<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div apple-content-edited="true"><div><div>Theory Seminar</div><div>Monday, September 18</div></div></div><div>1:00pm<br>CEBAF Center, Room L102<br><font color="#0f61c8"><br></font><b>Thomas Cohen (Maryland U.)</b><br><b>The sign problem and the theta term</b><br>This talk explores the sign problem in lattice calculations. For concreteness, the talk focuses on the energy density as a function of theta for gauge theories when a topological CP violating term is included. The emphasis is on subtleties associated with the the infinite volume limit. A key question addressed is the extent to which information about the infinite volume limit of the energy density as a function of topological charge density is sufficient to fully reconstruct the infinite volume energy density as a function of theta. Implications for more general problems in QCD where sign problems arise will be discussed.</div></body></html>