3,446 research outputs found
Surface Energy in Cold Asymmetrical Fermion Superfluids
We derive the energy of the surface between the normal and superfluid
components of a mixed phase of a system composed of two particle species with
different densities. The surface energy is obtained by the integration of the
free energy density in the interface between the two phases. We show that the
mixed phase remains as the favored ground state over the gapless phase in weak
coupling. We find that the surface energy effects emerge only at strong
coupling.Comment: 12 pages, 2 figures, typos corrected, published versio
Gravitational Waves and Intermediate-mass Black Hole Retention in Globular Clusters
The recent discovery of gravitational waves (GWs) has opened new horizons for physics. Current and upcoming missions, such as LIGO, VIRGO, KAGRA, and LISA, promise to shed light on black holes of every size from stellar mass (SBH) sizes up to supermassive black holes. The intermediate-mass black hole (IMBH) family has not been detected beyond any reasonable doubt. Recent analyses suggest observational evidence for the presence of IMBHs in the centers of two Galactic globular clusters (GCs). In this paper, we investigate the possibility that GCs were born with a central IMBH, which undergoes repeated merger events with SBHs in the cluster core. By means of a semi-analytical method, we follow the evolution of the primordial cluster population in the galactic potential and the mergers of the binary IMBH-SBH systems. Our models predict approximate to 1000 IMBHs within 1 kpc from the galactic center and show that the IMBH-SBH merger rate density changes from R approximate to 1000 Gpc(-3) yr(-1) beyond z approximate to 2 to R approximate to 1-10 Gpc(-3) yr(-1) at z approximate to 0. The rates at low redshifts may be significantly higher if young massive star clusters host IMBHs. The merger rates are dominated by IMBHs with masses between 10(3) and 10(4) M-circle dot. Currently, there are no LIGO/VIRGO upper limits for GW sources in this mass range, but our results show that at design sensitivity, these instruments will detect IMBH-SBH mergers in the coming years. LISA and the Einstein Telescope will be best suited to detect these events. The inspirals of IMBH-SBH systems may also generate an unresolved GW background
Hypervelocity A & B Stars should be slow rotators
The most commonly accepted explanation for the origin of hypervelocity stars
in the halo of the Milky Way is that they are the result of tidal disruption of
binaries by the massive black hole at the center of the Galaxy. We show that,
if this scenario is correct, and if the original binary properties are similar
to those in the local stellar neighbourhood, then the hypervelocity stars
should rotate with velocities measureably lower than those for field stars of
similar spectral type. This may prove to be a more direct test of the model
than trying to predict the position and velocity distributions.Comment: 11 pages, including 4 figures. To appear in Astrophysical Journal
Letter
Surface effects in magnetic superconductors with a spiral magnetic structure
We consider a magnetic superconductor MS with a spiral magnetic structure. On
the basis of generalized Eilenberger and Usadel equations we show that near the
boundary of the MS with an insulator or vacuum the condensate (Gor'kov's)
Green's functions are disturbed by boundary conditions and differ essentially
from their values in the bulk. Corrections to the bulk quasiclassical Green's
functions oscillate with the period of the magnetic spiral, , and
decay inside the superconductor over a length of the order (ballistic
limit) or (diffusive limit). We calculate the dc Josephson
current in an MS/I/MS tunnel junction and show that the critical Josephson
current differs substantially from that obtained with the help of the tunnel
Hamiltonian method and bulk Green's functions.Comment: 10 pages 3 Figs; some misprints in fromulae corrected; submitted to
Phys. Rev.
Hypervelocity Stars. I. The Spectroscopic Survey
We discuss our targeted search for hypervelocity stars (HVSs), stars
traveling with velocities so extreme that dynamical ejection from a massive
black hole is their only suggested origin. Our survey, now half complete, has
successfully identified a total of four probable HVSs plus a number of other
unusual objects. Here we report the most recently discovered two HVSs: SDSS
J110557.45+093439.5 and possibly SDSS J113312.12+010824, traveling with
Galactic rest-frame velocities at least +508+-12 and +418+-10 km/s,
respectively. The other late B-type objects in our survey are consistent with a
population of post main-sequence stars or blue stragglers in the Galactic halo,
with mean metallicity [Fe/H]=-1.3 and velocity dispersion 108+-5 km/s.
Interestingly, the velocity distribution shows a tail of objects with large
positive velocities that may be a mix of low-velocity HVSs and high-velocity
runaway stars. Our survey also includes a number of DA white dwarfs with
unusually red colors, possibly extremely low mass objects. Two of our objects
are B supergiants in the Leo A dwarf, providing the first spectroscopic
evidence for star formation in this dwarf galaxy within the last ~30 Myr.Comment: 10 pages, uses emulateapj, accepted by Ap
Lysophosphatides enhance superoxide responses of stimulated human neutrophils
Human neutrophils which are pretreated with subtoxic concentrations of a variety of lysophosphatides (lysophosphatidytcholine, lysophosphatidylcholine oleoyl, lysophosphatidylcholine myrioyl, lysophosphatidylcholine stearoyl, lysophosphatidylcholine gamma- O -hexadecyl, lysophosphatidylinositol, and lysophosphatidylglycerol) act synergistically with neutrophil agonists phorbol myristate acetate, immune complexes, poly- L -histidine, phytohemagglutinin, and N -formyl methionyl-leucyl-phenyalanine to cause enhanced generation of superoxide (O 2 − ). None of the lyso compounds by themselves caused generation of O 2 − . The lyso compounds strongly bound to the neutrophils and could not be washed away. All of the lyso compounds that collaborated with agonists to stimulate O 2 − generation were hemolytic for human red blood cells. On the other hand, lyso compounds that were nonhemolytic for red blood cells (lysophosphatidylcholine caproate, lysophosphatidylcholine decanoyl, lysophosphatidylethanolamine, lysophosphatidylserine) failed to collaborate with agonists to generate synergistic amounts of O 2 − . However, in the presence of cytochalasin B, both lysophosphatidyiethanolamine and lysophosphatidylserine also markedly enhanced O 2 − generation induced by immune complexes. O 2 − generation was also very markedly enhanced when substimulatory amounts of arachidonic acid or eicosapentanoic acid were added to PMNs in the presence of a variety of agonists. On the other hand, neither phospholipase C, streptolysin S (highly hemolytic), phospholipase A 2 , phosphatidylcholine, nor phosphatidylcholine dipalmitoyl (all nonhemolytic) had the capacity to synergize with any of the agonists tested to generate enhanced amounts of O 2 − . The data suggest that in addition to long-chain fatty acids, only those lyso compounds that possess fatty acids with more than 10 carbons and that are also highly hemolytic can cause enhanced generation of O 2 − in stimulated PMNs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44499/1/10753_2004_Article_BF00924787.pd
Skin effect with arbitrary specularity in Maxwellian plasma
The problem of skin effect with arbitrary specularity in maxwellian plasma
with specular--diffuse boundary conditions is solved. A new analytical method
is developed that makes it possible to to obtain a solution up to an arbitrary
degree of accuracy. The method is based on the idea of symmetric continuation
not only the electric field, but also electron distribution function. The
solution is obtained in a form of von Neumann series.Comment: 7 pages, 2 figure
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