11,828 research outputs found
2D Lattice Liquid Models
A family of novel models of liquid on a 2D lattice (2D lattice liquid models)
have been proposed as primitive models of soft-material membrane. As a first
step, we have formulated them as single-component, single-layered, classical
particle systems on a two-dimensional surface with no explicit viscosity. Among
the family of the models, we have shown and constructed two stochastic models,
a vicious walk model and a flow model, on an isotropic regular lattice and on
the rectangular honeycomb lattice of various sizes. In both cases, the dynamics
is governed by the nature of the frustration of the particle movements. By
simulations, we have found the approximate functional form of the frustration
probability, and peculiar anomalous diffusions in their time-averaged mean
square displacements in the flow model. The relations to other existing
statistical models and possible extensions of the models are also discussed.Comment: REVTeX4, 14 pages in double colomn, 12 figures; added references with
some comments, typos fixe
The origin of the phase separation in partially deuterated -(ET)Cu[N(CN)]Br studied by infrared magneto-optical imaging spectroscopy
The direct observation of the phase separation between the metallic and
insulating states of 75 %-deuterated -(ET)Cu[N(CN)]Br ()
using infrared magneto-optical imaging spectroscopy is reported, as well as the
associated temperature, cooling rate, and magnetic field dependencies of the
separation. The distribution of the center of spectral weight () of
did not change under any of the conditions in which data were taken and
was wider than that of the non-deuterated material. This result indicates that
the inhomogenity of the sample itself is important as part of the origin of the
metal - insulator phase separation.Comment: 4 pages, 3 figures, accepted for publication in Solid State Commu
Covariant Lyapunov vectors for rigid disk systems
We carry out extensive computer simulations to study the Lyapunov instability
of a two-dimensional hard disk system in a rectangular box with periodic
boundary conditions. The system is large enough to allow the formation of
Lyapunov modes parallel to the x axis of the box. The Oseledec splitting into
covariant subspaces of the tangent space is considered by computing the full
set of covariant perturbation vectors co-moving with the flow in tangent-space.
These vectors are shown to be transversal, but generally not orthogonal to each
other. Only the angle between covariant vectors associated with immediate
adjacent Lyapunov exponents in the Lyapunov spectrum may become small, but the
probability of this angle to vanish approaches zero. The stable and unstable
manifolds are transverse to each other and the system is hyperbolic.Comment: 23 pages, 17 figures; Chemical Physics, in press, June 2010. Chem.
Phys. (2010): cited as: H. Bosetti, H.A. Posch, Chem. Phys. (2010),
doi:10.1016/j.chemphys.2010.06.01
Enhancement of the Gilbert damping constant due to spin pumping in noncollinear ferromagnet/nonmagnet/ferromagnet trilayer systems
We analyzed the enhancement of the Gilbert damping constant due to spin
pumping in non-collinear ferromagnet / non-magnet / ferromagnet trilayer
systems. We show that the Gilbert damping constant depends both on the
precession angle of the magnetization of the free layer and on the direction of
the magntization of the fixed layer. We find the condition to be satisfied to
realize strong enhancement of the Gilbert damping constant.Comment: 4 pages, 3 figures, to be published in Phys. Rev.
Lyman Alpha Radiation From Collapsing Protogalaxies II: Observational Evidence for Gas Infall
We model the spectra and surface brightness distributions for the Lyman alpha
(Lya) radiation expected from protogalaxies that are caught in the early stages
of their assembly. We use the results of a companion paper to characterize the
radiation emerging from spherically collapsing gas clouds. We then modify the
intrinsic spectra to incorporate the effect of subsequent resonant scattering
in the intergalactic medium (IGM). Using these models, we interpret a number of
recent observations of extended Lya blobs (LABs) at high redshift. We suggest,
based on the angular size, energetics, as well as the relatively shallow
surface brightness profiles, and double-peaked spectra, that several of these
LABs may be associated with collapsing protogalaxies. We suggest two follow-up
observations to diagnose the presence of gas infall. High S/N spectra of LABs
should reveal a preferential flattening of the surface brightness profile at
the red side of the line. Complementary imaging of the blobs at redshifted
Balmer alpha wavelengths should reveal the intrinsic Lya emissivity and allow
its separation from radiative transfer effects. We show that Lya scattering by
infalling gas can reproduce the observed spectrum of Steidel et al's LAB2 as
accurately as a recently proposed outflow model. Finally, we find similar
evidence for infall in the spectra of point-like Lyman alpha emitters. The
presence of scattering by the infalling gas implies that the intrinsic Lya
luminosities, and derived quantities, such as the star-formation rate, in these
objects may have been underestimated by about an order of magnitude.Comment: Accepted for Publication in ApJ, 11 emulateapj pages with 6 figures,
together with a companion pape
Carbon nanotube quantum dots on hexagonal boron nitride
We report the fabrication details and low-temperature characteristics of the
first carbon nanotube (CNT) quantum dots on flakes of hexagonal boron nitride
(hBN) as substrate. We demonstrate that CNTs can be grown on hBN by standard
chemical vapor deposition and that standard scanning electron microscopy
imaging and lithography can be employed to fabricate nanoelectronic structures
when using optimized parameters. This proof of concept paves the way to more
complex devices on hBN, with more predictable and reproducible characteristics
and electronic stability.Comment: 4 pages, 4 figure
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