17 research outputs found
Holographic phase transitions from higgsed, non abelian charged black holes
We find solutions of a gravity-Yang-Mills-Higgs theory in four dimensions
that represent asymptotic anti-de Sitter charged black holes with partial/full
gauge symmetry breaking. We then apply the AdS/CFT correspondence to study the
strong coupling regime of a quantum field theory at temperature and
finite chemical potential, which undergoes transitions to phases exhibiting the
condensation of a composite charged vector operator below a critical
temperature , presumably describing -wave superconductors. In the
case of -wave superconductors the transitions are always of second order.
But for -wave superconductors we determine the existence of a critical value
of the gravitational coupling (for fixed Higgs v.e.v. parameter
) beyond which the transitions become of first order. As a
by-product, we show that the -wave phase is energetically favored over the
one, for any values of the parameters. We also find the ground state
solutions corresponding to zero temperature. Such states are described by
domain wall geometries that interpolate between spaces with different
light velocities, and for a given , they exist below a critical
value of the coupling. The behavior of the order parameter as function of the
gravitational coupling near the critical coupling suggests the presence of
second order quantum phase transitions. We finally study the dependence of the
solution on the Higgs coupling, and find the existence of a critical value
beyond which no condensed solution is present.Comment: 29 pages, 43 figure
Search for gamma-ray emission from DES dwarf spheroidal galaxy candidates with Fermi-LAT data
Due to their proximity, high dark-matter (DM) content, and apparent absence of non-thermal processes, Milky Way dwarf spheroidal satellite galaxies (dSphs) are excellent targets for the indirect detection of DM. Recently, eight new dSph candidates were discovered using the first year of data from the Dark Energy Survey (DES). We searched for gamma-ray emission coincident with the positions of these new objects in six years of Fermi Large Area Telescope data. We found no significant excesses of gamma-ray emission. Under the assumption that the DES candidates are dSphs with DM halo properties similar to the known dSphs, we computed individual and combined limits on the velocity-averaged DM annihilation cross section for these new targets. If the estimated DM content of these dSph candidates is confirmed, they will constrain the annihilation cross section to lie below the thermal relic cross section for DM particles with masses 20 GeV annihilating via the bb¯ or τ+τ− channels