31,124 research outputs found
Parallelism and tree regular constraints
Parallelism constraints are logical descriptions of trees. Parallelism constraints subsume dominance constraints and are equal in expressive power to context unification. Parallelism constraints belong to the constraint language for lambda structures (CLLS) which serves for modeling natural language
semantics. In this paper, we investigate the extension of parallelism constraints by tree regular constraints. This canonical extension is subsumed by the monadic second-order logic over parallelism constraints. We analyze the precise expressiveness of this extension on basis of a new relationship between tree automata and logic. Our result is relevant for classifying different
extensions of parallelism constraints, as in CLLS. Finally, we prove that parallelism constraints and context unification remain equivalent when extended with tree regular constraints
Type II Seesaw Dominance in Non-supersymmetric and Split Susy SO(10) and Proton Life Time
Recently type II seesaw dominance in a supersymmetric SO(10) framework has
been found useful in explaining large solar and atmospheric mixing angles as
well as larger values of while unifying quark and lepton masses.
An important question in these models is whether there exists consistency
between coupling unification and type II seesaw dominance. Scenarios where this
consistency can be demonstrated have been given in a SUSY framework. In this
paper we give examples where type II dominance occurs in SO(10) models without
supersymmetry but with additional TeV scale particles and also in models with
split-supersummetry. Grand unification is realized in a two-step process via
breaking of SO(10) to SU(5) and then to a TeV scale standard model supplemented
by extra fields and an SU(5) Higgs multiplet at a scale about
GeV to give type-II seesaw. The predictions for proton lifetime in
these models are in the range yrs. to yrs.. A number of recent numerical fits to GUT-scale fermion
masses can be accommodated within this model.Comment: 7 pages LaTeX, 3 figures, related areas: hep-ex, hep-th, astro-ph;
Reference added, typo corrected, version to appear in Physical Review
Interaction Grammars
Interaction Grammar (IG) is a grammatical formalism based on the notion of
polarity. Polarities express the resource sensitivity of natural languages by
modelling the distinction between saturated and unsaturated syntactic
structures. Syntactic composition is represented as a chemical reaction guided
by the saturation of polarities. It is expressed in a model-theoretic framework
where grammars are constraint systems using the notion of tree description and
parsing appears as a process of building tree description models satisfying
criteria of saturation and minimality
Supersymmetric Higgs and Radiative Electroweak breaking
We review the mechanism of radiative electroweak symmetry breaking taking
place in SUSY versions of the standard model. We further discuss different
proposals for the origin of SUSY-breaking and the corresponding induced
SUSY-breaking soft terms. Several proposals for the understanding of the little
hierarchy problem are critically discussed.Comment: To be published in Comptes Rendus de l'Academie des Science
Phenomenology of a Fluxed MSSM
We analyze the phenomenology of a set of minimal supersymmetric standard
model (MSSM) soft terms inspired by flux-induced supersymmetry (SUSY)-breaking
in Type IIB string orientifolds. The scheme is extremely constrained with
essentially only two free mass parameters: a parameter M, which sets the scale
of soft terms, and the mu parameter. After imposing consistent radiative
electro-weak symmetry breaking (EWSB) the model depends upon one mass parameter
(say, M). In spite of being so constrained one finds consistency with EWSB
conditions. We demonstrate that those conditions have two solutions for mu<0,
and none for mu>0. The parameter tan beta results as a prediction and is
approximately 3-5 for one solution, and 25-40 for the other, depending upon M
and the top mass. We examine further constraints on the model coming from b->s
gamma, the muon g-2, Higgs mass limits and WMAP constraints on dark matter. The
MSSM spectrum is predicted in terms of the single free parameter M. The low tan
beta branch is consistent with a relatively light spectrum although it is
compatible with standard cosmology only if the lightest neutralino is unstable.
The high tan beta branch is compatible with all phenomenological constraints,
but has quite a heavy spectrum. We argue that the fine-tuning associated to
this heavy spectrum would be substantially ameliorated if an additional
relationship mu=-2M were present in the underlying theory.Comment: 18 pages, minor revision
Type II see-saw dominance in SO(10)
Grand unified theories where the neutrino mass is given by Type II seesaw
have the potential to provide interesting connections between the neutrino and
charged fermion sectors. We explore the possibility of having a dominant Type
II seesaw contribution in supersymmetric SO(10). We show that this can be
achieved in the model where symmetry breaking is triggered by 54 and
45-dimensional representations, without the need for additional fields other
than those already required to have a realistic charged fermion mass spectrum.
Physical consequences, such as the implementation of the BSV mechanism, the
possibility of the fields responsible for Type II see-saw dominance being
messengers of supersymmetry breaking, and the realization of baryo and
leptogenesis in this theories are discussed.Comment: 14 pages, 3 figures. New version with references adde
Phenomenology of heterotic M-theory with five-branes
We analyze some phenomenological implications of heterotic M-theory with
five-branes. Recent results for the effective 4-dimensional action are used to
perform a systematic analysis of the parameter space, finding the restrictions
that result from requiring the volume of the Calabi-Yau to remain positive.
Then the different scales of the theory, namely, the 11-dimensional Planck
mass, the compactification scale and the orbifold scale, are evaluated.
The expressions for the soft supersymmetry-breaking terms are computed and
discussed in detail for the whole parameter space. With this information we
study the theoretical predictions for the supersymmetric contribution to the
muon anomalous magnetic moment, using the recent experimental result as a
constraint on the parameter space. We finally analyze the neutralino as a dark
matter candidate in this construction. In particular, the neutralino-nucleon
cross-section is computed and compared with the sensitivities explored by
present dark matter detectors.Comment: Final version to appear in Phys. Rev. D. Some comments and references
added. 37 pages, 19 figure
Power law scaling in Universal Extra Dimension scenarios
We study the power law running of gauge, Yukawa and quartic scalar couplings
in the universal extra dimension scenario where the extra dimension is accessed
by all the standard model fields. After compactifying on an
orbifold, we compute one-loop contributions of the relevant Kaluza-Klein (KK)
towers to the above couplings up to a cutoff scale . Beyond the scale
of inverse radius, once the KK states are excited, these couplings exhibit
power law dependence on . As a result of faster running, the gauge
couplings tend to unify at a relatively low scale, and we choose our cutoff
also around that scale. For example, for a radius , the
cutoff is around 30 TeV. We then examine the consequences of power law running
on the triviality and vacuum stability bounds on the Higgs mass. We also
comment that the supersymmetric extension of the scenario requires to
be larger than GeV in order that the gauge couplings remain
perturbative up to the scale where they tend to unify.Comment: Latex, 12 pages, 5 figures; v2: minor changes, to appear in Nucl.
Phys.
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