64,346 research outputs found
Is Gamma-ray Absorption by Induced Electric Fields Important in the Pulsar Magnetospheres?
Although the unified formula for gamma-ray absorption process involving both
the magnetic field and a perpendicular electric field derived by Daugherty &
Lerche (1975) is correct, we argued in this paper that their conclusion that
the induced electric fields are important in the pair formation process in the
pulsar magnetospheres is wrong and misleading. The key point is that usually
the direction of a gamma photon at the emission point observed in the
laboratory frame should be (v/c, 0, [1-(v/c)^2]^{1/2}) rather than (0, 0, 1),
where v is the co-rotating velocity. This emission direction is just the one
which results in zero attenuation coefficient of the gamma photon. Calculation
shows that after the photon has moved a distance, its direction lead to the
result that the induced electric field is also of minor importance. Thus only
gamma-B process is the important mechanism for the pair production in the
pulsar magnetospheres. The implications of the modification by ejecting the
induced electric field are also discussed.Comment: 4 pages, 2 Postscript figures, LaTeX, some miscomments on the
references of Harding et al are modified, Accepted for publication in
Astronomy and Astrophysics Letter
Phase diagram of two-species Bose-Einstein condensates in an optical lattice
The exact macroscopic wave functions of two-species Bose-Einstein condensates
in an optical lattice beyond the tight-binding approximation are studied by
solving the coupled nonlinear Schrodinger equations. The phase diagram for
superfluid and insulator phases of the condensates is determined analytically
according to the macroscopic wave functions of the condensates, which are seen
to be traveling matter waves.Comment: 13 pages, 2 figure
Controllable Persistent Atom Current of Bose-Einstein Condensates in an Optical Lattice Ring
In this paper the macroscopic quantum states of Bose-Einstein condensates in
optical lattices is studied by solving the periodic Gross-Pitaevskii equation
in one-dimensional geometry. It is shown that an exact solution seen to be a
travelling wave of excited macroscopic quantum states resultes in a persistent
atom current which can be controlled by adjusting of the barrier height of the
optical periodic potential. A critical condition to generate the travelling
wave is demonstrated and we moreover propose a practical experiment to realize
the persistent atom current in a toroidal atom waveguide.Comment: 9 pages, 1 figure
Self Interference of Single Electrodynamic Particle in Double Slit
It is by the long established fact in experiment and theory that
electromagnetic waves, here as one component of an IED particle, passing a
double slit will undergo self inference each, producing at a detector plane
fringed intensities. The wave generating point charge of a zero rest mass, as
the other component of the particle, is maintained a constant energy and speed
by a repeated radiation reabsorption/reemission scheme, and in turn steered in
direction in its linear motion by the reflected radiation field, and will
thereby travel to the detector along (one of) the optical path(s) of the waves
leading to a bright interference fringe. We elucidate the process formally
based on first principles solutions for the IED particle and known principles
for wave-matter interaction.Comment: Presentation at The 6th Int. Symp. Quantum Theory and Symmetries,
Univ. Kent, 2009
Efficient Cluster Algorithm for Spin Glasses in Any Space Dimension
Spin systems with frustration and disorder are notoriously difficult to study
both analytically and numerically. While the simulation of ferromagnetic
statistical mechanical models benefits greatly from cluster algorithms, these
accelerated dynamics methods remain elusive for generic spin-glass-like
systems. Here we present a cluster algorithm for Ising spin glasses that works
in any space dimension and speeds up thermalization by at least one order of
magnitude at temperatures where thermalization is typically difficult. Our
isoenergetic cluster moves are based on the Houdayer cluster algorithm for
two-dimensional spin glasses and lead to a speedup over conventional
state-of-the-art methods that increases with the system size. We illustrate the
benefits of the isoenergetic cluster moves in two and three space dimensions,
as well as the nonplanar chimera topology found in the D-Wave Inc.~quantum
annealing machine.Comment: 5 pages, 4 figure
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