264 research outputs found
Three principles for canonical quantum gravity
We outline three principles that should guide us in the construction of a theory of canonical quantum gravity: 1) diffeomorphism invariance, 2) implementing the proper dynamics and related constraint algebra, 3) local Lorentz invariance. We illustrate each of them with its role in model calculations in loop quantum gravity
Canonical quantum gravity and consistent discretizations
This is a summary of the talk presented by JP at ICGC2004. It covered some
developments in canonical quantum gravity occurred since ICGC2000, emphasizing
the recently introduced consistent discretizations of general relativity.Comment: 8 pages, to appear in Praman
The general solution of the quantum Einstein equations?
We suggest how to interpret the action of the quantum Hamiltonian constraint
of general relativity in the loop representation as a skein relation on the
space of knots. Therefore, by considering knot polynomials that are compatible
with that skein relation, one guarantees that all the quantum Einstein
equations are solved. We give a particular example of such invariant and
discuss the consistency of the constraint algebra in this approach.Comment: 3 pages, Revtex, 7 figures included with psfi
The Montevideo Interpretation of Quantum Mechanics: a short review
The Montevideo interpretation of quantum mechanics, which consists in
supplementing environmental decoherence with fundamental limitations in
measurement stemming from gravity, has been described in several publications.
However, some of them appeared before the full picture provided by the
interpretation was developed. As such it can be difficult to get a good
understanding via the published literature. Here we summarize it in a self
contained brief presentation including all its principal elements.Comment: 10 pages, RevTex, version published in special issue of Entrop
Emergence of string-like physics from Lorentz invariance in loop quantum gravity
We consider a quantum field theory on a spherically symmetric quantum space
time described by loop quantum gravity. The spin network description of space
time in such a theory leads to equations for the quantum field that are
discrete. We show that to avoid significant violations of Lorentz invariance
one needs to consider specific non-local interactions in the quantum field
theory similar to those that appear in string theory. This is the first sign
that loop quantum gravity places restrictions on the type of matter considered,
and points to a connection with string theory physics.Comment: Honorable mention Gravity Research Foundation 2014, 7 page
Gravitation in terms of observables
In the 1960's, Mandelstam proposed a new approach to gauge theories and
gravity based on loops. The program for gauge theories was completed for
Yang--Mills theories by Gambini and Trias in the 1980's. Gauge theories could
be understood as representations of certain group: the group of loops. The same
formalism could not be implemented at that time for the gravitational case.
Here we would like to propose an extension to the case of gravity. The
resulting theory is described in terms of loops and open paths and can provide
the underpinning for a new quantum representation for gravity distinct from the
one used in loop quantum gravity or string theory. In it, space-time points are
emergent entities that would only have quasi-classical status. The formulation
may be given entirely in terms of Dirac observables that form a complete set of
gauge invariant functions that completely define the Riemannian geometry of the
spacetime. At the quantum level this formulation will lead to a reduced phase
space quantization free of any constraints.Comment: 39 pages, 15 figures, RevTex, version published in CQ
Lorentz violations in canonical quantum gravity
This is a summary of a talk given at the CP01 meeting on possible Lorentz
anomalies in canonical quantum gravity. It briefly reviews some initial
explorations on the subject that have taken place recently, and should be only
be seen as a short pointer to the literature on the subject, mostly for
outsiders.Comment: 4 pages, Revtex. Talk given at CP01. To appear in proceeding
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