54 research outputs found
The relativistic glider
We present a purely relativistic effect according to which asymmetric
oscillations of a quasi-rigid body slow down or accelerate its fall in a
gravitational background.Comment: 3 pages, 2 figures. To appear in Phys Rev
New self-dual solutions of SU(2) Yang-Mills theory in Euclidean Schwarzschild space
We present a systematic study of spherically symmetric self-dual solutions of
SU(2) Yang-Mills theory on Euclidean Schwarzschild space. All the previously
known solutions are recovered and a new one-parameter family of instantons is
obtained. The newly found solutions have continuous actions and interpolate
between the classic Charap and Duff instantons. We examine the physical
properties of this family and show that it consists of dyons of unit (magnetic
and electric) charge.Comment: 12 pages, 5 figures. To appear in Phys Rev
The Topology of Dislocations in Smectic Liquid Crystals
The order parameter of the smectic liquid crystal phase is the same as that
of a superfluid or superconductor, namely a complex scalar field. We show that
the essential difference in boundary conditions between these systems leads to
a markedly different topological structure of the defects. Screw and edge
defects can be distinguished topologically. This implies an invariant on an
edge dislocation loop so that smectic defects can be topologically linked not
unlike defects in ordered systems with non-Abelian fundamental groups.Comment: 11 pages, many figures, the full catastrophe. Supplementary data with
two movies can be found at
http://iopscience.iop.org/article/10.1088/1367-2630/18/5/05301
Fisher Information and Kinetic-energy Functionals: A Dequantization Approach
We strengthen the connection between Information Theory and
quantum-mechanical systems using a recently developed dequantization procedure
whereby quantum fluctuations latent in the quantum momentum are suppressed. The
dequantization procedure results in a decomposition of the quantum kinetic
energy as the sum of a classical term and a purely quantum term. The purely
quantum term, which results from the quantum fluctuations, is essentially
identical to the Fisher information. The classical term is complementary to the
Fisher information and, in this sense, it plays a role analogous to that of the
Shannon entropy. We demonstrate the kinetic energy decomposition for both
stationary and nonstationary states and employ it to shed light on the nature
of kinetic-energy functionals.Comment: 13 pages, 3 figures. To appear in J. Comput. Appl. Mat
Analogue model for anti-de Sitter as a description of point sources in fluids
We introduce an analogue model for a nonglobally hyperbolic spacetime in
terms of a two-dimensional fluid. This is done by considering the propagation
of sound waves in a radial flow with constant velocity. We show that the
equation of motion satisfied by sound waves is the wave equation on
. Since this spacetime is not globally hyperbolic, the
dynamics of the Klein-Gordon field is not well defined until boundary
conditions at the spatial boundary of are prescribed. On the analogue
model end, those extra boundary conditions provide an effective description of
the point source at . For waves with circular symmetry, we relate the
different physical evolutions to the phase difference between ingoing and
outgoing scattered waves. We also show that the fluid configuration can be
stable or unstable depending on the chosen boundary condition.Comment: 6 pages, 1 figure. To appear in Phys Rev
Singular solutions to the Seiberg-Witten and Freund equations on flat space from an iterative method
Although it is well known that the Seiberg-Witten equations do not admit
nontrivial solutions in flat space, singular solutions to them have been
previously exhibited -- either in or in the dimensionally reduced spaces
and -- which have physical interest. In this work, we employ an
extension of the Hopf fibration to obtain an iterative procedure to generate
particular singular solutions to the Seiberg-Witten and Freund equations on
flat space. Examples of solutions obtained by such method are presented and
briefly discussed.Comment: 7 pages, minor changes. To appear in J. Math. Phy
Variational approach to dequantization
We present a dequantization procedure based on a variational approach whereby
quantum fluctuations latent in the quantum momentum are suppressed. This is
done by adding generic local deformations to the quantum momentum operator
which give rise to a deformed kinetic term quantifying the amount of
``fuzzyness'' caused by such fluctuations. Considered as a functional of such
deformations, the deformed kinetic term is shown to possess a unique minimum
which is seen to be the classical kinetic energy. Furthermore, we show that
extremization of the associated deformed action functional introduces an
essential nonlinearity to the resulting field equations which are seen to be
the classical Hamilton-Jacobi and continuity equations. Thus, a variational
procedure determines the particular deformation that has the effect of
suppressing the quantum fluctuations, resulting in dequantization of the
system.Comment: 6 pages, 1 figure. v2: changes in presentation and conten
Boundary conditions and renormalized stress-energy tensor on a Poincar\'e patch of
Quantum field theory on anti-de Sitter spacetime requires the introduction of
boundary conditions at its conformal boundary, due essentially to the absence
of global hyperbolicity. Here we calculate the renormalized stress-energy
tensor for a scalar field on the Poincar\'e patch of
and study how it depends on those boundary conditions. We show
that, except for the Dirichlet and Neumann cases, the boundary conditions break
the maximal invariance. As a result,
acquires a space dependence and is no longer
proportional to the metric. When the physical quantities are expanded in a
parameter which characterizes the boundary conditions (with
corresponding to Dirichlet and corresponding to Neumann), the
singularity of the Green's function is entirely subtracted at zeroth order in
. As a result, the contribution of nontrivial boundary conditions to the
stress-energy tensor is free of singular terms.Comment: 7 pages. Minor Correction. Matches published versio
Analogue gravity and radial fluid flows: The case of AdS and its deformations
An analogue model for the spacetime has been recently
introduced by Mosna, Pitelli and Richartz [Phys. Rev. D 94, 104065 (2016)] by
considering sound waves propagating on a fluid with an ill-defined velocity
profile at its source/sink. The wave propagation is then uniquely defined only
when one imposes an extra boundary condition at the source/sink (which
corresponds to the spatial infinity of ). Here we show that, once
this velocity profile is smoothed out at the source/sink, the need for extra
boundary conditions disappears. This, in turn, corresponds to deformations of
the spacetime near its spatial infinity. We also examine how
this regularization of the velocity profile picks up a specific boundary
condition for the idealized system, so that both models agree in the long
wavelength limit.Comment: 6 pages, 3 figures. To appear in Phys Rev
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