9,771 research outputs found
Quantum Einstein Gravity as a Topological Field Theory
General covariance in quantum gravity is seen once one integrates over all
possible metrics. In recent years topological field theories have given us a
different route to general covariance without integrating over all possible
metrics. Here we argue that Einstein quantum gravity may be viewed as a
topological field theory provided a certain constrant from the path integral
measure is satisfied.Comment: 10 pages, LaTe
Black Strings and Classical Hair
We examine the geometry near the event horizon of a family of black string
solutions with traveling waves. It has previously been shown that the metric is
continuous there. Contrary to expectations, we find that the geometry is not
smooth, and the horizon becomes singular whenever a wave is present. Both five
dimensional and six dimensional black strings are considered with similar
results.Comment: 14 pages, harvma
Topology, Quantum Gravity and Particle Physics
It is argued that quantum gravity has an interpretation as a topological
field theory provided a certain constraint from the path intergral measure is
respected. The constraint forces us to couple gauge and matter fields to
gravity for space - time dimensions different from 3. We then discuss possible
models which may be relevant to our universe.Comment: 18 pages, LaTeX. Replaced version corrects typos and has additional
reference
Where is the Information Stored in Black Holes?
It is shown that many modes of the gravitational field exist only inside the
horizon of an extreme black hole in string theory. At least in certain cases,
the number of such modes is sufficient to account for the Bekenstein-Hawking
entropy. These modes are associated with sources which carry Ramond-Ramond
charge, and so may be viewed as the strong coupling limit of D-branes. Although
these sources naturally live at the singularity, they are well defined and
generate modes which extend out to the horizon. This suggests that the
information in an extreme black hole is not localized near the singularity or
the horizon, but extends between them.Comment: 21 pages, reference corrected and comment adde
An Equivalence Between Momentum and Charge in String Theory
It is shown that for a translationally invariant solution to string theory,
spacetime duality interchanges the momentum in the symmetry direction and the
axion charge per unit length. As one application, we show explicitly that
charged black strings are equivalent to boosted (uncharged) black strings. The
extremal black strings (which correspond to the field outside of a fundamental
macroscopic string) are equivalent to plane fronted waves describing strings
moving at the speed of light.Comment: 10 page
DIMINISHING MARGINAL VALUE
The notion of diminishing marginal value has had a profound impact on the development of neoclassical theory. Early neoclassical scholars had considerable difficulty convincing contemporaries of the new paradigm's value until political economists, including Jevons and Walras, used the critical assumption of diminishing marginal value to link utility and demand. While diminishing marginal value remains a key component of modern economic intuition, there is surprisingly little empirical verification of its existence or level. This paper gathers field data across a myriad of subject pools--from undergraduate students to PTA members to sportscard enthusiasts--to examine several aspects of preferences in both price and exchange institutions. Examining behavior of nearly 900 subjects across several treatments, we find strong evidence of diminishing marginal value.Research Methods/ Statistical Methods,
Black Holes with Multiple Charges and the Correspondence Principle
We consider the entropy of near extremal black holes with multiple charges in
the context of the recently proposed correspondence principle of Horowitz and
Polchinski, including black holes with two, three and four Ramond-Ramond
charges. We find that at the matching point the black hole entropy can be
accounted for by massless open strings ending on the D-branes for all cases
except a black hole with four Ramond-Ramond charges, in which case a possible
resolution in terms of brane-antibrane excitations is considered.Comment: 26 pages, harvmac, minor correction
A Correspondence Principle for Black Holes and Strings
For most black holes in string theory, the Schwarzschild radius in string
units decreases as the string coupling is reduced. We formulate a
correspondence principle, which states that (i) when the size of the horizon
drops below the size of a string, the typical black hole state becomes a
typical state of strings and D-branes with the same charges, and (ii) the mass
does not change abruptly during the transition. This provides a statistical
interpretation of black hole entropy. This approach does not yield the
numerical coefficient, but gives the correct dependence on mass and charge in a
wide range of cases, including neutral black holes.Comment: 24 pages, one typo correcte
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