685 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
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
Towards a Realistic Model of Higgsless Electroweak Symmetry Breaking
We present a 5D gauge theory in warped space based on a bulk SU(2)_L x
SU(2)_R x U(1)_(B-L) gauge group where the gauge symmetry is broken by boundary
conditions. The symmetry breaking pattern and the mass spectrum resembles that
in the standard model (SM). To leading order in the warp factor the rho
parameter and the coupling of the Z (or equivalently the S-parameter) are as in
the SM, while corrections are expected at the level of a percent. From the
AdS/CFT point of view the model presented here can be viewed as the AdS dual of
a (walking) technicolor-like theory, in the sense that it is the presence of
the IR brane itself that breaks electroweak symmetry, and not a localized Higgs
on the IR brane (which should be interpreted as a composite Higgs model). This
model predicts the lightest W, Z and photon resonances to be at around 1.2 TeV,
and no fundamental (or composite) Higgs particles.Comment: 10 pages. v2: refs adde
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
Top and Bottom: a Brane of Their Own
We consider extra dimensional descriptions of models where there are two
separate strongly interacting sectors contributing to electroweak symmetry
breaking (``topcolor'' type models). In the extra dimensional picture there
would be two separate (anti-de Sitter) bulks meeting on the Planck brane, with
each bulk having its own corresponding IR (TeV) brane. Sources for electroweak
symmetry breaking can then be localized on both of these IR branes, while the
different generations of fermions may be separated from each other. We describe
the modes propagating in such a setup, and consider the cases where the
electroweak symmetry breaking on either of the two IR branes come either from a
higgsless scenario (via boundary conditions) or a (top-)Higgs. We show that the
tension that exists between obtaining a large top quark mass and the correct
value of the Zb\bar{b} couplings in ordinary higgsless models can be largely
relieved in the higgsless--top-Higgs versions of the two IR brane models. This
may also be true in the purely higgsless--higgsless case, however since that
model is necessarily in the strongly coupled regime the tree-level results for
the properties of the third generation may get large corrections. A necessary
consequence of such models is the appearance of additional pseudo-Goldstone
bosons (``top-pions''), which would be strongly coupled to the third
generation.Comment: 34 pages, LaTeX, 6 figures. v2: figure 2 fixed, footnote, comments
and references adde
The shortest cut in brane cosmology
We consider brane cosmology studying the shortest null path on the brane for
photons, and in the bulk for gravitons. We derive the differential equation for
the shortest path in the bulk for a 1+4 cosmological metric. The time cost and
the redshifts for photons and gravitons after traveling their respective path
are compared. We consider some numerical solutions of the shortest path
equation, and show that there is no shortest path in the bulk for the
Randall-Sundrum vacuum brane solution, the linear cosmological solution of
Bin\'etruy, et al for , and for some expanding brane
universes.Comment: 20 pages, 7 figure
Black Diamonds at Brane Junctions
We discuss the properties of black holes in brane-world scenarios where our
universe is viewed as a four-dimensional sub-manifold of some
higher-dimensional spacetime. We consider in detail such a model where
four-dimensional spacetime lies at the junction of several domain walls in a
higher dimensional anti-de Sitter spacetime. In this model there may be any
number p of infinitely large extra dimensions transverse to the brane-world. We
present an exact solution describing a black p-brane which will induce on the
brane-world the Schwarzschild solution. This exact solution is unstable to the
Gregory-Laflamme instability, whereby long-wavelength perturbations cause the
extended horizon to fragment. We therefore argue that at late times a
non-rotating uncharged black hole in the brane-world is described by a deformed
event horizon in p+4 dimensions which will induce, to good approximation, the
Schwarzschild solution in the four-dimensional brane world. When p=2, this
deformed horizon resembles a black diamond and more generally for p>2, a
polyhedron.Comment: 13 pages, 1 figure, latex, JHEP.cl
Dilatonic p-Branes and Brane Worlds
We study a general dilatonic p-brane solution in arbitrary dimensions in
relation to the Randall-Sundrum scenario. When the p-brane is fully localized
along its transverse directions, the Kaluza-Klein zero mode of bulk graviton is
not normalizable. When the p-brane is delocalized along its transverse
directions except one, the Kaluza-Klein zero mode of bulk graviton is
normalizable if the warp factor is chosen to increase, in which case there are
singularities at finite distance away from the p-brane. Such delocalized
p-brane can be regarded as a dilatonic domain wall as seen in higher
dimensions. This unusual property of the warp factor allows one to avoid a
problem of dilatonic domain wall with decreasing warp factor that free massive
particles are repelled from the domain wall and hit singularities, since
massive particles with finite energy are trapped around delocalized p-branes
with increasing warp factor by gravitational force and can never reach the
singularities.Comment: 13 pages, LaTe
Composite Intermediary and Mediator Models of Gauge-Mediated Supersymmetry Breaking
We discuss gauge-mediated models which employ a tree-level mass term in the
superpotential. We give explicit composite realizations in which the mass terms
are not fundamental. Instead, they arise as effective terms in the
superpotential from confining gauge dynamics.Comment: 20 pages, LaTeX, 1 figur
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