6,687 research outputs found
Solving the Constraints of General Relativity
I show in this letter that it is possible to solve some of the constraints of
the -ADM formalism for general relativity by using an approach similar
to the one introduced by Capovilla, Dell and Jacobson to solve the vector and
scalar constraints in the Ashtekar variables framework. I discuss the
advantages of using the ADM formalism and compare the result with similar
proposals for different Hamiltonian formulations of general relativity.Comment: 8 pages, LATEX, no figures, Preprint CGPG-94/11-
General Relativity as a Theory of Two Connections
We show in this paper that it is possible to formulate General Relativity in
a phase space coordinatized by two connections. We analyze first the
Husain-Kucha\v{r} model and find a two connection description for it.
Introducing a suitable scalar constraint in this phase space we get a
Hamiltonian formulation of gravity that is close to the Ashtekar one, from
which it is derived, but has some interesting features of its own. Among them a
possible mechanism for dealing with the degenerate metrics and a neat way of
writing the constraints of General Relativity.Comment: 18 pages, LATEX, Preprint CGPG-93/09-
From Euclidean to Lorentzian General Relativity: The Real Way
We study in this paper a new approach to the problem of relating solutions to
the Einstein field equations with Riemannian and Lorentzian signatures. The
procedure can be thought of as a "real Wick rotation". We give a modified
action for general relativity, depending on two real parameters, that can be
used to control the signature of the solutions to the field equations. We show
how this procedure works for the Schwarzschild metric and discuss some possible
applications of the formalism in the context of signature change, the problem
of time, black hole thermodynamics...Comment: 20 pages uuencoded gzipped tar format. Accepted in Phys. Rev. D. Some
references adde
A Comment on the Degrees of Freedom in the Ashtekar Formulation for 2+1 Gravity
We show that the recent claim that the 2+1 dimensional Ashtekar formulation
for General Relativity has a finite number of physical degrees of freedom is
not correct.Comment: 6 pages LaTex, to appear in Classical and Quantum Gravit
User's guide for a revised computer program to analyze the LRC 16 foot transonic dynamics tunnel active cable mount system
The revision of an existing digital program to analyze the stability of models mounted on a two-cable mount system used in a transonic dynamics wind tunnel is presented. The program revisions and analysis of an active feedback control system to be used for controlling the free-flying models are treated
User's guide for a computer program to analyze the LRC 16 ft transonic dynamics tunnel cable mount system
The theoretical derivation of the set of equations is discussed which is applicable to modeling the dynamic characteristics of aeroelastically-scaled models flown on the two-cable mount system in a 16 ft transonic dynamics tunnel. The computer program provided for the analysis is also described. The program calculates model trim conditions as well as 3 DOF longitudinal and lateral/directional dynamic conditions for various flying cable and snubber cable configurations. Sample input and output are included
SO(4,C)-covariant Ashtekar-Barbero gravity and the Immirzi parameter
An so(4,C)-covariant hamiltonian formulation of a family of generalized
Hilbert-Palatini actions depending on a parameter (the so called Immirzi
parameter) is developed. It encompasses the Ashtekar-Barbero gravity which
serves as a basis of quantum loop gravity. Dirac quantization of this system is
constructed. Next we study dependence of the quantum system on the Immirzi
parameter. The path integral quantization shows no dependence on it. A way to
modify the loop approach in the accordance with the formalism developed here is
briefly outlined.Comment: 14 pages, LATEX; minor changes; misprints corrected; commutator of
two secondary second class constraints correcte
Statistical description of the black hole degeneracy spectrum
We use mathematical methods based on generating functions to study the
statistical properties of the black hole degeneracy spectrum in loop quantum
gravity. In particular we will study the persistence of the observed effective
quantization of the entropy as a function of the horizon area. We will show
that this quantization disappears as the area increases despite the existence
of black hole configurations with a large degeneracy. The methods that we
describe here can be adapted to the study of the statistical properties of the
black hole degeneracy spectrum for all the existing proposals to define black
hole entropy in loop quantum gravity.Comment: 41 pages, 12 figure
Real Ashtekar Variables for Lorentzian Signature Space-times
I suggest in this letter a new strategy to attack the problem of the reality
conditions in the Ashtekar approach to classical and quantum general
relativity. By writing a modified Hamiltonian constraint in the usual
Yang-Mills phase space I show that it is possible to describe space-times with
Lorentzian signature without the introduction of complex variables. All the
features of the Ashtekar formalism related to the geometrical nature of the new
variables are retained; in particular, it is still possible, in principle, to
use the loop variables approach in the passage to the quantum theory. The key
issue in the new formulation is how to deal with the more complicated
Hamiltonian constraint that must be used in order to avoid the introduction of
complex fields.Comment: 10 pages, LATEX, Preprint CGPG-94/10-
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