6,968 research outputs found
Generalized Vaidya Solutions and Misner-Sharp mass for -dimensional massive gravity
Dynamical solutions are always of interest to people in gravity theories. We
derive a series of generalized Vaidya solutions in the -dimensional de
Rham-Gabadadze-Tolley (dRGT) massive gravity with a singular reference metric.
Similar to the case of the Einstein gravity, the generalized Vaidya solution
can describe shining/absorbing stars. Moreover, we also find a more general
Vaidya-like solution by introducing a more generic matter field than the pure
radiation in the original Vaidya spacetime. As a result, the above generalized
Vaidya solution is naturally included in this Vaidya-like solution as a special
case. We investigate the thermodynamics for this Vaidya-like spacetime by using
the unified first law, and present the generalized Misner-Sharp mass. Our
results show that the generalized Minser-Sharp mass does exist in this
spacetime. In addition, the usual Clausius relation holds on
the apparent horizon, which implicates that the massive gravity is in a
thermodynamic equilibrium state. We find that the work density vanishes for the
generalized Vaidya solution, while it appears in the more general Vaidya-like
solution. Furthermore, the covariant generalized Minser-Sharp mass in the
-dimensional de Rham-Gabadadze-Tolley massive gravity is also derived by
taking a general metric ansatz into account.Comment: 10 pages, no figure, version published in PR
The effects of massive graviton on the equilibrium between the black hole and radiation gas in an isolated box
It is well known that the black hole can has temperature and radiate the
particles with black body spectrum, i.e. Hawking radiation. Therefore, if the
black hole is surrounded by an isolated box, there is a thermal equilibrium
between the black hole and radiation gas. A simple case considering the thermal
equilibrium between the Schwarzschild black hole and radiation gas in an
isolated box has been well investigated previously in detail, i.e. taking the
conservation of energy and principle of maximal entropy for the isolated system
into account. In this paper, following the above spirit, the effects of massive
graviton on the thermal equilibrium will be investigated. For the gravity with
massive graviton, we will use the de Rham-Gabadadze-Tolley (dRGT) massive
gravity which has been proven to be ghost free. Because the graviton mass
depends on two parameters in the dRGT massive gravity, here we just investigate
two simple cases related to the two parameters, respectively. Our results show
that in the first case the massive graviton can suppress or increase the
condensation of black hole in the radiation gas although the diagram is
similar like the Schwarzschild black hole case. For the second case, a new
diagram has been obtained. Moreover, an interesting and important
prediction is that the condensation of black hole just increases from the zero
radius of horizon in this case, which is very different from the Schwarzschild
black hole case.Comment: 9 pages, 4 figure
Research on Innovation Ecosystem of the Crowd Innovation Space Based on System Dynamics
The crowd innovation space is a new innovation business service platform, developed from the traditional incubator, including makerspace, entrepreneurship café and so on. It is essential for mass entrepreneurship and innovation to get full use of the creativity of the crowed innovation space and explore new impetus in New Economic Norm. Based on the traditional enterprise innovation ecosystem theory, this paper explores the connotation of innovation ecosystem of the crowd innovation space. And then, we use the knowledge to model the innovation ecosystem of the crowd innovation space with system dynamics. Based on the model, we explore the operational mechanism of innovation ecosystem of the crowd innovation space. Through the analysis of the operational mechanism and connotation, we put forward to some proposal to improve the effectiveness of the service ability in innovation of the crowd innovation space
Value of superb microvascular imaging ultrasonography in the diagnosis of carpal tunnel syndrome: Compared with color Doppler and power Doppler.
The aim of this study was to compare the value of superb microvascular imaging (SMI) in carpal tunnel syndrome (CTS) with that of color Doppler ultrasonography (CDUS) and power Doppler ultrasonography (PDUS).Fifty patients with symptomatic CTS and 25 healthy volunteers were enrolled. The cross-sectional area (CSA), CDUS score, PDUS score, and SMI score of the median nerve (MN) at the carpal tunnel were recorded. The value of different ultrasonography (US) diagnostic strategies was calculated.The blood flow display ratio in the MN of the healthy volunteers had no statistical difference between CDUS, PDUS, and SMI (20%, 32%, and 48%, respectively, P \u3e.05). The blood flow display ratio for SMI in patients was significantly higher than that of CDUS and PDUS (90%, 52%, and 60%, respectively,
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