422 research outputs found
The MSSM from Scherk-Schwarz Supersymmetry Breaking
We present a five-dimensional model compactified on an interval where
supersymmetry is broken by the Scherk-Schwarz mechanism. The gauge sector
propagates in the bulk, two Higgs hypermultiplets are quasilocalized, and quark
and lepton multiplets localized, in one of the boundaries. The effective
four-dimensional theory is the MSSM with very heavy gauginos, heavy squarks and
light sleptons and Higgsinos. The soft tree-level squared masses of the Higgs
sector can be negative and they can (partially) cancel the positive one-loop
contributions from the gauge sector. Electroweak symmetry breaking can then
comfortably be triggered by two-loop radiative corrections from the top-stop
sector. The fine tuning required to obtain the electroweak scale is found to be
much smaller than in the MSSM, with essentially no fine-tuning for few TeV
gaugino masses. All bounds from direct Higgs searches at LEP and from
electroweak precision observables can be satisfied. The lightest supersymmetric
particle is a (Higgsino-like) neutralino that can accomodate the abundance of
Dark Matter consistently with recent WMAP observations.Comment: 23 pages, 3 figure
Fermions and Supersymmetry Breaking in the Interval
We study fermions, such as gravitinos and gauginos in supersymmetric
theories, propagating in a five-dimensional bulk where the fifth dimensional
component is assumed to be an interval. We show that the most general boundary
condition at each endpoint of the interval is encoded in a single complex
parameter representing a point in the Riemann sphere. Upon introducing a
boundary mass term, the variational principle uniquely determines the boundary
conditions and the bulk equations of motion. We show the mass spectrum becomes
independent from the Scherk-Schwarz parameter for a suitable choice of one of
the two boundary conditions. Furthermore, for any value of the Scherk-Schwarz
parameter, a zero-mode is present in the mass spectrum and supersymmetry is
recovered if the two complex parameters are tuned.Comment: 10 pages. v2: Paragraph on off-shell globally supersymmetric
Lagrangian added. Version published in PL
Non-local symmetry breaking in Kaluza-Klein theories
Scherk-Schwarz gauge symmetry breaking of a D-dimensional field theory model
compactified on a circle is analyzed. It is explicitly shown that forbidden
couplings in the unbroken theory appear in the one-loop effective action only
in a non-local way, implying that they are finite at all orders in perturbation
theory. This result can be understood as a consequence of the local gauge
symmetry, but it holds true also in the global limit.Comment: v2: Wilson loop contributions and generalization to SU(N) included;
references added. v3: version to appear in Phys. Rev. Let
Softly Broken Supersymmetric Desert from Orbifold Compactification
A new viewpoint for the gauge hierarchy problem is proposed: compactification
at a large scale, 1/R, leads to a low energy effective theory with
supersymmetry softly broken at a much lower scale, \alpha/R. The hierarchy is
induced by an extremely small angle \alpha which appears in the orbifold
compactification boundary conditions. The same orbifold boundary conditions
break Peccei-Quinn symmetry, leading to a new solution to the \mu problem.
