The QCD axion, precisely

The QCD axion is probably the most robust solution to the strong CP
problem and a natural dark matter candidate. While its properties, such as the
mass and the couplings, are mostly determined by non-perturbative QCD effects
I will present recent computations demonstrating that they can be reliably
extracted with percent accuracy, which is important for the theory
interpretation of experimental results. I will also discuss some recent
lattice QCD results highlighting a departure from the usual instanton

Naturalness in the Aristotelian Spacetime

Some of the most fundamental puzzles in theoretical physics can be phrased as puzzles of technical naturalness. Examples include the cosmological constant problem, the Higgs mass hierarchy problem, the linear scaling of resistivity with temperature in the strange metal phase of high-tempterature superconductors etc. I will re-examine the notion of technical naturalness in systems whose short-distance behavior exhibits nonrelativistic symmetries of "Aristotelian spacetime", pointing out various surprises and novelties, with possible applications in particle phenomenology, cosmology and con

Carroll Symmetry, Gravitational Memory and Soft Gravitons

In the first part of my talk I will discuss the notion of
relativity principle, kinematic algebras, the classification of Leblond and Bacry I will define
the Carroll group and its extensions. I will gave Applications to very
special Relativity String theory and the BMS algebras. In the second part I will discuss
plane gravitational waves and how the a subgroup of the Carroll group acts and how this can be used
illuminate the currently fashionable topics of gravitational memory and soft

Making the halo of Andromeda with the QCD Axion?

The QCD axion is a curious Dark Matter candidate, having a mass like the neutrino, but behaving as Cold Dark Matter during linear structure formation. I will review how this occurs, and speculate on the interesting question of how axions make galactic halos during non-linear structure formation, and whether observations could distinguish them from WIMPs.

The SM Higgs as the origin of the hot Big Bang

Under general circumstances, the Standard Model (SM) Higgs is excited in the form of a condensate during or towards the end of inflation. The Higgs condensate is then forced to decay afterwards — due to non-perturbative effects — into the rest of the SM species. I will present the cosmological implications of this primordial decay, quantifying the necessary conditions to achieve a successful mechanism for 'reheating’ the Universe into the SM. If there is enough time, I will also discuss the implications for primordial gravitational waves.

Boundary effects in entanglement entropy

Entanglement entropy is a useful tool which plays an important role in modern physics. The geometrical nature of entanglement entropy explains why it finds so many applications in various fields of physics, from black holes and holography to integrable models and quantum computers.

Infrared effects in de Sitter spacetime: nonperturbative treatment of secular terms

The study of interacting quantum fields in de Sitter geometry reveals
peculiarities that are of conceptual and phenomenological interest. In
this geometry, the exponential expansion of the metric produces an
effective growth in the self-interaction of light fields, breaking down
the standard perturbative expansion. Furthermore, in the massless limit
the free propagators do not respect the symmetries of the classical
theory, and neither do they decay at large distances.

Emergent gravity in graphene and in Dirac/Weyl semimetals

In graphene in the presence of strain the elasticity theory metric naturally appears. However, this is not the one experienced by fermionic quasiparticles. Fermions propagate in curved space, whose metric is defined by expansion of the effective Hamiltonian near the topologically protected Fermi point. We calculate the corresponding emergent gravitational fields. Next, we extend our consideration to the case, when the dislocations are present.

Interactions between inclusions in fluid two-dimensional membranes

Biological membranes are fluid surfaces with an elastic Hamiltonian function of the local curvature, mean and Gaussian. Proteins, that are included in such surfaces, deform them, and interact via the deformation they create. Since membranes exhibit large thermal fluctuations, these interactions have a 'Casimir' character. Proteins can be out-of-equilibrium objects actively changing conformation, while the membrane in which they live exhibit a complex dynamics ruled by the bilayer structure of the membrane. Proteins thus experience nontrivial dynamical interactions.

The new relationship between inflation and gravitational waves

It is well known that the amplitude of the gravitational wave (GW) produced from the vacuum fluctuation during inflation is proportional to the energy scale of inflation. Thus the observation of the inflationary GW by CMB B-mode is expected to reveal the energy scale of new physics as well as pin down the inflation model. However, alternative production mechanisms of GW during inflation has been discussed recently. We consider a coupled system between an axion and SU(2) gauge fields whose energy density is subdominant.

LABORATOIRE

ASTROPARTICULE & COSMOLOGIE

Théorie