541 research outputs found
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
Dynamical mass scale and approximate scaling symmetry in the Higgs sector
We investigate basic consequences of the assumption that the mass scale of
the perturbative sector responsible for the spontaneous symmetry breaking is
generated dynamically in a theory with a large UV scale. It is assumed that in
addition to an elementary scalar there exists an additional scalar, a modulus,
which controls the dynamical hierarchy of scales in the manner similar to that
of supersymmetric gaugino condensation. It is shown that a light degree of
freedom appears that couples to the gauge bosons and to charged fermions in a
specific way which is different from the couplings of the dilaton of the exact
scale invariance.Comment: 10 pages, no figure
Singular gauge transformations and supersymmetry breakdown on warped orbifolds
We have analyzed the breakdown of global supersymmetry by a non-vanishing
expectation value of the fifth component of the graviphoton on warped S^1/Z_2
orbifolds. It has been demonstrated that the setups where such a breakdown is
possible correspond to the models where the true gauge symmetry on the
orbifold, respecting the Z_2-parities and periodicity, is broken by boundary
terms. In the tuned models, giving Randall-Sundrum warp factor, gauge symmetry
stays intact, and any can be gauged away without violating supersymmetry.Comment: 11 pages, Latex, version published in Phys. Lett.
Warped brane world supergravity, flipping, and the Scherk-Schwarz mechanism
We demonstrate the relation between the Scherk-Schwarz mechanism and flipped
gauged brane-bulk supergravities in five dimensions. We discuss the form of
supersymmetry violating Scherk-Schwarz terms in pure supergravity and in
supergravity coupled to matter. Although the Lagrangian mass terms that arise
as the result of the Scherk-Schwarz redefinition of fields are naturally of the
order of the inverse radius of the orbifold, the effective 4d physical mass
terms are rather set by the scale \sqrt{|\bar{\Lambda}|}, where \bar{\Lambda}
is the 4d cosmlogical constant.Comment: 9 pages, talk given at the 1st International Conference on String
Phenomenology, Oxford, UK, July 6 - 11, 200
Boundary Terms in Brane Worlds
We clarify the relation between orbifold and interval pictures in 5d brane
worlds. We establish this correspondence for Z_2-even and Z_2-odd orbifold
fields. In the interval picture Gibbons-Hawking terms are necessary to fulfill
consistency conditions. We show how the brane world consistency conditions
arise in the interval picture. We apply the procedure to the situation where
the transverse dimension is terminated by naked singularities. In particular,
we find the boundary terms needed when the naive vacuum action is infinite.Comment: 15 pages, plain Latex, typos correcte
Thermally Favourable Gauge Mediation
We discuss the thermal evolution of the spurion and messenger fields of
ordinary gauge mediation models taking into account the Standard Model degrees
of freedom. It is shown that for thermalized messengers the metastable susy
breaking vacuum becomes thermally selected provided that the susy breaking
sector is sufficiently weakly coupled to messengers or to any other observable
field.Comment: 11 pages, 6 figures, plain latex; numerical factors corrected, final
versio
Back-door fine-tuning in supersymmetric low scale inflation
Low scale inflation has many virtues and it has been claimed that its natural
realisation in supersymmetric standard model can be achieved rather easily. In
this letter we have demonstrated that also in this case the dynamics of the
hidden sector responsible for supersymmetry breakdown and the structure of the
soft terms affects significantly, and in fact often spoils, the would-be
inflationary dynamics. Also, we point out that the issue if the cosmological
constant cancellation in the post-inflationary vacuum strongly affects
supersymmetric inflation. It is important to note the crucial difference
between freezing of the modulus and actually stabilising it - the first
approach misses parts of the scalar potential which turn out to be relevant for
inflation. We argue, that it is more likely that the low scale supersymmetric
inflation occurs at a critical point at the origin in the field space than at
an inflection point away from the origin, as the necessary fine-tuning in the
second case is typically larger.Comment: 10
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