144 research outputs found
Space--time torsion contribution to quantum interference phases
From the latest experimental readouts in this context an intriguing
discrepancy has been elicited. Indeed, theory and experiment dissent by one per
cent, and though this fact could be a consequence of the mounting of the
experimental device, it might also embody a difference between the way in which
gravity behaves in classical and quantum mechanics. In this work the effects,
upon the interference pattern, of space--time torsion will be analyzed heeding
its coupling with the spin of the neutron beam. It will be proved that, even
with this contribution, there is enough leeway for a further discussion of the
validity of the equivalence principle in nonrelativistic quantum mechanics.Comment: Contribution to the Proceedings of the Meeting ''Topics in
Mathematical Physics, General Relativity, and Cosmology''. On the Occasion of
the 75th Birthday of Jerzy F. Plebanski. CINVESTAV, September, 17th--20th,
200
Gowdy Cosmological Models in N=1 Supergravity
We investigate the canonical quantization of supergravity N=1 in the case of
a midisuperspace described by Gowdy cosmological models. The quantum
constraints are analyzed and the wave function of the universe is derived
explicitly. Unlike the minisuperspace case, we show the existence of physical
states in midisuperspace models. The analysis of the wave function of the
universe leads to the conclusion that the classical curvature singularity
present in the evolution of Gowdy models is removed at the quantum level due to
the presence of the Rarita-Schwinger field.Comment: 25 pages and 2 figure
Energy Extraction from Black Holes
In this lecture I give an introduction to the rotational energy extraction of
black holes by the electromagnetic Blandford-Znajek process and the generation
of relativistic jets. After some basic material on the electrodynamics of black
hole magnetospheres, we derive the most important results of Blandford and
Znajek by making use of Kerr-Schild coordinates, which are regular on the
horizon. In a final part we briefly describe results of recent numerical
simulations of accretion flows on rotating black holes, the resulting
large-scale outflows, and the formation of collimated relativistic jets with
high Lorentz factors.Comment: 19 pages, 5 figures,invited lecture given at the III Mexican Meeting
on Mathematical and Experimental Physics, September 10-14, 2007 at El Colegio
Nacional; to be published by the American Institute of Physic
Noncommutative Solitons
Solitonic objects play a central role in gauge and string theory (as, e.g.,
monopoles, black holes, D-branes, etc.). Certain string backgrounds produce a
noncommutative deformation of the low-energy effective field theory, which
allows for new types of solitonic solutions. I present the construction, moduli
spaces and dynamics of Moyal-deformed solitons, exemplified in the 2+1
dimensional Yang-Mills-Higgs theory and its Bogomolny system, which is
gauge-fixed to an integrable chiral sigma model (the Ward model).
Noncommutative solitons for various 1+1 dimensional integrable systems (such as
sine-Gordon) easily follow by dimensional and algebraic reduction.
Supersymmetric extensions exist as well and are related to twistor string
theory.Comment: 16 pages; talk given at the Third Mexican Meeting on Mathematical and
Experimental Physics at El Colegio Nacional, Mexico City, 10-14 September
200
Small-Scale Structure of Spacetime: Bounds and Conjectures
This review consists of two parts. The first part establishes certain
astrophysical bounds on the smoothness of classical spacetime. Some of the best
bounds to date are based on the absence of vacuum Cherenkov radiation in
ultrahigh-energy cosmic rays. The second part discusses possible implications
of these bounds for the quantum structure of spacetime. One conjecture is that
the fundamental length scale of quantum spacetime may be different from the
Planck length.Comment: 20 pages; invited talk at the Third Mexican Meeting on Mathematical
and Experimental Physics, September 10-14, 2007, El Colegio Nacional, Mexico
City; v3: final versio
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