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