THE GRAVITATIONAL VAVILOV–CHERENKOV EFFECT
ALBERTO SAA and MARCELO SCHIFFER
Departamento de Matemática Aplicada, IMECC, Universidade Estadual de Campinas, C.P. 6065, 13081-970 Campinas, SP, Brazil
E-mail: asaa@ime.unicamp.br
E-mail: schiffer@ime.unicamp.br
In this letter we show that an uncharged black hole moving
superluminally in a transparent dielectric medium violates Hawking's
area theorem. The violation can be overcome through the emission of
radiation. Since modes cannot emerge from the black hole itself, this
radiation must originate from a collective effect in the medium, in
complete analogy with the Vavilov–Cherenkov effect. However, because
the black hole is uncharged, the emission mechanism must be different.
We discuss the physical origin of the effect and obtain a Newtonian
estimation. Then we obtain the appropriate equations in the
relativistic case and show that the field which is radiated away is a
combination of gravitational and electromagnetic degrees of
freedom. Possible astrophysical relevance for the detection of
primordial black holes and binary systems is discussed.
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