2,450,466 research outputs found
Island formation without attractive interactions
We show that adsorbates on surfaces can form islands even if there are no
attractive interactions. Instead strong repulsion between adsorbates at short
distances can lead to islands, because such islands increase the entropy of the
adsorbates that are not part of the islands. We suggest that this mechanism
cause the observed island formation in O/Pt(111), but it may be important for
many other systems as well.Comment: 11 pages, 4 figure
Analysis of Super-Kamiokande 5-day Measurements of the Solar Neutrino Flux
Data in 5-day bins, recently released by the Super-Kamiodande Consortium, has
been analyzed by a likelihood procedure that has certain advantages over the
Lomb-Scargle procedure used by the consortium. The two most prominent peaks in
the power spectrum of the 10-day data were at 9.42 y-1 and 26.57 y-1, and it
was clear that one was an alias of the other caused by the regularity of the
binning. There were reasons to believe that the 9.42 y-1 peak was an alias of
the 26.57 y-1 peak, but analysis of the 5-day data makes it clear that the
reverse is the case. In addition to a strong peak near 9.42 y-1, we find peaks
at 43.72 y-1and at 39.28 y-1. After comparing this analysis with a
power-spectrum analysis of magnetic-field data, we suggest that these three
peaks may be attributed to a harmonic of the solar rotation rate and to an
r-mode oscillation with spherical harmonic indices l = 2, m = 2.Comment: Accepted for publication in Astrophysical Journa
Dynamics of kinks in the Ginzburg-Landau equation: Approach to a metastable shape and collapse of embedded pairs of kinks
We consider initial data for the real Ginzburg-Landau equation having two
widely separated zeros. We require these initial conditions to be locally close
to a stationary solution (the ``kink'' solution) except for a perturbation
supported in a small interval between the two kinks. We show that such a
perturbation vanishes on a time scale much shorter than the time scale for the
motion of the kinks. The consequences of this bound, in the context of earlier
studies of the dynamics of kinks in the Ginzburg-Landau equation, [ER], are as
follows: we consider initial conditions whose restriction to a bounded
interval have several zeros, not too regularly spaced, and other zeros of
are very far from . We show that all these zeros eventually disappear
by colliding with each other. This relaxation process is very slow: it takes a
time of order exponential of the length of
ESR study of the single-ion anisotropy in the pyrochlore antiferromagnet Gd2Sn2O7
Single-ion anisotropy is of importance for the magnetic ordering of the
frustrated pyrochlore antiferromagnets Gd2Ti2O7 and Gd2Sn2O7. The anisotropy
parameters for the Gd2Sn2O7 were measured using the electron spin resonance
(ESR) technique. The anisotropy was found to be of the easy plane type, with
the main constant D=140mK. This value is 35% smaller than the value of the
corresponding anisotropy constant in the related compound Gd2Ti2O7.Comment: 8 pages, 3 figure
Discovery of X-ray Jets in the Microquasar H 1743-322
We report on the formation and evolution of two large-scale,
synchrotron-emitting jets from the black hole candidate H 1743-322 following
its reactivation in 2003. In November 2003 after the end of its 2003 outburst,
we noticed, in observations with the Australia Telescope Compact Array, the
presence of a new and variable radio source about 4.6" to the East of H
1743-322, that was later found to move away from H 1743-322. In February 2004,
we detected a radio source to the West of H 1743-322, symmetrically placed
relative to the Eastern jet. In 2004, follow-up X-ray observations with {\em
Chandra} led to the discovery of X-ray emission associated with the two radio
sources. This likely indicates that we are witnessing the interaction of
relativistic jets from H 1743-322 with the interstellar medium causing in-situ
particle acceleration. The spectral energy distribution of the jets during the
decay phase is consistent with a classical synchrotron spectrum of a single
electron distribution from radio up to X-rays, implying the production of very
high energy ( 10 TeV) particles in those jets. We discuss the jet
kinematics, highlighting the presence of a significantly relativistic flow in H
1743-322 almost a year after the ejection event.Comment: Accepted for publication in The Astrophysical Journal. 17 pages, 9
figure
Primordial Adiabatic Fluctuations from Cosmic Defects
We point out that in the context of ``two-metric'' theories of gravity there
is the possibility that cosmic defects will produce a spectrum of primordial
adiabatic density perturbations. This will happen when the speed characterising
the defect-producing scalar field is much larger than the speed characterising
gravity and all standard model particles. This model will exactly mimic the
standard predictions of inflationary models, with the exception of a small
non-Gaussian signal which could be detected by future experiments. We briefly
discuss defect evolution in these scenarios and analyze their cosmological
consequences.Comment: 5 LaTeX pages, no figures; version to appear in Phys. Rev. Let
Algebraic Linearization of Dynamics of Calogero Type for any Coxeter Group
Calogero-Moser systems can be generalized for any root system (including the
non-crystallographic cases). The algebraic linearization of the generalized
Calogero-Moser systems and of their quadratic (resp. quartic) perturbations are
discussed.Comment: LaTeX2e, 13 pages, no figure
Effect of ancilla's structure on quantum error correction using the 7-qubit Calderbank-Shor-Steane code
In this work we discuss the ability of different types of ancillas to control
the decoherence of a qubit interacting with an environment. The error is
introduced into the numerical simulation via a depolarizing isotropic channel.
After the correction we calculate the fidelity as a quality criterion for the
qubit recovered. We observe that a recovery method with a three-qubit ancilla
provides reasonable good results bearing in mind its economy. If we want to go
further, we have to use fault-tolerant ancillas with a high degree of
parallelism, even if this condition implies introducing new ancilla
verification qubits.Comment: 24 pages, 10 Figures included. Accepted in Phys. Rev. A 200
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