1,563,707 research outputs found
Quantum Tomography twenty years later
A sample of some relevant developments that have taken place during the last
twenty years in classical and quantum tomography are displayed. We will present
a general conceptual framework that provides a simple unifying mathematical
picture for all of them and, as an effective use of it, three subjects have
been chosen that offer a wide panorama of the scope of classical and quantum
tomography: tomography along lines and submanifolds, coherent state tomography
and tomography in the abstract algebraic setting of quantum systems
Neutrino masses twenty-five years later
The discovery of neutrino mass marks a turning point in elementary particle
physics, with important implications for nuclear and astroparticle physics.
Here I give a brief update, where I summarize the current status of
three-neutrino oscillation parameters from current solar, atmospheric, reactor
and accelerator neutrino data, discuss the case for sterile neutrinos and LSND,
and also the importance of tritium and double beta decay experiments probing
the absolute scale of neutrino mass. In this opininated look at the present of
neutrino physics, I keep an eye in the future, and a perspective of the past,
taking the oportunity to highlight Joe Schechter's pioneering contribution,
which I have had the fortune to share, as his PhD student back in the early
eighties.Comment: Invited talk presented at MRST'03 (Joe-Fest), Syracuse, NY, May 2003,
20 pages, uses AIP style file
Twenty Years Later
Lyrics for a song written in response to the Kent and Jackson State shootings, by singer and activist Holly Near
Dirty Bosons: Twenty Years Later
A concise, somewhat personal, review of the problem of superfluidity and
quantum criticality in regular and disordered interacting Bose systems is
given, concentrating on general features and important symmetries that are
exhibited in different parts of the phase diagram, and that govern the
different possible types of critical behavior. A number of exact results for
various insulating phase boundaries, which may be used to constrain the results
of numerical simulations, can be derived using large rare region type
arguments. The nature of the insulator-superfluid transition is explored
through general scaling arguments, exact model calculations in one dimension,
numerical results in two dimensions, and approximate renormalization group
results in higher dimensions. Experiments on He-4 adsorbed in porous Vycor
glass, on thin film superconductors, and magnetically trapped atomic vapors in
a periodic optical potential, are used to illustrate many of the concepts.Comment: 26 pages, 9 figures, submitted to Modern Physics Letters B (Brief
Reviews
Accretion Disks Around Black Holes: Twenty Five Years Later
We study the progress of the theory of accretion disks around black holes in
last twenty five years and explain why advective disks are the best bet in
explaining varied stationary and non-stationary observations from black hole
candidates. We show also that the recently proposed advection dominated flows
are incorrect.Comment: 30 Latex pages including figures. Kluwer Style files included.
Appearing in `Observational Evidence for Black Holes in the Universe', ed.
Sandip K. Chakrabarti, Kluwer Academic Publishers (DORDRECHT: Holland
Recommended from our members
Competition and Insurance Twenty Years Later
We are honored to address the European Group of Risk and Insurance Economists and will take the opportunity to make some reflections on the rather uneasy relationship between insurance and competition. Economists generally prescribe competition as a solution for markets that do not work well. Competition allocates resources efficiently and encourages innovation and attention to what customers want. Insurance markets differ from most other markets because in insurance markets competition can destroy the market rather than make it work better. One of the dimensions along which insurance companies compete is underwriting--trying to ensure that the risks covered are "good" risks or that if a high risk is insured, the premium charged is at least commensurate with the potential cost. The resulting partitioning of risk limits the amount of insurance that potential insurance customers can buy. In the extreme case, such competitive behavior will destroy the insurance market altogether. A simple model illustrates
Simulator Sickness Questionnaire: Twenty Years Later
The present study used simulator sickness questionnaire data from nine different studies to validate and explore the work of the most widely used simulator sickness index. The ability to predict participant dropouts as a result of simulator sickness symptoms was also evaluated. Overall, participants experiencing nausea and nausea-related symptoms were the most likely to fail to complete simulations. Further, simulation specific factors that increase the discrepancy between visual and vestibular perceptions are also related to higher participant study dropout rates. As a result, it is suggested that simulations minimize turns, curves, stops, et cetera, if possible, in order to minimize participant simulation sickness symptoms. The present study highlights several factors to attend to in order to minimize elevated participant simulation sickness
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