7,927 research outputs found
Chain motion and viscoelasticity in highly entangled solutions of semiflexible rods
Brownian dynamics simulations are used to study highly entangled solutions of
semiflexible polymers. Bending fluctuations of semiflexible rods are
signficantly affected by entanglement only above a concentration ,
where for chains of similar length and
persistence length. For , the tube radius approaches a
dependence , and the linear viscoelastic response
develops an elastic contribution that is absent for . Experiments
on isotropic solutions of -actin span concentrations near for which
the predicted asymptotic scaling of the plateau modulus is
not yet valid.Comment: 4 pages, 5 figures, submitted to PR
Cosmic Acceleration from M Theory on Twisted Spaces
In a recent paper [I.P. Neupane and D.L. Wiltshire, Phys. Lett. B 619, 201
(2005).] we have found a new class of accelerating cosmologies arising from a
time--dependent compactification of classical supergravity on product spaces
that include one or more geometric twists along with non-trivial curved
internal spaces. With such effects, a scalar potential can have a local minimum
with positive vacuum energy. The existence of such a minimum generically
predicts a period of accelerated expansion in the four-dimensional
Einstein-conformal frame. Here we extend our knowledge of these cosmological
solutions by presenting new examples and discuss the properties of the
solutions in a more general setting. We also relate the known (asymptotic)
solutions for multi-scalar fields with exponential potentials to the
accelerating solutions arising from simple (or twisted) product spaces for
internal manifolds.Comment: 23 pages, 3 figures; added a summary Table, PRD versio
Abstract Data Types in Event-B - An Application of Generic Instantiation
Integrating formal methods into industrial practice is a challenging task.
Often, different kinds of expertise are required within the same development.
On the one hand, there are domain engineers who have specific knowledge of the
system under development. On the other hand, there are formal methods experts
who have experience in rigorously specifying and reasoning about formal
systems. Coordination between these groups is important for taking advantage of
their expertise. In this paper, we describe our approach of using generic
instantiation to facilitate this coordination. In particular, generic
instantiation enables a separation of concerns between the different parties
involved in developing formal systems.Comment: In Proceedings of DS-Event-B 2012: Workshop on the experience of and
advances in developing dependable systems in Event-B, in conjunction with
ICFEM 2012 - Kyoto, Japan, November 13, 201
Multi-Instantons and Multi-Cuts
We discuss various aspects of multi-instanton configurations in generic
multi-cut matrix models. Explicit formulae are presented in the two-cut case
and, in particular, we obtain general formulae for multi-instanton amplitudes
in the one-cut matrix model case as a degeneration of the two-cut case. These
formulae show that the instanton gas is ultra-dilute, due to the repulsion
among the matrix model eigenvalues. We exemplify and test our general results
in the cubic matrix model, where multi-instanton amplitudes can be also
computed with orthogonal polynomials. As an application, we derive general
expressions for multi-instanton contributions in two-dimensional quantum
gravity, verifying them by computing the instanton corrections to the string
equation. The resulting amplitudes can be interpreted as regularized partition
functions for multiple ZZ-branes, which take into full account their
back-reaction on the target geometry. Finally, we also derive structural
properties of the trans-series solution to the Painleve I equation.Comment: 34 pages, 3 figures, JHEP3.cls; v2: added references, minor changes;
v3: added 1 reference, more minor changes, final version for JMP; v4: more
typos correcte
Nickel bismuth boride, Ni23-xBixB6 [x = 2.44 (1)]
The τ-boride Ni23-xBixB6 [x = 2.44 (1)] adopts a ternary variant of the cubic Cr23C6-type structure, with Ni8 cubes and Ni12 cuboctahedra arranged in a NaCl-type pattern. Two of the four independent metal sites (8c, 3m symmetry; 4a, m
m symmetry) are occupied by a mixture of Ni and Bi atoms in a 0.106 (6):0.894 (6) and a 0.350 (7):0.650 (7) ratio, respectively
Detection of planet candidates around K giants, HD 40956, HD 111591, and HD 113996
Aims. The purpose of this paper is to detect and investigate the nature of
long-term radial velocity (RV) variations of K-type giants and to confirm
planetary companions around the stars.
Methods. We have conducted two planet search programs by precise RV
measurement using the 1.8 m telescope at Bohyunsan Optical Astronomy
Observatory (BOAO) and the 1.88 m telescope at Okayama Astrophysical
Observatory (OAO). The BOAO program searches for planets around 55 early K
giants. The OAO program is looking for 190 G-K type giants.
Results. In this paper, we report the detection of long-period RV variations
of three K giant stars, HD 40956, HD 111591, and HD 113996. We investigated the
cause of the observed RV variations and conclude the substellar companions are
most likely the cause of the RV variations. The orbital analyses yield P =
578.6 3.3 d, sin = 2.7 0.6 , = 1.4
0.1 AU for HD 40956; P = 1056.4 14.3 d, sin = 4.4 0.4
, = 2.5 0.1 AU for HD 111591; P = 610.2 3.8 d,
sin = 6.3 1.0 , = 1.6 0.1 AU for HD 113996.Comment: 10 pages, 12 figures. Accepted for publication in Astronomy &
Astrophysic
- …