207 research outputs found
Seesaw induced Higgs Mechanism
We discuss a two scalar doublets model which induces the Higgs mechanism by
means of a seesaw mechanism. This model naturally predicts a light Higgs scalar
whose mass is suppressed by the grand unification scale. The model predicts an
intermediate scale between the electroweak symmetry breaking scale and the
grand unification scale at GeV. Below this intermediate energy scale the
usual standard model appears as an effective theory. A seesaw mechanism in the
scalar sector of the model not only induces the standard Higgs mechanism, but
also solves the hierarchy problem. An implementation of this mechanism in
models where the Planck scale is in the TeV region is discussed.Comment: 4 page
Gravitational Corrections to Fermion Masses in Grand Unified Theories
We reconsider quantum gravitational threshold effects to the unification of
fermion masses in Grand Unified Theories. We show that the running of the
Planck mass can have a sizable effect on these thresholds which are thus much
more important than naively expected. These corrections make any extrapolation
from low energy measurements challenging.Comment: 7 page
Unitarity bounds on low scale quantum gravity
We study the unitarity of models with low scale quantum gravity both in four
dimensions and in models with a large extra-dimensional volume. We find that
models with low scale quantum gravity have problems with unitarity below the
scale at which gravity becomes strong. An important consequence of our work is
that their first signal at the Large Hadron Collider would not be of a
gravitational nature such as graviton emission or small black holes, but rather
linked to the mechanism which fixes the unitarity problem. We also study models
with scalar fields with non minimal couplings to the Ricci scalar. We consider
the strength of gravity in these models and study the consequences for
inflation models with non-minimally coupled scalar fields. We show that a
single scalar field with a large non-minimal coupling can lower the Planck mass
in the TeV region. In that model, it is possible to lower the scale at which
gravity becomes strong down to 14 TeV without violating unitarity below that
scale.Comment: 15 page
Grand Unification and Time Variation of the Gauge Couplings
Astrophysical indications that the fine structure constant is time dependent
are discussed in the framework of grand unification models. A variation of the
electromagnetic coupling constant could either be generated by a corresponding
time variation of the unified coupling constant or by a time variation of the
unification scale, or by both. The case in which the time variation of the
electromagnetic coupling constant is caused by a time variation of the
unification scale is of special interest. It is supported in addition by recent
hints towards a time change of the proton-electron mass ratio. Possible
implications for baryogenesis are discussed.Comment: talk given at the 10th International Conference on Supersymmetry and
Unification of Fundamental Interactions (SUSY02), Hamburg, Germany, 17-23
June 200
Hidden Supersymmetry
Inspired by the concept of complementarity, we present a illustrative model
for the weak interactions with unbroken gauge symmetry and unbroken
supersymmetry. The observable particles are bound states of some more
fundamental particles. Supersymmetry is broken at the macroscopic scale of the
observable particles by a discrete symmetry but remains exact at the scale of
the fundamental particle and is thus hidden. This provides a link between
theories at very high energies and the observed particle physics.
Supersymmetric particles are confined in usual matter.Comment: 9 page
Symmetries, Microcausality and Physics on Canonical Noncommutative Spacetime
In this paper we describe how to implement symmetries on a canonical noncommutative spacetime. We focus on noncommutative Lorentz transformations. We then discuss the structure of the light cone on a canonical noncommutative spacetime and show that field theories formulated on these spaces do not violate mircocausality
A Duality as a Theory for the Electroweak Interactions
We present a model based on a SU(2) confining theory which is dual to the
standard model. This duality allows to calculate the electroweak mixing angle
and the Higgs boson mass. Possible tests of this duality are discussed.Comment: Ph.D. thesi
Gravitational radiation in quantum gravity
The effective field theory of quantum gravity generically predicts non-locality to be present in the effective action, which results from the low-energy propagation of gravitons and massless matter. Working to second order in gravitational curvature, we reconsider the effects of quantum gravity on the gravitational radiation emitted from a binary system. In particular, we calculate for the first time the leading order quantum gravitational correction to the classical quadrupole radiation formula which appears at second order in Newton’s constant
What are the Bounds on Space-Time Noncommutativity?
In this article we consider the bounds on the noncommutative nature of
space-time. We argue that these bounds are extremely model dependent. In the
only phenomenologically viable framework, i.e. when the fields are taken to be
in the enveloping of the Lie algebra, the constraints are fairly loose and only
of the order of a few TeV.Comment: 10 page
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