7,664 research outputs found
Stretching of proteins in a uniform flow
Stretching of a protein by a fluid flow is compared to that in a force-clamp
apparatus. The comparison is made within a simple topology-based dynamical
model of a protein in which the effects of the flow are implemented using
Langevin dynamics. We demonstrate that unfolding induced by a uniform flow
shows a richer behavior than that in the force clamp. The dynamics of unfolding
is found to depend strongly on the selection of the amino acid, usually one of
the termini, which is anchored. These features offer potentially wider
diagnostic tools to investigate structure of proteins compared to experiments
based on the atomic force microscopy.Comment: J. Chem. Phys. (in press
Concurrence of mixed multi-partite quantum states
We propose generalizations of concurrence for multi-partite quantum systems
that can distinguish qualitatively distinct quantum correlations. All
introduced quantities can be evaluated efficiently for arbitrary mixed sates
Anomalous heat-kernel decay for random walk among bounded random conductances
We consider the nearest-neighbor simple random walk on , ,
driven by a field of bounded random conductances . The
conductance law is i.i.d. subject to the condition that the probability of
exceeds the threshold for bond percolation on . For
environments in which the origin is connected to infinity by bonds with
positive conductances, we study the decay of the -step return probability
. We prove that is bounded by a random
constant times in , while it is in and
in . By producing examples with anomalous heat-kernel
decay approaching we prove that the bound in is the
best possible. We also construct natural -dependent environments that
exhibit the extra factor in . See also math.PR/0701248.Comment: 22 pages. Includes a self-contained proof of isoperimetric inequality
for supercritical percolation clusters. Version to appear in AIHP +
additional correction
The Consistent Newtonian Limit of Einstein's Gravity with a Cosmological Constant
We derive the `exact' Newtonian limit of general relativity with a positive
cosmological constant . We point out that in contrast to the case with
, the presence of a positive in Einsteins's equations
enforces, via the condition , on the potential , a range
, within which the
Newtonian limit is valid. It also leads to the existence of a maximum mass,
. As a consequence we cannot put the boundary
condition for the solution of the Poisson equation at infinity. A boundary
condition suitably chosen now at a finite range will then get reflected in the
solution of provided the mass distribution is not spherically symmetric.Comment: Latex, 15 pages, no figures, errors correcte
Majorana neutrino magnetic moments
The presence of trilinear R-parity violating interactions in the MSSM
lagrangian leads to existence of quark-squark and lepton-slepton loops which
generate mass of the neutrino. By introducing interaction with an external
photon the magnetic moment is obtained. We derive bounds on that quantity being
around one order of magnitude stronger than those present in the literature.Comment: I've decided to move the collection of my papers to arXiv for easier
access. Proceedings of the Nuclear Physics Workshop in Kazimierz Dolny,
Poland, 200
Cosmic Archaeology with Gravitational Waves from Cosmic Strings
Cosmic strings are generic cosmological predictions of many extensions of the
Standard Model of particle physics, such as a symmetry breaking
phase transition in the early universe or remnants of superstring theory.
Unlike other topological defects, cosmic strings can reach a scaling regime
that maintains a small fixed fraction of the total energy density of the
universe from a very early epoch until today. If present, they will oscillate
and generate gravitational waves with a frequency spectrum that imprints the
dominant sources of total cosmic energy density throughout the history of the
universe. We demonstrate that current and future gravitational wave detectors,
such as LIGO and LISA, could be capable of measuring the frequency spectrum of
gravitational waves from cosmic strings and discerning the energy composition
of the universe at times well before primordial nucleosynthesis and the cosmic
microwave background where standard cosmology has yet to be tested. This work
establishes a benchmark case that gravitational waves may provide an
unprecedented, powerful tool for probing the evolutionary history of the very
early universe.Comment: 6 pages, 3 figure
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