Nonextremal Black Hole Microstates and U-duality

A six-parameter family of five-dimensional black hole solutions is constructed which are labeled by their mass, two asymptotic scalar fields and three charges. It is shown that the Bekenstein-Hawking entropy is exactly matched, arbitrarily far from extremality, by a simple but mysterious duality-invariant extension of previously derived formulae for the number of D-brane states in string theory.Comment: 19 page

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

Beyond Indifferent Players: On the Existence of Prisoners Dilemmas in games with amicable and adversarial preferences

Why don’t agents cooperate when they both stand to gain? This question ranks among the most fundamental in the social sciences. Explanations abound. Among the most compelling are various configurations of the prisoner’s dilemma (PD), or public goods problem. Payoffs in PD’s are specified in one of two ways: as primitive cardinal payoffs or as ordinal final utility. However, as final utility is objectively unobservable, only the primitive payoff games are ever observed. This paper explores mappings from primitive payoff to utility payoff games and demonstrates that though an observable game is a PD there are broad classes of utility functions for which there exists no associated utility PD. In particular we show that even small amounts of either altruism or enmity may disrupt the mapping from primitive payoff to utility PD. We then examine some implications of these results.

Revisiting Barter under the CISG

As the United Nations Commission on International Trade Law (hereinafter “UNCITRAL”) circulated a draft of what eventually became the United Nations Convention on Contracts for the International Sales of Goods (hereinafter “CISG”), it examined the need for uniform law with respect to barter transactions. At that time in 1978, various international organizations were concerned that, while barter transactions were infrequent at the domestic level, such transactions carried growing importance in international trade

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

An All-Sky Optical SETI Survey

We present plans for an all-sky search for pulsed optical SETI beacons at Agassiz station in Harvard, Massachusetts. We will use a 1.8 meter f/2.5 spherical “light bucket” (2-3 arcmin resolution) focused onto a multi-pixel camera consisting of sixteen 64-pixel photomultiplier tubes (with pixels measuring 1.5 arcmin on a side) in two matched focal planes. It will observe a 1.°6×0.°2 patch of the sky in transit mode, thereby covering the Northern sky (−20° < δ < +60°) in 150 clear nights. Fast custom IC electronics will monitor corresponding pixels for coincident optical pulses of nanosecond timescale, triggering storage of a detailed digitized waveform of the light flash. Analysis will be similar to that from our ongoing targeted search

Universal Low-Energy Dynamics for Rotating Black Holes

Fundamental string theory has been used to show that low energy excitations of certain black holes are described by a two dimensional conformal field theory. This picture has been found to be extremely robust. In this paper it is argued that many essential features of the low energy effective theory can be inferred directly from a semiclassical analysis of the general Kerr-Newman solution of supersymmetric four-dimensional Einstein-Maxwell gravity, without using string theory. We consider the absorption and emission of scalars with orbital angular momentum, which provide a sensitive probe of the black hole. We find that the semiclassical emission rates -including superradiant emission and greybody factors - for such scalars agree in striking detail with those computed in the effective conformal field theory, in both four and five dimensions. Also the value of the quantum mass gap to the lowest-lying excitation of a charge-$Q$ black hole, $E_{gap}=1/8Q^3$ in Planck units, can be derived without knowledge of fundamental string theory.Comment: 24 pages, no figures. Typos corrected, some comments adde