17,667 research outputs found
Polymer Translocation througha Pore in a Membrane
We construct a new statistical physical model of polymer translocation
through a pore in a membrane treated as the diffusion process across a free
energy barrier. We determine the translocation time in terms of chain
flexibility yielding an entropic barrier, as well as in terms of the driving
mechanisms such as transmembrane chemical potential difference and Brownian
ratchets. It turns out that, while the chemical potential differences induce
pronounced effects on translocation due to the long-chain nature of the
polymer, the ratchets suppress this effect and chain flexibility.Comment: 4 pages, 5 figures, published in Phys. Rev. Lett. 77, 783(1996
Low energy effective theory of Fermi surface coupled with U(1) gauge field in 2+1 dimensions
We study the low energy effective theory for a non-Fermi liquid state in 2+1
dimensions, where a transverse U(1) gauge field is coupled with a patch of
Fermi surface with N flavors of fermion in the large N limit. In the low energy
limit, quantum corrections are classified according to the genus of the 2d
surface on which Feynman diagrams can be drawn without a crossing in a double
line representation, and all planar diagrams are important in the leading
order. The emerging theory has the similar structure to the four dimensional
SU(N) gauge theory in the large N limit. Because of strong quantum fluctuations
caused by the abundant low energy excitations near the Fermi surface, low
energy fermions remain strongly coupled even in the large N limit. As a result,
there are infinitely many quantum corrections that contribute to the leading
frequency dependence of the Green's function of fermion on the Fermi surface.
On the contrary, the boson self energy is not modified beyond the one-loop
level and the theory is stable in the large N limit. The non-perturbative
nature of the theory also shows up in correlation functions of gauge invariant
operators.Comment: 14 pages, 20 figures; v2) Sec. V on correlation function of gauge
invariant operators added; v3) typos corrected, minor changes (to appear in
PRB
A verification library for multibody simulation software
A multibody dynamics verification library, that maintains and manages test and validation data is proposed, based on RRC Robot arm and CASE backhoe validation and a comparitive study of DADS, DISCOS, and CONTOPS that are existing public domain and commercial multibody dynamic simulation programs. Using simple representative problems, simulation results from each program are cross checked, and the validation results are presented. Functionalities of the verification library are defined, in order to automate validation procedure
Surface-Enhanced Plasmon Splitting in a Liquid-Crystal-Coated Gold Nanoparticle
We show that, when a gold nanoparticle is coated by a thin layer of nematic
liquid crystal, the deformation produced by the nanoparticle surface can
enhance the splitting of the nanoparticle surface plasmon. We consider three
plausible liquid crystal director configurations in zero electric field: boojum
pair (north-south pole configuration), baseball (tetrahedral), and homogeneous.
From a calculation using the Discrete Dipole Approximation, we find that the
surface plasmon splitting is largest for the boojum pair, intermediate for the
homogeneous, and smallest for the baseball configuration. The boojum pair
results are in good agreement with experiment. We conclude that the
nanoparticle surface has a strong effect on the director orientation, but,
surprisingly, that this deformation can actually enhance the surface plasmon
splitting.Comment: 5 pages, 3 figures To be published in PR
Patterns of Striped order in the Classical Lattice Coulomb Gas
We obtain via Monte Carlo simulations the low temperature charge
configurations in the lattice Coulomb gas on square lattices for charge filling
ratio in the range . We find a simple regularity in the low
temperature charge configurations which consist of a suitable periodic
combination of a few basic striped patterns characterized by the existence of
partially filled diagonal channels. In general there exist two separate
transitions where the lower temperature transition () corresponds to the
freezing of charges within the partially filled channels. is found to be
sensitively dependent on through the charge number density within the channels.Comment: 4 pages, 8 figure
Type II superconductivity in SrPd2Ge2
Previous investigations have shown that SrPd2Ge2, a compound isostructural
with "122" iron pnictides but iron- and pnictogen-free, is a conventional
superconductor with a single s-wave energy gap and a strongly three-dimensional
electronic structure. In this work we reveal the Abrikosov vortex lattice
formed in SrPd2Ge2 when exposed to magnetic field by means of scanning
tunneling microscopy and spectroscopy. Moreover, by examining the differential
conductance spectra across a vortex and estimating the upper and lower critical
magnetic fields by tunneling spectroscopy and local magnetization measurements,
we show that SrPd2Ge2 is a strong type II superconductor with \kappa >>
sqrt(2). Also, we compare the differential conductance spectra in various
magnetic fields to the pair breaking model of Maki - de Gennes for dirty limit
type II superconductor in the gapless region. This way we demonstrate that the
type II superconductivity is induced by the sample being in the dirty limit,
while in the clean limit it would be a type I superconductor with \kappa\ <<
sqrt(2), in concordance with our previous study (T. Kim et al., Phys. Rev. B
85, (2012)).Comment: 9 pages, 4 figure
Discrete Symmetries on the Light Front and a General Relation Connecting Nucleon Electric Dipole and Anomalous Magnetic Moments
We consider the electric dipole form factor, F_3(q^2), as well as the Dirac
and Pauli form factors, F_1(q^2) and F_2(q^2), of the nucleon in the
light-front formalism. We derive an exact formula for F_3(q^2) to complement
those known for F_1(q^2) and F_2(q^2). We derive the light-front representation
of the discrete symmetry transformations and show that time-reversal- and
parity-odd effects are captured by phases in the light-front wave functions. We
thus determine that the contributions to F_2(q^2) and F_3(q^2), Fock state by
Fock state, are related, independent of the fundamental mechanism through which
CP violation is generated. Our relation is not specific to the nucleon, but,
rather, is true of spin-1/2 systems in general, be they lepton or baryon. The
empirical values of the anomalous magnetic moments, in concert with empirical
bounds on the associated electric dipole moments, can better constrain theories
of CP violation. In particular, we find that the neutron and proton electric
dipole moments echo the isospin structure of the anomalous magnetic moments,
kappa^n ~ - kappa^p.Comment: 25 pages, 1 figure. Published version. Ref. adde
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