69,010 research outputs found
The Cosmological Constant
Various contributions to the cosmological constant are discussed and
confronted with its recent measurement. We briefly review different scenarious
-- and their difficulties -- for a solution of the cosmological constant
problem.Comment: Lecture given at the XIV Workshop "Beyond the Standard Model", Bad
Honnef, 11-14 March 200
The Cosmological Constant
This is a review of the physics and cosmology of the cosmological constant.
Focusing on recent developments, I present a pedagogical overview of cosmology
in the presence of a cosmological constant, observational constraints on its
magnitude, and the physics of a small (and potentially nonzero) vacuum energy.Comment: 50 pages. Submitted to Living Reviews in Relativity
(http://www.livingreviews.org/), December 199
Hiding the cosmological constant
Perhaps standard effective field theory arguments are right, and vacuum
fluctuations really do generate a huge cosmological constant. I show that if
one does not assume homogeneity and an arrow of time at the Planck scale, a
very large class of general relativistic initial data exhibit expansions,
shears, and curvatures that are enormous at small scales, but quickly average
to zero macroscopically. Subsequent evolution is more complex, but I argue that
quantum fluctuations may preserve these properties. The resulting picture is a
version of Wheeler's `spacetime foam,' in which the cosmological constant
produces high curvature at the Planck scale but is nearly invisible at
observable scales.Comment: 9+1 pages; v2: better discussion of evolution,m new references, some
rewriting for clarity; v3: even better discussion of evolution, added
references, minor editin
Gauge-Dependent Cosmological "Constant"
When the cosmological constant of spacetime is derived from the 5D
induced-matter theory of gravity, we show that a simple gauge transformation
changes it to a variable measure of the vacuum which is infinite at the big
bang and decays to an astrophysically-acceptable value at late epochs. We
outline implications of this for cosmology and galaxy formation.Comment: 14 pages, no figures, expanded version to be published in Class.
Quantum Gra
Cosmological constant and lensing
The effect of the cosmological constant on the curvature of light due to an
isolated spherical mass is recalculated without using the lens equation and
compared to a lensing cluster.Comment: 9 pages,4 figure
Deconstructing the Cosmological Constant
Deconstruction provides a novel way of dealing with the notoriously difficult
ultraviolet problems of four-dimensional gravity. This approach also naturally
leads to a new perspective on the holographic principle, tying it to the
fundamental requirements of unitarity and diffeomorphism invariance, as well as
to a new viewpoint on the cosmological constant problem. The numerical
smallness of the cosmological constant is implied by a unique combination of
holography and supersymmetry, opening a new window into the fundamental physics
of the vacuum.Comment: Fourth Prize, 2003 Gravity Research Foundation Essay Contest; 7
pages, LaTe
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