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

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

Field Theoretical Approach to Electrochemical Deposition

In this work we present an application of the lambda-phi^4 field theoretical model to the adsorption of atoms and molecules on metallic surfaces - the electrochemical deposition. The usual approach to this system consists in the computational simulation using Monte Carlo techniques of an effective lattice-gas Hamiltonian. We construct an effective model towards a comparison between the lattice-gas Hamiltonian and the discrete version of the lambda-phi^4 Hamiltonian, obtaining the relationships between the model parameters and electrochemical quantities. The lambda-phi^4 model is studied in the mean field approximation, and the results are fitted and compared to numerical simulated and experimental data.Comment: 9 pages, 5 figure

Microwave Scattering and Noise Emission from Afterglow Plasmas in a Magnetic Field

The microwave reflection and noise emission (extraordinary mode) from cylindrical rare‐gas (He, Ne, Ar) afterglow plasmas in an axial magnetic field is described. Reflection and noise emission are measured as a function of magnetic field near electron cyclotron resonance (ω ≈ ω_c) with electron density as a parameter (ω_p < ω). A broad peak, which shifts to lower values of ω_c/ω) as electron density increases, is observed for (ω_c/ω) ≤ 1. For all values of electron density a second sharp peak is found very close to cyclotron resonance in reflection measurements. This peak does not occur in the emission data. Calculations of reflection and emission using a theoretical model consisting of a one‐dimensional, cold plasma slab with nonuniform electron density yield results in qualitative agreement with the observations. Both the experimental and theoretical results suggest that the broad, density‐dependent peak involves resonance effects at the upper hybrid frequency ((ω_h)^2 = (ω_c)^2 + (ω_p)^2) of the plasma

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

Berry-phase blockade in single-molecule magnets

We formulate the problem of electron transport through a single-molecule magnet (SMM) in the Coulomb blockade regime taking into account topological interference effects for the tunneling of the large spin of a SMM. The interference originates from spin Berry phases associated with different tunneling paths. We show that in the case of incoherent spin states it is essential to place the SMM between oppositely spin-polarized source and drain leads in order to detect the spin tunneling in the stationary current, which exhibits topological zeros as a function of the transverse magnetic field.Comment: 4 pages, Revtex 4, 4 EPS figure