26,184 research outputs found
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
From computation to black holes and space-time foam
We show that quantum mechanics and general relativity limit the speed
of a simple computer (such as a black hole) and its memory space
to \tilde{\nu}^2 I^{-1} \lsim t_P^{-2}, where is the Planck time.
We also show that the life-time of a simple clock and its precision are
similarly limited. These bounds and the holographic bound originate from the
same physics that governs the quantum fluctuations of space-time. We further
show that these physical bounds are realized for black holes, yielding the
correct Hawking black hole lifetime, and that space-time undergoes much larger
quantum fluctuations than conventional wisdom claims -- almost within range of
detection with modern gravitational-wave interferometers.Comment: A misidentification of computer speeds is corrected. Our results for
black hole computation now agree with those given by S. Lloyd. All other
conclusions remain unchange
On Quantum Nature of Black-Hole Spacetime: A Possible New Source of Intense Radiation
Atoms and the planets acquire their stability from the quantum mechanical
incompatibility of the position and momentum measurements. This incompatibility
is expressed by the fundamental commutator [x, p_x]=i hbar, or equivalently,
via the Heisenberg's uncertainty principle Delta x Delta p_x sim hbar. A
further stability-related phenomenon where the quantum realm plays a dramatic
role is the collapse of certain stars into white dwarfs and neutron stars.
Here, an intervention of the Pauli exclusion principle, via the fermionic
degenerate pressure, stops the gravitational collapse. However, by the
neutron-star stage the standard quantum realm runs dry. One is left with the
problematic collapse of a black hole. This essay is devoted to a concrete
argument on why the black-hole spacetime itself should exhibit a quantum
nature. The proposed quantum aspect of spacetime is shown to prevent the
general-relativistic dictated problematic collapse. The quantum nature of
black-hole spacetime is deciphered from a recent result on the universal
equal-area spacing [=lambda_P^2 4 ln(3)] for black holes. In one interpretation
of the emergent picture, an astrophysical black hole can fluctuate to
sqrt{pi/ln(3)} approx 1.7 times its classical size, and thus allow radiation
and matter to escape to the outside observers. These fluctuations I conjecture
provide a new source, perhaps beyond Hawking radiation, of intense radiation
from astrophysical black holes and may be the primary source of observed
radiation from those galactic cores what carry black hole(s). The presented
interpretation may be used as a criterion to choose black holes from black hole
candidates.Comment: This essay received an "honorable mention" in the 1999 Essay
Competition of the Gravity Research Foundation - Ed. Int. J. Mod. Phys. D
(1999, in press). For Joseph Knech
Fast beam stacking using RF barriers
Two barrier RF systems were fabricated, tested and installed in the Fermilab
Main Injector. Each can provide 8 kV rectangular pulses (the RF barriers) at 90
kHz. When a stationary barrier is combined with a moving barrier, injected
beams from the Booster can be continuously deflected, folded and stacked in the
Main Injector, which leads to doubling of the beam intensity. This paper gives
a report on the beam experiment using this novel technology.Comment: 2007 Particle Accelerator Conference (PAC07
Chiral symmetry breaking in a uniform external magnetic field II. Symmetry restoration at high temperatures and chemical potentials
Chiral symmetry is dynamically broken in quenched, ladder QED at weak gauge
couplings when an external magnetic field is present. In this paper, we show
that chiral symmetry is restored above a critical chemical potential and the
corresponding phase transition is of first order. In contrast, the chiral
symmetry restoration at high temperatures (and at zero chemical potential) is a
second order phase transition.Comment: Latex; 12 pages; 8 postscript figures include
Classical and quantum general relativity: a new paradigm
We argue that recent developments in discretizations of classical and quantum
gravity imply a new paradigm for doing research in these areas. The paradigm
consists in discretizing the theory in such a way that the resulting discrete
theory has no constraints. This solves many of the hard conceptual problems of
quantum gravity. It also appears as a useful tool in some numerical simulations
of interest in classical relativity. We outline some of the salient aspects and
results of this new framework.Comment: 8 pages, one figure, fifth prize of the Gravity Research Foundation
2005 essay competitio
Space-time in light of Karolyhazy uncertainty relation
General relativity and quantum mechanics provide a natural explanation for
the existence of dark energy with its observed value and predict its dynamics.
Dark energy proves to be necessary for the existence of space-time itself and
determines the rate of its stability.Comment: 5 pages, Two misprints are correcte
Generalized Uncertainty Principle, Extra-dimensions and Holography
We consider Uncertainty Principles which take into account the role of
gravity and the possible existence of extra spatial dimensions. Explicit
expressions for such Generalized Uncertainty Principles in 4+n dimensions are
given and their holographic properties investigated. In particular, we show
that the predicted number of degrees of freedom enclosed in a given spatial
volume matches the holographic counting only for one of the available
generalizations and without extra dimensions.Comment: LaTeX, 13 pages, accepted for publication in Class. Quantum Gra
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