21,293 research outputs found
Statistical Mechanics of Relativistic One-Dimensional Self-Gravitating Systems
We consider the statistical mechanics of a general relativistic
one-dimensional self-gravitating system. The system consists of -particles
coupled to lineal gravity and can be considered as a model of
relativistically interacting sheets of uniform mass. The partition function and
one-particle distitrubion functions are computed to leading order in
where is the speed of light; as results for the
non-relativistic one-dimensional self-gravitating system are recovered. We find
that relativistic effects generally cause both position and momentum
distribution functions to become more sharply peaked, and that the temperature
of a relativistic gas is smaller than its non-relativistic counterpart at the
same fixed energy. We consider the large-N limit of our results and compare
this to the non-relativistic case.Comment: latex, 60 pages, 22 figure
New Types of Thermodynamics from -Dimensional Black Holes
For normal thermodynamic systems superadditivity , homogeneity \H and
concavity \C of the entropy hold, whereas for -dimensional black holes
the latter two properties are violated. We show that -dimensional black
holes exhibit qualitatively new types of thermodynamic behaviour, discussed
here for the first time, in which \C always holds, \H is always violated
and may or may not be violated, depending of the magnitude of the black
hole mass. Hence it is now seen that neither superadditivity nor concavity
encapsulate the meaning of the second law in all situations.Comment: WATPHYS-TH93/05, Latex, 10 pgs. 1 figure (available on request), to
appear in Class. Quant. Gra
N-body Gravity and the Schroedinger Equation
We consider the problem of the motion of bodies in a self-gravitating
system in two spacetime dimensions. We point out that this system can be mapped
onto the quantum-mechanical problem of an N-body generalization of the problem
of the H molecular ion in one dimension. The canonical gravitational
N-body formalism can be extended to include electromagnetic charges. We derive
a general algorithm for solving this problem, and show how it reduces to known
results for the 2-body and 3-body systems.Comment: 15 pages, Latex, references added, typos corrected, final version
that appears in CQ
Decoherent Histories Quantum Mechanics with One 'Real' Fine-Grained History
Decoherent histories quantum theory is reformulated with the assumption that
there is one "real" fine-grained history, specified in a preferred complete set
of sum-over-histories variables. This real history is described by embedding it
in an ensemble of comparable imagined fine-grained histories, not unlike the
familiar ensemble of statistical mechanics. These histories are assigned
extended probabilities, which can sometimes be negative or greater than one. As
we will show, this construction implies that the real history is not completely
accessible to experimental or other observational discovery. However,
sufficiently and appropriately coarse-grained sets of alternative histories
have standard probabilities providing information about the real fine-grained
history that can be compared with observation. We recover the probabilities of
decoherent histories quantum mechanics for sets of histories that are recorded
and therefore decohere. Quantum mechanics can be viewed as a classical
stochastic theory of histories with extended probabilities and a well-defined
notion of reality common to all decoherent sets of alternative coarse-grained
histories.Comment: 11 pages, one figure, expanded discussion and acknowledgment
Isolated critical point from Lovelock gravity
For any K(=2k+1)th-order Lovelock gravity with fine-tuned Lovelock couplings,
we demonstrate the existence of a special isolated critical point characterized
by non-standard critical exponents in the phase diagram of hyperbolic vacuum
black holes. In the Gibbs free energy this corresponds to a place wherefrom two
swallowtails emerge, giving rise to two first-order phase transitions between
small and large black holes. We believe that this is a first example of a
critical point with non-standard critical exponents obtained in a geometric
theory of gravity.Comment: 5 pages, 2 figure
Satellite refrigeration study. Part II TECHNICAL analysis
Low temperature refrigeration system for satellite mounted infrared sensor coolin
Study of a soft lander/support module for Mars missions. Volume 3 - Appendixes Final summary report
Soft lander support module for Mars missions - lunar module radar evaluation and vernier phase simulatio
Thermodynamic Volumes and Isoperimetric Inequalities for de Sitter Black Holes
We consider the thermodynamics of rotating and charged asymptotically de
Sitter black holes. Using Hamiltonian perturbation theory techniques, we derive
three different first law relations including variations in the cosmological
constant, and associated Smarr formulas that are satisfied by such spacetimes.
Each first law introduces a different thermodynamic volume conjugate to the
cosmological constant. We examine the relation between these thermodynamic
volumes and associated geometric volumes in a number of examples, including
Kerr-dS black holes in all dimensions and Kerr-Newman-dS black holes in D=4. We
also show that the Chong-Cvetic-Lu-Pope solution of D=5 minimal supergravity,
analytically continued to positive cosmological constant, describes black hole
solutions of the Einstein-Chern-Simons theory and include such charged
asymptotically de Sitter black holes in our analysis. In all these examples we
find that the particular thermodynamic volume associated with the region
between the black hole and cosmological horizons is equal to the naive
geometric volume. Isoperimetric inequalities, which hold in the examples
considered, are formulated for the different thermodynamic volumes and
conjectured to remain valid for all asymptotically de Sitter black holes. In
particular, in all examples considered, we find that for fixed volume of the
observable universe, the entropy is increased by adding black holes. We
conjecture that this is true in general.Comment: 13 pages, no figures v2:includes comments on the Nariai limit and
compressibility of the black hole horizon, added reference
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