4,644 research outputs found

### Low-Energy Effective Lagrangian from Non-Minimal Supergravity with Unified Gauge Symmetry

From general supergravity theory with unified gauge symmetry, we obtain the
low-energy effective Lagrangian by taking the flat limit and integrating out
the superheavy fields in model-independent manner. The scalar potential
possesses some excellent features. Some light fields classified by using
supersymmetric fermion mass, in general, would get intermediate masses at the
tree level after the supersymmetry is broken. We show that the stability of
weak scale can be guaranteed under some conditions. There exist extra
non-universal contributions to soft supersymmetry breaking terms which can give
an impact on phenomenological study.Comment: 37 pages, Figures not include

### Low-Energy Effective Lagrangian in Unified Theories with Non-Universal Supersymmetry Breaking Terms

Supersymmetric grand unified theories with non-universal soft supersymmetry
breaking terms are studied. By integrating out the superheavy fields at an
unification scale, we compute their low-energy effective Lagrangian. We find
new contributions to the scalar potential specific to the non-universal
supersymmetry breaking. $D$-term contribution to the scalar masses is one
example. The gauge hierarchy achieved by a fine-tuning in the superpotential
would be violated in general due to the non-universal SUSY breaking terms. We
show, however, it is preserved for a certain class of the soft terms derived
from a {\em hidden} ansatz. We also discuss some phenomenological implications
of the non-universal supersymmetry breaking, including predictions of the
radiative electroweak symmetry breaking scenario and of no-scale type models.Comment: 29 pages, LaTeX, DPSU-9402,LBL-35731,UCB-PTH-94/16,TU-45

### Options for Orbifold-GUT Model Building from Five-Dimensional Supergravity

This is the first paper of a series that will examine the options for
embedding supersymmetric orbifold-GUTs into five-dimensional N=2
Yang-Mills-Einstein supergravity theories (YMESGTs). In particular, we focus on
the allowed couplings of charged hypermultiplets in the lowest dimensional reps
of the gauge groups SU(5), SO(10) and E(6). Our results are within the
classification of homogeneous quaternionic scalar manifolds. In the minimal
coupling of a generation of bulk matter hypermultiplets, supergravity requires
the field content of an SO(10) scenario. In the minimal coupling of $n$ bulk
generations of matter and higgs hypermultiplets, supergravity requires the
field content of an E(6) scenario.
We also discuss the coupling of tensors and non-compact gaugings in 5D
YMESGTs, which can serve as alternative ways to obtain four-dimensional Higgs
sectors. Charged tensor couplings seem to be difficult to work with
phenomenologically since a U(1) gauge factor is always required when they are
present, and it is not clear if tensors can be put in unified multiplets with
other fields, if this is desired. This seems to imply that tensor coulpings in
GUT scenarios may be better suited in higher dimensional settings. The
non-compact gaugings discussed here are simple, and offer a novel unification
scenario in which the supergravity and vector multiplets are connected by gauge
transformations.
The main points are summarized in tables and the conclusion. Although the
discussion is in the spirit of a "bottom-up" approach, M-theory is taken as a
motivating background.Comment: V.2 Significant changes: shortened, typos corrected, main focus of
paper emphasized. Submitted to Nucl. Phys.

### Teleparallel Gravity and Dimensional Reductions of Noncommutative Gauge Theory

We study dimensional reductions of noncommutative electrodynamics on flat
space which lead to gauge theories of gravitation. For a general class of such
reductions, we show that the noncommutative gauge fields naturally yield a
Weitzenbock geometry on spacetime and that the induced diffeomorphism invariant
field theory can be made equivalent to a teleparallel formulation of gravity
which macroscopically describes general relativity. The Planck length is
determined in this setting by the Yang-Mills coupling constant and the
noncommutativity scale. The effective field theory can also contain
higher-curvature and non-local terms which are characteristic of string theory.
Some applications to D-brane dynamics and generalizations to include the
coupling of ordinary Yang-Mills theory to gravity are also described.Comment: 31 pages LaTeX; References adde

