January 26, 2009
Speaker: Walter Goldberger, Yale University
Title: "Gravitational models of non-relativistic conformal theories"
February 9, 2009
Speaker: Zohar Komargodski, Institute for Advanced Study
Title: "Aspects of SUSY and R-Symmetry Breaking"
We discuss aspects of Wess-Zumino models related to SUSY and R-symmetry breaking at tree-level. We deduce a general property shared by all tree-level SUSY breaking models that has broad application to model building. In particular, it explains why many models of direct gauge mediation have anomalously light gauginos (even if the R-symmetry is broken spontaneously by an order one amount). This suggests new approaches to dynamical SUSY breaking which can generate large enough gaugino masses.
February 16, 2009
Speaker: Bogdan Dobrescu, FNAL
Title: "How to search for new quarks"
All elementary fermions discovered so far are chiral, which means that their masses are not gauge invariant. It is possible that non-chiral fermions exist and have escaped detection due to their large mass.A heavy fermion of this kind may mix with the top quark, leading to interesting signatures at the Tevatron and LHC colliders. Such new physics at the TeV scale has the potential of revealing the origin of electroweak symmetry breaking.
February 23, 2009
Speaker: Clifford Cheung, Harvard University
Title: "Dark Sectors and Collider Physics"
Recent observations from cosmic ray astrophysics indicate an excess of e+e- that
may be evidence for DM annihilations or decays in the galactic halo. Motivated
by these and other experiments, we discuss the possibility that DM is charged
under a dark gauge group, and present a minimal abelian model. We also discuss
non-abelian models and their collider signatures.
March 9, 2009
Speaker: Donal O'Conel, Institute for Advanced Study
Title: "The Lee-Wick Standard Model"
"I will discuss an extension of the standard model of particle physics motivated by the hierarchy problem. This extension, the Lee-Wick standard model, is based on ideas of T.D. Lee and G. Wick. The theory has some successes but there is a price to pay. I will comment the successes of the theory as well as on the issues facing the theory and the resolution of some of them. The physics is exotic but nevertheless the model reduces to the standard model and appears to evade current experimental bounds."
March 23, 2009
Speaker: Raphael Bousso, University of California, Berkeley
Title: "Think Global Act Causal: Complementarity in the
April 13, 2009
Speaker: Gregory Gabadadze, New York University
Title: "A Theory of Charged Condensation in White Dwarfs"
I will discuss the possibility that cores of certain white dwarf stars may contain a new state of matter -- a condensate of charged spin-0 particles. I will discuss an effective field theory description of this state, and its consequences for cooling rates and magnetic fields of the dwarf stars.
April 20, 2009
Speaker: Hume Feldman, University of Kansas
Title: "Flow on 100 Mpc/h Scales and the Amplitude of Density Fluctuations in the Universe"
The bulk flow is a sensitive probe of matter density fluctuations on large scales. We introduce a new method of calculating bulk flow moments where velocities are weighted to give an optimal estimate of the bulk flow of an idealized survey, with the variance of the
difference between the estimate and the actual flow being minimized.
These ``minimum variance'' estimates can be designed to estimate the
bulk flow on a particular scale with minimal sensitivity to small scale power, and are comparable between surveys. We compile all major
peculiar velocity surveys and estimate the bulk flow on 100
Mpc/h scales to be ~400 km/s which indicates that there are significant density fluctuations on very large scales. The
WMAP5-normalized LCDM cosmology, predicts a r.m.s. velocity of ~100
km/s. The discrepancy in the amplitude of cosmological density
fluctuations is not confined only to large scales. The estimates of the
fluctuations on 8 Mpc/h scales (sigma_8) also vary considerably between various probes. However, different estimators examine the value
on different cosmological scales and do not take into account the nonlinear evolution of the parameter at late times. We show that
estimates of the fluctuations amplitude derived from cosmic flows are
systematically higher than those inferred at early epochs because of
nonlinear evolution at later times. Here we derive corrections to the
value of sigma_8 from both perturbation theory and numerical
simulations and compare amplitudes after accounting for this effect.
May 11, 2009
Speaker: David Poland, Harvard University
Title: "Hidden Sectors at a GeV"
I will discuss mechanisms for naturally generating GeV-scale hidden sectors in
the context of weak-scale supersymmetry. Such low mass scales can arise when
hidden sectors are more weakly coupled to supersymmetry breaking than the
visible sector, as happens when supersymmetry breaking is communicated to the
visible sector by gauge interactions under which the hidden sector is uncharged,
or if the hidden sector is sequestered from gravity-mediated supersymmetry
breaking. In this talk I will investigate the viability of the simplest Abelian
GeV-scale hidden sectors in the context of gauge mediation.