74 research outputs found
Collective Quantisation of a Gravitating Skyrmion
Collective quantisation of a B=1 gravitating skyrmion is described. The
rotational and isorotational modes are quantised in the same manner as the
skyrmion without gravity. It is shown in this paper how the static properties
of nucleons such as masses, charge densities, magnetic moments are modified by
the gravitational interaction.Comment: 10 pages, 9 figures, minor corrections, published versio
Skyrme Black Holes in the Isolated Horizons Formalism
We study static, spherically symmetric, Skyrme black holes in the context of
the assumption that they can be viewed as bound states between ordinary bare
black holes and solitons. This assumption and results stemming from the
isolated horizons formalism lead to several conjectures about the static black
hole solutions. These conjectures are tested against the Skyrme black hole
solutions. It is shown that, while there is in general good agreement with the
conjectures, a crucial aspect seems to violate one of the conjectures.Comment: Full journal version, 6 pages, 5 figure
The Cosmological Probability Density Function for Bianchi Class A Models in Quantum Supergravity
Nicolai's theorem suggests a simple stochastic interpetation for
supersymmetric Euclidean quantum theories, without requiring any inner product
to be defined on the space of states. In order to apply this idea to
supergravity, we first reduce to a one-dimensional theory with local
supersymmetry by the imposition of homogeneity conditions. We then make the
supersymmetry rigid by imposing gauge conditions, and quantise to obtain the
evolution equation for a time-dependent wave function. Owing to the inclusion
of a certain boundary term in the classical action, and a careful treatment of
the initial conditions, the evolution equation has the form of a Fokker-Planck
equation. Of particular interest is the static solution, as this satisfies all
the standard quantum constraints. This is naturally interpreted as a
cosmological probability density function, and is found to coincide with the
square of the magnitude of the conventional wave function for the wormhole
state.Comment: 22 pages, Late
Energy Momentum Tensor in Conformal Field Theories Near a Boundary
The requirements of conformal invariance for the two point function of the
energy momentum tensor in the neighbourhood of a plane boundary are
investigated, restricting the conformal group to those transformations leaving
the boundary invariant. It is shown that the general solution may contain an
arbitrary function of a single conformally invariant variable , except in
dimension 2. The functional dependence on is determined for free scalar and
fermion fields in arbitrary dimension and also to leading order in the
\vep expansion about for the non Gaussian fixed point in
theory. The two point correlation function of the energy momentum tensor and a
scalar field is also shown to have a unique expression in terms of and the
overall coefficient is determined by the operator product expansion. The energy
momentum tensor on a general curved manifold is further discussed by
considering variations of the metric. In the presence of a boundary this
procedure naturally defines extra boundary operators. By considering
diffeomorphisms these are related to components of the energy momentum tensor
on the boundary. The implications of Weyl invariance in this framework are also
derived.Comment: 22 pages, TeX with epsf.tex, DAMTP/93-1. (original uuencoded file was
corrupted enroute - resubmitted version has uuencoded figures pasted to the
ended of the Plain TeX file
Internal structure of Skyrme black hole
We consider the internal structure of the Skyrme black hole under a static
and spherically symmetric ansatz. $@u8(Be concentrate on solutions with the
node number one and with the "winding" number zero, where there exist two
solutions for each horizon radius; one solution is stable and the other is
unstable against linear perturbation. We find that a generic solution exhibits
an oscillating behavior near the sigularity, as similar to a solution in the
Einstein-Yang-Mills (EYM) system, independently to stability of the solution.
Comparing it with that in the EYM system, this oscillation becomes mild because
of the mass term of the Skyrme field. We also find Schwarzschild-like
exceptional solutions where no oscillating behavior is seen. Contrary to the
EYM system where there is one such solution branch if the node number is fixed,
there are two branches corresponding to the stable and the unstable ones.Comment: 5 pages, 4 figures, some contents adde
Statistical properties of stock order books: empirical results and models
We investigate several statistical properties of the order book of three
liquid stocks of the Paris Bourse. The results are to a large degree
independent of the stock studied. The most interesting features concern (i) the
statistics of incoming limit order prices, which follows a power-law around the
current price with a diverging mean; and (ii) the humped shape of the average
order book, which can be quantitatively reproduced using a `zero intelligence'
numerical model, and qualitatively predicted using a simple approximation.Comment: Revised version, 10 pages, 4 .eps figures. to appear in Quantitative
Financ
Regular and Black Hole Solutions in the Einstein-Skyrme Theory with Negative Cosmological Constant
We study spherically symmetric regular and black hole solutions in the
Einstein-Skyrme theory with a negative cosmological constant. The Skyrme field
configuration depends on the value of the cosmological constant in a similar
manner to effectively varying the gravitational constant. We find the maximum
value of the cosmological constant above which there exists no solution. The
properties of the solutions are discussed in comparison with the asymptotically
flat solutions. The stability is investigated in detail by solving the linearly
perturbed equation numerically. We show that there exists a critical value of
the cosmological constant above which the solution in the branch representing
unstable configuration in the asymptotically flat spacetime turns to be
linearly stable.Comment: 10 pages, 9 figures, comments and one reference added, to appear in
Class.Quant.Gra
Non-Abelian Black Holes in Brans-Dicke Theory
We find a black hole solution with non-Abelian field in Brans-Dicke theory.
It is an extension of non-Abelian black hole in general relativity. We discuss
two non-Abelian fields: "SU(2)" Yang-Mills field with a mass (Proca field) and
the SU(2)SU(2) Skyrme field. In both cases, as in general relativity,
there are two branches of solutions, i.e., two black hole solutions with the
same horizon radius. Masses of both black holes are always smaller than those
in general relativity. A cusp structure in the mass-horizon radius
(-) diagram, which is a typical symptom of stability change in
catastrophe theory, does not appear in the Brans-Dicke frame but is found in
the Einstein conformal frame. This suggests that catastrophe theory may be
simply applied for a stability analysis as it is if we use the variables in the
Einstein frame. We also discuss the effects of the Brans-Dicke scalar field on
black hole structure.Comment: 31 pages, revtex, 21 figure
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