6 research outputs found
A self-tuning mechanism in (3+p)d gravity-scalar theory
We present a new type of self-tuning mechanism for ()d brane world
models in the framework of gravity-scalar theory. This new type of self-tuning
mechanism exhibits a remarkable feature. In the limit , being
the string coupling, the geometry of bulk spacetime remains virtually unchanged
by an introduction of the Standard Model(SM)-brane, and consequently it is
virtually unaffected by quantum fluctuations of SM fields with support on the
SM-brane. Such a feature can be obtained by introducing Neveu-Schwarz(NS)-brane
as a background brane on which our SM-brane is to be set. Indeed, field
equations naturally suggest the existence of the background NS-brane. Among the
given such models, of the most interest is the case with , where
represents the bulk cosmological constant. This model contains a pair
of coincident branes (of the SM- and the NS-branes), one of which is a
codimension-2 brane placed at the origin of 2d transverse space (), another a codimension-1 brane placed at the edge of .
These two branes are (anti) T-duals of each other, and one of them may be
identified as our SM-brane plus the background NS-brane. In the presence of the
background NS-brane (and in the absence of ), the 2d transverse space
becomes an orbifold with an appropriate deficit angle.
But this is only possible if the ()d Planck scale and the string
scale () are of the same order, which
accords with the hierarchy assumption \cite{1,2,3} that the electroweak scale
is the only short distance scale existing in nature
More on the Tensorial Central Charges in N=1 Supersymmetric Gauge Theories (BPS Wall Junctions and Strings)
We study the central extensions of the N=1 superalgebras relevant to the
soliton solutions with the axial geometry - strings, wall junctions, etc. A
general expression valid in any four-dimensional gauge theory is obtained. We
prove that the only gauge theory admitting BPS strings at weak coupling is
supersymmetric electrodynamics with the Fayet-Iliopoulos term. The problem of
ambiguity of the (1/2,1/2) central charge in the generalized Wess-Zumino models
and gauge theories with matter is addressed and solved. A possibility of
existence of the BPS strings at strong coupling in N=2 theories is discussed. A
representation of different strings within the brane picture is presented.Comment: 26 pages, 2 figures, 1 reference added, typos corrected, Sec. 9.3
expanded. Final version accepted for publication in Phys.Rev.
Neutralino Dark Matter, b-tau Yukawa Unification and Non-Universal Sfermion Masses
We study the implications of minimal non-Universal Boundary Conditions in the
sfermion Soft SUSY Breaking (SSB) masses of mSUGRA. We impose asymptotic b-tau
Yukawa coupling Unification and we resort to a parameterization of the
deviation from Universality in the SSB motivated by the multiplet structure of
SU(5) GUT. A set of cosmo-phenomenological constraints, including the recent
results from WMAP, determines the allowed parameter space of the models under
consideration. We highlight a new coannihilation corridor where
neutralino-sbottom and neutralino-tau sneutrino-stau coannihilations
significantly contribute to the reduction of the neutralino relic density.Comment: 38 pages, 27 Figures, Latex; Version accepted for publication in PR