Théorie

Multi-messenger data of high energy neutrinos by IceCube and  gamma-rays by Tibet AS-gamma show new signal at 100 TeV energies outside of Galactic plane but below 20 degrees from it. This mysterious signal challenge conventional cosmic ray models, which predict major Galactic signal from Galactic plane and no significant flux at high galactic latitudes, as seen at GeV energies by Fermi LAT telescope.

Here we show that main assumption of continues distribution of cosmic rays in Galaxy is broken at PeV energies. 

I will present selected field theoretical aspects and Bayesian model selection studies in a particular class of modified gravity theories, so-called nonlocal gravity theories. In particular, I will focus on three nonlocal gravity models that have been proposed for explaining the late-time acceleration of the expansion of the universe and have been shown to provide a statistically equivalent fit to LCDM given recent cosmological data.

Abstract:
It is now recognized that primordial black holes (PBHs) may be produced in various models of inflation in the early universe. In this talk, I review several different scenarios of PBH formation from inflation, each of which has rather distinct features. Then I discuss how these models may be observationally tested in the not-so-distant future, particularly by gravitational wave observations.
 

Abstract. I’ll show the analysis we perform on gravitational microlensing signatures and how we estimate gravitational microlensing parameters to obtain information about several components of the dark matter in our galaxy like free-floating planets, brown dwarfs, primordial black holes, making use of actual and future space-based telescopes: Euclid, THESEUS, Gaia, Roman, etc.

We will have several talks by PhD students at the theory group:

1:30 p.m.: Konstantin Leyde, "A window for cosmic strings"

As an extension of Gabor signal processing, the covariant Weyl-Heisenberg integral quantization is implemented to transform  functions on the eight-dimensional  phase space (x,k) into Hilbertian operators. The x=(x^{\mu}) are space-time variables and the k=(k^{\mu}) are their conjugate wave vector-frequency variables. The procedure is first applied to the variables (x,k) and produces canonically conjugate essentially  self-adjoint operators.

We propose a physically sensible formulation of initial value problem for black hole perturbations in higher-order scalar-tensor theories. As a first application, we study monopole perturbations around stealth Schwarzschild solutions in a shift- and reflection-symmetric subclass of DHOST theories. In particular, we investigate the time evolution of the monopole perturbations by solving a two-dimensional wave equation and analyze the Vishveshwara’s classical scattering experiment, i.e., the time evolution of a Gaussian wave packet.

Astrophysical observations are largely based on electromagnetic signals still read with the Maxwellian massless and linear theory, possibly an approximation of a larger theory, as Newtonian gravity is for Einsteinian gravity in weak fields. Photons are the sole free massless particles in the Standard-Model (SM). Apart from massive formalisms (de Broglie-Proca, Bopp, Stueckelberg and others), the SM Extension dresses the photon of a mass dependent from the Lorentz-Poincaré symmetry violation.