121579534
Modular forms and the cosmological constant
Abstract The vacuum amplitude of the heterotic string in a flat background vanishes for the first twenty orders of string perturbation theory. The proof relies on the algebraic geometry of modular forms.
118337669
Symmetries of the Bosonic String S-Matrix
The bracket operation on mutually local BRST classes may be combined with Lorentz invariance and analyticity to write an infinite set of finite difference relations on string scattering amplitudes. When combined with some simple physical criteria these relations uniquely determine the genus zero string $S$-matrix for $N\leq 26$-particle scattering in $\IR^{25,1}$ in terms of a single parameter, $\kappa$, the string coupling. We propose that the high-energy limit of the relations are the Ward identities for the high-energy symmetries of string theory.
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.
124306496
The M theory three form and E(8) gauge theory
14205277
Melvin Models and Diophantine Approximation
Melvin models with irrational twist parameter provide an interesting example of conformal field theories with non-compact target space, and localized states which are arbitrarily close to being delocalized. We study the torus partition sum of these models, focusing on the properties of the regularized dimension of the space of localized states. We show that its behavior is related to interesting arithmetic properties of the twist parameter γ, such as the Lyapunov exponent. Moreover, for γ in a set of measure one the regularized dimension is in fact not a well-defined number but must be considered as a random variable in a probability distribution.
15868022
Donaldson Invariants for Non-Simply Connected Manifolds
Abstract:We study Coulomb branch (“u-plane”) integrals for supersymmetric SU(2),SO(3) Yang–Mills theory on 4-manifolds X of b1(X)>0, b2+(X)= 1. Using wall-crossing arguments we derive expressions for the Donaldson invariants for manifolds with b1(X)>0, b2+(X)>0. Explicit expressions for , where Fg is a Riemann surface of genus g are obtained using Kronecker's double series identity. The result might be useful in future studies of quantum cohomology.
12406747
Curing O(a) errors in 3D lattice SU(2) × U(1) Higgs theory
Abstract We show how to make O ( a ) corrections in the bare parameters of 3D lattice SU(2) × U(1) Higgs theory, which remove O ( a ) errors in the match between the infrared behavior and the infrared behavior of the continuum theory. The corrections substantially improve the convergence of lattice data to a small a limit.
17348300
Heavy quark diffusion in QCD and = 4 SYM at next-to-leading order
We present the full details of a calculation at next-to-leading order of the momentum diffusion coefficient of a heavy quark in a hot, weakly coupled, QCD plasma. Corrections arise at (gs); physically they represent interference between overlapping scatterings, as well as soft, electric scale (p ~ gT) gauge field physics, which we treat using the hard thermal loop (HTL) effective theory. In 3-color, 3-flavor QCD, the momentum diffusion constant of a fundamental representation heavy quark at NLO is κ = (16π/3)αs2T3(ln (1/gs)+0.07428+1.9026gs). We extend the computation to a heavy fundamental representation ``probe'' quark in large Nc, = 4 Super Yang-Mills theory, where the result is κ(SYM) = (λ2T3/6π)(ln (1/√λ)+0.4304+0.8010√λ) (where λ = g2Nc is the t'Hooft coupling). In the absence of some resummation technique, the convergence of perturbation theory is poor.
28821908
Measuring the broken phase sphaleron rate nonperturbatively
We present details for a method to compute the broken phase sphaleron rate (rate of hot baryon number violation below the electroweak phase transition) nonperturbatively, using a combination of multicanonical and real time lattice techniques. The calculation includes the ``dynamical prefactor,'' which accounts for prompt recrossings of the sphaleron barrier. The prefactor depends on the hard thermal loops, getting smaller with increasing Debye mass; but for realistic Debye masses the effect is not large. The baryon number erasure rate in the broken phase is slower than a perturbative estimate by about $\mathrm{exp}(\ensuremath{-}3.6).$ Assuming the electroweak phase transition has enough latent heat to reheat the universe to the equilibrium temperature, baryon number is preserved after the phase transition if the ratio of (``dimensionally reduced'' thermal) scalar to gauge couplings $\ensuremath{\lambda}{/g}^{2}$ is less than 0.037.
118835309
Thermalization in weakly coupled nonabelian plasmas
A bstractWe investigate how relativistic, nonabelian plasmas approach equilibrium in a general context. Our treatment is entirely parametric and for small Yang-Mills coupling α. First we study isotropic systems with an initially nonequilibrium momentum distribution. We consider both the case of initially very high occupancy and initially very low occupancy. Then we consider systems which are anisotropic. We consider both weak anisotropy and large anisotropy, and allow the occupancy to be parametrically large or small. Writing the typical momentum of an initial excitation as Q and the final temperature as Tfinal, full equilibration occurs in a time $ {t_{\text{eq}}} \sim {\alpha^{{ - {2}}}}T_{\text{final}}^{{ - 1}} $ for Tfinal > Q, and $ {t_{\text{eq}}} \sim {\alpha^{{ - 2}}}{Q^{{\frac{1}{2}}}}T_{\text{final}}^{{\frac{{ - 3}}{2}}} $ for Tfinal < Q, unless the initial system is sufficiently anisotropic and $ {T_{\text{final}}} > {\alpha^{{\frac{2}{3}}}}Q $, in which 7 case equilibration occurs somewhat faster, $ {t_{\text{eq}}} \sim \max \left( {{a^{{ - 2}}}{T^{{ - 1}}},\;{\alpha^{{\frac{{ - 13}}{7}}}}{Q^{{\frac{5}{7}}}}T_{\text{final}}^{{\frac{{ - 12}}{7}}}} \right) $.
14877410
Sphaleron rate in the symmetric electroweak phase
Recently Bo''deker presented an effective infrared theory for the dynamics of Yang-Mills theory, suitable for studying the rate of baryon number violation in the early universe. We extend his theory to include the Higgs boson fields, and study how much the Higgs boson affects the baryon number violation rate in the symmetric phase, at the phase coexistence temperature of a first order electroweak phase transition. The rate is about 20% smaller than in pure Yang-Mills theory. We also analyze the sphaleron rate in the analytic crossover regime. Our treatment relies on the ergodicity conjecture for 3D scalar {phi}{sup 4} theory.