1,683 research outputs found
Gravitational waves with dark matter minispikes: the combined effect
It was shown that the dark matter(DM) minihalo around an intermediate mass
black hole(IMBH) can be redistributed into a cusp, called the DM minispike. We
consider an intermediate-mass-ratio inspiral consisting of an IMBH harbored in
a DM minispike with nonannihilating DM particles and a small black hole(BH)
orbiting around it. We investigate gravitational waves(GWs) produced by this
system and analyze the waveforms with the comprehensive consideration of
gravitational pull, dynamical friction and accretion of the minispike and
calculate the time difference and phase difference caused by it. We find that
for a certain range of frequency, the inspiralling time of the system is
dramatically reduced for smaller central IMBH and large density of DM. For the
central IMBH with , the time of merger is ahead, which can be
distinguished by LISA, Taiji and Tianqin. We focus on the effect of accretion
and compare it with that of gravitational pull and friction. We find that the
accretion mass is a small quantity compared to the initial mass of the small BH
and the accretion effect is inconspicuous compared with friction. However, the
accumulated phase shift caused by accretion is large enough to be detected by
LISA, Taiji and Tianqin, which indicate that the accretion effect can not be
ignored in the detection of GWs.Comment: 10 pages, 14 figure
(E)-4-{[2-(2-FurylcarbonÂyl)hydrazinylÂidene]methÂyl}-2-methÂoxyÂphenyl acetate
The molÂecule of the title Schiff base compound, C15H14N2O5, was obtained from a condensation reaction of 4-acetÂoxy-3-methÂoxyÂbenzaldehyde and 2-furylÂcarbonylÂhydrazide. In the molÂecule, the furyl ring makes a dihedral angle of 14.63 (10)° with the benzene ring. In the crystal, interÂmolecular N—H⋯O hydrogen bonds link the molÂecules into chains along the b axis. Futhermore, weak C—H⋯O interÂactions connect the chains, forming corrugated layers parallel to (001). The dihedral angle between the rings is 14.63 (10)°
Dark matter: an efficient catalyst for intermediate-mass-ratio-inspiral events
Gravitational waves (GWs) can be produced if a stellar compact object, such
as a black hole (BH) or neutron star, inspirals into an intermediate-massive
black hole (IMBH) of . Such a system may be produced
in the center of a globular cluster (GC) or a nuclear star cluster (NSC), and
is known as an intermediate- or extreme-mass-ratio inspiral (IMRI or EMRI).
Motivated by the recent suggestions that dark matter minispikes could form
around IMBHs, we study the effect of dynamical friction against DM on the
merger rate of IMRIs/EMRIs. We find that the merger timescale of IMBHs with BHs
and NSs would be shortened by two to three orders of magnitude. As a result,
the event rate of IMRIs/EMRIs are enhanced by orders of magnitude relative to
that in the case of no DM minispikes. In the most extreme case where IMBHs are
small and the DM minispikes have a steep density profile, all the BH in GCs and
NSCs might be exhausted so that the mergers with NSs would dominate the current
IMRIs/EMRIs. Our results suggest that the mass function of the IMBHs below
would bear imprints of the distribution of DM minispikes
because these low-mass IMBHs can grow efficiently in the presence of DM
minispikes by merging with BHs and NSs. Future space-based GW detectors, like
LISA, Taiji, and Tianqin, can measure the IMRI/EMRI rate and hence constrain
the distribution of DM around IMBHs.Comment: 17 pages, 10 figure
Cloud computing resource scheduling and a survey of its evolutionary approaches
A disruptive technology fundamentally transforming the way that computing services are delivered, cloud computing offers information and communication technology users a new dimension of convenience of resources, as services via the Internet. Because cloud provides a finite pool of virtualized on-demand resources, optimally scheduling them has become an essential and rewarding topic, where a trend of using Evolutionary Computation (EC) algorithms is emerging rapidly. Through analyzing the cloud computing architecture, this survey first presents taxonomy at two levels of scheduling cloud resources. It then paints a landscape of the scheduling problem and solutions. According to the taxonomy, a comprehensive survey of state-of-the-art approaches is presented systematically. Looking forward, challenges and potential future research directions are investigated and invited, including real-time scheduling, adaptive dynamic scheduling, large-scale scheduling, multiobjective scheduling, and distributed and parallel scheduling. At the dawn of Industry 4.0, cloud computing scheduling for cyber-physical integration with the presence of big data is also discussed. Research in this area is only in its infancy, but with the rapid fusion of information and data technology, more exciting and agenda-setting topics are likely to emerge on the horizon
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