17,345 research outputs found
Limit Theorems For Quantum Walks Associated with Hadamard Matrices
We study a one-parameter family of discrete-time quantum walk models on the
line and in the xy-plane associated with the Hadamard walk. Weak convergence in
the long-time limit of all moments of the walker's pseudo-velocity on the line
and in the xy-plane is proved. Symmetrization on the line and in the xy-plane
is theoretically investigated, leading to the resolution of the
Konno-Namiki-Soshi conjecture in the special case of symmetrization of the
unbiased Hadamard walk on the line . A necessary condition for the existence of
a phenomenon known as localization is given
Regularity and stability of electrostatic solutions in Kaluza-Klein theory
We investigate the family of electrostatic spherically symmetric solutions of
the five-dimensional Kaluza-Klein theory. Besides black holes and wormholes, a
new class of geodesically complete solutions is identified. A monopole
perturbation is carried out, enabling us to prove analytically the stability of
a large class of solutions, including all black holes and neutral solutions.Comment: 2 pages, "mprocl.sty" with LATEX 2.09, contribution to the 9th Marcel
Grossmann meeting (MG9), Rome, July 200
Electrostatic solutions in Kaluza-Klein theory: geometry and stability
We investigate the family of electrostatic spherically symmetric solutions of
the five-dimensional Kaluza-Klein theory. Both charged and neutral cases are
considered. The analysis of the solutions, through their geometrical
properties, reveals the existence of black holes, wormholes and naked
singularities. A new class of regular solutions is identified. A monopole
perturbation study of all these solutions is carried out, enabling us to prove
analytically the stability of large classes of solutions. In particular, the
black hole solutions are stable, while for the regular solutions the stability
analysis leads to an eigenvalue problem.Comment: Latex file, 21 page
Search for Variable Stars in the Globular Cluster M3
We describe here results of a photometric time-sequence survey of the
globular cluster M3 (NGC 5272), in a search for contact and detached eclipsing
binary stars. We have discovered only one likely eclipsing binary and one SX
Phe type star in spite of monitoring 4077 stars with and observing 25
blue stragglers. The newly identified SX Phe star, V237, shows a light curve
with a variable amplitude. Variable V238 shows variability either with a period
of 0.49 d or with a period of 0.25 d. On the cluster colour-magnitude diagram,
the variable occupies a position a few hundredths of magnitude to the blue of
the base of the red giant branch. V238 is a likely descendent of a binary blue
straggler. As a side result we obtained high quality data for 42 of the
previously known RR Lyrae variables, including 33 of Bailey type ab, 7 type c
and 2 double-mode pulsators. We used equations that relate the physical
properties of RRc stars to their pulsation periods and Fourier parameters to
derive masses, luminosities, temperatures and helium parameters for five of the
RRc stars. One of the RRd stars (V79) has switched modes. In previous studies,
it was classified as RRab, but our observations show that it is an RRd star
with the first overtone mode dominating. This indicates blueward evolution on
the horizontal branch.Comment: 21 pages including 14 figures, Latex, requires mn.sty, psfig.sty.
Submitted, MNRA
Stripe formation in horizontally oscillating granular suspensions
We present the results of an experimental study of pattern formation in
horizontally oscillating granular suspensions. Starting from a homogeneous
state, the suspension turns into a striped pattern within a specific range of
frequencies and amplitudes of oscillation. We observe an initial development of
layered structures perpendicular to the vibration direction and a gradual
coarsening of the stripes. However, both processes gradually slow down and
eventually saturate. The probability distribution of the stripe width
approaches a nonmonotonic steady-state form which can be approximated by a
Poisson distribution. We observe similar structures in MD simulations of soft
spherical particles coupled to the motion of the surrounding fluid.Comment: 7 pages, 8 figures, to appear in Europhys. Lett. (2014
Effects of Uniform and Differential Rotation on Stellar Pulsations
We have investigated the effects of uniform rotation and a specific model for
differential rotation on the pulsation frequencies of 10 \Msun\ stellar models.
Uniform rotation decreases the frequencies for all modes. Differential rotation
does not appear to have a significant effect on the frequencies, except for the
most extreme differentially rotating models. In all cases, the large and small
separations show the effects of rotation at lower velocities than do the
individual frequencies. Unfortunately, to a certain extent, differential
rotation mimics the effects o f more rapid rotation, and only the presence of
some specific observed frequencies with well identified modes will be able to
uniquely constrain the internal rotation of pulsating stars.Comment: 33 pages, 16 figures. Accepted for publication in Ap
Bounds on the force between black holes
We treat the problem of N interacting, axisymmetric black holes and obtain
two relations among physical parameters of the system including the force
between the black holes. The first relation involves the total mass, the
angular momenta, the distances and the forces between the black holes. The
second one relates the angular momentum and area of each black hole with the
forces acting on it.Comment: 13 pages, no figure
The Distance of the First Overtone RR Lyrae Variables in the MACHO LMC Database: A New Method to Correct for the Effects of Crowding
Previous studies have indicated that many of the RR Lyrae variables in the
LMC have properties similar to the ones in the Galactic globular cluster M3.
Assuming that the M3 RR Lyrae variables follow the same relationships among
period, temperature, amplitude and Fourier phase parameter phi31 as their LMC
counterparts, we have used the M3 phi31-logP relation to identify the M3-like
unevolved first overtone RR Lyrae variables in 16 fields near the LMC bar. The
temperatures of these variables were calculated from the M3 logP-logTe relation
so that the extinction could be derived for each star separately. Since blended
stars have lower amplitudes for a given period, the period amplitude relation
should be a useful tool for identifying which stars are affected by crowding.
We find that the low amplitude stars are brighter. We remove them from the
sample and derive an LMC distance modulus 18.49+/-0.11.Comment: 30 pages, 7 figures, accepted for publication in the Astronomical
Journa
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