3,700 research outputs found
Perturbations of Dark Solitons
A method for approximating dark soliton solutions of the nonlinear
Schrodinger equation under the influence of perturbations is presented. The
problem is broken into an inner region, where core of the soliton resides, and
an outer region, which evolves independently of the soliton. It is shown that a
shelf develops around the soliton which propagates with speed determined by the
background intensity. Integral relations obtained from the conservation laws of
the nonlinear Schrodinger equation are used to approximate the shape of the
shelf. The analysis is developed for both constant and slowly evolving
backgrounds. A number of problems are investigated including linear and
nonlinear damping type perturbations
BRST Properties of New Superstring States
Brane-like states are defined by physical vertex operators in NSR superstring
theory, existing at nonzero pictures only. These states exist both in open and
closed string theories, in the NS and NS-NS sectors respectively. In this paper
we present a detailed analysis of their BRST properties, giving a proof that
these vertex operators are physical, i.e. BRST invariant and BRST non-trivial.Comment: 25 pages, harvmac.te
Extrasolar planetary dynamics with a generalized planar Laplace-Lagrange secular theory
The dynamical evolution of nearly half of the known extrasolar planets in
multiple-planet systems may be dominated by secular perturbations. The commonly
high eccentricities of the planetary orbits calls into question the utility of
the traditional Laplace-Lagrange (LL) secular theory in analyses of the motion.
We analytically generalize this theory to fourth-order in the eccentricities,
compare the result with the second-order theory and octupole-level theory, and
apply these theories to the likely secularly-dominated HD 12661, HD 168443, HD
38529 and Ups And multi-planet systems. The fourth-order scheme yields a
multiply-branched criterion for maintaining apsidal libration, and implies that
the apsidal rate of a small body is a function of its initial eccentricity,
dependencies which are absent from the traditional theory. Numerical results
indicate that the primary difference the second and fourth-order theories
reveal is an alteration in secular periodicities, and to a smaller extent
amplitudes of the planetary eccentricity variation. Comparison with numerical
integrations indicates that the improvement afforded by the fourth-order theory
over the second-order theory sometimes dwarfs the improvement needed to
reproduce the actual dynamical evolution. We conclude that LL secular theory,
to any order, generally represents a poor barometer for predicting secular
dynamics in extrasolar planetary systems, but does embody a useful tool for
extracting an accurate long-term dynamical description of systems with small
bodies and/or near-circular orbits.Comment: 14 pages, 12 figures, 1 table, accepted for publication in Ap
Transiting Disintegrating Planetary Debris around WD 1145+017
More than a decade after astronomers realized that disrupted planetary
material likely pollutes the surfaces of many white dwarf stars, the discovery
of transiting debris orbiting the white dwarf WD 1145+017 has opened the door
to new explorations of this process. We describe the observational evidence for
transiting planetary material and the current theoretical understanding (and in
some cases lack thereof) of the phenomenon.Comment: Invited review chapter. Accepted March 23, 2017 and published October
7, 2017 in the Handbook of Exoplanets. 15 pages, 10 figure
The thermal conductivity of silicon nitride membranes is not sensitive to stress
We have measured the thermal properties of suspended membranes from 10 K to
300 K for two amplitudes of internal stress (about 0.1 GPa and 1 GPa) and for
two different thicknesses (50 nm and 100 nm). The use of the original 3 \omega
-Volklein method has allowed the extraction of both the specific heat and the
thermal conductivity of each SiN membrane over a wide temperature range. The
mechanical properties of the same substrates have been measured at helium
temperatures using nanomechanical techniques. Our measurements show that the
thermal transport in freestanding SiN membranes is not affected by the presence
of internal stress. Consistently, mechanical dissipation is also unaffected
even though Qs increase with increasing tensile stress. We thus demonstrate
that the theory developed by Wu and Yu [Phys. Rev. B 84, 174109 (2011)] does
not apply to this amorphous material in this stress range. On the other hand,
our results can be viewed as a natural consequence of the "dissipation
dilution" argument [Y. L. Huang and P. R. Saulson, Rev. Sci. Instrum. 69, 544
(1998)] which has been introduced in the context of mechanical damping.Comment: 15 pages, 6 figures. Submitted to PR
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