6,008 research outputs found

### Primordial Inflation and Present-Day Cosmological Constant from Extra Dimensions

A semiclassical gravitation model is outlined which makes use of the Casimir
energy density of vacuum fluctuations in extra compactified dimensions to
produce the present-day cosmological constant as rho_LAMBDA ~ M^8/M_P^4, where
M_P is the Planck scale and M is the weak interaction scale. The model is based
on (4+D)-dimensional gravity, with D = 2 extra dimensions with radius b(t)
curled up at the ADD length scale b_0 = M_P/M^2 ~ 0.1 mm. Vacuum fluctuations
in the compactified space perturb b_0 very slightly, generating a small
present-day cosmological constant.
The radius of the compactified dimensions is predicted to be b_0 = k^{1/4}
0.09 mm (or equivalently M = 2.4 TeV/k^{1/8}), where the Casimir energy density
is k/b^4.
Primordial inflation of our three-dimensional space occurs as in the
cosmology of the ADD model as the inflaton b(t), which initially is on the
order of 1/M ~ 10^{-17} cm, rolls down its potential to b_0.Comment: 10 pages; Version 2: added discussion of brane tension and zero of
the stabilization potential; expanded abstrac

### Little Higgs Models: New Approaches to the Hierarchy Problem

In this note we present a review of the little Higgs models that stabilize
the electroweak by realizing the Standard Model Higgs as a pseudo-Goldstone
boson.Comment: Proceedings for ICHEP02, 3 pages, 2 figure

### Deconstructing Dimensional Deconstruction

Dimensional deconstruction (DD) abstracts from higher dimensional models
features of related 4--dimensional ones. DD was proposed in Refs.[1,2,3] as a
scheme for constructing models of {\it naturally} light composite Higgs boson.
These are models in which--{\it without fine--tuning of parameters}--the
composite Higgs's mass M and vacuum expectation value v are much lighter than
its binding energy scale \Lambda. We review the basic idea of DD. It is easy to
arrange M << \Lambda. We show, however, that DD fails to give v << \Lambda in a
model that is supposed to contain a naturally light composite Higgs [4].Comment: 4 pages, LaTex, with two eps figures, uses espcrc2.sty. Talk at The
31st International Conference on High Energy Physics, Amsterdam, The
Netherlands, July 24--31, 200

### Mooses, Topology and Higgs

New theories of electroweak symmetry breaking have recently been constructed
that stabilize the weak scale and do not rely upon supersymmetry. In these
theories the Higgs boson is a weakly coupled pseudo-Goldstone boson. In this
note we study the class of theories that can be described by theory spaces and
show that the fundamental group of theory space describes all the relevant
classical physics in the low energy theory. The relationship between the low
energy physics and the topological properties of theory space allow a
systematic method for constructing theory spaces that give any desired low
energy particle content and potential. This provides us with tools for
analyzing and constructing new theories of electroweak symmetry breaking.Comment: 16 pages, 11 figure

### Freedom in electroweak symmetry breaking and mass matrix of fermions in dimensional deconstruction model

There exists a freedom in a class of four-dimensional electroweak theories
proposed by Arkani-Hamed et al. relying on deconstruction and Coleman-Weinberg
mechanism. The freedom comes from the winding modes of the link variable
(Wilson operator) connecting non-nearest neighbours in the discrete fifth
dimension. Using this freedom, dynamical breaking of SU(2) gauge symmetry, mass
hierarchy patterns of fermions and Cabbibo-Kobayashi-Maskawa matrix may be
obtained.Comment: LaTeX file 15 pages, no figure, discussion is enlarged, references
are adde

### Chargino Pair Production at Linear Collider and Split Supersymmetry

Recently N. Arkani-Hamed and S. Dimopoulos proposed a supersymmetric model
\cite{Arkani-Hamed:2004fb}, dubbed "Split Supersymmetry" in Ref.
\cite{Giudice:2004tc}, which can remove most of the unpleasant shortcomings of
TeV Supersymmetry. In this model all scalars except one finely tuned Higgs
boson are ultra heavy while the neutralino and chargino might remain light in
order to achieve gauge coupling unification and accord with the dark matter
density. In this paper, we investigated the impact of this new model on
chargino pair production at next generation linear colliders. Our numerical
results show that this process can be used to probe sneutrino mass up to 10
TeV. Therefore, precise measurements of chargino pair production at the linear
colliders could distinguish Split Supersymmetry from TeV Supersymmetry.Comment: 14 pages, 5 eps figs included, minor clarification, refs adde

### Introducing the Little Higgs

Little Higgs theories are an exciting new possibility for physics at TeV
energies. In the Standard Model the Higgs mass suffers from an instability
under radiative corrections. This ``hierarchy problem'' motivates much of
current physics beyond the Standard Model research. Little Higgs theories offer
a new and very promising solution to this problem in which the Higgs is
naturally light as a result of non-linearly realized symmetries. This article
reviews some of the underlying ideas and gives a pedagogical introduction to
the Little Higgs. The examples provided are taken from the paper "A Little
Higgs from a Simple Group", by D.E. Kaplan and M. Schmaltz.Comment: 10 pages, 10 figs, Plenary talk "Physics Beyond the Standard Model
(Theory)" at The 31st International Conference on High Energy Physics,
Amsterdam, The Netherlands, July 24--31, 200

### Deconstructed U(1) and Supersymmetry Breaking

We discuss supersymmetry breaking induced by simultaneous presence of a
Wilson-line type superpotential and boundary-localized Fayet-Iliopoulos terms
in a four dimensional theory based on deconstruction of five-dimensional
abelian gauge theories on orbifolds. Large hierarchy between the scale of
supersymmetry breaking and the fundamental scale can be generated dynamically.
The model has several potentially interesting phenomenological applications. We
also discuss the conditions that are necessary for interpreting our $U(1)^N$
model as an ultra-violet completion of some 5d theory. In particular, the
corresponding 5d theory contains Chern-Simons couplings.Comment: 12 pages, late

### On the AdS/CFT Dual of Deconstruction

We consider a class of non-supersymmetric gauge theories obtained by
orbifolding the N=4 super-Yang-Mills theories. We focus on the resulting quiver
theories in their deconstructed phase, both at small and large coupling, where
a fifth dimension opens up. In particular we investigate the r\^ole played by
this extra dimension when evaluating the rectangular Wilson loops encoding the
interaction potential between quarks located at different points in the
orbifold. The large coupling potential of the deconstructed quiver theory is
determined using the AdS/CFT correspondence and analysing the corresponding
minimal surface solution for the dual gravitational metric. At small coupling,
the potential between quarks decreases with their angular distance while at
strong coupling we find a linear dependence at large distance along the
(deconstructed) fifth dimension.Comment: 19 pages, 3 figure

### Custodial supersymmetry in non-supersymmetric quiver theories

We consider non-supersymmetric quiver theories obtained by orbifolding the
N=4 supersymmetric U(K) gauge theory by a discrete Z_\Gamma group embedded in
the SU(4) R-symmetry group. We explicitly find that in such theories there are
no one-loop quadratic divergences in the effective potential.
Moreover, when the gauge group U(n)^\Gamma of the quiver theory is
spontaneously broken down to the diagonal U(n), we identify a custodial
supersymmetry which is responsible for the fermion-boson degeneracy of the mass
spectrum.Comment: 10 pages, latex, references added, discussion of custodial susy in
the zero-mode sector extende

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