SU(2) Lattice Gauge Theory Formulation of the (2+1)-Dimensional Antiferromagnetic Heisenberg Model

The equivalence of 2+1 antiferromagnetic Heisenberg model and the SU(2) Kogut Susskind lattice gauge theory is recapitulated and the naive Euclidean lattice action of the threedimensional an tiferromagnetic Heisen berg model is derived. The three-dimensional lattice gauge fermion theory is formulated to give the consistent lattice gauge theory of antiferromagnetic Heisenberg model. In continu um limit the two copies of two flavor fermions are resulted, which give the negative results of the microscopic derivation of the Chern-Simons terms. The Chern-Simons terms, the gauge invariant problem of effective action and the '%hiralityn are discussed.     

The Mass Gap of SU(2) Lattice Gauge Theory in 2+1 Dimensions

Coupled cluster expansions are applied to study the eigenvalue problem of the Hamiltonian lattice gauge theory with the orthogonal D-loop basis being used to expand wavefunctions. The 0⁺⁺ bound state wavefunction and its mass gap relative to the vacuum of SU(2) lattice gauge theory in 2+1 dimensions are calculated up to the 7th order.     

Finite temperature SU(2) lattice gauge theory

We discuss SU(2) lattice gauge theories at non-zero temperature and prove several rigorous results including i) the absence of confinement for sufficiently high temperature in the pure gauge theory, and ii) the absence of spontaneous chiral symmetry breaking for sufficiently high temperature in the theory with massless fundamental representation fermions.     

The SU(2) glueball spectrum in a small volume

We use lattice gauge theory simulation to evaluate the spectrum in pure gauge theory with an SU(2) colour group. Glueball states in all representations of the cubic group O_h are investigated. We compare our results for small spatial volumes with the analytic hamiltonian results of Koller and van Baal and with our large lattice results.     

Analytic calculation of Glueball Mass In (2+1)-D SU(2)Lattice Gauge Theory

In this paper,the glueball mass of 0⁺⁺ is calculated in the (2+1)－D SU(2) lattice gauge theory with connection graphs.The result shows a good scaling behavior.     

Monte-Carlo calculations of some quantities in SU(2) lattice gauge theory

Monte-Carlo calculations of the order parameter and the string tension in SU(2) lattice gauge theory are performed. The parameterization of the group elements of SU(2) used in our contribution differs from the standard one. The comparison with papers using standard parametrization is given and the obtained results are discussed.     

Topological charge of (lattice) gauge fields

Using recently derived explicit formulae for the 2- and 3-cochains in SU(2) gauge theory, we are able to integrate the Chern-Simons density analytically. We arrive — in SU(2) — at a local algebraic expression for the topological charge, which is the sum of local winding numbers associated with the corners (lattice points) of the cells covering the manifold plus contributions from possible isolated gauge singularities which manifest themselves as “vortices” in the 1-, 2- or 3-cochains. Among others we consider hypercubic geometry — i.e. covering the manifold by hypercubes — which is of particular interest to lattice Monte Carlo applications. Finally, we extend our results to SU(3) gauge theory.     

The quark-antiquark potential of SU(2) lattice gauge theory in 2+1 dimensions

Within the framework of a hamiltonian formulation of SU($\text{N}$) lattice gauge theory in two spatial dimensions we develop a weak coupling expansion in the static quark-antiquark sector. For SU(2) the quark-antiquark potential is calculated to fourth order. Moreover we extend the former calculation of the energy gap in the gauge invariant sector to general SU($\text{N}$) and extrapolate to the infinite lattice limit from large lattices. Due to the infrared divergence of the weak coupling expansion on infinite lattices the quark-antiquark potential contains a term diverging logarithmically with the lattice expansion. Hence the expansion has to be interpreted as a pseudo-perturbation expansion in the sense of Symanzik.     

Variational Cumulant Expansion on SU(2)⊗ SU(2) Chiral Model

The phase transition of the two-dimensional SU(2)⊗ SU(2) lattice chiral model has been studied by a variational cumulant expansion method. The internal energy and the specific heat are calculated to the 4th order correction and they are in good agreement with the Monte Carlo (MC) resdits. Except the behavior of the crossover region, similarities between this model and the four-dimensional SU(2) lattice gauge model are also discussed.     

Correlations in the SU(2) fundamental higgs model

Correlations in SU(2) lattice gauge theory with a Higgs doublet are studied by Monte Carlo calculation. Some qualitative consequences for the particle spectrum in isoscalar and isovector channels are discussed.     

