Théorie

Invitation to Random Tensors

Random matrices are ubiquitous in modern theoretical physics and provide insights on a wealth of phenomena, from the spectra of heavy nuclei to the theory of strong interactions or random two dimensional surfaces. The backbone of all the analytical results in matrix models is their 1/N expansion (where N is the size of the matrix). Despite early attempts in the '90, the generalization of this 1/N expansion to higher dimensional random tensor models has proven very challenging.

Solving the flatness problem with an anisotropic instanton in Horava-Lifshitz gravity

The first half of this talk reviews the basic construction and some
known cosmological implications of a renormalizable theory of
gravitation called Horava-Lishitz gravity. In particular, I will
explain that (i) the anisotropic scaling with the dynamical critical
exponent z=3 renders a field theory of gravity renormalizable, that
(ii) the same anisotropic scaling solves the horizon problem and leads
to scale-invariant cosmological perturbations even without inflation
and that (iii) the infrared instability of the so-called projectable

Intergalactic magnetic fields

I will review the status of observations  and modelling of intergalactic magnetic fields (IGMF), with an update on recent results from gamma-ray searches. These fields, present in the voids of the Large Scale Structure (LSS) are either relics from the Early Universe or are produced in result of the star formation feedback on the LSS. I will put the observational results in the context of to possible mechanisms of generation and evolution of the IGMF.

Testing gravity with relativistic effects in large-scale structure

The distribution of galaxies provides a powerful way to probe the properties of our universe. In order to exploit this observable properly it is necessary to understand what we are really measuring when we look at the large-scale structure. Since our universe is not completely homogeneous and isotropic, we only see a distorted picture of our sky. In this talk, I will discuss the various relativistic effects that distort our observations.

Infrared QCD: perturbative or non perturbative?

A model suited for calculating correlation functions in QCD from the ultraviolet to the infrared is reviewed. The model consist in standard Faddeev-Popov Lagrangian for Landau gauge with an extra mass term for gluons. It is shown that once this mass term is included, two and three point correlation functions can be calculated with good precision at one-loop order even at very low momenta in the quenched approximation. After that, the inclusion of quarks is analyzed.

A very light dilaton and naturally light Higgs

We study a very light dilaton, arising from a scale-invariant ultraviolet theory of the Higgs sector in the standard model  of particle physics. Imposing the scale symmetry below the ultraviolet scale of the Higgs sector, we alleviate the fine-tuning problem associated with the Higgs mass. When the electroweak symmetry is spontaneously broken radiatively  a la Coleman-Weinberg, the dilaton develops a vacuum expectation value away from the origin to give an extra contribution  to the Higgs potential so that the Higgs mass is around the electroweak scale.

Caustic free completion of k-essence

Both k-essence and the pressureless perfect fluid develop caustic singularities at finite time. We explore the connection between the two and show that they belong to the same class of models, which admits the caustic free completion by means of the canonical complex scalar field. Specifically, the free massive/self-interacting complex scalar reproduces dynamics of pressureless perfect fluid/shift-symmetric k-essence under certain initial conditions in the limit of large mass/sharp self-interacting potential.

Gravitational waves from first-order phase transitions

LISA may be able to detect the gravitational waves from a first order phase transition at the electroweak scale. We present results from a large campaign of simulations studying a model of such phase transitions, and determine the shape of the power spectrum with unparalleled accuracy. We make concrete predictions of the detectability of sound waves from such a scenario, and note that an accurate measurement could place constraints on the underlying phase transition parameters.

Neutron stars: probing ultra dense (and hot) matter

Observed for the first time in 1967 as pulsars, neutron stars
represent the most extreme bodies known in nowadays universe. Relict of the
gravitational collapse and subsequent supernova explosion of a massive
star at the end of its life, they gather a mass of up to twice that of
our sun in a sphere with a radius of about 10 km. Their phenomenology
is very rich and complex. They are not only very compact, but they are
also rotating at frequencies of up to 700 Hz and can have strong

Pages

S'abonner à RSS - Théorie