1,771 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
Naturalness of parity breaking in a supersymmetric SO(10) model
We consider a supersymmetric SO(10) model which remains renormalisable upto
Planck scale. The cosmology of such a model passes through a Left-Right
symmetric phase. Potential problems associated with domain walls can be evaded
if parity breaking is induced by soft terms when supersymmetry breaks in the
hidden sector. The smallness of this breaking permits a brief period of
domination by the domain walls ensuring dilution of gravitinos and other
unwanted relics. The requirement that domain walls disappear constrains some of
the soft parameters of the Higgs potential.Comment: 4 pages, To appear in Proceedings of SUSY06, the 14th International
Conference on Supersymmetry and the Unification of Fundamental Interactions,
UC Irvine, California, 12-17 June 200
Graceful exit via monopoles in a theory with O'Raifeartaigh type supersymmetry breaking
We study the stability of supersymmetry breaking metastable vacua and
supersymmetric vacua in the presence of solitons. The metastable vacua of
supersymmetric QCD and those found elsewhere such as in models based on the
SU(5) grand unified group support the existence of topological solitons. The
vacua containing such topological defects can become unstable against decay
into lower energy configurations. We show for a specific model that a finite
region of the available parameter space of couplings becomes disallowed due to
the presence of monopoles. In a manner similar to previous studies based on
cosmic strings, it is shown that soliton solutions arising in supersymmetric
theories can put constraints on the range of allowed values of the couplings
arising in the theories. Implications for cosmology are discussed.Comment: 20 pages, 7 figure
Cosmology in a supersymmetric model with gauged
We consider salient cosmological features of a supersymmetric model which is
Left-Right symmetric and therefore possessing gauged symmetry. The
requirement of breaking parity and also obtaining charge preserving vacua
introduces some unique features to this model (MSLRM), resulting in a
preference for non-thermal Leptogenesis. Assuming that the model preserves TeV
scale supersymmetry, we show that the vacuum structure generically possesses
domain walls, which can serve two important purposes. They can signal a
secondary inflation required to remove unwanted relics such as gravitino and
moduli and also generate lepton asymmetry by a mechanism similar to electroweak
baryogenesis. The requirement of disappearance of domain walls imposes
constraints on the soft parameters of the theory, testable at the TeV scale. We
also propose an alternative model with spontaneous parity violation
(MSLR\rlap/P). Incorporating the same cosmological considerations in this case
entails constraints on a different set of soft parameters.Comment: 18 pages. Minor changes in text, but conclusion remains same.
Published in Phys. Rev.
Neutrino and astroparticle physics : Working group report
The contributions made to the Working Group activities on neutrino and
astroparticle physics are summarised in this article. The topics discussed were
leptogenesis in Left-Right symmetric model, inflationary models in
Raman-Sundrum scenarios, ultra high energy cosmic rays and neutrino
oscillations in 4 flavour and decaying neutrino models.Comment: 11 pages; arXiv copy of contribution to WHEPP-6 proceeding
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