The structure of projected center vortices in lattice gauge theory

We investigate the structure of center vortices in maximal center gauge of SU(2) lattice gauge theory at zero and finite temperature. In center projec tion the vortices (called P-vortices) form connected two dimensional surfac es on the dual four-dimensional lattice. At zero temperature we find, in ag reement with the area law behaviour of Wilson loops, that most of the P-vor tex plaquettes are parts of a single huge vortex. Small P-vortices, and sho rt-range fluctuations of the large vortex surface, do not contribute to the string tension. All of the huge vortices detected in several thousand fiel d configurations turn out to be unorientable. We determine the Euler charac teristic of these surfaces and find that they have a very irregular structu re with many handles. At finite temperature P-vortices exist also in the de confined phase. They form cylindric objects which extend in time direction. After removal of unimportant short range fluctuations they consist only of space-space plaquettes, which is in accordance with the perimeter law beha viour of timelike Wilson loops, and the area law behaviour of spatial Wilso n loops in this phase.