2,262 research outputs found
Equation of state of a seven-dimensional hard-sphere fluid. Percus-Yevick theory and molecular dynamics simulations
Following the work of Leutheusser [Physica A 127, 667 (1984)], the solution
to the Percus-Yevick equation for a seven-dimensional hard-sphere fluid is
explicitly found. This allows the derivation of the equation of state for the
fluid taking both the virial and the compressibility routes. An analysis of the
virial coefficients and the determination of the radius of convergence of the
virial series are carried out. Molecular dynamics simulations of the same
system are also performed and a comparison between the simulation results for
the compressibility factor and theoretical expressions for the same quantity is
presented.Comment: 12 pages, 4 figures; v3: Equation (A.19) corrected (see
http://dx.doi.org/10.1063/1.2390712
Simple equation of state for hard disks on the hyperbolic plane
A simple equation of state for hard disks on the hyperbolic plane is
proposed. It yields the exact second virial coefficient and contains a pole at
the highest possible packing. A comparison with another very recent theoretical
proposal and simulation data is presented.Comment: 3 pages, 1 figur
Teleparallel loop quantum cosmology in a system of intersecting branes
Recently, some authors have removed the big bang singularity in teleparallel
Loop Quantum Cosmology (LQC) and have shown that the universe may undergo a
number of oscillations. We investigate the origin of this type of teleparallel
theory in a system of intersecting branes in M-theory in which the angle
between them changes with time. This system is constructed by two intersecting
anti-D8-branes, one compacted D4-brane and the other a D3-brane. These branes
are built by joining M0-branes which develop in decaying fundamental strings.
The compacted D4-brane is located between two intersecting anti-D8 branes and
glues to one of them. Our universe is located on the D3 brane which wraps the
D4 brane from one end and sticks to one of the anti-D8 branes from another one.
In this system, there are three types of fields, corresponding to compacted D4
branes, intersecting branes and D3-branes. These fields interact with each
other and make the angle between branes oscillate. By decreasing this angle and
approaching the intersecting anti-D8 branes towards each other, the D4 brane
rolls, the D3 brane wraps around the D4 brane, and t he universe contracts. By
separating the intersecting branes and increasing the angle, the D4 brane rolls
in the opposite direction, the D3 brane separates from it and the expansion
branch begins. Also, the interaction between branes in this system gives us the
exact form of the relevant Lagrangian for teleparallel LQC.Comment: 11 page
On the radial distribution function of a hard-sphere fluid
Two related approaches, one fairly recent [A. Trokhymchuk et al., J. Chem.
Phys. 123, 024501 (2005)] and the other one introduced fifteen years ago [S. B.
Yuste and A. Santos, Phys. Rev. A 43, 5418 (1991)], for the derivation of
analytical forms of the radial distribution function of a fluid of hard spheres
are compared. While they share similar starting philosophy, the first one
involves the determination of eleven parameters while the second is a simple
extension of the solution of the Percus-Yevick equation. It is found that the
{second} approach has a better global accuracy and the further asset of
counting already with a successful generalization to mixtures of hard spheres
and other related systems.Comment: 3 pages, 1 figure; v2: slightly shortened, figure changed, to be
published in JC
Cataglyphis cubicus (Forel, 1903) stat. nov. (Hymenoptera, Formicidae) y ♂ nov., grupo albicans, de Asilah, costa atlántica de Marruecos
Se describe el macho de Cataglyphis cubicus (Forel, 1903) (Hym. Formicidae), del grupo albicans, de Asilah, litoral noroeste de Marruecos. Se separa esta especie de C. rosenhaueri(Emery, 1906), del suroeste de España, no sólo por la genitalia de los machos, sino también por la morfometría de las obreras.The male of Cataglyphis cubicus (Forel, 1903), (Hym. Formicidae), group albicans, from Asilah, NW of Morocco, is described. This species is separated from C. rosenhaueri (Emery, 1906), from SW of Spain, not only by the genitalia, but also by the morphometry of workers
On the fate of the phantom dark energy universe in semiclassical gravity II: Scalar phantom fields
Quantum corrections coming from massless fields conformally coupled with
gravity are studied, in order to see if they can lead to avoidance of the
annoying Big Rip singularity which shows up in a flat
Friedmann-Robertson-Walker universe filled with dark energy and modeled by a
scalar phantom field. The dynamics of the model are discussed for all values of
the two parameters, named and , corresponding to the
regularization process. The new results are compared with the ones obtained in
\cite{hae11} previously, where dark energy was modeled by means of a phantom
fluid with equation of state , with
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