PHASE STRUCTURE OF THE SU(2)-SO(3) LATTICE SYSTEM IN AN IMPROVED VARIATIONAL APPROACH

An improved trial action in the variational approach of the lattice gauge field theory is in-troduced to acquire better lower bound for the convexity Inequality and used to calculate the phase structure of the SU(2)-SO(3) pure gauge system. The improvement is seen in comparing the old and new variational results with that by the Monte Carlo simulation.     

Phase Structures of U(l) and SU(2) Lattice Gauge Models at Finite Temperature

With the variational-cumulant expansion (VCE) method, the phase structures of the U(1) and SU(2) lattice gauge models at finite temperature are studied. The order parameter Polyakov line with N_T = 2 is calculated to the fourth order. For the U(1) and SU(2) lattice gauge models in D = 3 + 1 and D = 2 + 1 at finite temperature, the results show the existence of the second order phase transition.     

Some approximate calculations in SU(2) lattice mean field theory

Approximate calculations are performed for small Wilson loops of SU(2) lattice gauge theory in the mean field approximation. Reasonable agreement is found with Monte Carlo data. Ways of improving these calculations are discussed.     

The mean-field approximation in the SU(2) pure lattice gauge theory

The phase structure of the SU(2) pure lattice gauge theory with two coupling constants is derived in the mean-field approximation. The obtained phase diagram agrees with Monte Carlo results. The technique used here allows the computation of further corrections.     

On the stochastic confinement in SU(2) lattice gauge theory

We extend the Olesen approach to confinement, originally proposed for SU(∞) gauge theory, to the SU(2) group. We perform Monte Carlo calculations of the spectral density, which describes the distribution of eigenvalues of the Wilson loop in the SU(2) lattice gauge theory (LGT), for square loops up to size 4 × 4. Our results indicate the onset of disorder in the 4-dimensional LGT so that at weak coupling confinement is due to non-abelian fluctuations of the gauge field. We describe the Monte Carlo data by formulae of the 2-dimensional LGT with some effective coupling constant. We formulate how this effective coupling constant should depend on the size of the loop in order that the Olesen hypothesis about the dimensional reduction (i.e. approximate reduction of the 4-dimensional LGT to the effective 2-dimensional LGT in the confinement region) would be held. Using the strong-coupling expansion where the Olesen hypothesis holds in fourteen orders, we perform quantitative estimates. The density of simple vortices up to size 4 × 4 is calculated. A connection between the definitions of spectral densities for the SU(∞) and SU(2) groups is considered. Explicit formulae for the spectral density in the 2-dimensional SU(2) LGT are derived.     

Evaluation of Some Lattice SU(2) Group Integrals

A procedure for deriving a set of formulas of SU(2) group integrals in the lattice gauge theory by extensively using the properties of modified Bessel functions is presented. These formulas are extremely useful in the higher-order calculations of the cumulant expansion.     

The Deconfinement Transition in SU(2) Lattice Gauge Theory:An Analytical Study

We study SU(2) lattice gauge theory at finite temperature in the variational cumulant expansion approach. The deconfinement transition is given in four and five dimensions. The comparison with Monte Carlo results ia also presented.     

THE MC CALCULATION OF MASS GAP IN 2+1 DIMENSIONAL SU(2) LATTICE GAUGE THEORY

By combining Monte Carlo method and variational method,we calculate the mass gap of SU(2) lattice gauge theory in 18*18 lattice of 2+1 dimensions by means of the icosaheral subgroup (Y120) using a hamiltonian of which the ground state is exactly known.In the range 0<1/g²,we obtain the results which are in good agreement with analytical calculation of SU(2) group.The scaling behaviour of mass gap am=2.3g² is confirmed.     

Stochastic confinement and dimensional reduction (II). Three-dimensional SU(2) lattice gauge theory

We study 3-dimensional SU(2) lattice gauge theory with respect to dimensional reduction. By Monte Carlo calculations we find that this reduction is valid to a good approximation (within ≈10%). The adjoint string tension is found to scale approximately. We also compare the adjoint string tension with a string theory.     

Chiral and deconfinement transition from correlation functions: SU(2) vs. SU(3)

We study a gauge-invariant order parameter for deconfinement and the chiral condensate in SU(2) and SU(3) Yang–Mills theory in the vicinity of the deconfinement phase transition using the Landau gauge quark and gluon propagators. We determine the gluon propagator from lattice calculations and the quark propagator from its Dyson–Schwinger equation, using the gluon propagator as input. The critical temperature and a deconfinement order parameter are extracted from the gluon propagator and from the dependency of the quark propagator on the temporal boundary conditions. The chiral transition is determined using the quark condensate as order parameter. We investigate whether and how a difference in the chiral and deconfinement transition between SU(2) and SU(3) is manifest.