13918277
Real time simulations in lattice gauge theory
Abstract I review the study of real (Minkowski) time correlators in hot, weakly coupled Yang-Mills theory via lattice methods. I concentrate on the Minkowski time topological susceptibility, which is related to the efficiency of baryon number violation at high temperature. It can be computed by approximating the IR fields as classical and solving their dynamics nonperturbatively on the lattice. However it is essential to include the UV degrees of freedom. Their influence can be computed perturbatively and included in the lattice model by the addition of auxiliary fields.
10799212
Classical field dynamics of the electroweak phase transition
We investigate the thermodynamics and dynamics of the electroweak phase transition by modeling the infrared physics with classical Yang-Mills Higgs theory. We discuss the accuracy of this approach and conclude that, for quantities whose determination is dominated by the infrared, the classical method should be correct up to parametrically suppressed [i.e., O({alpha})] corrections. For a Higgs self-coupling which at the tree level corresponds to m{sub H}{approx_equal}50 GeV, we determine the jump in the order parameter to be {delta}{phi}=1.5gT, the surface tension to be {sigma}=0.07g{sup 4}T{sup 3}, and the friction coefficient on the moving bubble wall due to infrared bosons to be {eta}{equivalent_to}P/v{sub w}=0.03{plus_minus}0.004g{sup 6}T{sup 4}. We also investigate the response of the Chern-Simons number to a spatially uniform chemical potential and find that it falls off a short distance inside the bubble wall, both in equilibrium and below the equilibrium temperature. {copyright} {ital 1997} {ital The American Physical Society}
119279378
Bjorken flow, plasma instabilities, and thermalization
A bstractAt asymptotically high energies, thermalization in heavy ion collisions can be described via weak-coupling QCD. We present a complete treatment of how thermalization proceeds, at the parametric weak-coupling level. We show that plasma instabilities dominate the dynamics, from immediately after the collision until well after the plasma becomes nearly in equilibrium. Initially they drive the system close to isotropy, but Bjorken expansion and increasing diluteness makes the system again become more anisotropic. At time $ \tau \sim {\alpha^{{\frac{{ - 12}}{5}}}}Q_s^{{ - 1}} $ the dynamics become dominated by a nearly-thermal bath; and at time $ \tau \sim {\alpha^{{\frac{{ - 5}}{2}}}}Q_s^{{ - 1}} $ the bath comes to dominate the energy density, completing thermalization. After this time there is a nearly isotropic and thermal Quark-Gluon Plasma.
18843095
Classical sphaleron rate on fine lattices
We measure the sphaleron rate for hot, classical Yang-Mills theory on the lattice, in order to study its dependence on lattice spacing. By using a topological definition of Chern-Simons number and going to extremely fine lattices [up to $\ensuremath{\beta}=32,$ or lattice spacing ${a=1/(8g}^{2}T)]$ we demonstrate nontrivial scaling. The topological susceptibility, converted to physical units, falls with lattice spacing on fine lattices in a way which is consistent with linear dependence on a (the Arnold-Son-Yaffe scaling relation) and is difficult to reconcile with a nonzero continuum limit. We also explain some unusual behavior of the rate in small volumes, reported by Ambj\o{}rn and Krasnitz.
119023526
The phantom menaced: Constraints on low-energy effective ghosts
It has been suggested that a scalar field with negative kinetic energy, or ``ghost,'' could be the source of the observed late-time cosmological acceleration. Naively, such theories should be ruled out by the catastrophic quantum instability of the vacuum. We derive phenomenological bounds on the Lorentz-violating ultraviolet cutoff $\ensuremath{\Lambda}$ which must apply to low-energy effective theories of ghosts, in order to keep the instability at unobservable levels. Assuming only that ghosts interact at least gravitationally, we show that $\ensuremath{\Lambda}\ensuremath{\lesssim}3\mathrm{MeV}$ for consistency with the cosmic gamma ray background. We also show that theories of ghosts with a Lorentz-conserving cutoff are completely excluded.
118416779
Next-to-leading order thermal photon production in a weakly coupled quark-gluon plasma
A bstractWe compute the next-to-leading order O(g) correction to the thermal photon production rate in a QCD plasma. The NLO contributions can be expressed in terms of gauge invariant condensates on the light cone, which are amenable to novel sum rules and Euclidean techniques. We expect these technologies to be generalizable to other NLO calculations. For the phenomenologically interesting value of αs = 0.3, the NLO correction represents a 20% increase and has a functional form similar to the LO result.
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.
15355537
Counting BPS black holes in toroidal Type II string theory
We derive a $U$-duality invariant formula for the degeneracies of BPS multiplets in a D1-D5 system for toroidal compactification of the type II string. The elliptic genus for this system vanishes, but it is found that BPS states can nevertheless be counted using a certain topological partition function involving two insertions of the fermion number operator. This is possible due to four extra toroidal U(1) symmetries arising from a Wigner contraction of a large $\mathcal{N}=4$ algebra $\mathcal{A}_{\kappa,\kappa'}$ for $\kappa' \to \infty$. We also compare the answer with a counting formula derived from supergravity on $AdS_3\times S^3 \times T^4$ and find agreement within the expected range of validity.
9605613
Integrating over the Coulomb branch in N = 2 gauge theory
Abstract We review the relation of certain integrals over the Coulomb phase of d = 4, N = 2 SO (3) supersymmetric Yang-Mills theory with Donaldson-Witten theory. We describe a new way to write an important contact term in the theory and show how the integrals generalize to higher rank gauge groups.
16148242
Four-Dimensional Avatars of Two-Dimensional RCFT
We investigate a 4D analog of 2D WZW theory. The theory turns out to have surprising finiteness properties and an infinite-dimensional current algebra symmetry. Some correlation functions are determined by this symmetry. One way to define the theory systematically proceeds by the quantization of moduli spaces of holomorphic vector bundles over algebraic surfaces. We outline how one can define vertex operators in the theories. Finally, we define four-dimensional “conformal blocks” and present an analog of the Verlinde formula.
18626109
Yang-Mills Theory and Topological Field Theory
1994. We review recent developments in the physics and mathematics of Yang-Mills theory in two dimensional spacetimes.