8,230 research outputs found
Apparent horizon and gravitational thermodynamics of Universe in the Eddington-Born-Infeld theory
The thermodynamics of Universe in the Eddington-Born-Infeld (EBI) theory was
restudied by utilizing the holographic-style gravitational equations that
dominate the dynamics of the cosmical apparent horizon and the
evolution of Universe. We started in rewriting the EBI action of the Palatini
approach into the Bigravity-type action with an extra metric . With
the help of the holographic-style dynamical equations, we discussed the
property of the cosmical apparent horizon including timelike,
spacelike and null characters, which depends on the value of the parameter of
state in EBI Universe. The unified first law for the gravitational
thermodynamics and the total energy differential for the open system enveloped
by in EBI Universe were obtained. Finally, applying the
positive-heat-out sign convention, we derived the generalized second law of
gravitational thermodynamics in EBI universe.Comment: 23 pages, 0 figure
The Photometric Investigation of V921 Her using the Lunar-based Ultraviolet Telescope of Chang'e-3 mission
The light curve of V921 Her in ultraviolet band observed by the Lunar-based
Ultraviolet Telescope (LUT) is analyzed by the Wilson-Devinney code. Our
solutions conclude that V921 Her is an early type marginal contact binary
system with an additional close-in component. The binary system is under poor
thermal contact with a temperature difference of nearly between the two
components. The close-in component contributes about of the total
luminosity in the triple system. Combining the radial velocity study together
with our photometric solutions, the mass of the primary star and secondary one
are calculated to be , . The evolutionary scenario of V921 Her is discussed.
All times of light minimum of V921 Her available in the bibliography are taken
into account and the curve is analyzed for the first time. The most
probable fitting results are discussed in the paper, which also confirm the
existence of a third component ( year) around the binary system. The
period of V921 Her is also undergoing a continuously rapid increase at a rate
of , which may due to mass
transfer from the less massive component to the more massive one
Heterogeneity in structurally arrested hard spheres
When cooled or compressed sufficiently rapidly, a liquid vitrifies into a glassy amorphous state. Vitrification in a dense liquid is associated with jamming of the particles. For hard spheres, the density and degree of order in the final structure depend on the compression rate: simple intuition suggests, and previous computer simulation demonstrates, that slower compression results in states that are both denser and more ordered. In this work, we use the Lubachevsky-Stillinger algorithm to generate a sequence of structurally arrested hard-sphere states by varying the compression rate. We find that while the degree of order, as measured by both bond-orientation and translation order parameters, increases monotonically with decreasing compression rate, the density of the arrested state first increases, then decreases, then increases again, as the compression rate decreases, showing a minimum at an intermediate compression rate. Examination of the distribution of the local order parameters and the distribution of the root-mean-square fluctuation of the particle positions, as well as direct visual inspection of the arrested structures, reveal that they are structurally heterogeneous, consisting of disordered, amorphous regions and locally ordered crystal-like domains. In particular, the low-density arrested states correspond with many interconnected small crystal clusters that form a polycrystalline network interspersed in an amorphous background, suggesting that jamming by the domains may be an important mechanism for these states
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