### Topics in String Unification

I discuss several aspects of strings as unified theories. After recalling the
difficulties of the simplest supersymmetric grand unification schemes I
emphasize the distinct features of string unification. An important role in
constraining the effective low energy physics from strings is played by
$duality$ symmetries. The discussed topics include the unification of coupling
constants (computation of $\sin ^2\theta _W$ and $\alpha _s$ at the weak
scale), supersymmetry breaking through gaugino condensation, and properties of
the induced SUSY-breaking soft terms. I remark that departures from
universality in the soft terms are (in contrast to the minimal SUSY model)
generically expected.Comment: 22 pages. Talk given at the ``Workshop on Electroweak Physics Beyond
the Standard Model'', Valencia, 3-5 October 199

### Charge Quantization and Neutrino Mass from Planck-scale SUSY

We show a possibility for the charge quantization of the standard model (SM)
particles. If a global symmetry makes the three copies of a generation and
supersymmetry (SUSY) relates the Higgs boson to a lepton, all the charges of
the SM particles can be quantized through gauge-anomaly cancellation. In the
minimal model realizing the possibility, the gravitino mass around the
Planck-scale is needed to generate the SM couplings through (quantum)
supergravity. Much below the Planck-scale, the SM is obtained as the effective
theory. Interestingly, if the gaugino masses are generated through anomaly
mediation, one of the neutrino masses is predicted to be around the neutrino
oscillation scales. In an extension of the model, millicharged particles can
exist without introducing massless hidden photons.Comment: 17 pages, v2: version appears in PL

### Kahler Stabilized, Modular Invariant Heterotic String Models

We review the theory and phenomenology of effective supergravity theories
based on orbifold compactifications of the weakly-coupled heterotic string. In
particular, we consider theories in which the four-dimensional theory displays
target space modular invariance and where the dilatonic mode undergoes Kahler
stabilization. A self-contained exposition of effective Lagrangian approaches
to gaugino condensation and heterotic string theory is presented, leading to
the development of the models of Binetruy, Gaillard and Wu. Various aspects of
the phenomenology of this class of models are considered. These include issues
of supersymmetry breaking and superpartner spectra, the role of anomalous U(1)
factors, issues of flavor and R-parity conservation, collider signatures, axion
physics, and early universe cosmology. For the vast majority of
phenomenological considerations the theories reviewed here compare quite
favorably to other string-derived models in the literature. Theoretical
objections to the framework and directions for further research are identified
and discussed.Comment: Invited review article for International Journal of Modern Physic

### Bottom-Up Approach to Moduli Dynamics in Heavy Gravitino Scenario : Superpotential, Soft Terms and Sparticle Mass Spectrum

The physics of moduli fields is examined in the scenario where the gravitino
is relatively heavy with mass of order 10 TeV, which is favored in view of the
severe gravitino problem. The form of the moduli superpotential is shown to be
determined, if one imposes a phenomenological requirement that no physical CP
phase arise in gaugino masses from conformal anomaly mediation. This bottom-up
approach allows only two types of superpotential, each of which can have its
origins in a fundamental underlying theory such as superstring. One
superpotential is the sum of an exponential and a constant, which is identical
to that obtained by Kachru et al (KKLT), and the other is the racetrack
superpotential with two exponentials. The general form of soft supersymmetry
breaking masses is derived, and the pattern of the superparticle mass spectrum
in the minimal supersymmetric standard model is discussed with the KKLT-type
superpotential. It is shown that the moduli mediation and the anomaly mediation
make comparable contributions to the soft masses. At the weak scale, the
gaugino masses are rather degenerate compared to the minimal supergravity,
which bring characteristic features on the superparticle masses. In particular,
the lightest neutralino, which often constitutes the lightest superparticle and
thus a dark matter candidate, is a considerable admixture of gauginos and
higgsinos. We also find a small mass hierarchy among the moduli, gravitino, and
superpartners of the standard-model fields. Cosmological implications of the
scenario are briefly described.Comment: 45 pages, 10 figures, typos correcte

- …