639 research outputs found

### Teaching General Relativity

This Resource Letter provides some guidance on issues that arise in teaching
general relativity at both the undergraduate and graduate levels. Particular
emphasis is placed on strategies for presenting the mathematical material
needed for the formulation of general relativity.Comment: 14 pages, no figures; submitted as a "Resource Letter" to American
Journal of Physic

### The Formulation of Quantum Field Theory in Curved Spacetime

The usual formulations of quantum field theory in Minkowski spacetime make
crucial use of Poincare symmetry, positivity of total energy, and the existence
of a unique, Poincare invariant vacuum state. These and other key features of
quantum field theory do not generalize straightforwardly to curved spacetime.
We discuss the conceptual obstacles to formulating quantum field theory in
curved spacetime and how they can be overcomeComment: 14 pages, no figures; to appear in proceedings of Beyond Einstein
conferenc

### The First Law of Black Hole Mechanics

A simple proof of a strengthened form of the first law of black hole
mechanics is presented. The proof is based directly upon the Hamiltonian
formulation of general relativity, and it shows that the the first law
variational formula holds for arbitrary nonsingular, asymptotically flat
perturbations of a stationary, axisymmetric black hole, not merely for
perturbations to other stationary, axisymmetric black holes. As an application
of this strengthened form of the first law, we prove that there cannot exist
Einstein-Maxwell black holes whose ergoregion is disjoint from the horizon.
This closes a gap in the black hole uniqueness theorems.Comment: 9 pages, to appear in Misner Festschrif

### Black Holes and Thermodynamics

We review the remarkable relationship between the laws of black hole
mechanics and the ordinary laws of thermodynamics. It is emphasized that - in
analogy with the laws of thermodynamics - the validity the laws of black hole
mechanics does not appear to depend upon the details of the underlying
dynamical theory (i.e., upon the particular field equations of general
relativity). It also is emphasized that a number of unresolved issues arise in
``ordinary thermodynamics'' in the context of general relativity. Thus, a
deeper understanding of the relationship between black holes and thermodynamics
may provide us with an opportunity not only to gain a better understanding of
the nature of black holes in quantum gravity, but also to better understand
some aspects of the fundamental nature of thermodynamics itself.Comment: 26 pages, plain LaTeX; to appear in the proceedings of the Symposium
on Black Holes and Relativistic Stars (in honor of S. Chandrasekhar),
December 14-15, 199

### Gravitational Collapse and Cosmic Censorship

We review the status of the weak cosmic censorship conjecture, which asserts,
in essence, that all singularities of gravitational collapse are hidden within
black holes. Although little progress has been made toward a general proof (or
disproof) of this conjecture, there has been some notable recent progress in
the study of some examples and special cases related to the conjecture. These
results support the view that naked singularities cannot arise generically.Comment: 21 pages, plain latex, no figures. Corresponds closely to talk given
at the April, 1997 APS meeting in Washington, D.C. A few references adde

### Quantum Fields in Curved Spacetimes and Semiclassical Approaches: A Workshop Summary

I briefly review some of the recent progress in quantum field theory in
curved spacetime and other aspects of semiclassical gravity, as reported at the
D3 Workshop at GR15.Comment: 7 pages, plain LaTeX 2.09 fil

### The Arrow of Time and the Initial Conditions of the Universe

The existence of a thermodynamic arrow of time in the present universe
implies that the initial state of the observable portion of our universe at (or
near) the ``big bang'' must have been very ``special''. We argue that it is not
plausible that these special initial conditions have a dynamical origin.Comment: 5 pages, no figures; write-up of talk given at Seven Pines "Arrows of
Time" meeting, December, 200

### Introduction to Gravitational Self-Force

The motion of sufficiently small body in general relativity should be
accurately described by a geodesic. However, there should be ``gravitational
self-force'' corrections to geodesic motion, analogous to the ``radiation
reaction forces'' that occur in electrodynamics. It is of considerable
importance to be able to calculate these self-force corrections in order to be
able to determine such effects as inspiral motion in the extreme mass ratio
limit. However, severe difficulties arise if one attempts to consider point
particles in the context of general relativity. This article describes these
difficulties and how they have been dealt with.Comment: 11 pages, no figures, to appear in proceedings of CNRS School on Mas

### Gravitational Lensing in Inhomogeneous Universes

I describe a new approach (developed in collaboration with D.E. Holz) to
calculating the statistical distributions for magnification, shear, and
rotation of images of cosmological sources due to gravitational lensing by mass
inhomogeneities on galactic and smaller scales. Our approach is somewhat
similar to that used in ``Swiss cheese'' models, but the ``cheese'' has been
completely eliminated, the matter distribution in the ``voids'' need not be
spherically symmetric, the total mass in each void need equal the corresponding
Robertson-Walker mass only on average, and we do not impose an ``opaque
radius'' cutoff. In our approach, we integrate the geodesic deviation equation
backwards in time until the desired redshift is reached, using a Monte Carlo
procedure wherein each photon beam in effect ``creates its own universe'' as it
propagates. Our approach fully takes into account effects of multiple
encounters with gravitational lenses and is much easier to apply than ``ray
shooting'' methods.Comment: 9 pages, latex 2e. To appear in proceedings of XLIXth Yamada
Conference on Black Holes and High Energy Astrophysic

### The Cosmological Memory Effect

The "memory effect" is the permanent change in the relative separation of
test particles resulting from the passage of gravitational radiation. We
investigate the memory effect for a general, spatially flat FLRW cosmology by
considering the radiation associated with emission events involving
particle-like sources. We find that if the resulting perturbation is decomposed
into scalar, vector, and tensor parts, only the tensor part contributes to
memory. Furthermore, the tensor contribution to memory depends only on the
cosmological scale factor at the source and observation events, not on the
detailed expansion history of the universe. In particular, for sources at the
same luminosity distance, the memory effect in a spatially flat FLRW spacetime
is enhanced over the Minkowski case by a factor of $(1 + z)$.Comment: 22 pages, 1 figure. Eqs (53)-(55) have been correcte

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