5,958 research outputs found
Holographic Heat engine within the framework of massive gravity
Heat engine models are constructed within the framework of massive gravity in
this paper. For the four-dimensional charged black holes in massive gravity, it
is shown that the heat engines have a higher efficiency for the cases
than for the case when . Considering a specific example, we
show that the maximum efficiency can reach while the efficiency for
reads . The existence of graviton mass improves the heat engine
efficiency significantly. The situation is more complicated for the
five-dimensional neutral black holes. Not only the exert
influence on the efficiency, but also the constant corresponding to the
third massive potential contributes to the efficiency. When is higher than that of
the case . By studying the ratio , we also probe how the
massive gravity influences the behavior of the heat engine efficiency
approaching the Carnot efficiency.Comment: 9pages,4figure
Ratio of critical quantities related to Hawking temperature-entanglement entropy criticality
We revisit the Hawking temperatureentanglement entropy criticality of the
-dimensional charged AdS black hole with our attention concentrated on the
ratio . Comparing the results of this paper with
those of the ratio , one can find both the similarities
and differences. These two ratios are independent of the characteristic length
scale and dependent on the dimension . These similarities further
enhance the relation between the entanglement entropy and the
Bekenstein-Hawking entropy. However, the ratio
also relies on the size of the spherical entangling region. Moreover, these two
ratios take different values even under the same choices of parameters. The
differences between these two ratios can be attributed to the peculiar property
of the entanglement entropy since the research in this paper is far from the
regime where the behavior of the entanglement entropy is dominated by the
thermal entropy.Comment: Comments welcome. 11 pages, 3 figure
Revisiting van der Waals like behavior of f(R) AdS black holes via the two point correlation function
Van der Waals like behavior of AdS black holes is revisited via two
point correlation function, which is dual to the geodesic length in the bulk.
The equation of motion constrained by the boundary condition is solved
numerically and both the effect of boundary region size and gravity are
probed. Moreover, an analogous specific heat related to is
introduced. It is shown that the graphs of AdS black holes
exhibit reverse van der Waals like behavior just as the graphs do. Free
energy analysis is carried out to determine the first order phase transition
temperature and the unstable branch in curve is removed by a
bar . It is shown that the first order phase transition temperature is
the same at least to the order of for different choices of the
parameter although the values of free energy vary with . Our result
further supports the former finding that charged AdS black holes behave
much like RN-AdS black holes. We also check the analogous equal area law
numerically and find that the relative errors for both the cases
and are small enough. The fitting functions between and for both cases are also
obtained. It is shown that the slope is around 3, implying that the critical
exponent is about . This result is in accordance with those in former
literatures of specific heat related to the thermal entropy or entanglement
entropy.Comment: Revised version. Match the published version. 14pages,5figure
Empirical properties of inter-cancellation durations in the Chinese stock market
Order cancellation process plays a crucial role in the dynamics of price
formation in order-driven stock markets and is important in the construction
and validation of computational finance models. Based on the order flow data of
18 liquid stocks traded on the Shenzhen Stock Exchange in 2003, we investigate
the empirical statistical properties of inter-cancellation durations in units
of events defined as the waiting times between two consecutive cancellations.
The inter-cancellation durations for both buy and sell orders of all the stocks
favor a -exponential distribution when the maximum likelihood estimation
method is adopted; In contrast, both cancelled buy orders of 6 stocks and
cancelled sell orders of 3 stocks prefer Weibull distribution when the
nonlinear least-square estimation is used. Applying detrended fluctuation
analysis (DFA), centered detrending moving average (CDMA) and multifractal
detrended fluctuation analysis (MF-DFA) methods, we unveil that the
inter-cancellation duration time series process long memory and multifractal
nature for both buy and sell cancellations of all the stocks. Our findings show
that order cancellation processes exhibit long-range correlated bursty
behaviors and are thus not Poissonian.Comment: 14 pages, 7 figures and 5 table
Multi-color optical monitoring of the quasar 3C 273 from 2005 to 2016
We have monitored the quasar 3C 273 in optical , and bands from
2005 to 2016. Intraday variability (IDV) is detected on seven nights. The
variability amplitudes for most of nights are less than 10\% and four nights
more than 20\%. When considering the nights with time spans hours, the
value of duty cycle (DC) is 14.17 per cent. Over the twelve years, the overall
magnitude and color index variabilities are ,
, , and
respectively. The largest clear IDV has an
amplitude of 42% over just 5.8 minutes and the weakest detected IDV is 5.4%
over 175 minutes. The BWB (bluer when brighter) chromatic trend is dominant for
3C 273 and appears at different flux levels on intraday timescales. The BWB
trend exists for short-term timescales and intermediate-term timescales but
different timescales have different correlations. There is no BWB trend for our
whole time-series data sets. A significant anti-correlation between BWB trend
and length of timescales is found. Combining with -band data from previous
works, we find a possible quasi-periodicity of days. The
possible explanations for the observed variability, BWB chromatic trend and
periodicity are discussed.Comment: 63 pages, 11 figures, 6 tables. Accepted for publication in ApJ
Heat engine in the three-dimensional spacetime
We define a kind of heat engine via three-dimensional charged BTZ black
holes. This case is quite subtle and needs to be more careful. The heat flow
along the isochores does not equal to zero since the specific heat
and this point completely differs from the cases discussed before whose
isochores and adiabats are identical. So one cannot simply apply the paradigm
in the former literatures. However, if one introduces a new thermodynamic
parameter associated with the renormalization length scale, the above problem
can be solved. We obtain the analytical efficiency expression of the
three-dimensional charged BTZ black hole heat engine for two different schemes.
Moreover, we double check with the exact formula. Our result presents the first
specific example for the sound correctness of the exact efficiency formula. We
argue that the three-dimensional charged BTZ black hole can be viewed as a toy
model for further investigation of holographic heat engine. Furthermore, we
compare our result with that of the Carnot cycle and extend the former result
to three-dimensional spacetime. In this sense, the result in this paper would
be complementary to those obtained in four-dimensional spacetime or ever
higher. Last but not the least, the heat engine efficiency discussed in this
paper may serve as a criterion to discriminate the two thermodynamic approaches
introduced in Ref.[29] and our result seems to support the approach which
introduces a new thermodynamic parameter .Comment: Revised version. Discussions adde
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