10,975 research outputs found
Laser frequency combs and ultracold neutrons to probe braneworlds through induced matter swapping between branes
This paper investigates a new experimental framework to test the braneworld
hypothesis. Recent theoretical results have shown the possibility of matter
exchange between branes under the influence of suitable magnetic vector
potentials. It is shown that the required conditions might be achieved with
present-day technology. The experiment uses a source of pulsed and coherent
electromagnetic radiation and relies on the Hansch frequency comb technique
well-known in ultrahigh-precision spectroscopy. A good matter candidate for
testing the hypothesis is a polarized ultracold neutron gas for which the
number of swapped neutrons is measured.Comment: 14 pages, 4 figures. Published version. Published in Phys. Rev.
Fast and Compact Distributed Verification and Self-Stabilization of a DFS Tree
We present algorithms for distributed verification and silent-stabilization
of a DFS(Depth First Search) spanning tree of a connected network. Computing
and maintaining such a DFS tree is an important task, e.g., for constructing
efficient routing schemes. Our algorithm improves upon previous work in various
ways. Comparable previous work has space and time complexities of bits per node and respectively, where is the highest
degree of a node, is the number of nodes and is the diameter of the
network. In contrast, our algorithm has a space complexity of bits
per node, which is optimal for silent-stabilizing spanning trees and runs in
time. In addition, our solution is modular since it utilizes the
distributed verification algorithm as an independent subtask of the overall
solution. It is possible to use the verification algorithm as a stand alone
task or as a subtask in another algorithm. To demonstrate the simplicity of
constructing efficient DFS algorithms using the modular approach, We also
present a (non-sielnt) self-stabilizing DFS token circulation algorithm for
general networks based on our silent-stabilizing DFS tree. The complexities of
this token circulation algorithm are comparable to the known ones
Magnetic fields, winds and X-rays of the massive stars in the Orion Nebula Cluster
In some massive stars, magnetic fields are thought to confine the outflowing
radiatively-driven wind. Although theoretical models and MHD simulations are
able to illustrate the dynamics of such a magnetized wind, the impact of this
wind-field interaction on the observable properties of a magnetic star - X-ray
emission, photometric and spectral variability - is still unclear. The aim of
this study is to examine the relationship between magnetism, stellar winds and
X-ray emission of OB stars, by providing empirical observations and confronting
theory. In conjunction with the COUP survey of the Orion Nebula Cluster, we
carried out spectropolarimatric ESPaDOnS observations to determine the magnetic
properties of massive OB stars of this cluster.Comment: Proceedings of IAUS272: Active OB star
Structural behavior of uranium dioxide under pressure by LSDA+U calculations
The structural behavior of UO2 under high pressure up to 300GPa has been
studied by first-principles calculations with LSDA+U approximation. The results
show that a pressure-induced structural transition to the cotunnite-type
(orthorhombic Pnma) phase occurs at 38GPa. It agrees well with the
experimentally observed ~42 GPa. An isostructural transition following that is
also predicted to take place from 80 to 130GPa, which has not yet been observed
in experiments. Further high compression beyond 226GPa will result in a
metallic and paramagnetic transition. It corresponds to a volume of 90A^3 per
cell, in good agreement with a previous theoretical analysis in the reduction
of volume required to delocalize 5f states.Comment: 10 pages, 8 figure
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