143 research outputs found
Canonical Quantization of Spherically Symmetric Gravity in Ashtekar's Self-Dual Representation
We show that the quantization of spherically symmetric pure gravity can be
carried out completely in the framework of Ashtekar's self-dual representation.
Consistent operator orderings can be given for the constraint functionals
yielding two kinds of solutions for the constraint equations, corresponding
classically to globally nondegenerate or degenerate metrics. The physical state
functionals can be determined by quadratures and the reduced Hamiltonian system
possesses 2 degrees of freedom, one of them corresponding to the classical
Schwarzschild mass squared and the canonically conjugate one representing a
measure for the deviation of the nonstatic field configurations from the static
Schwarzschild one. There is a natural choice for the scalar product making the
2 fundamental observables self-adjoint. Finally, a unitary transformation is
performed in order to calculate the triad-representation of the physical state
functionals and to provide for a solution of the appropriately regularized
Wheeler-DeWitt equation.Comment: 43 page
Classical aspects of Hawking radiation verified in analogue gravity experiment
There is an analogy between the propagation of fields on a curved spacetime
and shallow water waves in an open channel flow. By placing a streamlined
obstacle into an open channel flow we create a region of high velocity over the
obstacle that can include wave horizons. Long (shallow water) waves propagating
upstream towards this region are blocked and converted into short (deep water)
waves. This is the analogue of the stimulated Hawking emission by a white hole
(the time inverse of a black hole). The measurements of amplitudes of the
converted waves demonstrate that they appear in pairs and are classically
correlated; the spectra of the conversion process is described by a
Boltzmann-distribution; and the Boltzmann-distribution is determined by the
determined by the change in flow across the white hole horizon.Comment: 17 pages, 10 figures; draft of a chapter submitted to the proceedings
of the IX'th SIGRAV graduate school: Analogue Gravity, Lake Como, Italy, May
201
Spacetime Foam Model of the Schwarzschild Horizon
We consider a spacetime foam model of the Schwarzschild horizon, where the
horizon consists of Planck size black holes. According to our model the entropy
of the Schwarzschild black hole is proportional to the area of its event
horizon. It is possible to express geometrical arguments to the effect that the
constant of proportionality is, in natural units, equal to one quarter.Comment: 16 pages, 2 figures, improved and extended version with some
significant changes. Accepted for publication in Phys.Rev.
Hamiltonian dynamics for Einstein's action in G0 limit
The Hamiltonian analysis for the Einstein's action in limit is
performed. Considering the original configuration space without involve the
usual variables we show that the version for Einstein's action
is devoid of physical degrees of freedom. In addition, we will identify the
relevant symmetries of the theory such as the extended action, the extended
Hamiltonian, the gauge transformations and the algebra of the constraints. As
complement part of this work, we develop the covariant canonical formalism
where will be constructed a closed and gauge invariant symplectic form. In
particular, using the geometric form we will obtain by means of other way the
same symmetries that we found using the Hamiltonian analysis
Loop quantum gravity and light propagation
Within loop quantum gravity we construct a coarse-grained approximation for
the Einstein-Maxwell theory that yields effective Maxwell equations in flat
spacetime comprising Planck scale corrections.
The corresponding Hamiltonian is defined as the expectation value of the
electromagnetic term in the Einstein-Maxwell Hamiltonian constraint,
regularized a la Thiemann, with respect to a would-be semiclassical state. The
resulting energy dispersion relations entail Planck scale corrections to those
in flat spacetime. Both the helicity dependent contribution of Gambini and
Pullin [GP] and, for a value of a parameter of our approximation, that of Ellis
et. al. [ELLISETAL] are recovered. The electric/magnetic asymmetry in the
regularization procedure yields nonlinearities only in the magnetic sector
which are briefly discussed. Observations of cosmological Gamma Ray Bursts
might eventually lead to the needed accuracy to study some of these quantum
gravity effects.Comment: Latex, 45 pages, shorter abstract, additional reference
Black Hole Thermodynamics and Statistical Mechanics
We have known for more than thirty years that black holes behave as
thermodynamic systems, radiating as black bodies with characteristic
temperatures and entropies. This behavior is not only interesting in its own
right; it could also, through a statistical mechanical description, cast light
on some of the deep problems of quantizing gravity. In these lectures, I review
what we currently know about black hole thermodynamics and statistical
mechanics, suggest a rather speculative "universal" characterization of the
underlying states, and describe some key open questions.Comment: 35 pages, Springer macros; for the Proceedings of the 4th Aegean
Summer School on Black Hole
Steam-Electric Power-Plant-Cooling Handbook
The Steam-Electric Power Plant Cooling Handbook provides summary data on steam-electric power plant capacity, generation and number of plants for each cooling means, by Electric Regions, Water Resource Regions and National Electric Reliability Council Areas. Water consumption by once-through cooling, cooling ponds and wet evaporative towers is discussed and a methodology for computation of water consumption is provided for a typical steam-electric plant which uses a wet evaporative tower or cooling pond for cooling
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