850 research outputs found
Higgsless Electroweak Theory following from the Spherical Geometry
A new formulation of the Electroweak Model with 3-dimensional spherical
geometry in the target space is suggested. The free Lagrangian in the spherical
field space along with the standard gauge field Lagrangian form the full
Higgsless Lagrangian of the model, whose second order terms reproduce the same
fields with the same masses as the Standard Electroweak Model. The vector
bosons and electron masses are generated automatically, so there is no need in
special mechanism.Comment: 6 page
New Confining N=1 Supersymmetric Gauge Theories
We examine N=1 supersymmetric gauge theories which confine in the presence of
a tree-level superpotential. We show the confining spectra which satisfy the 't
Hooft anomaly matching conditions and give a simple method to find the
confining superpotential. Using this method we fix the confining
superpotentials in the simplest cases, and show how these superpotentials are
generated by multi-instanton effects in the dual theory. These new type of
confining theories may be useful for model building, since the size of the
matter content is not restricted by an index constraint. Therefore, one expects
that a large variety of new confining spectra can be obtained using such
models.Comment: 26 pages, LaTe
The Minimal Set of Electroweak Precision Parameters
We present a simple method for analyzing the impact of precision electroweak
data above and below the Z-peak on flavour-conserving heavy new physics. We
find that experiments have probed about ten combinations of new physics
effects, which to a good approximation can be condensed into the effective
oblique parameters Shat, That, Uhat, V, X, W, Y (we prove positivity
constraints W, Y >= 0) and three combinations of quark couplings (including a
distinct parameter for the bottom). We apply our method to generic extra Z'
vectors.Comment: 22 pages, 3 figure
Gauge-Higgs Unification in Orbifold Models
Six-dimensional orbifold models where the Higgs field is identified with some
internal component of a gauge field are considered. We classify all possible
T^2/Z_N orbifold constructions based on a SU(3) electroweak gauge symmetry.
Depending on the orbifold twist, models with two, one or zero Higgs doublets
can be obtained. Models with one Higgs doublet are particularly interesting
because they lead to a prediction for the Higgs mass, which is twice the W
boson mass at leading order: m_H=2 m_W. The electroweak scale is quadratically
sensitive to the cut-off, but only through very specific localized operators.
We study in detail the structure of these operators at one loop, and identify a
class of models where they do not destabilize the electroweak scale at the
leading order. This provides a very promising framework to construct realistic
and predictive models of electroweak symmetry breaking.Comment: 27 pages, uses axodraw.sty; v2: version to appear in JHE
Chiral Compactification on a Square
We study quantum field theory in six dimensions with two of them compactified
on a square. A simple boundary condition is the identification of two pairs of
adjacent sides of the square such that the values of a field at two identified
points differ by an arbitrary phase. This allows a chiral fermion content for
the four-dimensional theory obtained after integrating over the square. We find
that nontrivial solutions for the field equations exist only when the phase is
a multiple of \pi/2, so that this compactification turns out to be equivalent
to a T^2/Z_4 orbifold associated with toroidal boundary conditions that are
either periodic or anti-periodic. The equality of the Lagrangian densities at
the identified points in conjunction with six-dimensional Lorentz invariance
leads to an exact Z_8\times Z_2 symmetry, where the Z_2 parity ensures the
stability of the lightest Kaluza-Klein particle.Comment: 28 pages, latex. References added. Clarifying remarks included in
section 2. Minor corrections made in section
A New Custodian for a Realistic Higgsless Model
We present an example of a realistic Higgsless model that makes use of
alternative assignments for the top and bottom quarks recently
proposed by Agashe et al. which results in an enhanced custodial symmetry.
Using these new representat ions reduces the deviations in the
coupling to for a wide range of parameters,
while this remaining correction can also be eliminated by varying the
localization parameter (bulk mass) for .Comment: 11 pages, 2 figure
Odd Decays from Even Anomalies: Gauge Mediation Signatures Without SUSY
We analyze the theory and phenomenology of anomalous global chiral symmetries
in the presence of an extra dimension. We propose a simple extension of the
Standard Model in 5D whose signatures closely resemble those of supersymmetry
with gauge mediation, and we suggest a novel scalar dark matter candidate.Comment: 26 pages, 1 figure; v2: references added; discussion of direct
collider constraints added; v3: corrected dark matter calculation in chapter
4.2 and replaced figure 1
Vacuum Energy Density and Cosmological Constant in dS Brane World
We discuss the vacuum energy density and the cosmological constant of dS
brane world with a dilaton field. It is shown that a stable AdS brane can
be constructed and gravity localization can be realized. An explicit relation
between the dS bulk cosmological constant and the brane cosmological constant
is obtained. The discrete mass spectrum of the massive scalar field in the
AdS brane is used to acquire the relationship between the brane
cosmological constant and the vacuum energy density. The vacuum energy density
in the brane gotten by this method is in agreement with astronomical
observations.Comment: 16 pages,4 figure
Static Solutions for Brane Models with a Bulk Scalar Field
We present static solutions of the 5-dimensional Einstein equations in the
brane-world scenario by using two different approaches for the stabilization of
the extra dimension. Assuming a ``phenomenological'' stabilization mechanism,
that creates a non-vanishing in the bulk, we construct a two-brane
model, which allows both branes to have positive self-energies. We then
consider a candidate theory for the dynamical stabilization, through the
introduction of a massless scalar field in the bulk, which interacts with the
branes. We find exact static solutions for the metric and scalar field in the
bulk and demonstrate that the inter-brane distance is determined by the
parameters of scalar field-brane interactions. However, these solutions are
always accompanied by a correlation between the bulk cosmological constant, the
brane self-energies and the interaction terms of the scalar field with the
branes and thus cannot be considered as candidates for the phenomenologically
viable stabilized geometry. We find that the aforementioned correlation cannot
be avoided even in the case of a single-brane solution with positive
self-energy where the fifth dimension ends on a singularity.Comment: 16 pages, revised version, to appear in Phys. Lett.
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