Recently a new class of theories of electroweak symmetry breaking have been constructed. These models, based on deconstruction and the physics of theory space, provide the first alternative to weak-scale supersymmetry with naturally light Higgs fields and perturbative new physics at the TeV scale. The Higgs is light because it is a pseudo-Goldstone boson, and the quadratically divergent contributions to the Higgs mass are cancelled by new TeV scale "partners" of the same statistics. In this paper we present the minimal theory space model of electroweak symmetry breaking, with two sites and four link fields, and the minimal set of fermions. There are very few parameters and degrees of freedom beyond the Standard Model. Below a TeV, we have the Standard Model with two light Higgs doublets, and an additional complex scalar weak triplet and singlet. At the TeV scale, the new particles that cancel the 1-loop quadratic divergences in the Higgs mass are revealed. The entire Higgs potential needed for electroweak symmetry breaking-the quartic couplings as well as the familiar negative mass squared-can be generated by the top Yukawa coupling, providing a novel link between the physics of flavor and electroweak symmetry breaking.
We study whether a violation of the null energy condition necessarily implies the presence of instabilities. We prove that this is the case in a large class of situations, including isotropic solids and fluids relevant for cosmology. On the other hand we present several counter-examples of consistent effective field theories possessing a stable background where the null energy condition is violated. Two necessary features of these counter-examples are the lack of isotropy of the background and the presence of superluminal modes. We argue that many of the properties of massive gravity can be understood by associating it to a solid at the edge of violating the null energy condition. We briefly analyze the difficulties of mimicking Ḣ > 0 in scalar tensor theories of gravity.
We present an explicit formulation of supersymmetric Yang-Mills theories from D = 5 to 10 dimensions in the familiar N = 1, D = 4 superspace. This provides the rules for globally supersymmetric model building with extra dimensions and in particular allows us to simply write down N = 1 SUSY preserving interactions between bulk fields and fields localized on branes. We present a few applications of the formalism by way of illustration, including supersymmetric "shining" of bulk fields, orbifolds and localization of chiral fermions, anomaly inflow and super-Chern-Simons theories.observation is that, whatever the higher-dimensional theories are, they certainly contain the ordinary 4D SUSY, and therefore they must have an ordinary 4D superspace description. The superfield content of the 4D theory is easy to guess, simply by knowing the total number of SUSY generators in the full theory. For instance in 5D, the smallest spinor is a Dirac spinor with 8 real components, which means there are a minimum of 8 supercharges, or N = 2 in 4D. From the 4D viewpoint, we have either hypermultiplets or vector multiplets. Consider hypermultiplets for simplicity. In N = 1 language, they break into two chiral multiplets H, H c . Furthermore, we have one of these superfields for each point x 5 in the 5'th dimension. So, our field content consist of superfields H(x 5 ), H c (x 5 ). From the 4D point of view x 5 can simply be thought of as a label. Now, our task is to write down a superspace action for these fields that, once all auxilliary fields have been integrated out, reduces to the correct component action for the 5D theory. This is very easy to do, as the possible terms are heavily constrained by various symmetries. For this particular example this was done in [11], and will be reviewed in the next section. We will carry this procedure out for all globally supersymmetric theories from D = 5 to 10 dimensions in this paper. But in any case, once we have the action for the bulk theory written in 4D superspace, it is trivial to couple bulk fields to fields localized on 3-branes, in a way preserving N = 1 SUSY. We simply add additional 4D superspace interactions localized at particular locations in the transverse dimensions.We will begin by describing SUSY gauge theories in 5, 6 dimensions, where the field content is the same as N = 2 in 4D. We then move on to the cases D = 7 to 10, where the field content is that of N = 4 in 4D. For the gauge multiplets, we first discuss the Abelian theory before giving the non-Abelian generalizations. We then discuss a number of applications in the remainder of the paper.After this work was posted to hep-th, we were informed by A. Sagnotti and W. Siegel that a superfield formulation of D = 10 SYM was given in [12]. The formulation there is essentially identical to the one we present for this case. The action given in [12] has an extra Wess-Zumino-Witten type term required to make it fully gauge invariant-this term was missed in the first version of our paper. However, the new term vanishes in Wess-Zu...
This document proposes a collection of simplified models relevant to the design of new-physics searches at the Large Hadron Collider (LHC) and the characterization of their results. Both ATLAS and CMS have already presented some results in terms of simplified models, and we encourage them to continue and expand this effort, which supplements both signature-based results and benchmark model interpretations. A simplified model is defined by an effective Lagrangian describing the interactions of a small number of new particles. Simplified models can equally well be described by a small number of masses and cross-sections. These parameters are directly related to collider physics observables, making simplified models a particularly effective framework for evaluating searches and a useful starting point for characterizing positive signals of new physics. This document serves as an official summary of the results from the 'Topologies for Early LHC Searches' workshop, held at SLAC in September
Recently, a new class of realistic models for electroweak symmetry breaking have been constructed, without supersymmetry. These theories have naturally light Higgs bosons and perturbative new physics at the TeV scale. We describe these models in detail, and show that electroweak symmetry breaking can be triggered by a large top quark Yukawa coupling. A rich spectrum of particles is predicted, with a pair of light Higgs doublets accompanied by new light weak triplet and singlet scalars. The lightest of these new scalars is charged under a geometric discrete symmetry and is therefore stable, providing a new candidate for WIMP dark matter. At TeV energies, a plethora of new heavy scalars, gauge bosons and fermions are revealed, with distinctive quantum numbers and decay modes.
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