187 research outputs found
On the verge of Umdeutung in Minnesota: Van Vleck and the correspondence principle (Part One)
In October 1924, the Physical Review, a relatively minor journal at the time,
published a remarkable two-part paper by John H. Van Vleck, working in virtual
isolation at the University of Minnesota. Van Vleck combined advanced
techniques of classical mechanics with Bohr's correspondence principle and
Einstein's quantum theory of radiation to find quantum analogues of classical
expressions for the emission, absorption, and dispersion of radiation. For
modern readers Van Vleck's paper is much easier to follow than the famous paper
by Kramers and Heisenberg on dispersion theory, which covers similar terrain
and is widely credited to have led directly to Heisenberg's "Umdeutung" paper.
This makes Van Vleck's paper extremely valuable for the reconstruction of the
genesis of matrix mechanics. It also makes it tempting to ask why Van Vleck did
not take the next step and develop matrix mechanics himself.Comment: 82 page
-Dimensional Lorentzian Wormholes in an Expanding Cosmological Background
We discuss -dimensional dynamical wormholes in an evolving
cosmological background with a throat expanding with time. These solutions are
examined in the general relativity framework. A linear relation between
diagonal elements of an anisotropic energy-momentum tensor is used to obtain
the solutions. The energy-momentum tensor elements approach the vacuum case
when we are far from the central object for one class of solutions. Finally, we
discuss the energy-momentum tensor which supports this geometry, taking into
account the energy conditions .Comment: 12 pages, 14 figures, references added, to appear in Astophysics and
Space Scienc
Quantum gauge models without classical Higgs mechanism
We examine the status of massive gauge theories, such as those usually
obtained by spontaneous symmetry breakdown, from the viewpoint of causal
(Epstein-Glaser) renormalization. The BRS formulation of gauge invariance in
this framework, starting from canonical quantization of massive (as well as
massless) vector bosons as fundamental entities, and proceeding perturbatively,
allows one to rederive the reductive group symmetry of interactions, the need
for scalar fields in gauge theory, and the covariant derivative. Thus the
presence of higgs particles is explained without recourse to a
Higgs(-Englert-Brout-Guralnik-Hagen-Kibble) mechanism. Along the way, we dispel
doubts about the compatibility of causal gauge invariance with grand unified
theories.Comment: 20 pages in two-column EPJC format, shortened version accepted for
publication. For more details, consult version
Relativistic superfluid models for rotating neutron stars
This article starts by providing an introductory overview of the theoretical
mechanics of rotating neutron stars as developped to account for the frequency
variations, and particularly the discontinuous glitches, observed in pulsars.
The theory suggests, and the observations seem to confirm, that an essential
role is played by the interaction between the solid crust and inner layers
whose superfluid nature allows them to rotate independently. However many
significant details remain to be clarified, even in much studied cases such as
the Crab and Vela. The second part of this article is more technical,
concentrating on just one of the many physical aspects that needs further
development, namely the provision of a satisfactorily relativistic (local but
not microscopic) treatment of the effects of the neutron superfluidity that is
involved.Comment: 42 pages LateX. Contribution to Physics of Neutron Star Interiors,
ed. D. Blasche, N.K. Glendenning, A. Sedrakian (ECT workshop, Trento, June
2000
IMG 305 - PEMBUNGKUSAN MAKANAN NOV.05.
We discuss the use of Agent-based Modelling for the development and testing of theories about emergent social phenomena in marketing and the social sciences in general. We address both theoretical aspects about the types of phenomena that are suitably addressed with this approach and practical guidelines to help plan and structure the development of a theory about the causes of such a phenomenon in conjunction with a matching ABM. We argue that research about complex social phenomena is still largely fundamental research and therefore an iterative and cyclical development process of both theory and model is to be expected. To better anticipate and manage this process, we provide theoretical and practical guidelines. These may help to identify and structure the domain of candidate explanations for a social phenomenon, and furthermore assist the process of model implementation and subsequent development. The main goal of this paper was to make research on complex social systems more accessible and help anticipate and structure the research process
A user's view of BALLOTS
BALLOTS (Bibliographic Automation of Large Library Operations using a
Time -sharing System) is an on-line interactive library automation system that
supports the acquisition and cataloging functions of the Stanford University
Libraries' technical processing operations. The BALLOTS system is being
implemented in a series of eleven modules. A large part of BALLOTS'
development up to the development of the first module was funded by a
grant from the U.S. Office of Education, Department of Health, Education,
and Welfare. This paper describes the first module, BALLOTS-MARC (or
simply, the MARC module), and various aspects of system hardware and
software as they pertain to this module. The MARC module was scheduled for
implementation in the late summer of 1972. The other modules are briefly
described at the end of this paper.published or submitted for publicatio
Bounds on the unstable eigenvalue for the asymmetric renormalization operator for period doubling
We establish rigorous bounds for the unstable eigenvalue of the period-doubling renormalization operator for asymmetric unimodal maps. Herglotz-function techniques and cone invariance ideas are used. Our result generalizes an established result for conventional period doubling
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