750 research outputs found
Gauge Coupling Constant Unification With Planck Scale Values Of Moduli
Convergence of the standard model gauge coupling constants to a common value
at around GeV is studied in the context of orbifold theories
where the modular symmetry groups for and moduli are broken to
subgroups of . The values of the moduli required for this
unification of coupling constants are studied for this case and also for the
case where string unification is accompanied by unification to a gauge group
larger then Comment: Tex, 15 pages, minor typos corrected and some references adde
CP-violating phases in the CKM matrix in orbifold compactifications
The picture of CP-violation in orbifold compactifications in which the
-modulus is at a complex fixed point of the modular group is studied.
CP-violation in the neutral kaon system and in the neutron electric dipole
moment are both discussed. The situation where the -modulus takes complex
values on the unit circle which are not at a fixed point is also discussed.Comment: LaTeX file 17 page
Phase Structure of Color Superconductivity
We investigate color superconductivity and chiral symmetry restoration at
finite temperature and baryon density in the frame of standard two flavor
Nambu--Jona-Lasinio model. We derive the diquark mass in RPA, discuss its
constraint on the coupling constant in the diquark channel, and find a strong
competition between the two phase transitions when the coupling constant is
large enough.Comment: Talk presented at Conference on Non-Perturbative Quantum Field
Theory: Lattice and Beyond, Guangzhou, China, Dec.16--18, 200
An exact renormalization group approach to frustrated magnets
Frustrated magnets are a notorious example where usual perturbative methods
fail. Having recourse to an exact renormalization group approach, one gets a
coherent picture of the physics of Heisenberg frustrated magnets everywhere
between d=2 and d=4: all known perturbative results are recovered in a single
framework, their apparent conflict is explained while the description of the
phase transition in d=3 is found to be in good agreement with the experimental
context.Comment: 4 pages, Latex, invited talk at the Second Conference on the Exact
Renormalization Group, Rome, September 2000, for technical details see
http://www.lpthe.jussieu.fr/~tissie
Dark Matter Constraints in Heterotic M-Theory with Five-Brane Dominance
The phenomenological implications of the M-theory limit in which
supersymmetry is broken by the auxiliary fields of five-brane moduli is
investigated.
Assuming that the lightest neutralino provides the dark matter in the
universe, constraints on the sparticle spectrum are obtained. Direct detection
rates for dark matter are estimated.Comment: 10 pages, LaTeX file plus 8 EPS figure
Vacuum fluctuations in a supersymmetric model in FRW spacetime
We study a noninteracting supersymmetric model in an expanding FRW spacetime.
A soft supersymmetry breaking induces a nonzero contribution to the vacuum
energy density. A short distance cutoff of the order of Planck length provides
a scale for the vacuum energy density comparable with the observed cosmological
constant. Assuming the presence of a dark energy substance in addition to the
vacuum fluctuations of the field an effective equation of state is derived in a
selfconsistent approach. The effective equation of state is sensitive to the
choice of the cut-off but no fine tuning is needed.Comment: 19 pages, accepted for publication in Phys. Rev.
CP Violation and Moduli Stabilization in Heterotic Models
The role of moduli stabilization in predictions for CP violation is examined
in the context of four-dimensional effective supergravity models obtained from
the weakly coupled heterotic string. We point out that while stabilization of
compactification moduli has been studied extensively, the determination of
background values for other scalars by dynamical means has not been subjected
to the same degree of scrutiny. These other complex scalars are important
potential sources of CP violation and we show in a simple model how their
background values (including complex phases) may be determined from the
minimization of the supergravity scalar potential, subject to the constraint of
vanishing cosmological constant.Comment: 8 Pages. Based on a talk given at the CP Violation Conference,
University of Michigan, Ann Arbor, November 4-18, 2001, correction to Eq.
(27
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