17,529 research outputs found
A Spin-Statistics Theorem for Certain Topological Geons
We review the mechanism in quantum gravity whereby topological geons,
particles made from non-trivial spatial topology, are endowed with nontrivial
spin and statistics. In a theory without topology change there is no
obstruction to ``anomalous'' spin-statistics pairings for geons. However, in a
sum-over-histories formulation including topology change, we show that
non-chiral abelian geons do satisfy a spin-statistics correlation if they are
described by a wave function which is given by a functional integral over
metrics on a particular four-manifold. This manifold describes a topology
changing process which creates a pair of geons from .Comment: 21 pages, Plain TeX with harvmac, 3 figures included via eps
Gravitational Geons in 1+1 Dimensions
It is well known that general relativity does not admit gravitational geons
that are stationary, asymptotically flat, singularity free and topologically
trivial. However, it is likely that general relativity will receive corrections
at large curvatures and the modified field equations may admit solutions
corresponding to this type of geon. If geons are produced in the early universe
and survive until today they could account for some of the dark matter that has
been "observed" in galaxies and galactic clusters.
In this paper I consider gravitational geons in 1+1 dimensional theories of
gravity. I show that the Jackiw-Teitelboim theory with corrections proportional
to and admits gravitational geons. I also show that
gravitational geons exist in a class of theories that includes Lagrangians
proportional to .Comment: 8 pages, a comment added, two references corrected, to appear in
Classical and Quantum Gravit
Addendum to `Gravitational Geons in 1+1 Dimensions'
In a recent paper [arXiv:0807.0611] I found gravitational geons in two
classes of 1+1 dimensional theories of gravity. In this paper I examine these
theories, with the possibility of a cosmological constant, and find strong
field gravitational geons. In the spacetimes in [arXiv:0807.0611] a test
particle that is reflected from the origin suffers a discontinuity in
. The geons found in this paper do not suffer from this problem.Comment: To appear in Classical and Quantum Gravit
Quantum Topology Change in (2 + 1)d
The topology of orientable (2 + 1)d spacetimes can be captured by certain
lumps of non-trivial topology called topological geons. They are the
topological analogues of conventional solitons. We give a description of
topological geons where the degrees of freedom related to topology are
separated from the complete theory that contains metric (dynamical) degrees of
freedom. The formalism also allows us to investigate processes of quantum
topology change. They correspond to creation and annihilation of quantum geons.
Selection rules for such processes are derived.Comment: LaTeX file, 33 pages, 10 postscript figures, some typos corrected,
references updated, and other minor change
Quantum Geons and Noncommutative Spacetimes
Physical considerations strongly indicate that spacetime at Planck scales is
noncommutative. A popular model for such a spacetime is the Moyal plane. The
Poincar\`e group algebra acts on it with a Drinfel'd-twisted coproduct. But the
latter is not appropriate for more complicated spacetimes such as those
containing the Friedman-Sorkin (topological) geons. They have rich
diffeomorphism groups and in particular mapping class groups, so that the
statistics groups for N identical geons is strikingly different from the
permutation group . We generalise the Drinfel'd twist to (essentially)
generic groups including to finite and discrete ones and use it to modify the
commutative spacetime algebras of geons as well to noncommutative algebras. The
latter support twisted actions of diffeos of geon spacetimes and associated
twisted statistics. The notion of covariant fields for geons is formulated and
their twisted versions are constructed from their untwisted versions.
Non-associative spacetime algebras arise naturally in our analysis. Physical
consequences, such as the violation of Pauli principle, seem to be the outcomes
of such nonassociativity.
The richness of the statistics groups of identical geons comes from the
nontrivial fundamental groups of their spatial slices. As discussed long ago,
extended objects like rings and D-branes also have similar rich fundamental
groups. This work is recalled and its relevance to the present quantum geon
context is pointed out.Comment: 41 page
Black resonators and geons in AdS
We construct dynamical black hole solutions with a helical symmetry in
AdS, called black resonators, as well as their horizonless limits, called
geons. We introduce a cohomogeneity-1 metric describing a class of black
resonators and geons whose isometry group is . This allows us to
study them in a wide range of parameters. We obtain the phase diagram for the
black resonators, geons, and Myers-Perry-AdS, where the black resonators
emerge from the onset of a superradiant instability of the Myers-Perry-AdS
with equal angular momenta and are connected to the geons in the small horizon
limit. The angular velocities of the black resonators always satisfy
in units of the AdS radius. A black resonator is shown to have higher entropy
than a Myers-Perry-AdS black hole with the same asymptotic charges. This
implies that the Myers-Perry-AdS can dynamically evolve into the black
resonator under the exact -symmetry although its endpoint will be
further unstable to -violating perturbations.Comment: 27 pages, 9 figure
Geons of Galileons
We suggest that galileon theories should have an additional self-coupling of
the fields to the trace of their own energy-momentum tensor. We explore the
classical features of one such model, in flat 4D spacetime, with emphasis on
solutions that are scalar analogues of gravitational geons. We discuss the
stability of these scalar geons, and some of their possible signatures,
including shock fronts.Comment: References added in v
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