# Mercredi 3 mai 2017

### Hot topics in Modern Cosmology

Hot Topics in Modern Cosmology, Spontaneous Workshop XI,

Co-organisée par R. Triay (CPT)

Spontaneous Workshop (SW) brings together specialists on recent insights in Particle Physics, Astrophysics and Cosmology. The aim is to stimulate debate on common topics in views of providing us with innovating ideas on emerging problems. The workshop’s organization is based on an optimal number of concise presentations and with enough space for discussions in order to favour interactions among participants. Postdocs and PhD students are encouraged to attend.

14h00 – 15h00, Amphi 5 du CPT

### Résumé

We are interested in the Lyapunov exponent of ergodic Schrödinger cocycles when those have potentials that are mixed quasi-periodic and random.
These cocycles occur in the analysis of solutions to the discrete Schrödinger equation on $\mathbb Z$ at energy E where the potential is defined with that type of ergodic dynamics :
[-(u_n+1+u_n-1)+v_n u_n = E u_n\textrm with v_n=\lambda (W_n(\omega)+V(x+n\alpha)).]
Many results have been obtained separately in the purely quasi-periodic (Dinaburg-Sinai, Bourgain, Goldstein, Avila, Jitomyrskaya, etc.) or purely random cases (Thouless, Aizenmann-Molchanov, Figotin-Pastur, Chulaevsky and Spencer, Sadel and Schulz-Baldes, etc.).
We will expose our main result for the mixed potential : an asymptotic development for the Lyapunov exponent of Schrödinger cocycles at small coupling ($\lambda\to 0$) similar to the pre-existing results in the non-mixed regimes, with some restrictions on the energy parameter $E$.

15h30 – 16h30, Amphi 5 du CPT

### Can we detect a graviton ?

#### Pierre Van Hove (Institut de Physique Théorique, CEA)

The direct detection of gravitational waves provides an extraordinary confirmation of the general relativity. This opens a new window on our observable Universe. Shortly after having formulated the theory of general relativity, Albert Einstein said that quantum mechanism requires modifying his new theory of gravity. Today, we are still looking for experimental and observational indication of quantum gravity effects.

I will present the point of view of effective field theory approach to gravity. This approach allows computing classical general relativity effects as well as quantum gravity effects. I will explain that at large distance some quantum gravity effects are universal being independent of the high-energy description. This approach may be a route for finding signature of quantum gravity.

Slides of the talk are available at