12,095 research outputs found
Statistical Description of Hydrodynamic Processes in Ionic Melts with taking into account Polarization Effects
Statistical description of hydrodynamic processes for ionic melts is proposed
with taking into account polarization effects caused by the deformation of
external ionic shells. This description is carried out by means of the Zubarev
nonequilibrium statistical operator method, appropriate for investigations of
both strong and weak nonequilibrium processes. The nonequilibrium statistical
operator and the generalized hydrodynamic equations that take into account
polarization processes are received for ionic-polarization model of ionic
molten salts when the nonequilibrium averaged values of densities of ions
number, their momentum, dipole momentum and total energy are chosen for the
reduced description parameters. A spectrum of collective excitations is
investigated within the viscoelastic approximation for ion-polarization model
of ionic melts.Comment: 24 pages, RevTex4.1-format, no figure
Liquid heat capacity in the approach from the solid state: anharmonic theory
Calculating liquid energy and heat capacity in general form is an open
problem in condensed matter physics. We develop a recent approach to liquids
from the solid state by accounting for the contribution of anharmonicity and
thermal expansion to liquid energy and heat capacity. We subsequently compare
theoretical predictions to the experiments results of 5 commonly discussed
liquids, and find a good agreement with no free fitting parameters. We discuss
and compare the proposed theory to previous approaches.Comment: 8 pages, 6 figure
Practical dispersion relations for strongly coupled plasma fluids
Very simple explicit analytical expressions are discussed, which are able to
describe the dispersion relations of longitudinal waves in strongly coupled
plasma systems such as one-component plasma and weakly screened Yukawa fluids
with a very good accuracy. Applications to other systems with soft pairwise
interactions are briefly discussed.Comment: 11 pages, 3 figures; Related to arXiv:1711.0615
Power, norms and institutional change in the European Union: the protection of the free movement of goods
How do institutions of the European Union change? Using an institutionalist approach, this article highlights the interplay between power, cognitive limits, and the normative order that underpins institutional settings and assesses their impact upon the process of institutional change. Empirical evidence from recent attempts to reinforce the protection of the free movement of goods in the EU suggests that, under conditions of uncertainty, actors with ambiguous preferences assess attempts at institutional change on the basis of the historically defined normative order which holds a given institutional structure together. Hence, path dependent and incremental change occurs even when more ambitious and functionally superior proposals are on offer
Party finance reform as constitutional engineering? The effectiveness and unintended consequences of party finance reform in France and Britain
In both Britain and France, party funding was traditionally characterized by a laissez faire approach and a conspicuous lack of regulation. In France, this was tantamount to a 'legislative vacuum'. In the last two decades, however, both countries have sought to fundamentally reform their political finance regulation regimes. This prompted, in Britain, the Political Parties, Elections and Referendums Act 2000, and in France a bout of 'legislative incontinence' â profoundly transforming the political finance regime between 1988 and 1995. This article seeks to explore and compare the impacts of the reforms in each country in a bid to explain the unintended consequences of the alternative paths taken and the effectiveness of the new party finance regime in each country. It finds that constitutional engineering through party finance reform is a singularly inexact science, largely due to the imperfect nature of information, the limited predictability of cause and effect, and the constraining influence of non-party actors, such as the Constitutional Council in France, and the Electoral Commission in Britain
Information entropy and nucleon correlations in nuclei
The information entropies in coordinate and momentum spaces and their sum
(, , ) are evaluated for many nuclei using "experimental"
densities or/and momentum distributions. The results are compared with the
harmonic oscillator model and with the short-range correlated distributions. It
is found that depends strongly on and does not depend very much
on the model. The behaviour of is opposite. The various cases we consider
can be classified according to either the quantity of the experimental data we
use or by the values of , i.e., the increase of the quality of the density
and of the momentum distributions leads to an increase of the values of . In
all cases, apart from the linear relation , the linear relation
also holds. V is the mean volume of the nucleus. If is
considered as an ensemble entropy, a relation between or and the
ensemble volume can be found. Finally, comparing different electron scattering
experiments for the same nucleus, it is found that the larger the momentum
transfer ranges, the larger the information entropy is. It is concluded that
could be used to compare different experiments for the same nucleus and to
choose the most reliable one.Comment: 14 pages, 4 figures, 2 table
Evolution: Complexity, uncertainty and innovation
Complexity science provides a general mathematical basis for evolutionary thinking. It makes us face the inherent, irreducible nature of uncertainty and the limits to knowledge and prediction. Complex, evolutionary systems work on the basis of on-going, continuous internal processes of exploration, experimentation and innovation at their underlying levels. This is acted upon by the level above, leading to a selection process on the lower levels and a probing of the stability of the level above. This could either be an organizational level above, or the potential market place. Models aimed at predicting system behaviour therefore consist of assumptions of constraints on the micro-level â and because of inertia or conformity may be approximately true for some unspecified time. However, systems without strong mechanisms of repression and conformity will evolve, innovate and change, creating new emergent structures, capabilities and characteristics. Systems with no individual freedom at their lower levels will have predictable behaviour in the short term â but will not survive in the long term. Creative, innovative, evolving systems, on the other hand, will more probably survive over longer times, but will not have predictable characteristics or behaviour. These minimal mechanisms are all that are required to explain (though not predict) the co-evolutionary processes occurring in markets, organizations, and indeed in emergent, evolutionary communities of practice. Some examples will be presented briefly
Temperature dependence of density profiles for a cloud of non-interacting fermions moving inside a harmonic trap in one dimension
We extend to finite temperature a Green's function method that was previously
proposed to evaluate ground-state properties of mesoscopic clouds of
non-interacting fermions moving under harmonic confinement in one dimension. By
calculations of the particle and kinetic energy density profiles we illustrate
the role of thermal excitations in smoothing out the quantum shell structure of
the cloud and in spreading the particle spill-out from quantum tunnel at the
edges. We also discuss the approach of the exact density profiles to the
predictions of a semiclassical model often used in the theory of confined
atomic gases at finite temperature.Comment: 7 pages, 4 figure
Average ground-state energy of finite Fermi systems
Semiclassical theories like the Thomas-Fermi and Wigner-Kirkwood methods give
a good description of the smooth average part of the total energy of a Fermi
gas in some external potential when the chemical potential is varied. However,
in systems with a fixed number of particles N, these methods overbind the
actual average of the quantum energy as N is varied. We describe a theory that
accounts for this effect. Numerical illustrations are discussed for fermions
trapped in a harmonic oscillator potential and in a hard wall cavity, and for
self-consistent calculations of atomic nuclei. In the latter case, the
influence of deformations on the average behavior of the energy is also
considered.Comment: 10 pages, 8 figure
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