190 research outputs found
Superconducting circuit boundary conditions beyond the Dynamical Casimir Effect
We study analytically the time-dependent boundary conditions of
superconducting microwave circuit experiments in the high plasma frequency
limit, in which the conditions are Robin-type and relate the value of the field
to the spatial derivative of the field. We give an explicit solution to the
field evolution for boundary condition modulations that are small in magnitude
but may have arbitrary time dependence, in a formalism that applies both to a
semiopen waveguide and to a closed waveguide with two independently adjustable
boundaries. The correspondence between the microwave Robin boundary conditions
and the mechanically-moving Dirichlet boundary conditions of the Dynamical
Casimir Effect is shown to break down at high field frequencies, approximately
one order of magnitude above the frequencies probed in the 2011 experiment of
Wilson et al. Our results bound the parameter regime in which a microwave
circuit can be used to model relativistic effects in a mechanically-moving
cavity, and they show that beyond this parameter regime moving mirrors produce
more particles and generate more entanglement than their non-moving microwave
waveguide simulations.Comment: 29 pages, 2 figures. v3: minor updates, including a change in the
title. Published versio
Hamiltonian evolution and quantization for extremal black holes
We present and contrast two distinct ways of including extremal black holes
in a Lorentzian Hamiltonian quantization of spherically symmetric
Einstein-Maxwell theory. First, we formulate the classical Hamiltonian dynamics
with boundary conditions appropriate for extremal black holes only. The
Hamiltonian contains no surface term at the internal infinity, for reasons
related to the vanishing of the extremal hole surface gravity, and quantization
yields a vanishing black hole entropy. Second, we give a Hamiltonian
quantization that incorporates extremal black holes as a limiting case of
nonextremal ones, and examine the classical limit in terms of wave packets. The
spreading of the packets, even the ones centered about extremal black holes, is
consistent with continuity of the entropy in the extremal limit, and thus with
the Bekenstein-Hawking entropy even for the extremal holes. The discussion
takes place throughout within Lorentz-signature spacetimes.Comment: 16 pages, LaTeX using REVTeX v3.1. (v2: Reference added.
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