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Physics

Zero Temperature Limit Of Holographic Superconductors
 Date Added:
 09/20/2011
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We consider holographic superconductors whose bulk description consists of
gravity minimally coupled to a Maxwell field and charged scalar field with general potential.
We give an analytic argument that there is no “hard gap”: the real part of the conductivity
at low frequency remains nonzero (although typically exponentially small) even at zero
temperature. We also numerically construct the gravitational dual of the ground state
of some holographic superconductors. Depending on the charge and dimension of the
condensate, the infrared theory can have emergent conformal or just Poincare symmetry.
In all cases studied, the area of the horizon of the dual black hole goes to zero in the
extremal limit, consistent with a nondegenerate ground state. 
Zamolodchikov Asymptotic Formula And Instanton Expansion In N = 2 SUSY Nf = 2Nc QCD
 Date Added:
 09/24/2011
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The AGT relations allow to convert the Zamolodchikov asymptotic formula
for conformal block into the instanton expansion of the SeibergWitten prepotential for
the theory with two colors and four fundamental flavors. This provides an explicit formula
for the instanton corrections in this model. 
Z? Boson Mixings With Z? And Charge Assignments
 Date Added:
 02/11/2011
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Based on the general description for Z??Z?
mixing as derived from the
electroweak chiral Lagrangian, we characterize and classify the various new physics models
involving the Z? boson that have appeared in the literature into five classes: 1. Models
with minimal Z??Z mass mixing; 2. Models with minimal Z??Z kinetic mixing; 3. Models
with general Z??Z mixing; 4. Models with Z??
kinetic and Z??Z mixing; and 5. Models
with Stueckelbergtype mixing. The corresponding mixing matrices are explicitly evaluated
for each of these classes. We constrain and classify the Z? boson charges with respect to
quarkleptons by anomaly cancellation conditions. 
Yukawa Structure From U(1) Fluxes In FTheory Grand Unification
 Date Added:
 04/16/2010
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 1
In Ftheory GUT constructions Yukawa couplings necessarily take place at the
intersection of three matter curves. For generic geometric configurations this gives rise to
problematic Yukawa couplings unable to reproduce the observed hierarchies. We point out
that if the U(1)B?L/U(1)Y flux breaking the SO(10)/SU(5) GUT symmetry is allowed to
go through pairs of matter curves with the same GUT representation, the quark/lepton
content is redistributed in such a way that all quark and leptons are allowed to have
hierarchical Yukawas. 
Yangian Symmetry Of Scattering Amplitudes In N = 4 Super YangMills Theory
 Date Added:
 12/20/2010
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Treelevel scattering amplitudes in N = 4 super YangMills theory have recently
been shown to transform covariantly with respect to a ‘dual’ superconformal symmetry
algebra, thus extending the conventional superconformal symmetry algebra psu(2, 24)
of the theory.