30,328 research outputs found
Analytical theory for dark soliton interaction in nonlocal nonlinear materials with arbitrary degree of nonlocality
We investigate theoretically the interaction of dark solitons in materials
with a spatially nonlocal nonlinearity. In particular we do this analytically
and for arbitrary degree of nonlocality. We employ the variational technique to
show that nonlocality induces an attractive force in the otherwise repulsive
soliton interaction.Comment: submitted for publicatio
SS Ari: a shallow-contact close binary system
Two CCD epochs of light minimum and a complete R light curve of SS Ari are
presented. The light curve obtained in 2007 was analyzed with the 2003 version
of the W-D code. It is shown that SS Ari is a shallow contact binary system
with a mass ratio and a degree of contact factor f=9.4(\pm0.8%). A
period investigation based on all available data shows that there may exist two
distinct solutions about the assumed third body. One, assuming eccentric orbit
of the third body and constant orbital period of the eclipsing pair results in
a massive third body with and P_3=87.00.278M_{\odot}$. Both of the cases
suggest the presence of an unseen third component in the system.Comment: 28 pages, 9 figures and 5 table
The triangular Ising model with nearest- and next-nearest-neighbor couplings in a field
We study the Ising model on the triangular lattice with nearest-neighbor
couplings , next-nearest-neighbor couplings , and a
magnetic field . This work is done by means of finite-size scaling of
numerical results of transfer matrix calculations, and Monte Carlo simulations.
We determine the phase diagram and confirm the character of the critical
manifolds. The emphasis of this work is on the antiferromagnetic case , but we also explore the ferromagnetic regime for H=0.
For and H=0 we locate a critical phase presumably covering the
whole range . For , we locate a
plane of phase transitions containing a line of tricritical three-state Potts
transitions. In the limit this line leads to a tricritical model
of hard hexagons with an attractive next-nearest-neighbor potential
COMPUTER SIMULATION OF "SPLASH CONTROL IN COMPETITIVE DIVING
The purpose of the study was to examine the relationship between the hand pattern and the water splash height during a diver's entry using a computer simulation method. A physical and mathematical model of the impact of a wedged solid object with an ideal fluid was developed. The motion equation (interaction function of solid and fluid) of the solid was established with satisfaction of control functions and initial boundary conditions of the fluid. A finite element method was used to simulate the impact process, with the wedge angle changed from 4" to 80- during the impact. The results suggested that the fluid splash height is inversely proportional to the wedge angle. The "splash control" technique derived from the simulation was also applied in training professional divers and positive results were obtained
Thermodynamical quantities of lattice full QCD from an efficient method
I extend to QCD an efficient method for lattice gauge theory with dynamical
fermions. Once the eigenvalues of the Dirac operator and the density of states
of pure gluonic configurations at a set of plaquette energies (proportional to
the gauge action) are computed, thermodynamical quantities deriving from the
partition function can be obtained for arbitrary flavor number, quark masses
and wide range of coupling constants, without additional computational cost.
Results for the chiral condensate and gauge action are presented on the
lattice at flavor number , 1, 2, 3, 4 and many quark masses and coupling
constants. New results in the chiral limit for the gauge action and its
correlation with the chiral condensate, which are useful for analyzing the QCD
chiral phase structure, are also provided.Comment: Latex, 11 figures, version accepted for publicatio
How to Build a Dichoptic Presentation System That Includes an Eye Tracker
The presentation of different stimuli to the two eyes, dichoptic presentation, is essential for studies involving 3D vision and interocular suppression. There is a growing literature on the unique experimental value of pupillary and oculomotor measures, especially for research on interocular suppression. Although obtaining eye-tracking measures would thus benefit studies that use dichoptic presentation, the hardware essential for dichoptic presentation (e.g. mirrors) often interferes with high-quality eye tracking, especially when using a video-based eye tracker. We recently described an experimental setup that combines a standard dichoptic presentation system with an infrared eye tracker by using infrared-transparent mirrors1. The setup is compatible with standard monitors and eye trackers, easy to implement, and affordable (on the order of US$1,000). Relative to existing methods it has the benefits of not requiring special equipment and posing few limits on the nature and quality of the visual stimulus. Here we provide a visual guide to the construction and use of our setup
The most plausible explanation of the cyclical period changes in close binaries: the case of the RS CVn-type binary WW Dra
We searched the orbital period changes in 182 EA-type (including the 101
Algol systems used by \cite{hal89}), 43 EB-type and 53 EW-type binaries with
known both the mass ratio and the spectral type of their secondary components.
We reproduced and improved the same diagram as Hall's (1989) according to the
new collected data. Our plots do not support the conclusion derived by
\cite{hal89} that all cases of cyclical period changes are restricted to
binaries having the secondary component with spectral types later than F5. The
presence of period changes also among stars with secondary component of early
type indicates that the magnetic activity is one cause, but not the only one,
for the period variation. It is discovered that cyclic period changes, likely
due to the presence of a third body are more frequent in EW-type binaries among
close binaries. Therefore, the most plausible explanation of the cyclical
period changes is the LTTE via the presence of a third body. By using the
century-long historical record of the times of light minimum, we analyzed the
cyclical period change in the Algol binary WW Dra. It is found that the orbital
period of the binary shows a cyclic variation
with an amplitude of . The cyclic oscillation
can be attributed to the LTTE via a third body with a mass no less than . However, no spectral lines of the third body were discovered
indicating that it may be a candidate black hole. The third body is orbiting
the binary at a distance shorter than 14.4 AU and it may play an important role
in the evolution of this system.Comment: 9 pages, 5 figures, published by MNRA
Diverse Supernova Sources for the r-Process
(Abridged) It is shown that a semi-quantitative agreement with the gross
solar r-process abundance pattern near and above mass number A=130 can be
obtained by a superposition of two distinctive kinds of supernova r-process
events. These correspond to a low frequency case L and a high frequency case H,
which takes into account the low abundance of I129 and the high abundance of
Hf182 in the early solar nebula. The lifetime of Hf182 associates the events in
case H with the most common Type II supernovae. These events would be mainly
responsible for the r-process nuclei near and above A=195. They would also make
a significant amount of the nuclei between A=130 and 195, including Hf182, but
very little I129. In order to match the solar r-process abundance pattern and
to satisfy the I129 and Hf182 constraints, the events in case L, which would
make the r-process nuclei near A=130 and the bulk of those between A=130 and
195, must occur 10 times less frequently but eject 10--20 times more r-process
material in each event. We speculate that the usual neutron star remnants, and
hence prolonged ejection of r-process material, are associated with the events
in case L, whereas the more frequently occurring events in case H have ejection
of other r-process material terminated by black hole formation during the
neutrino cooling phase of the protoneutron star.Comment: 23 pages, AAS LATEX, 8 Postscript figure
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