A Non-renormalization Theorem for the Wilsonian Gauge Couplings in Supersymmetric Theories

We show that the holomorphic Wilsonian beta-function of a renormalizable asymptotically free supersymmetric gauge theory with an arbitrary semi-simple gauge group, matter content, and renormalizable superpotential is exhausted at 1-loop with no higher loops and no non-perturbative contributions. This is a non-perturbative extension of the well known result of Shifman and Vainshtein.Comment: 10 pages, LaTeX; added references and clarified credit

Hunting Asymmetric Stops

We point out that in the irreducible natural SUSY spectrum, stops have comparable branching fractions to chargino-bottom and neutralino-top in the vast bulk of parameter space, provided only that both decay modes are kinematically accessible. The total stop pair branching fractions into ttbar + MET can therefore be reduced to O(50%), while b bbar + X branching fractions are typically much smaller, O(10%), thus limiting the reach of traditional stop searches. We propose a new stop search targeting the asymmetric final state \~t\~t* --> t chi^0 b chi^pm, which can restore sensitivity to natural stops in the 7 and 8 TeV LHC runs. In addition we present a new variable, topness, which efficiently suppresses the dominant top backgrounds to semi-leptonic top partner searches. We demonstrate the utility of topness in both our asymmetric search channel and traditional \~t\~t* --> ttbar + MET searches and show that it matches or out-performs existing variables.Comment: 5 pages, 4 figures. V2: version accepted for publication in PR

Cosmology of One Extra Dimension with Localized Gravity

We examine the cosmology of the two recently proposed scenarios for a five dimensional universe with localized gravity. We find that the scenario with a non-compact fifth dimension is potentially viable, while the scenario which might solve the hierarchy problem predicts a contracting universe, leading to a variety of cosmological problems.Comment: 10 pages, LaTeX. Reference adde

Brane World Susy Breaking

In brane world models of nature, supersymmetry breaking is often isolated on a distant brane in a higher dimensional space. The form of the Kahler potential in generic string and M-theory brane world backgrounds is shown to give rise to tree-level non-universal squark and slepton masses. This results from the exchange of bulk supergravity fields and warping of the internal geometry. This is contrary to the notion that bulk locality gives rise to a sequestered no-scale form of the Kahler potential with vanishing tree-level masses and solves the supersymmetric flavor problem. As a result, a radiatively generated anomaly mediated superpartner spectrum is not a generic outcome of these theories.Comment: 13 pages, Late

Late Inflation and the Moduli Problem of Sub-Millimeter Dimensions

We consider a recent model with sub-millimeter sized extra dimensions, where the field that determines the size of the extra dimensions (the radion) also acts as an inflaton. The radion is also a stable modulus, and its coherent oscillations can potentially overclose the Universe. It has been suggested that a second round of late inflation can solve this problem, however we find that this scenario does not allow for sufficient reheating of the Universe.Comment: 9 pages, LaTe

Minimum Length from First Principles

We show that no device or gedanken experiment is capable of measuring a distance less than the Planck length. By "measuring a distance less than the Planck length" we mean, technically, resolve the eigenvalues of the position operator to within that accuracy. The only assumptions in our argument are causality, the uncertainty principle from quantum mechanics and a dynamical criteria for gravitational collapse from classical general relativity called the hoop conjecture. The inability of any gedanken experiment to measure a sub-Planckian distance suggests the existence of a minimal length.Comment: 8 pages, Honorable Mention in the 2005 Gravity Research Foundation Essay Competitio

Towards a High Energy Theory for the Higgs Phase of Gravity

Spontaneous Lorentz violation due to a time-dependent expectation value for a massless scalar has been suggested as a method for dynamically generating dark energy. A natural candidate for the scalar is a Goldstone boson arising from the spontaneous breaking of a U(1) symmetry. We investigate the low-energy effective action for such a Goldstone boson in a general class of models involving only scalars, proving that if the scalars have standard kinetic terms then at the {\em classical} level the effective action does not have the required features for spontaneous Lorentz violation to occur asymptotically $(t \to \infty)$ in an expanding FRW universe. Then we study the large $N$ limit of a renormalizable field theory with a complex scalar coupled to massive fermions. In this model an effective action for the Goldstone boson with the properties required for spontaneous Lorentz violation can be generated. Although the model has shortcomings, we feel it represents progress towards finding a high energy completion for the Higgs phase of gravity.Comment: 20 pages, 5 figures;fixed typos and added reference