4,124 research outputs found
Relativistic kinetic theory of magnetoplasmas
Recently, an increasing interest in astrophysical as well as laboratory
plasmas has been manifested in reference to the existence of relativistic
flows, related in turn to the production of intense electric fields in
magnetized systems. Such phenomena require their description in the framework
of a consistent relativistic kinetic theory, rather than on relativistic MHD
equations, subject to specific closure conditions. The purpose of this work is
to apply the relativistic single-particle guiding-center theory developed by
Beklemishev and Tessarotto, including the nonlinear treatment of
small-wavelength EM perturbations which may naturally arise in such systems. As
a result, a closed set of relativistic gyrokinetic equations, consisting of the
collisionless relativistic kinetic equation, expressed in hybrid gyrokinetic
variables, and the averaged Maxwell's equations, is derived for an arbitrary
four-dimensional coordinate system.Comment: 6 pages, 1 figure. Contributed to the Proceedings of the 24th
International Symposium on Rarefied Gas Dynamics, July 10-16, 2004 Porto
Giardino Monopoli (Bari), Ital
IKT approach for quantum hydrodynamic equations
A striking feature of standard quantum mechanics is its analogy with
classical fluid dynamics. In particular it is well known the Schr\"{o}dinger
equation can be viewed as describing a classical compressible and non-viscous
fluid, described by two (quantum) fluid fields {\rho ,% \mathbf{V}} , to be
identified with the quantum probability density and velocity field. This
feature has suggested the construction of a phase-space hidden-variable
description based on a suitable inverse kinetic theory (IKT; Tessarotto et al.,
2007). The discovery of this approach has potentially important consequences
since it permits to identify the classical dynamical system which advances in
time the quantum fluid fields. This type of approach, however requires the
identification of additional fluid fields. These can be generally identified
with suitable directional fluid temperatures (for ), to be
related to the expectation values of momentum fluctuations appearing in the
Heisenberg inequalities. Nevertheless the definition given previously for them
(Tessarotto et al., 2007) is non-unique. In this paper we intend to propose a
criterion, based on the validity of a constant H-theorem, which provides an
unique definition for the quantum temperatures.Comment: Contributed paper at RGD26 (Kyoto, Japan, July 2008
Geometric model of black hole quantum -portrait, extradimensions and thermodynamics
Recently a short scale modified black hole metric, known as holographic
metric, has been proposed in order to capture the self-complete character of
gravity. In this paper we show that such a metric can reproduce some geometric
features expected from the quantum -portrait beyond the semi-classical
limit. We show that for a generic this corresponds to having an effective
energy momentum tensor in Einstein equations or, equivalently, non-local terms
in the gravity action. We also consider the higher dimensional extension of the
metric and the case of an AdS cosmological term. We provide a detailed
thermodynamic analysis of both cases, with particular reference to the
repercussions on the Hawking-Page phase transition.Comment: 36 pages, 8 figures, invited paper to the special issue "Entropy in
Quantum Gravity and Quantum Cosmology" edited by R. Garattini for the journal
"Entropy", accepted for publication; v2 version matching that published on
the journa
Unparticle Casimir effect
In this paper we present the un-Casimir effect, namely the study of the
Casimir energy in the presence of an unparticle component in addition to the
electromagnetic field contribution. The distinctive feature of the un-Casimir
effect is a fractalization of metallic plates. This result emerges through a
new dependence of the Casimir energy on the plate separation that scales with a
continuous power controlled by the unparticle dimension. As long as the perfect
conductor approximation is valid, we find bounds on the unparticle scale that
are independent of the effective coupling constant between the scale invariant
sector and ordinary matter. We find regions of the parameter space such that
for plate distances around m and larger the un-Casimir bound wins over
the other bounds.Comment: 13 pages, 3 figures; v2: improved discussion, additional references,
v3: title slightly changed, version matching that in press on Physics Letters
Ian Ward. The Trials of Charles I, London, Bloomsbury, 2022, pp. 264
The review examines Ian Ward's book by highlighting its legal and interdisciplinary features
Localization of emerging leakages in water distribution systems: A complex networks approach
Water distribution networks are infrastructural systems designed for providing potable water to consumers. In these last decades, the importance of assessing and identifying emerging leakages has become a primary issue, because of the high level of water loss characterizing such systems worldwide. In this paper, a new approach aimed at the prompt localization of leakages occurring in water distribution systems is introduced. The methodology relies on the analysis of real-time pressure measurements and on Complex Networks Theory. Starting from a collection of nodes representing the locations of pressure sensors, links of a virtual, complex network are created on the basis of the values assumed by correlation coefficients between pressure measurements: if such values are above a given threshold, relevant nodes are considered to be connected to each other. In this way, information about the structure and topology of the complex network is easily derived. In particular, the degree centrality of the nodes is a key parameter allowing to identify the position of a leakage. The paper first analyzes a well-known literature example, and then proves the high reliability of the methodology for a real water distribution system
Mapping the Legacy of the Past: Colonial Laws and Customary Traditions in Africa
The essay offers a critical survey of how comparative legal studies examine the interrelations between colonial legacies and African legal traditions. By challenging the colonial and ethnocentric attitude of mainstream comparative legal scholars, it reappraises the traditional classification of African law. Anchoring the article there are two critical contentions: firstly, that African law is a composite of different legal traditions; secondly, that critical comparative law must redraw the boundaries between the different geographical areas within which colonial legacies and African law intertwines
The Play of Law in Modern British Theatre
The review examines a book that assesses the multiple relationships between the law and performance within the context of theatre
Generalized covariant gyrokinetic dynamics of magnetoplasmas
A basic prerequisite for the investigation of relativistic astrophysical
magnetoplasmas, occurring typically in the vicinity of massive stellar objects
(black holes, neutron stars, active galactic nuclei, etc.), is the accurate
description of single-particle covariant dynamics, based on gyrokinetic theory
(Beklemishev et al.,1999-2005). Provided radiation-reaction effects are
negligible, this is usually based on the assumption that both the space-time
metric and the EM fields (in particular the magnetic field) are suitably
prescribed and are considered independent of single-particle dynamics, while
allowing for the possible presence of gravitational/EM perturbations driven by
plasma collective interactions which may naturally arise in such systems. The
purpose of this work is the formulation of a generalized gyrokinetic theory
based on the synchronous variational principle recently pointed out (Tessarotto
et al., 2007) which permits to satisfy exactly the physical realizability
condition for the four-velocity. The theory here developed includes the
treatment of nonlinear perturbations (gravitational and/or EM) characterized
locally, i.e., in the rest frame of a test particle, by short wavelength and
high frequency. Basic feature of the approach is to ensure the validity of the
theory both for large and vanishing parallel electric field. It is shown that
the correct treatment of EM perturbations occurring in the presence of an
intense background magnetic field generally implies the appearance of
appropriate four-velocity corrections, which are essential for the description
of single-particle gyrokinetic dynamics.Comment: Contributed paper at RGD26 (Kyoto, Japan, July 2008
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