Fall 2012

Results of dark matter searches in dwarf galaxies with Fermi I will present new results from a search for both continuum and line emission from dark matter annihilation in Milky Way dwarfs. These results are based on the joint analysis of dwarf galaxy data from the Fermi Gamma-ray Space Telescope using a statistically optimal weighting of photons including both spatial and spectral information. This new technique, applied to the indirect dark matter search, is strong enough to probe generic WIMP candidates that reproduce the relic abundance. I will discuss the details of the framework and how it may be applied to other situations, including making predictions for future experiments.

The Shape of Light Stops The recent LHC discovery of a new particle at 125 GeV has created a flurry of interest in light stop squarks that are found in models of supersymmetry. However, current experimental constraints on stop squarks are fairly weak due to the small production cross-sections and difficult backgrounds. I will talk about using shape analyses based on missing transverse energy distributions to significantly improve the bounds on stop squarks, particularly in what are considered the most difficult to probe regions of parameter space.

In this talk we will discuss Fayet-Iliopoulos parameters in four dimensional N=1 supergravity. Although for many years there was lore that they did not exist in supergravity, it was recently argued by Seiberg that they could exist but are quantized, and we will review that quantization. We will also discuss related issues in nonlinear sigma models with a restriction on nonperturbative sectors. In such theories, the FI quantization above is modified, and we will discuss how that modification has a simple mathematical understanding.

We study the phenomenological aspect of the PQ invariant extension of NMSSM in view of recent discovery of 125 GeV Higgs boson. The minimal model does not have supersymmetric mass of singlet supermultiplet. This fact results in very light singlino-like LSP. The model is strongly constrained by the Higgs invisible decay and dark matter properties of the LSP, while some constraints can be relieved by late-time entropy production of saxion decay. The collider signal of the model contains multi-jet and h/W/Z plus missing energy, which can be discovered in the early stage of the 14 TeV LHC.

We will discuss some formal results and conjectures about accidental symmetries in SUSY gauge theories while paying special attention to the particle physics implications. In particular, we will apply our discussion to study certain softly-broken SUSY theories and find constraints on possible light scalars in such theories.

I will review some recent progresses in understanding scattering amplitudes in gravitational theories. We apply the matrix-tree theorem to establish a link between certain diagrammatic and determinant expressions, which appear ubiquitously in gravity amplitudes. Two notable examples include the diagrammatic expansion of Hodges' new formula for tree-level, maximally-helicity-violating (MHV) amplitude, and the matrix form of the one-loop rational part in N=4 supergravity. Furthermore, from a recent "twistor-string like" formula by Cachazo and Skinner, we use a similar approach to derive the Grassmannian formulation for N=8 supergravity, which contains all the tree-level amplitudes and possibly loop-level leading singularities of the theory.

I will explain how the S^5 partition function of 5d superconformal field theories with gravity duals may be computed in the large N limit. This involves applying the techniques of localization to non-renormalizable 5d Yang-Mills theories obtained by deformation of these SCFTs by a relevant operator. The result matches exactly the leading supergravity behavior of the holographic entanglement entropy in the dual AdS6 geometry in massive IIA.

In the wake of the discovery of a Higgs-like resonance near 125 GeV at the LHC, determining its properties in detail has become extremely important. The observed production and decay modes appear to be broadly consistent with those expected from a Standard Model Higgs. However, there are hints that some modes (decays to two photons in particular) may show some discrepancy with Standard Model predictions. While future data will shed light on this possibility, we explore the effects that an extended scalar sector and vector-like fermions can have on Higgs' properties. We study the sensitivity of LHC experiments and those at lower energies to scenarios where the Higgs differs from that of the Standard Model.

Measurements of CMB anisotropies place strong bounds on the properties of thermal freeze-out WIMP dark matter. These bounds are expected to tighten considerably, or possibly provide a positive signal, with upcoming Planck measurements. I will describe work in progress to calculate a novel effect, the possible imprint of dark matter annihilation in CMB non-gaussianity.

We apply localization techniques to study loop operators in 3D N=2 SCFTs on S^3 supported on great circles. After reviewing the localization formalism, we construct certain "vortex loops", topological defect operators supported on loops in the manifold. We show how their expectation values can be computed by localization, and use this to gain some new insight into dualities.

I will discuss Conformal Field Theories (CFTs) in spacetime dimensions d>2. First, assuming that the theory has higher spin conserved current I will demonstrate that the theory is essentially free. Secondly, I will consider higher spin symmetry to be broken at the quantum level. I will show that in this case certain observables are fixed by the broken higher spin symmetry. Finally, I will talk about the most general higher spin symmetry breaking scenario and explain how one can use unitarity and crossing to constrain the spectrum in the broken phase. This will lead us to certain predictions about the spectrum of general CFTs, in particular, models relevant for 3d phase transitions like 3d Ising model.