MPEJ Volume 10, No. 7, 18 pp. Received: May 19, 2004. Revised: Jun 24, 2004. Accepted: Jul 2, 2004. A.B. Amor Invariance of essential spectra for generalized Schrodinger operators ABSTRACT: We give a new sufficient condition for the invariance of the essential spectrum of $-\Delta+\mu$, where $\mu$ is a signed Radon measure. This condition is formulated in term of the behavior of the ratio of the $|\mu|$-measure of compact subsets by their $2$-order capacity at infinity. Our method recovers a large class of measures. http://www.maia.ub.es/mpej/Vol/10/7.ps http://www.maia.ub.es/mpej/Vol/10/7.pdf http://www.ma.utexas.edu/mpej/Vol/10/7.ps http://www.ma.utexas.edu/mpej/Vol/10/7.pdf http://mpej.unige.ch/mpej/Vol/10/7.ps http://mpej.unige.ch/mpej/Vol/10/7.pdf