4,740 research outputs found
Spacetime Defects: von K\'arm\'an vortex street like configurations
A special arrangement of spinning strings with dislocations similar to a von
K\'arm\'an vortex street is studied. We numerically solve the geodesic
equations for the special case of a test particle moving along twoinfinite rows
of pure dislocations and also discuss the case of pure spinning defects.Comment: 9 pages, 2figures, CQG in pres
Cosmic censorship and spherical gravitational collapse with tangential pressure
We study the spherical gravitational collapse of a compact object under the
approximation that the radial pressure is identically zero, and the tangential
pressure is related to the density by a linear equation of state. It turns out
that the Einstein equations can be reduced to the solution of an integral for
the evolution of the area radius. We show that for positive pressure there is a
finite region near the center which necessarily expands outwards, if collapse
begins from rest. This region could be surrounded by an inward moving one which
could collapse to a singularity - any such singularity will necessarily be
covered by a horizon. For negative pressure the entire object collapses
inwards, but any singularities that could arise are not naked. Thus the nature
of the evolution is very different from that of dust, even when the ratio of
pressure to density is infinitesimally small.Comment: 16 pages, Latex file, two figures, uses epsf.st
Translocation Dynamics with Attractive Nanopore-Polymer Interactions
Using Langevin dynamics simulations, we investigate the influence of
polymer-pore interactions on the dynamics of biopolymer translocation through
nanopores. We find that an attractive interaction can significantly change the
translocation dynamics. This can be understood by examining the three
components of the total translocation time
corresponding to the initial filling of the pore, transfer of polymer from the
\textit{cis} side to the \textit{trans} side, and emptying of the pore,
respectively. We find that the dynamics for the last process of emptying of the
pore changes from non-activated to activated in nature as the strength of the
attractive interaction increases, and becomes the dominant
contribution to the total translocation time for strong attraction. This leads
to a new dependence of as a function of driving force and chain length.
Our results are in good agreement with recent experimental findings, and
provide a possible explanation for the different scaling behavior observed in
solid state nanopores {\it vs.} that for the natural -hemolysin
channel.Comment: 8 pages, 11 figure
On the gravitational field of static and stationary axial symmetric bodies with multi-polar structure
We give a physical interpretation to the multi-polar Erez-Rozen-Quevedo
solution of the Einstein Equations in terms of bars. We find that each
multi-pole correspond to the Newtonian potential of a bar with linear density
proportional to a Legendre Polynomial. We use this fact to find an integral
representation of the function. These integral representations are
used in the context of the inverse scattering method to find solutions
associated to one or more rotating bodies each one with their own multi-polar
structure.Comment: To be published in Classical and Quantum Gravit
Language of Lullabies: The Russification and De-Russification of the Baltic States
This article argues that the laws for promotion of the national languages are a legitimate means for the Baltic states to establish their cultural independence from Russia and the former Soviet Union
A review of the decoherent histories approach to the arrival time problem in quantum theory
We review recent progress in understanding the arrival time problem in
quantum mechanics, from the point of view of the decoherent histories approach
to quantum theory. We begin by discussing the arrival time problem, focussing
in particular on the role of the probability current in the expected classical
solution. After a brief introduction to decoherent histories we review the use
of complex potentials in the construction of appropriate class operators. We
then discuss the arrival time problem for a particle coupled to an environment,
and review how the arrival time probability can be expressed in terms of a POVM
in this case. We turn finally to the question of decoherence of the
corresponding histories, and we show that this can be achieved for simple
states in the case of a free particle, and for general states for a particle
coupled to an environment.Comment: 10 pages. To appear in DICE 2010 conference proceeding
Influence of polymer-pore interactions on translocation
We investigate the influence of polymer-pore interactions on the
translocation dynamics using Langevin dynamics simulations. An attractive
interaction can greatly improve translocation probability. At the same time, it
also increases translocation time slowly for weak attraction while exponential
dependence is observed for strong attraction. For fixed driving force and chain
length the histogram of translocation time has a transition from Gaussian
distribution to long-tailed distribution with increasing attraction. Under a
weak driving force and a strong attractive force, both the translocation time
and the residence time in the pore show a non-monotonic behavior as a function
of the chain length. Our simulations results are in good agreement with recent
experimental data.Comment: 4 pages, 5 figures, Submitted to Phys. Rev. Let
Effects of R-parity violating supersymmetry in top pair production at linear colliders with polarized beams
In the minimal supersymmetric standard model with R-parity violation, the
lepton number violating top quark interactions can contribute to the top pair
production at a linear collider via tree-level u-channel squark exchange
diagrams. We calculate such contributions and find that in the allowed range of
these R-violating couplings, the top pair production rate as well as the top
quark polarization and the forward-backward asymmetry can be significantly
altered. By comparing the unpolarized beams with the polarized beams, we find
that the polarized beams are more powerful in probing such new physics.Comment: 10 pages, 6 fig
Semantic analysis of citizen sensing, crowdsourcing and VGI
This paper describes a semantic analysis of terms used to describe citizen sensing and crowdsourced data use in scientific analyses. It applies a latency analysis to journal abstracts downloaded from Scopus that matched one of number of terms related to crowd sourced data and citizen science. The latency analysis shows how the terms associated with crowdsourcing are related and how they have evolved over time.JRC.H.6-Digital Earth and Reference Dat
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