“Procurando por uma Agulha no Palheiro Quântico com o LHC”
Data do Evento:
20/03/2019 - 18:00
Convite à Física 2019
Colóquios dedicados ao público geral, em especial aos alunos ingressantes da USP.
Convite à Física 2019
Colóquios dedicados ao público geral, em especial aos alunos ingressantes da USP.
In this talk, I will present two dark matter frameworks where a mass splitting in the dark sector dramatically alters the expectations for indirect detection rates. In the first case, the presence of a quasi-degenerate metastable state, where the dark matter number is stored, allows for sub-GeV relics with large s-wave annihilation cross section and not excluded by CMB bounds. In the second case, dark matter particles inelastically up-scatter in the interstellar plasma to a quasi-degenerate heavier partner, whose subsequent decays generate X-ray lines with unique spectrum and morphology.
Since the late 90's we have known that neutrinos oscillate between their three leptonian flavours, which lead to the 2015 Nobel Prize conclusion that these particles are massive. However, particle physics experiments can only tell us about the mass difference between some neutrino species and, consequently, their minimum mass. The neutrino mass hierarchy and the maximum value for the sum of their masses are still unknown. Cosmology, on the other hand, is sensitive to different aspects of neutrino physics since the number of massive neutrino species and the total sum of neutrino masses influence the evolution and formation of structure in the Universe. In this talk, I will present how a spherical harmonic analysis of the Baryon Oscillation Spectroscopic Survey (BOSS) large-scale structure galaxy sample can help set constraints on the sum of neutrino masses, their mass hierarchy and the mass of the lightest neutrino family. When combining the BOSS sample with Cosmic Microwave Background data from the Planck Satellite, Big Bang Nucleosynthesis constraints, and the latest SNe Type Ia data from the Pantheon compilation, we are able to obtain reliable neutrino mass constraints using physically motivated prior models.
We discuss the possible phases dual to the AdS hairy black holes in Horndeski theory. In the probe limit breaking the translational invariance, we study the conductivity and we find a non-trivial structure indicating a collective excitation of the charge carriers. Going beyond the probe limit, we investigate the spontaneous breaking of translational invariance near the critical temperature and discuss the stability of the theory. We consider the backreaction of the charged scalar field to the metric and we construct numerically the hairy black hole solution. To determine the dual phases of a hairy black hole, we compute the conductivity. When the wave number of the scalar field is zero, the DC conductivity is divergent due to the conservation of translational invariance. For nonzero wave parameter with finite DC conductivity, we find two phases in the dual theory. For low temperatures and for positive couplings, as the temperature is lower, the DC conductivity increases therefore the dual theory is in metal phase, while if the coupling is negative we have the opposite behavior and it is dual to an insulating phase. We argue that this behavior of the coupling of the scalar field to Einstein tensor can be attributed to its role as an impurity parameter in the dual theory.
*Local: Sala Jayme Tiomno*
