17 research outputs found
Hawking radiation from acoustic black holes in hydrodynamic flow of electrons
Acoustic black holes are formed when a fluid flowing with subsonic
velocities, accelerates and becomes supersonic. When the flow is directed from
the subsonic to supersonic region, the surface on which the normal component of
fluid velocity equals the local speed of sound acts as an acoustic horizon.
This is because no acoustic perturbation from the supersonic region can cross
it to reach the subsonic part of the fluid. One can show that if the fluid
velocity is locally irrotational, the field equations for acoustic
perturbations of the velocity potential are identical to that of a massless
scalar field propagating in a black hole background. One, therefore, expects
Hawking radiation in the form of a thermal spectrum of phonons. There have been
numerous investigations of this possibility, theoretically, as well as
experimentally, in systems ranging from cold atom systems to quark-gluon plasma
formed in relativistic heavy-ion collisions. Here we investigate this
possibility in the hydrodynamic flow of electrons. Resulting Hawking radiation
in this case should be observable in terms of current fluctuations. Further,
current fluctuations on both sides of the acoustic horizon should show
correlations expected for pairs of Hawking particles.Comment: 7 pages, 2 figure
A realisation of Lorentz algebra in Lorentz violating theory
A Lorentz non-invariant higher derivative effective action in flat spacetime,
characterised by a constant vector, can be made invariant under infinitesimal
Lorentz transformations by restricting the allowed field configurations. These
restricted fields are defined as functions of the background vector in such a
way that background dependance of the dynamics of the physical system is no
longer manifest. We show here that they also provide a field basis for the
realisation of Lorentz algebra and allow the construction of a Poincar\'e
invariant symplectic two form on the covariant phase space of the theory.Comment: text body edited, reference adde