8,311 research outputs found
Rouse Modes of Self-avoiding Flexible Polymers
Using a lattice-based Monte Carlo code for simulating self-avoiding flexible
polymers in three dimensions in the absence of explicit hydrodynamics, we study
their Rouse modes. For self-avoiding polymers, the Rouse modes are not expected
to be statistically independent; nevertheless, we demonstrate that numerically
these modes maintain a high degree of statistical independence. Based on
high-precision simulation data we put forward an approximate analytical
expression for the mode amplitude correlation functions for long polymers. From
this, we derive analytically and confirm numerically several scaling properties
for self-avoiding flexible polymers, such as (i) the real-space end-to-end
distance, (ii) the end-to-end vector correlation function, (iii) the
correlation function of the small spatial vector connecting two nearby monomers
at the middle of a polymer, and (iv) the anomalous dynamics of the middle
monomer. Importantly, expanding on our recent work on the theory of polymer
translocation, we also demonstrate that the anomalous dynamics of the middle
monomer can be obtained from the forces it experiences, by the use of the
fluctuation-dissipation theorem.Comment: 16 pages (double spaced), 5 figures, small changes and corrections,
to appear in J. Chem. Phy
Nuclear force in Lattice QCD
We perform the quenched lattice QCD analysis on the nuclear force
(baryon-baryon interactions). We employ lattice at
( fm) with the standard gauge action and the Wilson quark action
with the hopping parameters , and generate about
200 gauge configurations. We measure the temporal correlators of the two-baryon
system which consists of heavy-light-light quarks. We extract the inter-baryon
force as a function of the relative distance . We also evaluate the
contribution to the nuclear force from each ``Feynman diagram'' such as the
quark-exchange diagram individually, and single out the roles of Pauli-blocking
effects or quark exchanges in the inter-baryon interactions.Comment: Presented at Particles and Nuclei International Conference (PANIC05),
Santa Fe, NM, Oct. 24-28, 2005; 3 pages, 2figure
The lattice QCD simulation of the quark-gluon mixed condensate g<\bar{q} \sigma G q> at finite temperature and the phase transition of QCD
The thermal effects on the quark-gluon mixed condensate g<\bar{q} \sigma G
q>, which is another chiral order parameter, are studied using the SU(3)c
lattice QCD with the Kogut-Susskind fermion at the quenched level. We perform
the accurate measurement of the mixed condensate as well as the quark
condensate for 0MeV<=T<=500MeV. We observe the sharp decrease of both the
condensates around T_c \simeq 280MeV, while the thermal effects below T_c are
found to be weak. We also find that the ratio m_0^2 = g<\bar{q} \sigma G
q>/ is almost independent of the temperature even in the very
vicinity of T_c, which indicates that the two condensates have nontrivial
similarity in the chiral behaviors. We also present the correlation between the
condensates and the Polyakov loop to understand the vacuum structure of QCD.Comment: Talk given at the XXII International Symposium on Lattice Field
Theory (LATTICE 2004), Fermilab, Batavia, Illinois, USA, 21-26 June 2004,
Lattice2004(non-zero), 3 pages, 3 figure
Field-theoretical approach to a dense polymer with an ideal binary mixture of clustering centers
We propose a field-theoretical approach to a polymer system immersed in an
ideal mixture of clustering centers. The system contains several species of
these clustering centers with different functionality, each of which connects a
fixed number segments of the chain to each other. The field-theory is solved
using the saddle point approximation and evaluated for dense polymer melts
using the Random Phase Approximation. We find a short-ranged effective
inter-segment interaction with strength dependent on the average segment
density and discuss the structure factor within this approximation. We also
determine the fractions of linkers of the different functionalities.Comment: 27 pages, 9 figures, accepted on Phys. Rev.
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
Doubly magic nuclei from Lattice QCD forces at 469 MeV/c
We perform ab initio self-consistent Green's function calculations of the
closed shell nuclei He, O and Ca, based on
two-nucleon potentials derived from Lattice QCD simulations, in the flavor
SU(3) limit and at the pseudo-scalar meson mass of 469~MeV/c. The
nucleon-nucleon interaction is obtained using the HAL QCD method and its
short-distance repulsion is treated by means of ladder resummations outside the
model space. Our results show that this approach diagonalises ultraviolet
degrees of freedom correctly. Therefore, ground state energies can be obtained
from infrared extrapolations even for the relatively hard potentials of HAL
QCD. Comparing to previous Brueckner Hartree-Fock calculations, the total
binding energies are sensibly improved by the full account of many-body
correlations. The results suggest an interesting possible behaviour in which
nuclei are unbound at very large pion masses and islands of stability appear at
first around the traditional doubly-magic numbers when the pion mass is lowered
toward its physical value. The calculated one-nucleon spectral distributions
are qualitatively close to those of real nuclei even for the pseudo-scalar
meson mass considered here.Comment: 7 pages, 4 figures, RIKEN-QHP-286, RIKEN-iTHEMS-Report-1
Meson-Meson and Meson-Baryon Interactions in Lattice QCD
We study the meson-meson and meson-baryon interactions in lattice QCD. The
simulation is performed on 20^3 * 24 lattice at \beta=5.7 using Wilson gauge
action and Wilson fermion at the quenched level. By adopting one static quark
for each hadron as "heavy-light meson" and "heavy-light-light baryon", we
define the distance of two hadrons and extract the inter-hadron potential
from the energy difference of the two-particle state and its asymptotic state.
We find that both of the meson-meson and meson-baryon potentials are
nontrivially weak for the whole range of 0.2 fm <= r <= 0.8 fm. The effect of
including/excluding the quark-exchange diagrams is found to be marginal.Comment: Talk given at Particles and Nuclei International Conference
(PANIC05), Santa Fe, NM, USA, 24-28 Oct. 2005. 3 pages, 2 figure
Monoidal Hom-Hopf algebras
Hom-structures (Lie algebras, algebras, coalgebras, Hopf algebras) have been
investigated in the literature recently. We study Hom-structures from the point
of view of monoidal categories; in particular, we introduce a symmetric
monoidal category such that Hom-algebras coincide with algebras in this
monoidal category, and similar properties for coalgebras, Hopf algebras and Lie
algebras.Comment: 25 pages; extended version: compared to the version that appeared in
Comm. Algebra, the Section Preliminary Results and Remarks 5.1 and 6.1 have
been adde
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