52,223 research outputs found
Nonlinear Gravity from Entanglement in Conformal Field Theories
In this paper, we demonstrate the emergence of nonlinear gravitational
equations directly from the physics of a broad class of conformal field
theories. We consider CFT excited states defined by adding sources for scalar
primary or stress tensor operators to the Euclidean path integral defining the
vacuum state. For these states, we show that up to second order in the sources,
the entanglement entropy for all ball-shaped regions can always be represented
geometrically (via the Ryu-Takayanagi formula) by an asymptotically AdS
geometry. We show that such a geometry necessarily satisfies Einstein's
equations perturbatively up to second order, with a stress energy tensor
arising from matter fields associated with the sourced primary operators. We
make no assumptions about AdS/CFT duality, so our work serves as both a
consistency check for the AdS/CFT correspondence and a direct demonstration
that spacetime and gravitational physics can emerge from the description of
entanglement in conformal field theories.Comment: 55 pages, 8 figure
Perfect mirrors and the self-accelerating box paradox
We consider the question raised by Unruh and Wald of whether mirrored boxes
can self-accelerate in flat spacetime (the ``self-accelerating box paradox'').
From the point of view of the box, which perceives the acceleration as an
impressed gravitational field, this is equivalent to asking whether the box can
be supported by the buoyant force arising from its immersion in a perceived
bath of thermal (Unruh) radiation. The perfect mirrors we study are of the type
that rely on light internal degrees of freedom which adjust to and reflect
impinging radiation. We suggest that a minimum of one internal mirror degree of
freedom is required for each bulk field degree of freedom reflected. A short
calculation then shows that such mirrors necessarily absorb enough heat from
the thermal bath that their increased mass prevents them from floating on the
thermal radiation. For this type of mirror the paradox is therefore resolved.
We also observe that this failure of boxes to ``float'' invalidates one of the
assumptions going into the Unruh-Wald analysis of entropy balances involving
boxes lowered adiabatically toward black holes. Nevertheless, their broad
argument can be maintained until the box reaches a new regime in which
box-antibox pairs dominate over massless fields as contributions to thermal
radiation.Comment: 11 pages, Revtex4, changes made in response to referee and to enhance
clarity, discussion of massive fields correcte
Einstein's fluctuation formula. A historical overview
A historical overview is given on the basic results which appeared by the
year 1926 concerning Einstein's fluctuation formula of black-body radiation, in
the context of light-quanta and wave-particle duality. On the basis of the
original publications (from Planck's derivation of the black-body spectrum and
Einstein's introduction of the photons up to the results of Born, Heisenberg
and Jordan on the quantization of a continuum) a comparative study is presented
on the first line of thoughts that led to the concept of quanta. The nature of
the particle-like fluctuations and the wave-like fluctuations are analysed by
using several approaches. With the help of the classical probability theory, it
is shown that the infinite divisibility of the Bose distribution leads to the
new concept of classical poissonian photo-multiplets or to the binary
photo-multiplets of fermionic character. As an application, Einstein's
fluctuation formula is derived as a sum of fermion type fluctuations of the
binary photo-multiplets.Comment: 34 page
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