68 research outputs found
Magnetic domain walls of relic fermions as Dark Energy
We show that relic fermions of the Big Bang can enter a ferromagnetic state
if they possess a magnetic moment and satisfy the requirements of Stoner theory
of itinerant ferromagnetism. The domain walls of this ferromagnetism can
successfully simulate Dark Energy over the observable epoch spanning
billion years. We obtain conditions on the anomalous magnetic moment of such
fermions and their masses. Known neutrinos fail to satisfy the requirements
thus pointing to the possibility of a new ultralight sector in Particle
Physics.Comment: Essentially same as version 2; to appear in AIP proceedings of PASCOS
200
Gauged B-L unification and cosmology
We discuss some cosmological implications of low energy gauged B-L symmetry
with and without supersymmetry. Generic possibility of leptogenesis from a
domain wall driven first order phase transition is shown to be a characteristic
of such models.Comment: 6 pages. Talk given at IWTHEP 2007, IIT Roorke
Production and decay rates of excited leptons in a left-right symmetric scenario
We merge two leading Beyond Standard Model scenarios, namely compositeness
and left-right symmetry, and probe the resulting collider signatures in the
leptonic case. The constraints on composite models for fermions leave open the
possibility of vector like excitations of Standard Model (SM) fermions. Here we
consider the possibility of low scale left-right gauge symmetry , with the simplifying assumption that the
right like excited sector of fermions is significantly heavier than the
excitations of the left chiral fermions. It is found that the right handed
currents still contribute to observable processes, and alter the existing
bounds on the scale of compositeness. The cross section times branching ratio
of the photon decay channel is strongly depressed, bringing down the exclusion
limit of the mass of excited electrons from about 2 TeV to below 1 TeV. On the
other hand, cross section times branching ratio of the Z decay channel is
significantly enhanced and remains greater than that of the photon channel. We
thus propose analyzing the Z decay channel in existing collider data in order
to search for signature of left-right symmetry as well as excited leptons with
masses above 1 TeV.Comment: 10 figures updated. Incorporated constraints from muon anomalous
magnetic moment, and lepton flavour violation processes. Table I adde
Spontaneously broken parity and consistent cosmology with transitory domain walls
Domain wall structure which may form in theories with spontaneously broken
parity is generically in conflict with standard cosmology. It has been argued
that Planck scale suppressed effects can be sufficient for removing such domain
walls. We study this possibility for three specific evolution scenarios for the
domain walls, with evolution during radiation dominated era, during matter
dominated era, and that accompanied by weak inflation. We determine the
operators permitted by the supergravity formalism and find that the field
content introduced to achieve desired spontaneous parity breaking makes
possible Planck scale suppressed terms which can potentially remove the domain
walls safely. However, the parity breaking scale, equivalently the majorana
mass scale of the right handed neutrino, does get constrained in some of
the cases, notably for the matter dominated evolution case which would be
generic to string theory inspired models giving rise to moduli fields. One
left-right symmetric model with only triplets and bidoublets is found to be
more constrainted than another admitting a gauge singlet
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