20,298 research outputs found
The holographic principle
There is strong evidence that the area of any surface limits the information
content of adjacent spacetime regions, at 10^(69) bits per square meter. We
review the developments that have led to the recognition of this entropy bound,
placing special emphasis on the quantum properties of black holes. The
construction of light-sheets, which associate relevant spacetime regions to any
given surface, is discussed in detail. We explain how the bound is tested and
demonstrate its validity in a wide range of examples.
A universal relation between geometry and information is thus uncovered. It
has yet to be explained. The holographic principle asserts that its origin must
lie in the number of fundamental degrees of freedom involved in a unified
description of spacetime and matter. It must be manifest in an underlying
quantum theory of gravity. We survey some successes and challenges in
implementing the holographic principle.Comment: 52 pages, 10 figures, invited review for Rev. Mod. Phys; v2:
reference adde
Spacetime Foam, Holographic Principle, and Black Hole Quantum Computers
Spacetime foam, also known as quantum foam, has its origin in quantum
fluctuations of spacetime. Arguably it is the source of the holographic
principle, which severely limits how densely information can be packed in
space. Its physics is also intimately linked to that of black holes and
computation. In particular, the same underlying physics is shown to govern the
computational power of black hole quantum computers.Comment: 8 pages, LaTeX; Talk given by Jack Ng, in celebration of Paul
Frampton's 60th birthday, at the Coral Gables Conference (in Fort Lauderdale,
Florida on December 17, 2003). To appear in the Proceedings of the 2003 Coral
Gables Conferenc
Holography, Time and Quantum Mechanics
In this talk we entertain the possibility that the synthesis of general
covariance and quantum mechanics requires an extension of the basic kinematical
setup of quantum mechanics. According to the holographic principle, regions of
spacetime bounded by a finite area carry finite entropy. When we in addition
assume that the origin of the entropy is a finite dimensional Hilbert space,
and apply this to cosmological solutions using a suitable notion of
complementarity, we find as a consequence that gravitational effects can lead
to dynamical variation in the dimensionality of such Hilbert spaces. This
happens generally in cosmological settings like our own universe.Comment: Talk presented at the 3rd Sakharov International Conference on
Physics, Moscow, June 2002; to appear in the proceedings of the conferenc
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