# semester, 2008

Thursday, January 24th 2008
12:15 pm:
Speaker: There will be no seminar this week.

Thursday, January 31st 2008
12:15 pm:
Speaker: Mikhail Voloshin, University of Minnesota
Subject: "Unusual Peaks around the Open Charm Threshold"

Thursday, February 7th 2008
12:15 pm:
Speaker: Masahiro Ibe, SLAC
Subject: "Sweet Spot Supersymmetry and LHC"

Thursday, February 14th 2008
12:15 pm:
Speaker: Alyosha Yung, University of Minnesota
Subject: "Heterotic flux tubes"

Thursday, February 21st 2008
12:15 pm:
Speaker: Will Kinney, University at Buffalo
Subject: "Inflationary Cosmology and Upcoming Observational Programs"

Thursday, February 28th 2008
12:15 pm:
Speaker: Antigone Nounou, University of Minnesota
Subject: "One Real Gauge Potential is One too Many"

Thursday, March 6th 2008
12:15 pm:
Speaker: Graham Kribs, University of Oregon
Subject: "Supersymmetric Flavor Problem, R-Symmetry, and the LHC"

Thursday, March 13th 2008
12:15 pm:
Speaker: David Tucker-Smith, Williams
Subject: "Mixed sneutrinos at the LHC"

Monday, March 17th 2008
12:15 pm:
Speaker: TBA

Thursday, March 20th 2008
12:15 pm:
Speaker: No Speaker This Week!

Thursday, March 27th 2008
12:15 pm:
Speaker: Scott Dodelson, FermiLab
Subject: "Dark Matter v. Modified Gravity"

Thursday, April 3rd 2008
12:15 pm:
Speaker: Howard Baer, Flordia State University
Subject: SO(10) SUSY GUTs: consequences for cosmology and collider searches

Thursday, April 10th 2008
12:15 pm:
Speaker: Sally Dawson, Brookhaven National Lab
Subject: "b's and Higgs Physics"

Thursday, April 17th 2008
12:15 pm:
Speaker: Brian Batell, University of Minnesota
Subject: Elementary/composite mixing in Randall-Sundrum models

Thursday, April 24th 2008
12:15 pm:
Speaker: Richard Holman, Carnegie Melon University
Subject: "Enhanced Non-Gaussianity from Excited Initial States"

Thursday, May 1st 2008
12:15 pm:
Speaker: Zackaria Chacko, University of Maryland
Subject: Folded Supersymmetry and the LEP Paradox

Thursday, May 8th 2008
12:15 pm:
Speaker: Mu-Chun Chen, UCI
Subject: Tri-bimaximal Neutrino Mixing and Quark CKM Matrix from Finite Group (d)T

The current experimental values for neutrino mixing angles are very close to the predictions of the so-called tri-bimaximal'' mixing matrix. I will describe a recent model which gives rise to, for the first time, the tri-bimaximal neutrino mixing and realistic quark CKM matrix simultaneously. The model is based on SU(5) GUT combined with the double tetrahedral group as a family symmetry, and it has only nine parameters to account for all 18 fermion masses and mixing angles. The model also predicts a new sum rule relating the solar mixing angle for the neutrinos and the Cabibbo angle in the quark sector, as a result of the Georgi-Jarlskog relations. The double tetrahedral group may be originated from extra dimensions as a residual symmetry upon orbifold compactification.

Thursday, May 15th 2008
12:15 pm:
Speaker: TBA

Thursday, May 22nd 2008
12:15 pm:
The seminar has ended for the semester. It will return in September 2008

Thursday, September 4th 2008
12:15 pm:
Speaker: TBA

Thursday, September 11th 2008
12:15 pm:
Speaker: TBA

Thursday, September 18th 2008
12:15 pm:
Speaker: Alexander Monin
Subject: The spontaneous breaking of a metastable string

We consider the phase transition of a string with tension to a string with a smaller tension . The transition proceeds through quantum tunneling, and we calculate in arbitrary number of dimensions the pre-exponential factor multiplying the leading semiclassical exponential expression for the rate of the process. At the found formula for the decay rate also describes a break up of a metastable string into two pieces.

Thursday, September 25th 2008
12:15 pm:
Speaker: Peter Koroteev, University of Minnesota
Subject: Braneworld Models with Broken Bulk Lorentz Invariance.

We study deformations of the Randall--Sundrum 2 model with broken bulk Lorentz invariance. First, we prove a theorem which forbids a static smooth five-dimensional background to exist provided that null energy conditions for a matter on a brane and in a bulk are satisfied. However, if the Lorentz invariance is unbroken such a setup exists. Second, we derive perturbation spectra of scalar and spin-1/2 fermion particles in the backgrounds in question and show that, in spite of the full theory is manifestly not Lorentz invariant, the effective four-dimensional theory can be made approximately Lorentz invariant at low energies. We also investigate localization of particles on a brane in various scenarios with broken Lorentz invariance.

Thursday, October 2nd 2008
12:15 pm:
Speaker: Dr. Tonnis ter Veldhuis, Macalester College
Subject: Brane Vector Phenomenology

Local oscillations of the brane world are manifested as massive vector fields. Their coupling to the Standard Model can be obtained using the method of nonlinear realizations of the spontaneously broken higher dimensional space-time symmetries, and to an extent, are model independent. Phenomenological limits on these vector field parameters are obtained using current collider data and dark matter constraints. The reach of a future linear collider and the LHC to further investigate the parameter space is determined.

