114 research outputs found
Heavy Thresholds, Slepton Masses and the Term in Anomaly Mediated Supersymmetry Breaking
The effects of heavy mass thresholds on anomaly-mediated soft supersymmetry
breaking terms are discussed. While heavy thresholds completely decouple to
lowest order in the supersymmetry breaking, it is argued that they do affect
the breaking terms at higher orders. The relevant contributions typically occur
at lower order in the loop expansion compared to purely anomaly mediated
contributions. The non decoupling contributions may be used to render models in
which the only source of supersymmetry breaking is anomaly mediation viable, by
generating positive contributions to the sleptons' masses squared. They can
also be used to generate acceptable mu- and B-terms.Comment: 25 pages, late
Visible Effects of the Hidden Sector
The renormalization of operators responsible for soft supersymmetry breaking
is usually calculated by starting at some high scale and including only visible
sector interactions in the evolution equations, while ignoring hidden sector
interactions. Here we explain why this is correct only for the most trivial
structures in the hidden sector, and discuss possible implications. This
investigation was prompted by the idea of conformal sequestering. In that
framework hidden sector renormalizations by nearly conformal dynamics are
critical. In the original models of conformal sequestering it was necessary to
impose hidden sector flavor symmetries to achieve the sequestered form. We
present models which can evade this requirement and lead to no-scale or anomaly
mediated boundary conditions; but the necessary structures do not seem generic.
More generally, the ratios of scalar masses to gaugino masses, the -term,
the -term, -terms, and the gravitino mass can be significantly
affected.Comment: 23 pages, no figure
Massive Supergravity and Deconstruction
We present a simple superfield Lagrangian for massive supergravity. It
comprises the minimal supergravity Lagrangian with interactions as well as mass
terms for the metric superfield and the chiral compensator. This is the natural
generalization of the Fierz-Pauli Lagrangian for massive gravity which
comprises mass terms for the metric and its trace. We show that the on-shell
bosonic and fermionic fields are degenerate and have the appropriate spins: 2,
3/2, 3/2 and 1. We then study this interacting Lagrangian using goldstone
superfields. We find that a chiral multiplet of goldstones gets a kinetic term
through mixing, just as the scalar goldstone does in the non-supersymmetric
case. This produces Planck scale (Mpl) interactions with matter and all the
discontinuities and unitarity bounds associated with massive gravity. In
particular, the scale of strong coupling is (Mpl m^4)^1/5, where m is the
multiplet's mass. Next, we consider applications of massive supergravity to
deconstruction. We estimate various quantum effects which generate non-local
operators in theory space. As an example, we show that the single massive
supergravity multiplet in a 2-site model can serve the function of an extra
dimension in anomaly mediation.Comment: 24 pages, 2 figures, some color. Typos fixed and refs added in v
Dynamics Of The Formation Of Carbon Nanotube Serpentines.
Recently, Geblinger et al. [Nat. Nanotechnol. 3, 195 (2008)] reported the experimental realization of carbon nanotube S-like shaped nanostructures, the so-called carbon nanotube serpentines. We report here results from multimillion fully atomistic molecular dynamics simulations of their formation. We consider one-Όm-long carbon nanotubes placed on stepped substrates with and without a catalyst nanoparticle on the top free end of the tube. A force is applied to the upper part of the tube during a short period of time and turned off; then the system is set free to evolve in time. Our results show that these conditions are sufficient to form robust serpentines and validates the general features of the falling spaghetti model proposed to explain their formation.11010550
Gaugino condensation scale of one family hidden SU(5)', dilaton stabilization and gravitino mass
The hidden SU(5)' with one family, 10 and 5-bar, breaks supersymmetry
dynamically. From the effective Lagrangian approach, we estimate the hidden
sector gaugino candensation scale, the dilaton stabilization and the resulting
gravitino mass. In some models, this gravitino mass can be smaller than the
previous naive estimate. Then, it is possible to raise the SU(5)' confining
scale above 10^{13} GeV.Comment: 8 pages, 4 figure
GMSB at a stable vacuum and MSSM without exotics from heterotic string
We show that it is possible to introduce the confining hidden sector gauge
group SU(5)' with the chiral matter 10 plus 5-bar, which are neutral under the
standard model gauge group, toward a gauge mediated supersymmetry breaking
(GMSB) in a Z_{12-I} orbifold compactification of E_8xE_8 heterotic string.
Three families of MSSM result without exotics. We also find a desirable matter
parity P (or R-parity) assignment. We note that this model contains the
spectrum of the Lee-Weinberg model which has a nice solution of the mu problem.Comment: 17 pages, references and DOI adde
The GUT Scale and Superpartner Masses from Anomaly Mediated Supersymmetry Breaking
We consider models of anomaly-mediated supersymmetry breaking (AMSB) in which
the grand unification (GUT) scale is determined by the vacuum expectation value
of a chiral superfield. If the anomaly-mediated contributions to the potential
are balanced by gravitational-strength interactions, we find a
model-independent prediction for the GUT scale of order . The GUT threshold also affects superpartner masses, and can easily
give rise to realistic predictions if the GUT gauge group is asymptotically
free. We give an explicit example of a model with these features, in which the
doublet-triplet splitting problem is solved. The resulting superpartner
spectrum is very different from that of previously considered AMSB models, with
gaugino masses typically unifying at the GUT scale.Comment: 17 page
Models of Dynamical Supersymmetry Breaking with Gauged Symmetry
We present simple models of dynamical supersymmetry breaking with gauged
U(1)_R symmetry. The minimal supersymmetric standard model and supersymmetric
SU(5) GUT are considered as the visible sector. The anomaly cancellation
conditions for U(1)_R are investigated in detail and simple solutions of the
R-charge assignments are found. We show that this scenario of dynamical
supersymmetry breaking is phenomenologically viable with the gravitino mass of
order 1 TeV or 10 TeV.Comment: 15 pages, uses REVTEX macro, No figure
Dynamical Supersymmetry Breaking
Supersymmetry is one of the most plausible and theoretically motivated
frameworks for extending the Standard Model. However, any supersymmetry in
Nature must be a broken symmetry. Dynamical supersymmetry breaking (DSB) is an
attractive idea for incorporating supersymmetry into a successful description
of Nature. The study of DSB has recently enjoyed dramatic progress, fueled by
advances in our understanding of the dynamics of supersymmetric field theories.
These advances have allowed for direct analysis of DSB in strongly coupled
theories, and for the discovery of new DSB theories, some of which contradict
early criteria for DSB. We review these criteria, emphasizing recently
discovered exceptions. We also describe, through many examples, various
techniques for directly establishing DSB by studying the infrared theory,
including both older techniques in regions of weak coupling, and new techniques
in regions of strong coupling. Finally, we present a list of representative DSB
models, their main properties, and the relations between them.Comment: 113 pages, Revtex. Minor changes, references added and corrected. To
appear in Reviews of Modern Physic
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