arXiv:hep-lat/9507006v2 20 Aug 1995 FTUAM/95-23 Gauge invariant structures and Confinement 1 A. Gonz´ alez-Arroyo, P. Mart´ ınez 2 and A. Montero Departamento de F´ ısica Te´orica C-XI, Universidad Aut´ onoma de Madrid, 28049 Madrid, Spain. June 1995 Abstract By looking at cooled configurations on the lattice, we study the presence of peaks in the action density, or its electric and magnetic components, in the SU(2) gauge vacuum. The peaks are seen to be of instanton-like nature and their number variation takes care of the drop in the string tension observed when cooling. Possible explanations of this finding are analysed. 1 Accepted for publication in Physics Letters B. 2 Present adress: Dept. of Physics, The University of Edinburgh, Edinburgh EH9 3JZ, Scotland. 1