628 research outputs found
Stabilized Singlets in Supergravity as a Source of the mu-parameter
Within the context of supergravity-coupled supersymmetry, fields which are
gauge and global singlets are usually considered anathema. Their vacuum
expectation values are shifted by quadratically divergent tadpole diagrams
which are cutoff at the Planck scale, destabilizing the classical potential and
driving the singlet field to large values. We demonstrate a new and generic
mechanism which stabilizes the singlet in the presence of an extended gauge
symmetry. Such a symmetry will be broken down to the Standard Model by the
supergravity interactions near the scale of spontaneous supersymmetry-breaking
in the hidden-sector (about 10^{10-11} GeV). The resulting singlet expectation
value is stabilized and naturally of order the gravitino mass, providing
therefore a weak-scale mass for the Higgs fields of the supersymmetric Standard
Model (a "mu-parameter"). The resulting low-energy theory is the minimal
supersymmetric Standard Model, with all new fields decoupling at the
intermediate scale.Comment: 9 pages, LaTe
String corrections to gauge couplings from a field theory approach
An effective field theory approach is introduced to compute one-loop
radiative corrections to the gauge couplings due to Kaluza-Klein states
associated with a two-torus compactification. The results are compared with
those of the string in the field theory ``limit'' alpha'-> 0. The whole U and
the leading T moduli dependence of the gauge dependent part of the string
corrections to gauge couplings can be recovered using the effective field
theory approach.Comment: 8 pages, Late
Small SUSY phases in string-inspired supergravity
In supersymmetric models, there are new CP violating phases which, if
unsuppressed, would give a too large neutron electric dipole moment. We examine
the possibility of small SUSY phases in string-inspired supergravity models in
which supersymmetry is broken by the auxiliary components of the dilaton and
moduli superfields. It is found that the SUSY phases can be suppressed by a
small factor governing the breakdown of the approximate Peccei Quinn symmetries
nonlinearly realized for the moduli superfields that participate in
supersymmetry breaking. In many cases, the symmetry breaking factors are
exponentially small for moderately large values of the moduli, leading to small
phase values in a natural way.Comment: 15pages, Latex, SNUTP 93-8
Gluino Condensation in Strongly Coupled Heterotic String Theory
Strongly coupled heterotic string theory, compactified to
four dimensions on a large Calabi-Yau manifold , may represent a
viable candidate for the description of low-energy particle phenomenology. In
this regime, heterotic string theory is adequately described by low-energy
-theory on , with the two
's supported at the two boundaries of the world. In this paper we study
the effects of gluino condensation, as a mechanism for supersymmetry breaking
in this -theory regime. We show that when a gluino condensate forms in
-theory, the conditions for unbroken supersymmetry can still be satisfied
locally in the orbifold dimension . Supersymmetry is then
only broken by the global topology of the orbifold dimension, in a mechanism
similar to the Casimir effect. This mechanism leads to a natural hierarchy of
scales, and elucidates some aspects of heterotic string theory that might be
relevant to the stabilization of moduli and the smallness of the cosmological
constant.Comment: 22 pages, harvmac, no figure
Cosmological constant in SUGRA models and the multiple point principle
The tiny order of magnitude of the cosmological constant is sought to be
explained in a model involving the following ingredients: supersymmetry
breaking in N=1 supergravity and the multiple point principle. We demonstrate
the viability of this scenario in the minimal SUGRA model.Comment: 18 pages, 2 figures, Talk given at Nuclear Physics Department of the
Russian Academy of Sciences (RAS) Conference on Physics of Fundamental
Interactions, Moscow, Russia, 2-6 Dec 2002; to appear in Phys.Atom.Nuc
Stationary Points of Scalar Fields Coupled to Gravity
We investigate the dynamics of gravity coupled to a scalar field using a
non-canonical form of the kinetic term. It is shown that its singular point
represents an attractor for classical solutions and the stationary value of the
field may occur distant from the minimum of the potential. In this paper
properties of universes with such stationary states are considered. We reveal
that such state can be responsible for modern dark energy density.Comment: H. Kroger, invited talk, FFP6, Udine (2004), revised version with
corrected author lis
Some Implications of a Supersymmetric Model with R-Parity Breaking Bilinear Interactions
We investigate a supersymmetric scenario where R-parity is explicitly broken
through a term bilinear in the lepton and Higgs superfields in the
superpotential. We show that keeping such a term alone can lead to trilinear
interactions, similar to those that are parametrized by -and
in the literature, involving the physical fields. The upper limits
of such interactions are predictable from the constraints on the parameter
space imposed by the lepton masses and the neutrino mass limits. It is observed
that thus the resulting trilinear interactions are restricted to values that
are smaller than the existing bounds on most of the -and
-parameters. Some phenomenological consequences of such a scenario
are discussed.Comment: 26 Pages, 6 Postscript figures, Latex. An additional set of
references has been included. Typographic corrections have been made. Figures
remain all unchanged. An additional typographic correction has been mad
Gauged extended supergravity without cosmological constant: no-scale structure and supersymmetry breaking
We consider the interplay of duality symmetries and gauged isometries of
supergravity models giving N-extended, spontaneously broken supergravity with a
no-scale structure. Some examples, motivated by superstring and M-theory
compactifications are described.Comment: AMS-LaTeX, 16 pages. Invited paper to appear in the review section of
the IJMP
Generalizing Minimal Supergravity
In Grand Unified Theories (GUTs), the Standard Model (SM) gauge couplings
need not be unified at the GUT scale due to the high-dimensional operators.
Considering gravity mediated supersymmetry breaking, we study for the first
time the generic gauge coupling relations at the GUT scale, and the general
gaugino mass relations which are valid from the GUT scale to the electroweak
scale at one loop. We define the index k for these relations, which can be
calculated in GUTs and can be determined at the Large Hadron Collider and the
future International Linear Collider. Thus, we give a concrete definition of
the GUT scale in these theories, and suggest a new way to test general GUTs at
future experiments. We also discuss five special scenarios with interesting
possibilities. With our generic formulae, we present all the GUT-scale gauge
coupling relations and all the gaugino mass relations in the SU(5) and SO(10)
models, and calculate the corresponding indices k. Especially, the index k is
5/3 in the traditional SU(5) and SO(10) models that have been studied
extensively so far. Furthermore, we discuss the field theory realization of the
U(1) flux effects on the SM gauge kinetic functions in F-theory GUTs, and
calculate their indices k as well.Comment: RevTex4, 14 pages, 4 tables, references added, version in PL
Derivation of and in the Minimal Supersymmetric Standard Model
In the minimal supersymmetric standard model, the Higgs sector has two
unknown parameters, usually taken to be and ,
the mass of its one physical pseudoscalar particle. By minimizing the minimum
of the Higgs potential along a certain direction in parameter space, it is
shown that + radiative correction, and if one further plausible
assumption is made, .Comment: 7 pages, University of California, Riverside Report No. UCRHEP-T105
(Feb 1993). [Discussion of radiative correction is now included.
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