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### Event Number 2109

**Condensed Matter Theory Group Seminar****Weyl Problem and the Casimir Effect in Spherical Shell Geometry****Time:**4:30 pm**Place:**5310 Chamberlin**Speaker:**Hussain Zaidi, University of Virginia**Abstract:**We compute the generic mode sum that quantifies the effect of the change of spectrum of a harmonic field when a spherical shell is inserted into the vacuum. This encompasses a variety of problems including the Weyl spectral problem and the Casimir effect of quantum electrodynamics. The connection between the Weyl problem and the Casimir energy allows us to resolve a long-standing controversy regarding the question of universality of the Casimir self-energy. Specifically we demonstrate that in the case of a scalar field obeying Dirichlet boundary conditions on the shell surface the Casimir self-energy is cutoff-dependent, while in the case of a conductive shell the Casimir self-energy is universal.**Host:**Maxim Vavilov- Add this event to your calendar