24 research outputs found
Sparticle Spectrum and Dark Matter in M-Theory
The phenomenological implications of the eleven dimensional limit of
-theory (strongly coupled ) are investigated. In particular
we calculate the supersymmetric spectrum subject to constraints of correct
electroweak symmetry breaking and the requirement that the lighest
supersymmetric particle provides the dark matter of the universe. The -soft
term associated with the generation of a term in the superpotential is
calculated and its phenomenology is discussed.Comment: LaTeX file 15 pages,1 figure adde
The effect of Wilson line moduli on CP-violation by soft supersymmetry breaking terms
The CP-violating phases in the soft supersymmetry-breaking sector in orbifold
compactifications with a continuous Wilson line are investigated. In this case
the modular symmetry is the Siegel modular group of genus two. In
particular, we study the case that the hidden sector non-perturbative
superpotential is determined by the Igusa cusp form of modular
weight 12. The effect of large non-perturbative corrections to the dilaton
K\"ahler potential on the resulting CP-violating phases is also investigated.Comment: LaTeX file, 12 pages plus 7 figures, to appear in Phys.Lett.
Cosmological Inflation with orbifold moduli as inflatons
Cosmological inflation is studied in the case where the inflaton is the
overall modulus for an orbifold. General forms of the (non-perturbative)
superpotential are considered to ensure that is modular
invariant. We find generically that these models do not produce a potential
flat enough for slow roll to a supersymmetric minimum, although we do find a
model which produces up to 20 e-folds of inflation to a non-supersymmetric
minimum.Comment: LaTeX file, 16 pages including 5 figures, v3 is the published versio
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
Particle motion and gravitational lensing in the metric of a dilaton black hole in a de Sitter universe
We consider the metric exterior to a charged dilaton black hole in a de
Sitter universe. We study the motion of a test particle in this metric.
Conserved quantities are identified and the Hamilton-Jacobi method is employed
for the solutions of the equations of motion. At large distances from the black
hole the Hubble expansion of the universe modifies the effective potential such
that bound orbits could exist up to an upper limit of the angular momentum per
mass for the orbiting test particle. We then study the phenomenon of strong
field gravitational lensing by these black holes by extending the standard
formalism of strong lensing to the non-asymptotically flat dilaton-de Sitter
metric. Expressions for the various lensing quantities are obtained in terms of
the metric coefficients.Comment: 8 pages, RevTex, 1 eps figures; discussion improved; typos corrected;
references adde
CP Violation By Soft Supersymmetry Breaking Terms in Orbifold Compactifications
The possibility of spontaneous breaking of CP symmetry by the expectation
values of orbifold moduli is investigated with particular reference to
violating phases in soft supersymmetry breaking terms. The effect of different
mechanisms for stabilizing the dilaton and the form of the non-perturbative
superpotential on the existence and size of these phases is studied.
Non-perturbative superpotentials involving the absolute modular invariant
, such as may arise from F-theory compactifications, are considered.Comment: LaTeX file 12 pages, A reference amended and a typo corrected. To
appear in Phys.Lett.
Sparticle spectrum and dark matter in type I string theory with an intermediate scale
The supersymmetric particle spectrum is calculated in type I string theories
formulated as orientifold compactifications of type IIB string theory. A string
scale at an intermediate value of GeV is assumed and extra
vector-like matter states are introduced to allow unification of gauge coupling
constants to occur at this scale. The qualitative features of the spectrum are
compared with Calabi-Yau compactification of the weakly coupled heterotic
string and with the eleven dimensional supergravity limit of -theory. Some
striking differences are observed. Assuming that the lightest neutralino
provides the dark matter in the universe, further constraints on the sparticle
spectrum are obtained. Direct detection rates for dark matter are estimated.Comment: LaTeX file (10 pages+10 figures), improved references, v3: typos
fixed, accepted for publication in Physics Letters
Standard-like models from intersecting D4-branes
We construct a one-parameter set of intersecting D4-brane models, with six
stacks, that yield the (non-supersymmetric) standard model plus extra
vector-like matter. Twisted tadpoles and gauge anomalies are cancelled, and the
model contains all of the Yukawa couplings to the tachyonic Higgs doublets that
are needed to generate mass terms for the fermions.
A string scale in the range 1-10 TeV and a Higgs mass not much greater than
the current bound is obtained for certain values of the parameters,
consistently with the observed values of the gauge coupling constants.Comment: LaTeX file, 12 pages, v3 to appear in Phys. Lett.
Standard-like models from Intersecting D5-branes
We construct intersecting D5-brane orbifold models that yield the
(non-supersymmetric) standard model up to vector-like matter and
charged-singlet scalars.
The models are constrained by the requirement that twisted tadpoles cancel,
and that the gauge boson coupled to the weak hypercharge does not get
a string-scale mass via a generalised Green-Schwarz mechanism. Gauge coupling
constant ratios close to those measured are easily obtained for reasonable
values of the parameters, consistently with having the string scale close to
the electroweak scale, as required to avoid the hierarchy problem.Comment: 13 pages, LaTeX file, version to appear in Physics Letters
The Supersymmetric CP problem in Orbifold Compactifications
The possibility of spontaneous breaking of CP symmetry by the expectation
values of orbifold moduli is investigated with particular reference to
violating phases in soft supersymmetry breaking terms. The effect of different
mechanisms for stabilizing the dilaton and the form of the non-perturbative
superpotential on the existence and size of these phases is studied. Models
with modular symmetries which are subgroups of , as well as the
single overall modulus case with the full modular symmetry, are
discussed. Non-perturbative superpotentials involving the absolute modular
invariant , such as may arise from F-theory compactifications, are
considered.Comment: LaTeX file 20 pages,16 ps figures (one figure added), two references
added and typos corrected. Submitted to NP