192 research outputs found
Generalized messengers of supersymmetry breaking and the sparticle mass spectrum
We investigate the sparticle spectrum in models of gauge-mediated
supersymmetry breaking. In these models, supersymmetry is spontaneously broken
at an energy scale only a few orders of magnitude above the electroweak scale.
The breakdown of supersymmetry is communicated to the standard model particles
and their superpartners by "messenger" fields through their ordinary gauge
interactions. We study the effects of a messenger sector in which the
supersymmetry-violating F-term contributions to messenger scalar masses are
comparable to the supersymmetry-preserving ones. We also argue that it is not
particularly natural to restrict attention to models in which the messenger
fields lie in complete SU(5) GUT multiplets, and we identify a much larger
class of viable models. Remarkably, however, we find that the superpartner mass
parameters in these models are still subject to many significant contraints.Comment: 24 pages, LaTeX, uses epsf.sty, 4 figures. Assumptions clarified,
numerical bounds tweaked, typos correcte
One-Loop Corrections to Bubble Nucleation Rate at Finite Temperature
We present an evaluation of the 1-loop prefactor in the lifetime of a
metastable state which decays at finite temperature by bubble nucleation. Such
a state is considered in one-component phi^4 model in three space dimensions.
The calculation serves as a prototype application of a fast numerical method
for evaluating the functional determinants that appear in semiclassical
approximations.Comment: DO-TH-93/18, 15 pages, 11 Figures available on request, LaTeX, no
macros neede
Transmission of Supersymmetry Breaking from a 4-Dimensional Boundary
In the strong-coupling limit of the heterotic string theory constructed by
Horava and Witten, an 11-dimensional supergravity theory is coupled to matter
multiplets confined to 10-dimensional mirror planes. This structure suggests
that realistic unification models are obtained, after compactification of 6
dimensions, as theories of 5-dimensional supergravity in an interval, coupling
to matter fields on 4-dimensional walls. Supersymmetry breaking may be
communicated from one boundary to another by the 5-dimensional fields. In this
paper, we study a toy model of this communication in which 5-dimensional
super-Yang-Mills theory in the bulk couples to chiral multiplets on the walls.
Using the auxiliary fields of the Yang-Mills multiplet, we find a simple
algorithm for coupling the bulk and boundary fields. We demonstrate two
different mechanisms for generating soft supersymmetry breaking terms in the
boundary theory. We also compute the Casimir energy generated by supersymmetry
breaking.Comment: 26 pages, latex + 7 eps figures, final correction
On the Inconsistency of Fayet-Iliopoulos Terms in Supergravity Theories
Motivated by recent discussions, we revisit the issue of whether globally
supersymmetric theories with non-zero Fayet-Iliopoulos terms may be
consistently coupled to supergravity. In particular, we examine claims that a
fundamental inconsistency arises due to the conflicting requirements which are
imposed on the -symmetry properties of the theory by the supergravity
framework. We also prove that certain kinds of Fayet-Iliopoulos contributions
to the supercurrent supermultiplets of theories with non-zero Fayet-Iliopoulos
terms fail to exist. A key feature of our discussion is an explicit comparison
between results from the chiral (or ``old minimal'') and linear (or ``new
minimal'') formulations of supergravity, and the effects within each of these
formalisms that are induced by the presence of non-zero Fayet-Iliopoulos terms.Comment: Comments: 69 pages, LaTeX, 2 figures, 7 tables. Significant new
material on conformal-compensator formalisms added, previous results
clarified and extended, references adde
The Tokyo Axion Helioscope Experiment
A preliminary result of the solar axion search experiment at the University
of Tokyo is presented. We searched for axions which could be produced in the
solar core by exploiting the axion helioscope. The helioscope consists of a
superconducting magnet with field strength of 4 Tesla over 2.3 meters. From the
absence of the axion signal we set a 95 % confidence level upper limit on the
axion coupling to two photons for the axion mass eV. This is the first solar axion
search experiment whose sensitivity to exceeds the limit
inferred from the solar age consideration.Comment: 5 pages, 5 eps files included, uses espcrc2.sty, to be published in
Proc. AXION WORKSHOP, Gainesville, Florida, 13-15 March 1998, ed. by
P.Sikivi
Localized tadpoles of anomalous heterotic U(1)'s
We investigate the properties of localized anomalous U(1)'s in heterotic
string theory on the orbifold T^6/Z_3. We argue that the local four dimensional
and original ten dimensional Green-Schwarz mechanisms can be implemented
simultaneously, making the theory manifestly gauge invariant everywhere, in the
bulk and at the fixed points. We compute the shape of the Fayet-Iliopoulos
tadpoles, and cross check this derivation for the four dimensional auxiliary
fields by a direct calculation of the tadpoles of the internal gauge fields.
Finally we study some resulting consequences for spontaneous symmetry breaking,
and derive the profile of the internal gauge field background over the
orbifold.Comment: 35 pages, LaTeX, with figure
Dark Matters in Axino Gravitino Cosmology
It is suggested that the axino mass in the 1 MeV region and gravitino mass in
the eV region can provide an axino lifetime of order of the time of photon
decoupling. In this case, some undecayed axinos act like cold dark matters and
some axino decay products (gravitinos and hot axions) act like hot dark matters
at the time of galaxy formation.Comment: 9 pages, Late
One-loop corrections to the metastable vacuum decay
We evaluate the one-loop prefactor in the false vacuum decay rate in a theory
of a self interacting scalar field in 3+1 dimensions. We use a numerical
method, established some time ago, which is based on a well-known theorem on
functional determinants. The proper handling of zero modes and of
renormalization is discussed. The numerical results in particular show that
quantum corrections become smaller away from the thin-wall case. In the
thin-wall limit the numerical results are found to join into those obtained by
a gradient expansion.Comment: 31 pages, 7 figure
Superconformal Flavor Simplified
A simple explanation of the flavor hierarchies can arise if matter fields
interact with a conformal sector and different generations have different
anomalous dimensions under the CFT. However, in the original study by Nelson
and Strassler many supersymmetric models of this type were considered to be
'incalculable' because the R-charges were not sufficiently constrained by the
superpotential. We point out that nearly all such models are calculable with
the use of a-maximization. Utilizing this, we construct the simplest
vector-like flavor models and discuss their viability. A significant constraint
on these models comes from requiring that the visible gauge couplings remain
perturbative throughout the conformal window needed to generate the
hierarchies. However, we find that there is a small class of simple flavor
models that can evade this bound.Comment: 43 pages, 1 figure; V3: small corrections and clarifications,
references adde
New supersymmetric higher-derivative couplings: Full N=2 superspace does not count!
An extended class of N=2 locally supersymmetric invariants with
higher-derivative couplings based on full superspace integrals, is constructed.
These invariants may depend on unrestricted chiral supermultiplets, on vector
supermultiplets and on the Weyl supermultiplet. Supersymmetry is realized
off-shell. A non-renormalization theorem is proven according to which none of
these invariants can contribute to the entropy and electric charges of BPS
black holes. Some of these invariants may be relevant for topological string
deformations.Comment: 24 pages, v2: version published in JHEP, one reference added and
typos corrected, v3: reference adde
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