The spectrum of Yang-Mills theory in a small twisted box

We compute the low-lying energy levels of Yang-Mills theory with twisted boundary conditions. One striking feature is that the 2⁺ state lies higher than the 0⁺ state in contrast to the periodic case; thus level crossings in at least one type of boundary condition are inevitable.     

Quark confinement in 2+1 dimensional pure Yang-Mills theory

We report some progress on the quark confinement problem in 2 + 1 dim. pure Yang-Mills theory, using Euclidean instanton methods. The instantons are regularized Wu-Yang ‘monopoles’, whose long range Coulomb field is screened by collective effects. Such configurations are stable to small perturbations unlike the case of singular, undressed monopoles. Using exact non-perturbative results for the 3-dim. Coulomb gas, where Debye screening holds for arbitrarily low temperatures, we show in a self-consistent way that a mass gap is dynamically generated in the gauge theory. The mass gap also determines the size of the monopoles. We also identify the disorder operator of the model in terms of the Sine-Gordon field of the Coulomb gas and hence obtain a dual representation whose symmetry is the centre ofSU(2).     

Coulomb gauge vacua of (2+1) dimensional Yang-Mills theory

The vacuum structure of the (2+1) dimensional Yang-Mills theory is analysed. The non-trivial spherically symmetric vacuum fields in this theory can be calculated in closed form. It is shown that these non-trivial vacuum fields fall faster than 1/r at large r unlike the (3+1) dimensional case, where the vacuum is uniquely A_i = 0 if one requires lim_r→∞rA_i=0.     

The qualitative behavior of Yang-Mills theory in 2 + 1 dimensions

The SU(2) gauge theory of gluons (no quarks) is studied in two space and one time dimensions. Only qualitative or suggestive discussions are made. Starting from the quantum field equations it is argued that the necessary gauge invariance of the wave functional results, in this non-abelian case, in a finite energy for any excitation (“glueball”) above the ground state. Furthermore, fluctuations in which gauging factors change sign can occur independently in regions adequately separated in space. This results in a potential between distant massive quarks rising linearly with distance (quark confinement). The situation in 3 + 1 dimensions is not discussed.     

Some analytic results concerning the mass spectrum of Yang-Mills gauge theories on a torus

When non-abelian gauge fields are enclosed in a box with periodic boundary conditions, the spectrum of the hamiltonian becomes discrete and the energy values can be expanded in a power series of $\text{ifλ = g}{}^{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{(g:}\text{renormalized coupling constant)}$. A method to obtain these expansions is explained and worked out to one-loop order. No numbers for the low-lying levels are given here, but some interesting properties of the mass spectrum already become visible.     

Center-symmetric dimensional reduction of hot Yang-Mills theory

It is expected that incorporating the center symmetry in the conventional dimensionally reduced effective theory for high-temperature SU(N_c) Yang-Mills theory, EQCD, will considerably extend its applicability towards the deconfinement transition. The construction of such a center-symmetric effective theory for the case of two colors is reviewed and lattice simulation results are presented. The simulations demonstrate that unlike EQCD, the new center-symmetric theory undergoes a second order confining phase transition in complete analogy with the full theory.     

Global existence of coupled Yang-Mills and scalar fields in 2 + 1 dimensional space-time

We present results on the Cauchy problem for coupled classical Yang-Mills and scalar fields in n + 1 dimensional space-time both in the temporal and in the Lorentz gauge. We prove the existence of local solutions for any n, and the existence of global solutions for n = 1, 2 in the temporal gauge and for n = 1 in the Lorentz gauge. The last result also holds for massive Yang-Mill fields.     

1+1 dimensional compactifications of string theory

We argue that stable, maximally symmetric compactifications of string theory to 1+1 dimensions are in conflict with holography. In particular, the finite horizon entropies of the Rindler wedge in 1+1 dimensional Minkowski and anti-de Sitter space, and of the de Sitter horizon in any dimension, are inconsistent with the symmetries of these spaces. The argument parallels one made recently by the same authors, in which we demonstrated the incompatibility of the finiteness of the entropy and the symmetries of de Sitter space in any dimension. If the horizon entropy is either infinite or zero, the conflict is resolved.     

Lattice model calculations for SU(2) Yang-Mills theory in 1 + 1 dimensions

Lattice model techniques are employed to study the low-energy spectrum of SU(2) Yang-Mills theory in 1 + 1 dimensions. The Hamiltonian formulation of Kogut and Susskind is employed. The strong coupling expansion is carried to eighth order for a few of the lower-lying states. These expansions are extrapolated to the continuum limit using Padé approximants, both for finite quark masses and in the non-relativistic limit (quark mass goes to infinity). These methods succeed in giving a qualitative picture of the spectrum, but their quantitative accuracy is poor.     

The low-lying mass spectrum of the N = 1 SU(2) SUSY Yang-Mills theory with Wilson fermions

We analyze the low energy spectrum of bound states of the N = 1 SU(2) SUSY Yang-Mills Theory (SYM). This work continues the investigation of the non-perturbative properties of SYM by Monte Carlo simulations in the Wilson discretization with dynamical gluinos. The dynamics of the gluinos is included by the Two-Step Multi-Bosonic Algorithm (TSMB) for dynamical fermions. A new set of configurations has been generated on a lattice at and . The analysis also includes sets of configurations previously generated on a smaller ( ) lattice at and 0.1955. Guided by predictions from low energy Lagrangians, we consider spin-1/2, scalar and pseudoscalar particles. The spectrum of SYM is a challenging subject of investigation because of the extremely noisy correlators. In particular, meson-like correlators contain disconnected contributions. The larger time-extension of the lattice allows to observe two-state signals in the effective mass. Finite-volume effects are monitored by comparing results from the two lattice sizes.Received: 14 September 2004, Revised: 29 October 2004, Published online: 21 December 2004     

Yang-Mills theory on a cylinder

Yang-Mills theory on a two dimensional cylinder is studied in the hamiltonian formalism, without using gauge conditions. Since the only gauge invariant variable is the Wilson loop (holonomy) this system is equivalent to a finite dimensional system. The eigenstates and eigenvalues of the hamiltonian are found exactly.     

U(1) gauge theory on a torus

U(1) gauge theory with the Villain action on a cubic lattice approximation of three- and four-dimensional torus is considered. As the lattice spacing approaches zero, provided the coupling constant correspondingly approaches zero, the naturally chosen correlation functions converge to the correlation functions of theR-gauge electrodynamics on three- and four-dimensional torus. When the torus radius tends to infinity these correlation functions converge to the correlation functions of theR-gauge Euclidean electrodynamics.Supported by the Russian Foundation of Fundamental Researches under Grant 93-011-147     

SU(2) Yang-Mills theory in (1 + 1) dimensions: A finite-lattice approach

Finite-lattice methods are used to calculate the masses of the lowest-lying baryon and meson states in the two-dimensional SU(2) Yang-Mills theory. No sign of a phase transition is seen at non-zero quark mass m. Both the meson and baryon mass vanish at m = 0: this is presumably a “chiral protection” mechanism.