71,118 research outputs found
Astronomy: Starbursts near and far
Observations of intensely bright star-forming galaxies both close by and in
the distant Universe at first glance seem to emphasize their similarity. But
look a little closer, and differences emerge.Comment: 6 pages including 1 figur
Analytic description of atomic interaction at ultracold temperatures II: Scattering around a magnetic Feshbach resonance
Starting from a multichannel quantum-defect theory, we derive analytic
descriptions of a magnetic Feshbach resonance in an arbitrary partial wave ,
and the atomic interactions around it. An analytic formula, applicable to both
broad and narrow resonances of arbitrary , is presented for ultracold atomic
scattering around a Feshbach resonance. Other related issues addressed include
(a) the parametrization of a magnetic Feshbach resonance of arbitrary , (b)
rigorous definitions of "broad" and "narrow" resonances of arbitrary and
their different scattering characteristics, and (c) the tuning of the effective
range and the generalized effective range by a magnetic field.Comment: 13 pages, 4 figure
Effective nonlinear optical properties of composite media of graded spherical particles
We have developed a nonlinear differential effective dipole approximation
(NDEDA), in an attempt to investigate the effective linear and third-order
nonlinear susceptibility of composite media in which graded spherical
inclusions with weak nonlinearity are randomly embedded in a linear host
medium. Alternatively, based on a first-principles approach, we derived exactly
the linear local field inside the graded particles having power-law dielectric
gradation profiles. As a result, we obtain also the effective linear dielectric
constant and third-order nonlinear susceptibility. Excellent agreement between
the two methods is numerically demonstrated. As an application, we apply the
NDEDA to investigate the surface plasma resonant effect on the optical
absorption, optical nonlinearity enhancement, and figure of merit of
metal-dielectric composites. It is found that the presence of gradation in
metal particles yields a broad resonant band in the optical region, and further
enhances the figure of merit.Comment: 20 pages, 5 figure
A consistent description of kinetic equation with triangle anomaly
We provide a consistent description of the kinetic equation with triangle
anomaly which is compatible with the entropy principle of the second law of
thermodynamics and the charge/energy-momentum conservation equations. In
general an anomalous source term is necessary to ensure that the equations for
the charge and energy-momentum conservation are satisfied and that the
correction terms of distribution functions are compatible to these equations.
The constraining equations from the entropy principle are derived for the
anomaly-induced leading order corrections to the particle distribution
functions. The correction terms can be determined for minimum number of unknown
coefficients in one charge and two charge cases by solving the constraining
equations.Comment: RevTex 4, 11 pages; With minor changes: typos are corrected and one
reference is added. Accepted version to PR
Generalized modified gravity with the second order acceleration equation
In the theories of generalized modified gravity, the acceleration equation is
generally fourth order. So it is hard to analyze the evolution of the Universe.
In this paper, we present a class of generalized modified gravity theories
which have the acceleration equation of second order derivative. Then both the
cosmic evolution and the weak-field limit of the theories are easily
investigated. We find that not only the Big-bang singularity problem but also
the current cosmic acceleration problem could be easily dealt with.Comment: 8 pages, 2 figures. To appear in Phys. Rev.
Peltier effect in normal metal-insulator-heavy fermion metal junctions
A theoretical study has been undertaken of the Peltier effect in normal metal
- insulator - heavy fermion metal junctions. The results indicate that, at
temperatures below the Kondo temperature, such junctions can be used as
electronic microrefrigerators to cool the normal metal electrode and are
several times more efficient in cooling than the normal metal - heavy fermion
metal junctions.Comment: 3 pages in REVTeX, 2 figures, to be published in Appl. Phys. Lett.,
April 7, 200
- …