297 research outputs found
Andrzej Pekalski networks of scientific interests with internal degrees of freedom through self-citation analysis
Old and recent theoretical works by Andrzej Pekalski (APE) are recalled as
possible sources of interest for describing network formation and clustering in
complex (scientific) communities, through self-organisation and percolation
processes. Emphasis is placed on APE self-citation network over four decades.
The method is that used for detecting scientists field mobility by focusing on
author's self-citation, co-authorships and article topics networks as in [1,2].
It is shown that APE's self-citation patterns reveal important information on
APE interest for research topics over time as well as APE engagement on
different scientific topics and in different networks of collaboration. Its
interesting complexity results from "degrees of freedom" and external fields
leading to so called internal shock resistance. It is found that APE network of
scientific interests belongs to independent clusters and occurs through rare or
drastic events as in irreversible "preferential attachment processes", similar
to those found in usual mechanics and thermodynamics phase transitions.Comment: 7 pages, 1 table, 44 references, submitted to Int J Mod Phys
The evolution of classification systems: Ontogeny of the UDC
To classify is to put things in meaningful groups, but the criteria for doing
so can be problematic. Study of evolution of classification includes
ontogenetic analysis of change in classification over time. We present an
empirical analysis of the UDC over the entire period of its development. We
demonstrate stability in main classes, with major change driven by 20th century
scientific developments. But we also demonstrate a vast increase in the
complexity of auxiliaries. This study illustrates an alternative to Tennis'
"scheme-versioning" method.Comment: ISKO conference 201
Can Light Signals Travel Faster than c in Nontrivial Vacuua in Flat space-time? Relativistic Causality II
In this paper we show that the Scharnhorst effect (Vacuum with boundaries or
a Casimir type vacuum) cannot be used to generate signals showing measurable
faster-than-c speeds. Furthermore, we aim to show that the Scharnhorst effect
would violate special relativity, by allowing for a variable speed of light in
vacuum, unless one can specify a small invariant length scale. This invariant
length scale would be agreed upon by all inertial observers. We hypothesize the
approximate scale of the invariant length.Comment: 12 pages no figure
Enhancing Scholarly Publications: Developing Hybrid Monographs in the Humanities and Social Sciences
Enhancing publications has a long history but is gaining acceleration as authors and publishers explore electronic tablets as devices for dissemination and presentation. Enhancement of scholarly publications, in contrast, more often takes place in a Web environment and is coupled with presentation of supplementary materials related to research. The approach to enhancing scholarly publications presented in this article goes a step further and involves the interlinking of the “objects” of a document: datasets, supplementary materials, secondary analyses, and post-publication interventions. This approach connects the user-centricity of Web 2.0 with the Semantic Web. It aims at facilitating long-term content structure through standardized formats intended to improve interoperability between concepts and terms within and across knowledge domains. We explored this conception of enhancement on a small set of books prepared for traditional academic publishers. While the project was primarily an exercise in development, the conclusion section of the article reflects on areas where conceptual and empirical studies could be initiated to complement this new direction in scholarly publishing.FSW - CWTS - Ou
One-loop graviton corrections to Maxwell's equations
We compute the graviton induced corrections to Maxwell's equations in the
one-loop and weak field approximations. The corrected equations are analogous
to the classical equations in anisotropic and inhomogeneous media. We analyze
in particular the corrections to the dispersion relations. When the wavelength
of the electromagnetic field is much smaller than a typical length scale of the
graviton two-point function, the speed of light depends on the direction of
propagation and on the polarisation of the radiation. In the opposite case, the
speed of light may also depend on the energy of the electromagnetic radiation.
We study in detail wave propagation in two special backgrounds, flat
Robertson-Walker and static, spherically symmetric spacetimes. In the case of a
flat Robertson-Walker gravitational background we find that the corrected
electromagnetic field equations correspond to an isotropic medium with a
time-dependent effective refractive index. For a static, spherically symmetric
background the graviton fluctuations induce a vacuum structure which causes
birefringence in the propagation of light.Comment: 15 pages, revte
Geometrical aspects of light propagation in nonlinear electrodynamics
We analyze the propagation of light in the context of nonlinear
electrodynamics, as it occurs in modified QED vacua. We show that the
corresponding characteristic equation can be described in terms of a
modification of the effective geometry of the underlying spacetime structure.
We present the general form for this effective geometry and exhibit some new
consequences that result from such approach.Comment: LaTex, 11 pages, accepted for publication in Phys. Rev.
Superluminal pions in a hadronic fluid
We study the propagation of pions at finite temperature and finite chemical
potential in the framework of the linear sigma model with 2 quark flavors and
colors. The velocity of massless pions in general differs from that of
light. One-loop calculations show that in the chiral symmetry broken phase
pions, under certain conditions, propagate faster than light.Comment: 8 pages, 3 figures included. Considerably revised, discussions
expanded, one figure added, typos corrected, results unchanged. To be
published in Phys. Rev.
Spontaneous emission between an unusual pair of plates
We compute the modification in the spontaneous emission rate for a two-level
atom when it is located between two parallel plates of different nature: a
perfectly conducting plate and an infinitely permeable
one . We also discuss the case of two infinitely permeable
plates. We compare our results with those found in the literature for the case
of two perfectly conducting plates.Comment: latex file 4 pages, 4 figure
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