20,056 research outputs found
Universal Loop-Free Super-Stabilization
We propose an univesal scheme to design loop-free and super-stabilizing
protocols for constructing spanning trees optimizing any tree metrics (not only
those that are isomorphic to a shortest path tree). Our scheme combines a novel
super-stabilizing loop-free BFS with an existing self-stabilizing spanning tree
that optimizes a given metric. The composition result preserves the best
properties of both worlds: super-stabilization, loop-freedom, and optimization
of the original metric without any stabilization time penalty. As case study we
apply our composition mechanism to two well known metric-dependent spanning
trees: the maximum-flow tree and the minimum degree spanning tree
Super No-Scale F-SU(5): A Dynamic Determination of M_{1/2} and tan beta
We study the Higgs potential in No-Scale F-SU(5), a model built on the
tripodal foundations of the Flipped SU(5) x U(1)_X Grand Unified Theory, extra
F-theory derived TeV scale vector-like particle multiplets, and the high scale
boundary conditions of No-Scale Supergravity. V_min, the minimum of the
potential following radiative electroweak symmetry breaking, is a function at
fixed Z-Boson mass of the universal gaugino boundary mass M_{1/2} and
tan{\beta}, the ratio of Higgs vacuum expectation values. The No-Scale
nullification of the bilinear Higgs soft term B_mu at the boundary reduces
V_min(M_{1/2}) to a one dimensional dependency, which may be secondarily
minimized. This "Super No-Scale" condition dynamically fixes tan beta and
M_{1/2} at the local minimum minimorum of V_min. Fantastically, the walls of
this theoretically established secondary potential coalesce in descent to a
striking concurrency with the previously phenomenologically favored "golden
point" and "golden strip".Comment: V2, As accepted to Physics Letters B; 8 Pages, 2 Plots, 1 Tabl
Low Energy Supersymmetry in Warped Brane Worlds
We discuss physical implications of the four-dimensional effective
supergravity, that describes low-energy physics of the Randall--Sundrum model
with moduli fields in the bulk and charged chiral matter living on the branes.
Cosmological constant can be cancelled through the introduction of a brane
Polonyi field and a brane superpotential for the 4d dilaton. We deduce a
generalization of the effective 4d action to the case of a general, not
necessarily exponential, warp factor. We note, that breakdown of supersymmetry
in generic warped models may lead to the stabilization of the interbrane
distance.Comment: 9 pages, Latex, Talk given at SUSY'01, June 11-17 2001, Dubna, Russi
Superpartners at LHC and Future Colliders: Predictions from Constrained Compactified M-Theory
We study a realistic top-down M-theory compactification with low-scale
effective Supersymmetry, consistent with phenomenological constraints. A
combination of top-down and generic phenomenological constraints fix the
spectrum. The gluino mass is predicted to be about 1.5 TeV. Three and only
three superpartner channels, , and
(where are Wino-like), are expected
to be observable at LHC-14. We also investigate the prospects of finding heavy
squarks and Higgsinos at future colliders. Gluino-stop-top,
gluino-sbottom-bottom associated production and first generation squark
associated production should be observable at a 100 TeV collider, along with
direct production of heavy Higgsinos. Within this framework the discovery of a
single sparticle is sufficient to determine uniquely the SUSY spectrum,
yielding a number of concrete testable predictions for LHC-14 and future
colliders, and determination of and thereby other fundamental
quantities.Comment: 19 pages, 4 figure
Gauge mediated supersymmetry breaking and supergravity
We analyze simple models of gauge mediated supersymmetry breaking in the
context of supergravity. We distinguish two cases. One is when the messenger of
the supersymmetry breaking is a non Abelian gauge force and the other is when
the messenger is a pseudoanomalous U(1). We assume that these models originate
from string theory and we impose the constraint of the vanishing of the
cosmological constant requiring also the stabilization of the dilaton. In the
first case, we do not find vacua that are consistent with the constraints of
gauge mediation and have a zero tree level cosmological constant. In the second
case, no such conflict arises. In addition, by looking at the one loop
cosmological constant, we show that the dilaton F-term can not be neglected in
either case. For the gauge mediated case our considerations suggest that the
dilaton must be frozen out of the low energy field theory by non-perturbative
string dynamics.Comment: Revised version. Significant changes in Introduction and Conclusion,
9 page
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
Non-perturbative and Flux superpotentials for Type I strings on the Z_3 orbifold
Non-perturbative effects are studied for Type I strings on the Z_3 orbifold
with Chan-Paton symmetry broken by Wilson lines. Generalizing previous analyses
that have focussed on (bi)fundamentals, it is argued that (anti)symmetric
representations of the resulting gauge group play a decisive role in generating
an ADS-like superpotential in this and related cases. Non perturbative
corrections in the closed string moduli are only allowed if properly dressed
with open string fields charged under the anomalous U(1) of the orbifold. A
general discussion of instanton effects in SYM and string theories is given.
Non-perturbative superpotentials induced by both 's and ED1's are
analyzed. The superpotential generated by closed string fluxes, viz.
Scherk-Schwarz shifts (torsion), R-R 3-form flux as well as non-geometric
fluxes is derived. Some preliminary comments on the compatibility of the two
kinds of superpotentials and the issue of moduli stabilization are presented.Comment: Latex, 30 pages; v2: misprints corrected and a few explanations adde
Phenomenology and cosmology of weakly coupled string theory
The weakly coupled vacuum of heterotic string theory remains
an attractive scenario for phenomenolgy and cosmology. The particle spectrum is
reviewed and the issues of gauge coupling unification, dilaton stabilization
and modular cosmology are discussed. A specific model for condensation and
supersymmetry breaking, that respects known constraints from string theory and
is phenomenologically viable, is described.Comment: 24 pages, talk presented at The Richard Arnowitt Fest, April 5-8,
1998, Texas A & M University, College Station, TX, to be published in the
proceedings, full postscript available from
http://phyweb.lbl.gov/theorypapers/preprints.html/41110.p
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