# Bonn 2001 – wissenschaftliches Programm

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# T: Teilchenphysik

## T 304: Feldtheorie 2

### T 304.2: Vortrag

### Dienstag, 27. März 2001, 16:30–16:45, HS III

**Variational Calculations and Random Phase Approximation in Yang-Mills Theories** — •O. Schröder and H. Reinhardt — Institut für Theoretische Physik, Eberhard-Karls Universität Tübingen, D-72076 Tübingen

We perform (Rayleigh-Ritz type) variational calculations in Yang-Mills theories. An essential problem is that test wave functionals, which allow explicit calculations, do not share the basic symmetries, namely gauge invariance. Thus, we start from a gauge-noninvariant Gaussian test wave functional and go beyond the mean field level by implementing the Random Phase Approximation (RPA). The RPA restores the gauge symmetry by approximating the Hamiltonian and the Gauss’ law operator in a consistent manner. We obtain corrections to the mean field energy that are due to the fact that the Gaussian wave functional contains spurious excitations that are (at least partially) removed by the RPA. We also seek contact with perturbation theory.