A finite ultraviolet cutoff near a reflecting boundary yields a stress tensor that violates the basic energy-pressure relation. Therefore, a "soft" wall described by a power-law potential, which needs no ad hoc cutoff, is being investigated by the collaboration centered at Texas A&M University and the University of Oklahoma. Progress is reported here.Keywords: vacuum energy; stress tensor; boundary; soft wall. PACS numbers: 03.70.+k, 11.10.Gh
Hard Walls: The Pressure Paradox
Basic formalism and empty spaceWe model the electromagnetic vacuum-energy problem by a massless scalar field in three space dimensions, subjected to the Dirichlet boundary condition on the "conducting" boundaries. The vacuum energy can be calculated from a Green function, such as the "cylinder kernel", 1,2,3where the φ n are the normalized eigenfunctions with frequencies ω n . The classical formulas for the components of the vacuum expectation value of the stress-energy