Thursday, October 9th 2008
12:15 pm:
Speaker: Jose A.R. Cembranos, University of Minnesota
Subject: Gravitational Dark Matter

The modification of Einstein gravity at high energies is mandatory from a quantum approach. In this talk, I will point out that this modification necessarily introduces new degrees of freedom. We will discuss the possibility that these new gravitational states can provide the main contribution to the non-baryonic dark matter of the Universe. I will illustrate this idea with the simplest high energy modification of the Einstein-Hilbert action: R2-gravity.

Thursday, October 16th 2008
12:15 pm:
Speaker: Guido Festuccia, University of California, Santa Cruz
Subject: Symmetric Points in the Landscape as Cosmological Attractors

Wednesday, October 22nd 2008
1:30 pm:
Speaker: Tirthabir Biswas, IGC at PennState University.
Subject: Dark Energy vs. Local Void

Thursday, October 23rd 2008
12:15 pm:
Speaker: Wan-il Park, Korea Advanced Institute of Science and Technology
Subject: Thermal Inflation, Gravitiational Waves, Baryogenesis and Dark Matter

We propose a simple extension of the Minimal Supersymmetric Standard Model which gives rise to thermal inflation, baryogenesis and dark matter in a natural and remarkably consistent way. We consider the λφ = 0- special case of our previous model, which is the minimal way to incorporate a Peccei-Quinn symmetry. The axino becomes the lightest supersymmetric particle with $m_{\tilde{a}} \sim 1 \textrm{ to } 10 \GeV$ and is typically over-produced during the flaton decay.
Interestingly though, the dark matter abundance is minimized for , $f_a \sim 10^{11} \textrm{ to } 10^{12} \GeVand |\mu| \sim 400 \GeV \textrm{ to } 1 \TeV$ at an abundance coincident with the observed abundance and with significant amounts of both axions and axinos. Futhermore, for these values the baryon abundance naturally matches the observed abundance.
As an observable, thermal inflation which is the key idea of the model produces a background of gravitational waves.
It is likely to be detected at BBO and DECIGO style direct detection experiments.

Thursday, October 30th 2008
12:15 pm:
Speaker: Stefano Profumo, University of California Santa Cruz
Subject: Electro-weak Baryogenesis: a Multi-faceted Approach

We study supersymmetric models that include a viable dark
matter candidate and that generate the observed baryon asymmetry of the Universe at the electro-weak phase transition. We focus on the possibility of probing these models with searches for the permanent electric dipole moment (EDM) of the electron, with direct and indirect dark matter searches, with high energy colliders and with Gravitational Wave detection. We point out that the lightest neutralino might play a key role for the generation of both baryonic and dark matter. We show that models
overproducing relic neutralinos put tighter constraints on successful electro-weak baryogenesis. We present new results on two-loop electric dipole moments and investigate in detail the entire parameter space of the minimal supersymmetric extension of the standard model where electro-weak baryogenesis can account for the baryon asymmetry of the universe. We claim that the ensemble of experimental tests we consider makes ours a
testable framework for the origin of both the dark matter and the baryonic matter-antimatter asymmetry in the Universe.

Thursday, November 6th 2008
12:15 pm:
Speaker: Nemanja Kaloper, University of California, Davis

Thursday, November 13th 2008
12:15 pm:
Speaker: Alfredo Aranda Fernandez, Universidad de Colima
Subject: Electroweak scale neutrinos and Higgses

Minimal extensions of the scalar sector of the SM can be obtained in order to explore neutrino physics. In particular we are interested in scenarios where the seesaw mechanism for neutrino mass generation could be tested at colliders, thus requiring the right-handed neutrinos to have electroweak scale masses. We present two simple realizations of this type of scheme and explore their scalar phenomenology.

Thursday, November 20th 2008
12:15 pm:
Speaker: Andreas Weiler, Cornell University
Subject:  "Warped extra dimensions as a model of flavor: GIM, RS-GIM and flavor symmetries"

Thursday, November 27th 2008
12:15 pm:
Speaker: No Speaker Today
Subject: Thanksgiving Holiday, University Closed

Thursday, December 4th 2008
12:15 pm:
Speaker: Brian Wecht, IAS
Subject: Semi-direct Gauge Mediation

Thursday, December 11th 2008
12:15 pm:
Speaker: Moved to Friday at 2:30pm in 435 Physics

Friday, December 12th 2008
2:30 pm:
Speaker: Katie Freese, University of Michigan
Subject: Dark Stars: a new phase of stellar evolution due to dark matter annihilation

The first phase of stellar evolution in the history of the universe may be Dark Stars, powered by dark matter heating rather than by fusion. Weakly interacting massive particles, which are their own antiparticles, can annihilate and provide an important heat source for the first stars in the the universe. This talk presents the story of these Dark Stars. We make predictions that the first stars are very massive (\sim 800 M_\odot), cool (6000 K), bright (\sim 10^6 L_\odot), long-lived (10^6 years), and probable precursors to (otherwise unexplained) supermassive black holes. Later, once the initial DM fuel runs out and fusion sets in, DM annihilation can predominate again if the scattering cross section is strong enough, so that Dark Stars may persist for a very long time.

Thursday, December 18th 2008
12:15 pm:
Speaker: TBA
Subject: Finals Week

Thursday, December 25th 2008
12:15 pm:
Speaker: No Speaker Today
Subject: Holiday, Univeristy Closed

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