The calculation of critical amplitudes in SU(2) lattice gauge theory
We calculate the critical amplitudes of the Polyakov loop and its susceptibility at the deconfinement transition of (3 + 1)-dimensional SU(2) gauge theory. To this end we study the corrections due to irrelevant exponents in the scaling functions. As a guiding line for determining the critical amplitudes we use envelope equations which we derive from the finite site scaling formulae of the observables. We have produced new high precision data on N-sigma(3) x 4 lattices for N-sigma = 12, 18, 26 and 36, With these data we find different corrections to the asymptotic scaling behaviour above and below the transition. Our result for the universal ratio of the susceptibility amplitudes is C+/C- = 4.72(11) and thus in excellent agreement with a recent measurement for the 3d Ising model. (C) 1999 Published by Elsevier Science B.V.
Determination of anisotropy coefficients for SU(3) gauge actions from the integral and matching methods
Abstract We use two non-perturbative methods to obtain the anisotropy derivatives of the coupling constants (the anisotropy coefficients) of SU(3) lattice gauge theory. These coefficients appear in the derivative formulae for the energy density and the pressure. We calculate them for the standard Wilson and two improved actions, the (2×2) and the Square Symanzik action. Both methods lead for all investigated actions to compatible results which are clearly different from their known asymptotic perturbative limits. With increasing β the limits are however approached in all cases. Our findings strongly support the equivalence of the integral and derivative methods for the calculation of energy density and pressure.
Slotted Waveguide Antenna With Two Radiation Nulls
A design of a linear array antenna having two radiation nulls and otherwise omnidirectional radiation pattern is reported. A new configuration of a waveguide broad wall longitudinal slot doublet with positive and negative offsets with respect to the waveguide center line is used to design the array. This type of doublet produces two radiation nulls. Each of the null directions can be shifted at least up to plusmn25deg by proper choice of slot offset. Resonance and radiation characteristics of the proposed doublet are also presented. Finally, one linear array antenna consisting of seven doublets has been fabricated. Measurements show that the 15 dB null widths are 14.2deg and the null depths are at least 24.8 dB. Maximum gain ripple in the omnidirectional region is 1.75 dB.