122595912
Anomalies in Nonlinear $\sigma$ Models
Certain nonlinear sigma models with fermions suffer from an anomaly similar to the one in non-Abelian gauge theory. We exhibit this anomaly using both perturbative and global methods. The affected theories are ill defined and hence unsuitable for describing low-energy dynamics. They include certain supersymmetric models in four space-time dimensions.
125232166
Matrix Models of 2D Gravity and Isomonodromic Deformation
One of the principal goals of the theory of 2D gravity is making sense of the formal expression 
 
$$Z\left( {\mu ,\kappa ;{t_i}} \right) = \sum\limits_h {{{\int_{ME{T_h}} {dge} }^{\mu \int {\sqrt g + k\int {\sqrt g } + k} }}} {Z_{QFT\left( {{t_i}} \right)}}\left[ g \right]$$ 
 
(1.1) 
 
where we integrate over metrics g on surfaces with h handles with a weight defined by the Einstein-Hilbert action (μ is the cosmological constant and κ is Newton’s constant, or, equivalently, the string coupling) together with the partition function of some 2D quantum field theory, QFT(t i ). The parameters t i are coordinates on a subspace of the space of 2D field theories, or, equivalently, coordinates for a space of string backgrounds.
124306496
The M theory three form and E(8) gauge theory
6777210
Remarks on tachyon condensation in superstring field theory
We generalize recent results on tachyon condensation in boundary string field theory to the superstring.
119635081
D-branes, Quivers, and ALE Instantons
Effective field theories in type I and II superstring theories for D-branes located at points in the orbifold C^2/Z_n are supersymmetric gauge theories whose field content is conveniently summarized by a `quiver diagram,' and whose Lagrangian includes non-metric couplings to the orbifold moduli: in particular, twisted sector moduli couple as Fayet-Iliopoulos terms in the gauge theory. These theories describe D-branes on resolved ALE spaces. Their spaces of vacua are moduli spaces of smooth ALE metrics and Yang-Mills instantons, whose metrics are explicitly computable. For U(N) instantons, the construction exactly reproduces results of Kronheimer and Nakajima.
13804747
Three-manifold topology and the Donaldson-Witten partition function
Abstract We consider Donaldson-Witten theory on four-manifolds of the form X = Y × S 1 where Y is a compact three-manifold. We show that there are interesting relations between the four-dimensional Donaldson invariants of X and certain topological invariants of Y. In particular, we reinterpret a result of Meng-Taubes relating the Seiberg-Witten invariants to Reidemeister-Milnor torsion. If b1(Y) > 1 we show that the partition function reduces to the Casson-Walker-Lescop invariant of Y, as expected on formal grounds. In the case b1(Y) = 1 there is a correction. Consequently, in the case b1(Y) = 1, we observe an interesting subtlety in the standard expectations of Kaluza-Klein theory when applied to supersymmetric gauge theory compactified on a circle of small radius.
119104096
Limits on Lorentz violation from the highest energy cosmic rays
We place several new limits on Lorentz violating effects, which can modify particles' dispersion relations, by considering the highest energy cosmic rays observed. Since these are hadrons, this involves considering the partonic content of such cosmic rays. We get a number of bounds on differences in maximum propagation speeds, which are typically bounded at the 10{sup -21} level, and on momentum dependent dispersion corrections of the form v=1{+-}p{sup 2}/{lambda}{sup 2}, which typically bound {lambda}>10{sup 21} GeV, well above the Planck scale. For (CPT violating) dispersion correction of the form v=1+p/{lambda}, the bounds are up to 15 orders of magnitude beyond the Planck scale.
117910269
New algorithm for classical gauge theory simulations in an expanding box
We propose a new algorithm for classical statistical simulations in scalar and gauge theories undergoing a one dimensional expansion, which allows simulations to study boxes of larger transverse extent and to continue for longer times, without losing lattice resolution in the expanding direction.
118805589
Second order hydrodynamic coefficients from kinetic theory
In a relativistic setting, hydrodynamic calculations which include shear viscosity (which is first order in an expansion in gradients of the flow velocity) are unstable and acausal unless they also include terms to second order in gradients. To date such terms have only been computed in supersymmetric N=4 super-Yang-Mills theory at infinite coupling. Here we compute these second-order hydrodynamic coefficients in weakly coupled QCD, perturbatively to leading order in the QCD coupling, using kinetic theory. We also compute them in QED and scalar {lambda}{phi}{sup 4} theory.
118963546
Numerical studies of QGP instabilities and implications
Abstract.Because of the flat initial shape of the QGP in a heavy-ion collision, the momentum distribution becomes anisotropic after a short time. This leads to plasma instabilities, which may help explain how the plasma isotropizes. We explain the physics of instabilities and give the latest results of numerical simulations into their evolution. Non-Abelian interactions cut off the size to which the soft unstable fields grow, and energy in the soft fields subsequently cascades towards more ultraviolet scales. We present first results for the power spectrum of this cascade.
119247360
Thermodynamical second-order hydrodynamic coefficients
A bstractTransport coefficients in non-conformal second-order hydrodynamics can be classified as either dynamical or thermodynamical. We derive Kubo formuale for the thermodynamical coefficients and compute them at leading perturbative order in a theory with general matter content. We also discuss how to approach their evaluation on the lattice.