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.

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.

Observational constraints and Bayesian model comparison in non-local gravity

I present the cosmological predictions of two non-local modifications of General Relativity recently proposed by our group, the so-called RT and RR models. Both models have the same number of parameters as Lambda-CDM, with a mass parameter m replacing the cosmological constant. In implementing their cosmological background and perturbations equations into the CLASS Boltzmann code, we constrain the non-local models using the Planck 2015, isotropic and anisotropic BAO, JLA supernovae, H_0 measurements and growth rate data.

Classical & Quantum Black Hole Hair from Goldstone Modes

Although there is direct experimental evidence for the existence of black holes from the recent measurements of gravitational waves,  black holes are still mysterious objects from the theoretical point of view. According to the seminal work of Stephen Hawking, all information about the collapsing matter that forms a black hole is lost during the evaporation of Hawking radiation. This loss of information is in sharp conflict with the rules of quantum mechanics.


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