1,519 research outputs found
A More Minimal Messenger Model of Gauge-Mediated Supersymmetry Breaking?
This Letter addresses a provocative question: ``Can the standard electroweak
Higgs doublets and their color-triplet partners be the messengers of a low
energy gauge-mediated SUSY breaking?" Such a possibility does not seem to be
immediately ruled out. If so, it can lead to a very economical scheme with
clear-cut predictions quite distinct from those of the conventional
gauge-mediated scenario. Namely, we get (i) a single light Higgs below the
original SUSY- breaking scale; (ii) tan(beta) = 1; (iii) flavor non-universal,
but automatically flavor-conserving soft scalar masses; (iv) a light colored
scalar with peculiar phenomenology. The familiar mu problem looses its meaning
in this approach.Comment: 10 pages, LATEX, no figure
Dynamical Supersymmetry Breaking and Low Energy Gauge Mediation
Dynamical breaking of supersymmetry was long thought to be an exceptional
phenomenon, but recent developments have altered this view. A question of great
interest in the current framework is the value of the underlying scale of
supersymmetry breaking. The "little hierarchy" problem suggests that
supersymmetry should be broken at low energies. Within one class of models, low
energy breaking be achieved as a consequence of symmetries, without requiring
odd coincidences. The low energy theories are distinguished by the presence or
absence of symmetries; in either case, and especially the latter one often
finds modifications of the minimal gauge-mediated spectrum which can further
ameliorate problems of fine tuning. Various natural mechanisms exist to solve
the problem in this framework.Comment: 20 pages (minor change in referencing
Status of the Standard Model and Beyond
We present a concise review of the status of the Standard Model and of the
search for new physics.Comment: Talk given at Winter'03 Conference
A Self Consistent Study of the Phase Transition in the Scalar Electroweak Theory at Finite Temperature
We propose the study of the phase transition in the scalar electroweak theory
at finite temperature by a two - step method. It combines i) dimensional
reduction to a 3-dimensional {\it lattice\/} theory via perturbative blockspin
transformation, and ii) either further real space renormalization group
transformations, or solution of gap equations, for the 3d lattice theory. A gap
equation can be obtained by using the Peierls inequality to find the best
quadratic approximation to the 3d action. % This method avoids the lack of self
consistency of the usual treatments which do not separate infrared and
UV-problems by introduction of a lattice cutoff. The effective 3d lattice
action could also be used in computer simulations.Comment: 3 pages, LaTeX file, contribution to Lattice 9
Remarks on the Racetrack Scheme
There are only a small number of ideas for stabilizing the moduli of string
theory. One of the most appealing of these is the racetrack mechanism, in which
a delicate interplay between two strongly interacting gauge groups fixes the
value of the coupling constant. In this note, we explore this scenario. We find
that quite generally, some number of discrete tunings are required in order
that the mechanism yield a small gauge coupling. Even then, there is no sense
in which a weak coupling approximation is valid. On the other hand, certain
holomorphic quantities can be computed, so such a scheme is in principle
predictive. Searching for models which realize this mechanism is thus of great
interest. We also remark on cosmology in these schemes.Comment: 20 pp, latex, discussion of calculability modifie
A Model of Direct Gauge Mediation
We present a simple model of gauge mediation (GM) which does not have a
messenger sector or gauge singlet fields. The standard model gauge groups
couple directly to the sector which breaks supersymmetry dynamically. This is
the first phenomenologically viable example of this type in the literature.
Despite the direct coupling, the model can preserve perturbative gauge
unification. This is achieved by the inverted hierarchy mechanism which
generates a large scalar expectation value compared to the size of
supersymmetry breaking. There is no dangerous negative contribution to the
squark, slepton masses due to two-loop renormalization group equation. The
potentially non-universal supergravity contribution to the scalar masses can be
suppressed enough to maintain the virtue of the gauge mediation. The model is
completely chiral, and one does not need to forbid mass terms for the messenger
fields by hand. Beyond the simplicity of the model, it possesses cosmologically
desirable features compared to the original models of GM: an improved gravitino
and string moduli cosmology. The Polonyi problem is back unlike in the original
GM models, but is still much less serious than in hidden sector models.Comment: LaTeX, 12 page
D-Term Inflation
We show that inflation which is dominated by the D-term density avoids the
`slow-roll' problem of inflation in supergravity. Such an inflationary scenario
can naturally emerge in theories with non-anomalous or anomalous U(1) gauge
symmetry. In the latter case the scale of inflation is fixed by the
Green--Schwarz mechanism of anomaly cancellation. The crucial point is that the
(super)gravity-mediated curvature of all the scalar fields (and, in particular,
of the inflaton), which in the standard F-dominated case is of the order of the
Hubble parameter, is absent in the D-term inflation case. The curvature of
moduli and of all other flat directions during such an inflation crucially
depends on their gauge charges.Comment: 10 pages, revtex, no figure
The Superpartner Spectrum of Gaugino Mediation
We compute the superpartner masses in a class of models with gaugino
mediation (or no-scale) boundary conditions at a scale between the GUT and
Planck scales. These models are compelling because they are simple, solve the
supersymmetric flavor and CP problems, satisfy all constraints from colliders
and cosmology, and predict the superpartner masses in terms of very few
parameters. Our analysis includes the renormalization group evolution of the
soft-breaking terms above the GUT scale. We show that the running above the GUT
scale is largely model independent and find that a phenomenologically viable
spectrum is obtained.Comment: 15 page
Supersymmetry, Axions and Cosmology
Various authors have noted that in particular models, the upper bound on the
axion decay constant may not hold. We point out that within supersymmetry, this
is a generic issue. For large decay constants, the cosmological problems
associated with the axion's scalar partner are far more severe than those of
the axion. We survey a variety of models, both for the axion multiplet and for
cosmology, and find that in many cases where the cosmological problems of the
saxion are solved, the usual upper bound on the axion is significantly relaxed.
We discuss, more generally, the cosmological issues raised by the pseudoscalar
members of moduli multiplets, and find that they are potentially quite severe.Comment: 27 pages, published version, some discussions clarifie
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