33 research outputs found
Exact solution of multi-angle quantum many-body collective neutrino flavor oscillations
I study the flavor evolution of a dense neutrino gas by considering vacuum
contributions, matter effects and neutrino self-interactions. Assuming a system
of two flavors in a uniform matter background, the time evolution of the
many-body system in discretized momentum space is computed. The multi-angle
neutrino-neutrino interactions are treated exactly and compared to both the
single-angle approximation and mean field calculations. %The time unit chosen
is . The mono-energetic two neutrino
beam scenario is solved analytically. I proceed to solve flavor oscillations
for mono-energetic cubic lattices and quadratic lattices of two energy levels.
In addition I study various configurations of twelve, sixteen, and twenty
neutrinos. I find that when all neutrinos are initially of the same flavor, all
methods agree. When both flavors are present, I find collective oscillations
and flavor equilibration develop in the many body treatment but not in the mean
field method. This difference persists in dense matter with tiny mixing angle
and it can be ascribed to non-negligible flavor polarization correlations being
present. Entanglement entropy is significant in all such cases. The relevance
for supernovae or neutron stars mergers is contingent upon the value of the
normalization volume and the large dependence of the timescale
associated with oscillations. In future work, I intend to study this dependence
using larger lattices and also include anti-neutrinos
Rate of dark photon emission from electron positron annihilation in massive stars
We calculate the rate of production of dark photons from electron-positron
pair annihilation in hot and dense matter characteristic of supernova
progenitors. Given the non-linear dependence of the emission rate on the dark
photon mass and current astrophysical constraints on the dark photon parameter
space, we focus on the mass range of 1--10 MeV. For the conditions under
consideration both mixing with the in-medium photon and plasma effects on the
electron dispersion relation are non-negligible and are explored in detail. We
perform our calculations to the leading order in the fine-structure constant.
Transverse and longitudinal photon modes are treated separately given their
different dispersion relations. We consider the implications for the evolution
of massive stars when dark photons decay either into particles of the standard
model or of the dark sector.Comment: 6 pages, 4 figure
Charmonium in lattice QCD and the non-relativistic quark-model
We compare the results of a numerical lattice QCD calculation of the
charmonium spectrum with the structure of a general non-relativistic potential
model. To achieve this we form the non-relativistic reduction of
derivative-based fermion bilinear interpolating fields used in lattice QCD
calculations and compute their overlap with c-cbar meson states at rest
constructed in the non-relativistic quark model, providing a bound-state model
interpretation for the lattice data. Essential gluonic components in the
bound-states, usually called hybrids, are identified by considering
interpolating fields that involve the gluonic field-strength tensor and which
have zero overlap onto simple c-cbar model states