37 research outputs found
Can Dark Matter be an artifact of extended theories of gravity?
In this article, we propose different background models of extended theories
of gravity, which are minimally coupled to the SM fields, to explain the
possibility of genesis of dark matter without affecting the SM particle sector.
We modify the gravity sector by allowing quantum corrections motivated from (1)
local gravity and (2) non-minimally coupled gravity with SM sector and
dilaton field. Next we apply conformal transformation on the metric to
transform the action back to the Einstein frame. We also show that an effective
theory constructed from these extended theories of gravity and SM sector looks
exactly the same. Using the relic constraint observed by Planck 2015, we
constrain the scale of the effective field theory () as well as
the dark matter mass (). We consider two cases- (1) light dark matter (LDM)
and (2) heavy dark matter (HDM), and deduce upper bounds on thermally averaged
cross section of dark matter annihilating to SM particles. Further we show that
our model naturally incorporates self interactions of dark matter. Using these
self interactions, we derive the constraints on the parameters of the (1) local
gravity and (2) non-minimally coupled gravity from dark matter self
interaction. Finally, we propose some different UV complete models from a
particle physics point of view, which can give rise to the same effective
theory that we have deduced from extended theories of gravity.Comment: 45 pages, 8 figures, Accepted for publication in European Physical
Journal
Fast neutrino flavor conversions near the supernova core with realistic flavor-dependent angular distributions
It has been recently pointed out that neutrino fluxes from a supernova can
show substantial flavor conversions almost immediately above the core. Using
linear stability analyses and numerical solutions of the fully nonlinear
equations of motion, we perform a detailed study of these fast conversions,
focussing on the region just above the supernova core. We carefully specify the
instabilities for evolution in space or time, andfind that neutrinos travelling
towards the core make fast conversions more generic, i.e., possible for a wider
range of flux ratios and angular asymmetries that produce a crossing between
the zenith-angle spectra of and . Using fluxes and angular
distributions predicted by supernova simulations, we find that fast conversions
can occur within tens of nanoseconds, only a few meters away from the putative
neutrinospheres. If these fast flavor conversions indeed take place, they would
have important implications for the supernova explosion mechanism and
nucleosynthesis.Comment: 18 pages, 7 figures (Improved presentation and new panel in Fig.6
On probing turbulence in core-collapse supernovae in upcoming neutrino detectors
Neutrino propagation through a turbulent medium can be highly non-adiabatic
leading to distinct signatures in the survival probabilities. A core-collapse
supernova can be host to a number of hydrodynamic instabilities which occur
behind the shockfront. Such instabilities between the forward shock and a
possible reverse shock can lead to cascades introducing turbulence in the
associated matter profile, which can imprint itself in the neutrino signal. In
this work, we consider realistic matter profiles and seed in the turbulence
using a randomization scheme to study its effects on neutrino propagation in an
effective two-flavor framework. In particular, we find that the double-dip
feature, originally predicted in the neutrino spectra associated with forward
and reverse shocks, can be completely washed away in the presence of
turbulence, leading to total flavor depolarization. We also study the
sensitivity of upcoming neutrino detectors - DUNE and Hyper-Kamiokande- to the
power spectrum of turbulence to check for deviations from the usual Kolmogorov
() inverse power law. We find that while these experiments can effectively
constrain the parameter space for the amplitude of the turbulence power
spectra, they will only be mildly sensitive to the spectral index.Comment: 18 pages, 8 figure