17,203 research outputs found
A Measure of Space for Computing over the Reals
We propose a new complexity measure of space for the BSS model of
computation. We define LOGSPACE\_W and PSPACE\_W complexity classes over the
reals. We prove that LOGSPACE\_W is included in NC^2\_R and in P\_W, i.e. is
small enough for being relevant. We prove that the Real Circuit Decision
Problem is P\_R-complete under LOGSPACE\_W reductions, i.e. that LOGSPACE\_W is
large enough for containing natural algorithms. We also prove that PSPACE\_W is
included in PAR\_R
Towards an analytical theory for charged hard spheres
Ion mixtures require an exclusion core to avoid collapse. The Debye Hueckel
theory, where ions are point charges, is accurate only in the limit of infinite
dilution. The MSA is the embedding of hard cores into DH, is valid for higher
densities. In the MSA the properties of any ionic mixture can be represented by
a single screening parameter . For equal ionic size restricted model is
obtained from the Debye parameter . This one parameter representation
(BIMSA) is valid for complex and associating systems, such as the general
n-polyelectrolytes. The BIMSA is the only theory that satisfies the infinite
dilution limit of the DH theory for any chain length. The contact pair
distribution function of hard ions mixture is a functional of and a
small mean field parameter. This yields good agreement with the Monte Carlo
(Bresme et al. Phys. Rev. E {\textbf 51} 289 (1995)) .Comment: 6 pages, 1 figur
Do Wilson Fermions Induce an Adjoint Gauge Coupling?
Expansions of the Wilson determinant in lattice QCD with quarks produce gauge
action terms which shift the coupling constant of the fundamental
representation plaquette action and induce an adjoint representation plaquette
action. We study the magnitude of these induced couplings with two flavors of
Wilson fermions. We utilize a microcanonical demon method, which allows us to
measure the induced couplings directly from gauge configurations generated by
full fermionic simulations.Comment: 3 pages postscript, proceedings for LATTICE '9
Real time plasma equilibrium reconstruction in a Tokamak
The problem of equilibrium of a plasma in a Tokamak is a free boundary
problemdescribed by the Grad-Shafranov equation in axisymmetric configurations.
The right hand side of this equation is a non linear source, which represents
the toroidal component of the plasma current density. This paper deals with the
real time identification of this non linear source from experimental
measurements. The proposed method is based on a fixed point algorithm, a finite
element resolution, a reduced basis method and a least-square optimization
formulation
Development of a mass spectrometer design Final report, Jun. 1, 1964 - Dec. 31, 1964
Cold cathode ion source mated to quadrupole mass spectrometer for use as residual gas analyze
Golden Ratio Prediction for Solar Neutrino Mixing
It has recently been speculated that the solar neutrino mixing angle is
connected to the golden ratio phi. Two such proposals have been made, cot
theta_{12} = phi and cos theta_{12} = phi/2. We compare these Ansatze and
discuss a model leading to cos theta_{12} = phi/2 based on the dihedral group
D_{10}. This symmetry is a natural candidate because the angle in the
expression cos theta_{12} = phi/2 is simply pi/5, or 36 degrees. This is the
exterior angle of a decagon and D_{10} is its rotational symmetry group. We
also estimate radiative corrections to the golden ratio predictions.Comment: 15 pages, 1 figure. Matches published versio
Scaling in Complex Systems: Analytical Theory of Charged Pores
In this paper we find an analytical solution of the equilibrium ion
distribution for a toroidal model of a ionic channel, using the Perfect
Screening Theorem (PST). The ions are charged hard spheres, and are treated
using a variational Mean Spherical Approximation (VMSA) .
Understanding ion channels is still a very open problem, because of the many
exquisite tuning details of real life channels. It is clear that the electric
field plays a major role in the channel behaviour, and for that reason there
has been a lot of work on simple models that are able to provide workable
theories. Recently a number of interesting papers have appeared that discuss
models in which the effect of the geometry, excluded volume and non-linear
behaviour is considered.
We present here a 3D model of ionic channels which consists of a charged,
deformable torus with a circular or elliptical cross section, which can be flat
or vertical (close to a cylinder). Extensive comparisons to MC simulations were
performed.
The new solution opens new possibilities, such as studying flexible pores,
and water phase transformations inside the pores using an approach similar to
that used on flat crystal surfaces
- …