9,658 research outputs found
3.5 keV X-ray Line Signal from Decay of Right-Handed Neutrino due to Transition Magnetic Moment
We consider the dark matter model with radiative neutrino mass generation
where the Standard Model is extended with three right-handed singlet neutrinos
(, and ) and one additional SU(2) doublet scalar .
One of the right-handed neutrinos (), being lightest among them, is a
leptophilic fermionic dark matter candidate whose stability is ensured by the
imposed symmetry on this model. The second lightest right-handed
neutrino () is assumed to be nearly degenerated with the lightest one
enhancing the co-annihilation between them. The effective interaction term
among the lightest, second lightest right-handed neutrinos and photon
containing transition magnetic moment is responsible for the decay of heavier
right-handed neutrino to the lightest one and a photon ().
This radiative decay of heavier right-handed neutrino %to the the lightest one
with charged scalar and leptons in internal lines could explain the X-ray line
signal keV recently claimed by XMM-Newton X-ray observatory from
different galaxy clusters and Andromeda galaxy (M31). The value of the
transition magnetic moment is computed and found to be several orders of
magnitude below the current reach of various direct dark matter searches. The
other parameter space in this framework in the light of the observed signal is
further investigated.Comment: 11 Pages LaTeX, 2 Figures, 1 Tabl
Finite size scaling in crossover among different random matrix ensembles in microscopic lattice models
Using numerical diagonalization we study the crossover among different random
matrix ensembles [Poissonian, Gaussian Orthogonal Ensemble (GOE), Gaussian
Unitary Ensemble (GUE) and Gaussian Symplectic Ensemble (GSE)] realized in two
different microscopic models. The specific diagnostic tool used to study the
crossovers is the level spacing distribution. The first model is a one
dimensional lattice model of interacting hard core bosons (or equivalently spin
1/2 objects) and the other a higher dimensional model of non-interacting
particles with disorder and spin orbit coupling. We find that the perturbation
causing the crossover among the different ensembles scales to zero with system
size as a power law with an exponent that depends on the ensembles between
which the crossover takes place. This exponent is independent of microscopic
details of the perturbation. We also find that the crossover from the
Poissonian ensemble to the other three is dominated by the Poissonian to GOE
crossover which introduces level repulsion while the crossover from GOE to GUE
or GOE to GSE associated with symmetry breaking introduces a subdominant
contribution. We also conjecture that the exponent is dependent on whether the
system contains interactions among the elementary degrees of freedom or not and
is independent of the dimensionality of the system.Comment: 15 pages, 8 figure
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