Centre de Physique Théorique


Juin 2018

Vendredi 1er juin 14:00-15:00, Amphi 5 du CPT

Geometrical construction of reduced phase spaces

Alberto Cattaneo

The reduced phase space of a field theory is the space of its possible initial conditions endowed with a natural symplectic structure. An alternative to Dirac’s method, relying on natural geometric aspects of variational problems, was introduced by Kijowski and Tulczijev. This method also has the advantage of having a natural generalization in the BV context. In this talk, I will explain the method and describe some examples, focusing in particular on the tetradic version of general relativity in four dimensions.

Vendredi 8 juin 14:00-15:00, Amphi 5 du CPT

Chern-Weil theorem and boundary terms in gravity actions

Nelson MERINO (APC, Paris)

There are two mathematical approaches that are commonly used in the construction of gravity theories : tensorial and Cartan language. It is usually said that they are completely equivalent and that the translation between them should be evident. However, as we show in this work, there are cases where a result in one side is not clearly understood in the other, because the translation is not obvious. This is the case of the Katz procedure, which being constructed in the tensorial language, allows to have a well-defined variational principle and to define finite conserved charges in general relativity. Up to now, it was not known how this method reads in Cartan language, neither how it could be generalized to more general theories (e.g., Einstein-Gauss-Bonnet and Lovelock gravity). In this work we use the Chern-Weil theorem and a topological-algebraic structure called transgression form to provide the translation of the Katz boundary term into the Cartan language. As a consequence, this gives us a guideline to make the generalization of the Katz procedure for a generic Lovelock gravity.

Du 11 au 15 juin, Paris

NetSci 2018

NetSci 2018, the flagship conference of the Network Science Society, aims to bring together leading researchers and practitioners working in the emerging area of network science. The conference fosters interdisciplinary communication and collaboration in network science research across computer and information sciences, physics, mathematics, statistics, the life sciences, neuroscience, environmental sciences, social sciences, finance and business, arts and design.

Mercredi 13 juin 14:00-15:00, Amphi 5 du CPT

Approche Hamilton-Jacobi pour des modèles venant de la biologie évolutive

Sepideh Mirrahimi (IMT, Université de Toulouse)


Nous nous intéressons à une classe d’équations intégro-différentielles paraboliques venant de la biologie évolutive. Ces équations décrivent la dynamique d’une population structurée par trait phénotypique sous l’effet des mutations et de la sélection. Les solutions de ces équations se concentrent, à la limite de petite diffusion (mutations) et en temps long, sous forme de masses de Dirac.
Dans cet exposé, nous présentons les ingrédients de base d’une approche basée sur des équations de Hamilton-Jacobi avec contrainte pour étudier ce type de problème. En outre, à travers un exemple où on considère un environnement qui varie périodiquement en temps, on montre comment cette approche peut mener à des résultats quantitatifs pour des applications en biologie.

Vendredi 15 juin 14:00-15:00, Amphi 5 du CPT

Walking and multi-scale dynamics from gauge-gravity duality

Daniel ELANDER, Lab. Charles Coulomb, Montpellier

Strongly coupled theories exhibiting walking dynamics provide a scenario for beyond the Standard Model physics, in which electro-weak symmetry is broken dynamically and the large hierarchy between the electro-weak and Planck energy scales is naturally generated. In this talk, we discuss the construction of walking and multi-scale theories within the context of gauge-gravity duality, focusing in particular on the circumstances under which a parametrically light composite state, the dilaton, is present in the spectrum. The examples we provide come both from bottom-up models as well as top-down models embedded in M-theory and type-IIB supergravity, and include the baryonic branch of the Klebanov-Strassler field theory, as well as an example of a three-dimensional field theory with a strongly coupled IR fixed point.

Vendredi 29 juin 14:00-15:00, Amphi 5 du CPT

Cosmological Implications of Electroweak Monopole

Yongmin Cho (Konkuk and Seoul Universities)

We discuss the cosmological production and the successive evolution of the electroweak monopole in the standard model, and estimate the remnant monopole density at present universe. We con-firm that, although the electroweak phase transition is of the fi-rst order, it is very mildly fi-rst order.
So, the monopole production arises from the thermal fluctuations of the Higgs -field after the phase transition, not the vacuum bubble collisions during the phase transition. Moreover, while the monopoles are produced copiously around the Ginzburg temperature T_G \simeq 59.6 TeV, most of
them are annihilated as soon as created. This annihilation process continues very long, untill the temperature cools down to about 29.5 MeV. As the result the remnant monopole density in the present universe becomes very small, of 10^-􀀀11 of the critical density, too small to a-ect the standard cosmology and too small comprise a major component of dark matter. We discuss the
physical implications of our results on the ongoing monopole detection experiments, in particular on MoEDAL, IceCube, ANTARES, and Auger.