8,840 research outputs found
Compatible Quantum Theory
Formulations of quantum mechanics can be characterized as realistic,
operationalist, or a combination of the two. In this paper a realistic theory
is defined as describing a closed system entirely by means of entities and
concepts pertaining to the system. An operationalist theory, on the other hand,
requires in addition entities external to the system. A realistic formulation
comprises an ontology, the set of (mathematical) entities that describe the
system, and assertions, the set of correct statements (predictions) the theory
makes about the objects in the ontology. Classical mechanics is the prime
example of a realistic physical theory. The present realistic formulation of
the histories approach originally introduced by Griffiths, which we call
'Compatible Quantum Theory (CQT)', consists of a 'microscopic' part (MIQM),
which applies to a closed quantum system of any size, and a 'macroscopic' part
(MAQM), which requires the participation of a large (ideally, an infinite)
system. The first (MIQM) can be fully formulated based solely on the assumption
of a Hilbert space ontology and the noncontextuality of probability values,
relying in an essential way on Gleason's theorem and on an application to
dynamics due in large part to Nistico. The microscopic theory does not,
however, possess a unique corpus of assertions, but rather a multiplicity of
contextual truths ('c-truths'), each one associated with a different framework.
This circumstance leads us to consider the microscopic theory to be physically
indeterminate and therefore incomplete, though logically coherent. The
completion of the theory requires a macroscopic mechanism for selecting a
physical framework, which is part of the macroscopic theory (MAQM). Detailed
definitions and proofs are presented in the appendice
An introduction to the Ginzburg-Landau theory of phase transitions and nonequilibrium patterns
This paper presents an introduction to phase transitions and critical
phenomena on the one hand, and nonequilibrium patterns on the other, using the
Ginzburg-Landau theory as a unified language. In the first part, mean-field
theory is presented, for both statics and dynamics, and its validity tested
self-consistently. As is well known, the mean-field approximation breaks down
below four spatial dimensions, where it can be replaced by a scaling
phenomenology. The Ginzburg-Landau formalism can then be used to justify the
phenomenological theory using the renormalization group, which elucidates the
physical and mathematical mechanism for universality. In the second part of the
paper it is shown how near pattern forming linear instabilities of dynamical
systems, a formally similar Ginzburg-Landau theory can be derived for
nonequilibrium macroscopic phenomena. The real and complex Ginzburg-Landau
equations thus obtained yield nontrivial solutions of the original dynamical
system, valid near the linear instability. Examples of such solutions are plane
waves, defects such as dislocations or spirals, and states of temporal or
spatiotemporal (extensive) chaos
A simple system with two temperatures
We study the stationary nonequilibrium regime which settles in when two
single-spin paramagnets each in contact with its own thermal bath are coupled.
The response vs. correlation plot exhibits some features of aging systems, in
particular the existence, in some regimes, of effective temperatures.Comment: 7 pages, 3 figure
Dynamic aspect of the chiral phase transition in the mode coupling theory
We analyze the dynamic aspect of the chiral phase transition. We apply the
mode coupling theory to the linear sigma model and derive the kinetic equation
for the chiral phase transition. We challenge Hohenberg and Halperin's
classification scheme of dynamic critical phenomena in which the dynamic
universality class of the chiral phase transition has been identified with that
of the antiferromagnet. We point out a crucial difference between the chiral
dynamics and the antiferromagnet system. We also calculate the dynamic critical
exponent for the chiral phase transition. Our result is
which is contrasted with of the antiferromagnet.Comment: 57 pages, no figure
Conditions for extreme sensitivity of protein diffusion in membranes to cell environments
We study protein diffusion in multicomponent lipid membranes close to a rigid
substrate separated by a layer of viscous fluid. The large-distance, long-time
asymptotics for Brownian motion are calculated using a nonlinear stochastic
Navier-Stokes equation including the effect of friction with the substrate. The
advective nonlinearity, neglected in previous treatments, gives only a small
correction to the renormalized viscosity and diffusion coefficient at room
temperature. We find, however, that in realistic multicomponent lipid mixtures,
close to a critical point for phase separation, protein diffusion acquires a
strong power-law dependence on temperature and the distance to the substrate
, making it much more sensitive to cell environment, unlike the logarithmic
dependence on and very small thermal correction away from the critical
point.Comment: 19 pages, 4 figure
Development of a Kohn-Sham like potential in the Self-Consistent Atomic Deformation Model
This is a brief description of how to derive the local ``atomic'' potentials
from the Self-Consistent Atomic Deformation (SCAD) model density function.
Particular attention is paid to the spherically averaged case.Comment: 5 Pages, LaTeX, no figure
Maximum thickness of a two-dimensional trapped Bose system
The trapped Bose system can be regarded as two-dimensional if the thermal
fluctuation energy is less than the lowest energy in the perpendicular
direction. Under this assumption, we derive an expression for the maximum
thickness of an effective two-dimensional trapped Bose system.Comment: 1 pages, 0 figure
Electronic structure of amorphous germanium disulfide via density functional molecular dynamics simulations
Using density functional molecular dynamics simulations we study the
electronic properties of glassy g-GeS. We compute the electronic density of
states, which compares very well with XPS measurements, as well as the partial
EDOS and the inverse participation ratio. We show the electronic contour plots
corresponding to different structural environments, in order to determine the
nature of the covalent bonds between the atoms. We finally study the local
atomic charges, and analyze the impact of the local environment on the charge
transfers between the atoms. The broken chemical order inherent to amorphous
systems leads to locally charged zones when integrating the atomic charges up
to nearest-neighbor distances.Comment: 13 pages, 9 figures; to appear in Phys. Rev.
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