7,650 research outputs found
Holographic Van der Waals phase transition for a hairy black hole
The Van der Waals(VdW) phase transition in a hairy black hole is investigated
by analogizing its charge, temperature, and entropy as the temperature,
pressure, and volume in the fluid respectively. The two point correlation
function(TCF), which is dual to the geodesic length, is employed to probe this
phase transition. We find the phase structure in the temperaturegeodesic
length plane resembles as that in the temperaturethermal entropy plane
besides the scale of the horizontal coordinate. In addition, we find the equal
area law(EAL) for the first order phase transition and critical exponent of the
heat capacity for the second order phase transition in the
temperaturegeodesic length plane are consistent with that in
temperaturethermal entropy plane, which implies that the TCF is a good probe
to probe the phase structure of the back hole.Comment: Accepted by Advances in High Energy Physics(The special issue:
Applications of the Holographic Duality to Strongly Coupled Quantum Systems
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
Correlations and Scaling Laws in Human Mobility
Human mobility patterns deeply affect the dynamics of many social systems. In
this paper, we empirically analyze the real-world human movements based GPS
records, and observe rich scaling properties in the temporal-spatial patterns
as well as an abnormal transition in the speed-displacement patterns. We notice
that the displacements at the population level show significant positive
correlation, indicating a cascade-like nature in human movements. Furthermore,
our analysis at the individual level finds that the displacement distributions
of users with strong correlation of displacements are closer to power laws,
implying a relationship between the positive correlation of the series of
displacements and the form of an individual's displacement distribution. These
findings from our empirical analysis show a factor directly relevant to the
origin of the scaling properties in human mobility.Comment: 10 pages, 9 figure
Centralizer of fixed point free separating flows
In this paper, we study the centralizer of a separating continuous flow
without fixed points. We show that if is a compact metric space and
is a separating flow without fixed points, then has a
quasi-trivial centralizer, that is, if a continuous flow commutes with
, then there exists a continuous function which is
invariant along the orbit of such that
holds for all . We also show that if is a compact Riemannian
manifold without boundary and is a separating
-action on , then has a quasi-trivial centralizer,
that is, if is a -action on commuting with ,
then there is a continuous map
which is invariant along orbit of such that
for all . These improve Theorem 1 of
\cite{O} and Theorem 2 of \cite{BRV} respectively
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