Explicit 5d theories are constructed with gauge groups SU(3) \times SU(2)
\times U(1) and SU(5), with matter in the bulk or on the brane, which lead to
the (next-to) minimal supersymmetric standard model below the compactification
scale. In all cases the soft supersymmetry-breaking and \mu parameters
originate from bulk kinetic energy terms, and are highly constrained. The
supersymmetric flavor and CP problems are solved.Comment: 18 pages, Latex, corrected values for A parameter
An algorithm for the Cartan-Dieudonn\'e theorem on generalized scalar product spaces
We present an algorithmic proof of the Cartan-Dieudonn\'e theorem on
generalized real scalar product spaces with arbitrary signature. We use
Clifford algebras to compute the factorization of a given orthogonal
transformation as a product of reflections with respect to hyperplanes. The
relationship with the Cartan-Dieudonn\'e-Scherk theorem is also discussed in
relation to the minimum number of reflections required to decompose a given
orthogonal transformation.Comment: 25 page
Symmetry breaking from Scherk-Schwarz compactification
We analyze the classical stable configurations of an extra-dimensional gauge
theory, in which the extra dimensions are compactified on a torus. Depending on
the particular choice of gauge group and the number of extra dimensions, the
classical vacua compatible with four-dimensional Poincar\'e invariance and zero
instanton number may have zero energy. For SU(N) on a two-dimensional torus, we
find and catalogue all possible degenerate zero-energy stable configurations in
terms of continuous or discrete parameters, for the case of trivial or
non-trivial 't Hooft non-abelian flux, respectively. We then describe the
residual symmetries of each vacua.Comment: 24 pages, 1 figure, Section 4 modifie
Naturally split supersymmetry
Nonobservation of superparticles till date, new Higgs mass limits from the
CMS and ATLAS experiments, WMAP constraints on relic density, various other low
energy data, and the naturalness consideration, all considered simultaneously
imply a paradigm shift of supersymmetric model building. In this paper we
perform, for the first time, a detailed numerical study of brane-world induced
supersymmetry breaking for both minimal and next-to-minimal scenarios. We
observe that a naturally hierarchical spectrum emerges through an interplay of
bulk, brane-localized and quasi-localized fields, which can gain more relevance
in the subsequent phases of the LHC run.Comment: 6 pages, 6 eps figures; v2: minor updates, to appear in JHE
Radius Stabilization by Two-Loop Casimir Energy
It is well known that the Casimir energy of bulk fields induces a non-trivial
potential for the compactification radius of higher-dimensional field theories.
On dimensional grounds, the 1-loop potential is ~ 1/R^4. Since the 5d gauge
coupling constant g^2 has the dimension of length, the two-loop correction is ~
g^2/R^5. The interplay of these two terms leads, under very general
circumstances (including other interacting theories and more compact
dimensions), to a stabilization at finite radius. Perturbative control or,
equivalently, a parametrically large compact radius is ensured if the 1-loop
coefficient is small because of an approximate fermion-boson cancellation. This
is similar to the perturbativity argument underlying the Banks-Zaks fixed point
proposal. Our analysis includes a scalar toy model, 5d Yang-Mills theory with
charged matter, the examination of S^1 and S^1/Z_2 geometries, as well as a
brief discussion of the supersymmetric case with Scherk-Schwarz SUSY breaking.
2-Loop calculability in the S^1/Z_2 case relies on the log-enhancement of
boundary kinetic terms at the 1-loop level.Comment: 18 pages, 2 figures, uses axodraw, references adde
Kaehler Corrections for the Volume Modulus of Flux Compactifications
No-scale models arise in many compactifications of string theory and
supergravity, the most prominent recent example being type IIB flux
compactifications. Focussing on the case where the no-scale field is a single
unstabilized volume modulus (radion), we analyse the general form of
supergravity loop corrections that affect the no-scale structure of the Kaehler
potential. These corrections contribute to the 4d scalar potential of the
radion in a way that is similar to the Casimir effect. We discuss the interplay
of this loop effect with string-theoretic alpha' corrections and its possible
role in the stabilization of the radion.Comment: 8 pages, references adde
Quantum Equivalence of Massive Antisymmetric Tensor Field Models in Curved Space
We study the effective actions for massive rank-2 and rank-3 antisymmetric
tensor field models in curved space-time. These models are classically
equivalent to massive vector field and massive scalar field with minimal
coupling to gravity respectively. We prove that effective action for massive
rank-2 antisymmetric tensor field is exactly equal to one for massive vector
field and effective action for massive rank-3 antisymmetric tensor field is
exactly equal to one for massive scalar field. Prove is based on an identity
for mass-dependent zeta-functions associated with Laplacians acting on
-forms.Comment: 8 pages, REVTeX fil
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