121 research outputs found
The Accelerated Kepler Problem
The accelerated Kepler problem is obtained by adding a constant acceleration
to the classical two-body Kepler problem. This setting models the dynamics of a
jet-sustaining accretion disk and its content of forming planets as the disk
loses linear momentum through the asymmetric jet-counterjet system it powers.
The dynamics of the accelerated Kepler problem is analyzed using physical as
well as parabolic coordinates. The latter naturally separate the problem's
Hamiltonian into two unidimensional Hamiltonians. In particular, we identify
the origin of the secular resonance in the accelerated Kepler problem and
determine analytically the radius of stability boundary of initially circular
orbits that are of particular interest to the problem of radial migration in
binary systems as well as to the truncation of accretion disks through stellar
jet acceleration.Comment: 16 pages, 9 figures, in press at Celestial Mechanics and Dynamical
Astronom
Stages of steady diffusion growth of a gas bubble in strongly supersaturated gas-liquid solution
Gas bubble growth as a result of diffusion flux of dissolved gas molecules
from the surrounding supersaturated solution to the bubble surface is studied.
The condition of the flux steadiness is revealed. A limitation from below on
the bubble radius is considered. Its fulfillment guarantees the smallness of
fluctuation influence on bubble growth and irreversibility of this process.
Under the conditions of steadiness of diffusion flux three stages of bubble
growth are marked out. With account for Laplace forces in the bubble intervals
of bubble size change and time intervals of these stages are found. The trend
of the third stage towards the self-similar regime of the bubble growth, when
Laplace forces in the bubble are completely neglected, is described
analytically.Comment: 22 page
Vortices in superfluid trapped Fermi gases at zero temperature
We discuss various aspects of the vortex state of a dilute superfluid atomic
Fermi gas at T=0. The energy of the vortex in a trapped gas is calculated and
we provide an expression for the thermodynamic critical rotation frequency of
the trap for its formation. Furthermore, we propose a method to detect the
presence of a vortex by calculating the effect of its associated velocity field
on the collective mode spectrum of the gas
Gravitational waves from inspiralling compact binaries: Energy loss and waveform to second--post-Newtonian order
Gravitational waves generated by inspiralling compact binaries are
investigated to the second--post-Newtonian (2PN) approximation of general
relativity. Using a recently developed 2PN-accurate wave generation formalism,
we compute the gravitational waveform and associated energy loss rate from a
binary system of point-masses moving on a quasi-circular orbit. The crucial new
input is our computation of the 2PN-accurate ``source'' quadrupole moment of
the binary. Tails in both the waveform and energy loss rate at infinity are
explicitly computed. Gravitational radiation reaction effects on the orbital
frequency and phase of the binary are deduced from the energy loss. In the
limiting case of a very small mass ratio between the two bodies we recover the
results obtained by black hole perturbation methods. We find that finite mass
ratio effects are very significant as they increase the 2PN contribution to the
phase by up to 52\%. The results of this paper should be of use when
deciphering the signals observed by the future LIGO/VIRGO network of
gravitational-wave detectors.Comment: 43 pages, LaTeX-ReVTeX, no figures
Euclidean Configuration Space Renormalization, Residues and Dilation Anomaly1
Configuration (x-)space renormalization of euclidean Feynman amplitudes in a massless quantum field theory is reduced to the study of local extensions of associate homogeneous distributions. Primitively divergent graphs are renormalized, in particular, by subtracting the residue of an analytically regularized expression. Examples are given of computing residues that involve zeta values. The renormalized Green functions are again associate homogeneous distributions of the same degree that transform under indecomposable representations of the dilation group
Relativistic superfluid models for rotating neutron stars
This article starts by providing an introductory overview of the theoretical
mechanics of rotating neutron stars as developped to account for the frequency
variations, and particularly the discontinuous glitches, observed in pulsars.
The theory suggests, and the observations seem to confirm, that an essential
role is played by the interaction between the solid crust and inner layers
whose superfluid nature allows them to rotate independently. However many
significant details remain to be clarified, even in much studied cases such as
the Crab and Vela. The second part of this article is more technical,
concentrating on just one of the many physical aspects that needs further
development, namely the provision of a satisfactorily relativistic (local but
not microscopic) treatment of the effects of the neutron superfluidity that is
involved.Comment: 42 pages LateX. Contribution to Physics of Neutron Star Interiors,
ed. D. Blasche, N.K. Glendenning, A. Sedrakian (ECT workshop, Trento, June
2000
Mode of lysozyme protein adsorption at end-tethered polyethylene oxide brushes on gold surfaces determined by neutron reflectivity
Influência da cobertura vegetal de inverno e da adubação orgânica e, ou, mineral sobre as propriedades físicas de uma Terra Roxa Estruturada
Heterogeneity of elemental composition and natural abundance of stables isotopes of C and N in soils and leaves of mangroves at their southernmost West Atlantic range
Homologs of genes and anonymous loci on human Chromosome 13 map to mouse Chromosomes 8 and 14
To enhance the comparative map for human Chromosome (Chr) 13, we identified clones for human genes and anonymous loci that cross-hybridized with their mouse homologs and then used linkage crosses for mapping. Of the clones for four genes and twelve anonymous loci tested, cross-hybridization was found for six, COL4A1, COL4A2, D13S26, D13S35, F10, and PCCA. Strong evidence for homology was found for COL4A1, COL4A2, D13S26, D13S35, and F10, but only circumstantial homology evidence was obtained for PCCA. To genetically map these mouse homologs ( Cf10, Col4a1, Col4a2, D14H13S26, D8H13S35 , and Pcca-rs ), we used interspecific and intersubspecific mapping panels. D14H13S26 and Pcca-rs were located on the distal portion of mouse Chr 14 extending by ∼30 cM the conserved linkage between human Chr 13 and mouse Chr 14, assuming that Pcca-rs is the mouse homolog of PCCA. By contrast, Cf10, Col4a1, Col4a2 , and D8H13S35 mapped near the centromere of mouse Chr 8, defining a new conserved linkage. Finally, we identified either a closely linked sequence related to Col4a2 , or a recombination hot-spot between Col4a1 and Col4a2 that has been conserved in humans and mice.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47022/1/335_2004_Article_BF00352413.pd
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