gravity to Quantum Amplitudes (2/4)
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 One-Body (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 two-body systems, from traditional post-Newtonian computations of the effective two-body 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 - post-Newtonian theory of the motion of point particles; \\ 3 - Multipolar post-Minkowskian theory of the gravitational radiation of general sources; \\ 4 - Effective One-Body (EOB) theory of the motion and radiation of binary systems. \par The EOB formalism was initially based on a resummation of post-Newtonian-expanded results. The post-Newtonian 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 post-Newtonian description of the motion and radiation of binary black holes to the strong-field, high-velocity regime reached during the last orbits, and the merger. EOB theory initially used a dictionary to translate post-Newtonian-expanded results on (slow-motion) 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 post-Minkowskian approach which does not assume that velocities are small. This led to new insights in the high-energy limit of gravitational scattering and opened the way to transcribe quantum gravitational scattering amplitudes into their EOB Hamiltonian description. For instance, some two-loop ultra high-energy quantum scattering results of Amati, Ciafaloni and Veneziano could be transcribed into an improved knowledge of the high-energy limit of the classical gravitational interaction of two black holes. This leads also to interesting predictions about a linear-Regge-trajectory behavior of high-angular-momenta, high-energy circular orbits.
Fichiers attachés:
  • 2018_Damour.pdf (4806309 bytes) OPEN

Vendredi 19 Octobre 2018, 10:00 à IPHT, Salle Claude Itzykson, Bât. 774
( https://courses.ipht.cnrs.fr/?q=en/node/220 )
COURS (Cours) astro-ph|gr-qc
Thibault Damour ( IHES ) From Classical Gravity to Quantum Amplitudes (3/4)
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 One-Body (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 two-body systems, from traditional post-Newtonian computations of the effective two-body 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 - post-Newtonian theory of the motion of point particles; \\ 3 - Multipolar post-Minkowskian theory of the gravitational radiation of general sources; \\ 4 - Effective One-Body (EOB) theory of the motion and radiation of binary systems. \par The EOB formalism was initially based on a resummation of post-Newtonian-expanded results. The post-Newtonian 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 post-Newtonian description of the motion and radiation of binary black holes to the strong-field, high-velocity regime reached during the last orbits, and the merger. EOB theory initially used a dictionary to translate post-Newtonian-expanded results on (slow-motion) 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 post-Minkowskian approach which does not assume that velocities are small. This led to new insights in the high-energy limit of gravitational scattering and opened the way to transcribe quantum gravitational scattering amplitudes into their EOB Hamiltonian description. For instance, some two-loop ultra high-energy quantum scattering results of Amati, Ciafaloni and Veneziano could be transcribed into an improved knowledge of the high-energy limit of the classical gravitational interaction of two black holes. This leads also to interesting predictions about a linear-Regge-trajectory behavior of high-angular-momenta, high-energy circular orbits.
Fichiers attachés:
  • 2018_Damour.pdf (4806309 bytes) OPEN

Vendredi 19 Octobre 2018, 14:15 à IPHT, Salle Claude Itzykson, Bât. 774
( https://courses.ipht.cnrs.fr/?q=en/node/220 )
COURS (Cours) astro-ph|gr-qc
Thibault Damour ( IHES ) From Classical Gravity to Quantum Amplitudes (4/4)
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 One-Body (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 two-body systems, from traditional post-Newtonian computations of the effective two-body 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 - post-Newtonian theory of the motion of point particles; \\ 3 - Multipolar post-Minkowskian theory of the gravitational radiation of general sources; \\ 4 - Effective One-Body (EOB) theory of the motion and radiation of binary systems. \par The EOB formalism was initially based on a resummation of post-Newtonian-expanded results. The post-Newtonian 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 post-Newtonian description of the motion and radiation of binary black holes to the strong-field, high-velocity regime reached during the last orbits, and the merger. EOB theory initially used a dictionary to translate post-Newtonian-expanded results on (slow-motion) 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 post-Minkowskian approach which does not assume that velocities are small. This led to new insights in the high-energy limit of gravitational scattering and opened the way to transcribe quantum gravitational scattering amplitudes into their EOB Hamiltonian description. For instance, some two-loop ultra high-energy quantum scattering results of Amati, Ciafaloni and Veneziano could be transcribed into an improved knowledge of the high-energy limit of the classical gravitational interaction of two black holes. This leads also to interesting predictions about a linear-Regge-trajectory behavior of high-angular-momenta, high-energy circular orbits.
Fichiers attachés:
  • 2018_Damour.pdf (4806309 bytes) OPEN

Mercredi 24 Octobre 2018, 14:15 à IPHT, Salle Claude Itzykson, Bât. 774 IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires) hep-th
Pablo Cano ( UAM ) (TBA)

Vendredi 28 Décembre 2018, 16:00 à LPT, 114 LPT-PTH (Particle Theory Seminar of LPT Orsay) hep-ph
Mathias Pierre ( LPT Orsay ) Dark matter phenomenology: from simplified WIMP models to refined alternative solutions
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 non-abelian 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 non-thermal scenarios.

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