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

Flickr: A case study of Web2.0

The “photosharing” site Flickr is one of the most commonly cited examples used to define Web2.0. This paper explores where Flickr’s real novelty lies, examining its functionality and its place in the world of amateur photography. The paper draws on a wide range of sources including published interviews with its developers, user opinions expressed in forums, telephone interviews and content analysis of user profiles and activity. Flickr’s development path passes from an innovative social game to a relatively familiar model of a website, itself developed through intense user participation but later stabilising with the reassertion of a commercial relationship to the membership. The broader context of the impact of Flickr is examined by looking at the institutions of amateur photography and particularly the code of pictorialism promoted by the clubs and industry during the C20th. The nature of Flickr as a benign space is premised on the way the democratic potential of photography is controlled by such institutions. Several optimistic views of the impact of Flickr such as its facilitation of citizen journalism, “vernacular creativity” and in learning as an “affinity space” are evaluated. The limits of these claims are identified in the way that the system is designed to satisfy commercial purposes, continuing digital divides in access and the low interactivity and criticality on Flickr. Flickr is an interesting source of change, but can only to be understood in the perspective of long term development of the hobby and wider social processes

Mineta Transportation Institute Report F-00-2

United States Secretary of Transportation Rodney E. Slater, as part of his annual transportation tour for 2000, took part in a round table discussion regarding the transportation needs of the Silicon Valley. The event was co-sponsored by the California Commonwealth Club and the Mineta Transportation Institute on June 24, 2000. Secretary Slater was joined by a panel of local transportation leaders and stakeholders. This publication is a transcript of that forum, 2025 Visioning Session — Silicon Valley.” Panelists included: • United States Secretary of transportation Rodney E. Slater • Steve Berglund, President and CEO, Trimble Navigation • Larry Dahms, Executive Director of the Metropolitan Transportation Commission • Dr. John A. Dearien, CEO, CyberTran International • Rod Diridon, Executive Director, the Mineta Transportation Institute • Dr. Gloria C. Duffy, Ph.D, Chief Executive Officer, Commonwealth Club of California • David Esmaili, Director, Advanced Transportation Technologies, West Valley College • Neil Garcia-Sinclair, Vice President, CyberTran International • Larry Gerston, Professor, Political Science, San José State University • Abdelaziz Hanif, Manager, Realty and Regional Transportation Specialist, NASA-Ames Research Center • Dr. Kathryn Heatley, Director, Outreach, member SVMG • The Honorable Zoe Lofgren, 16th Congressional District of California • Bill Lynch, Director of Navigation Services, Lockheed Martin Corporation • Norm McCraim, Deputy Chief of Staff, U.S. Department of Transportation • Norman Y.Mineta, Senior Vice President, Lockheed Transportation Systems Division • Jeff Morales, Director, Caltrans • The Honorable James Oberstar, 8th Congressional District of Minnesota • Dr. Donald L. Paul, Vice President of Technology and Environmental Affairs, Chevron Corporation • Dr. Stephen Van Beek, Deputy Administrator, U.S.Department of Transportation, Research and Special Programs Administration • Craig Van Kessell, Transportation Coordinator, Altran

A Time Dependent Multi-Determinant approach to nuclear dynamics

We study a multi-determinant approach to the time evolution of the nuclear wave functions (TDMD). We employ the Dirac variational principle and use as anzatz for the nuclear wave-function a linear combination of Slater determinants and derive the equations of motion. We demonstrate explicitly that the norm of the wave function and the energy are conserved during the time evolution. This approach is a direct generalization of the time dependent Hartree-Fock method. We apply this approach to a case study of ${}^6Li$ using the N3LO interaction renormalized to 4 major harmonic oscillator shells. We solve the TDMD equations of motion using Krylov subspace methods of Lanczos type. We discuss as an application the isoscalar monopole strength function.Comment: 38 pages, additional calculations included. Accepted for publication, Int. J. of Mod. Phys.

Pinning of Fermionic Occupation Numbers

The Pauli exclusion principle is a constraint on the natural occupation numbers of fermionic states. It has been suspected since at least the 1970's, and only proved very recently, that there is a multitude of further constraints on these numbers, generalizing the Pauli principle. Here, we provide the first analytic analysis of the physical relevance of these constraints. We compute the natural occupation numbers for the ground states of a family of interacting fermions in a harmonic potential. Intriguingly, we find that the occupation numbers are almost, but not exactly, pinned to the boundary of the allowed region (quasi-pinned). The result suggests that the physics behind the phenomenon is richer than previously appreciated. In particular, it shows that for some models, the generalized Pauli constraints play a role for the ground state, even though they do not limit the ground-state energy. Our findings suggest a generalization of the Hartree-Fock approximation

From presence to consciousness through virtual reality

Immersive virtual environments can break the deep, everyday connection between where our senses tell us we are and where we are actually located and whom we are with. The concept of 'presence' refers to the phenomenon of behaving and feeling as if we are in the virtual world created by computer displays. In this article, we argue that presence is worthy of study by neuroscientists, and that it might aid the study of perception and consciousness

Navigating large-scale virtual environments: what differences occur between helmet-mounted and desk-top displays?

Participants used a helmet-mounted display (HMD) and a desk-top (monitor) display to learn the layouts of two large-scale virtual environments (VEs) through repeated, direct navigational experience. Both VEs were ‘‘virtual buildings’’ containing more than seventy rooms. Participants using the HMD navigated the buildings significantly more quickly and developed a significantly more accurate sense of relative straight-line distance. There was no significant difference between the two types of display in terms of the distance that participants traveled or the mean accuracy of their direction estimates. Behavioral analyses showed that participants took advantage of the natural, head-tracked interface provided by the HMD in ways that included ‘‘looking around’’more often while traveling through the VEs, and spending less time stationary in the VEs while choosing a direction in which to travel

Validation of fluorescence transition probability calculations

A systematic and quantitative validation of the K and L shell X-ray transition probability calculations according to different theoretical methods has been performed against experimental data. This study is relevant to the optimization of data libraries used by software systems, namely Monte Carlo codes, dealing with X-ray fluorescence. The results support the adoption of transition probabilities calculated according to the Hartree-Fock approach, which manifest better agreement with experimental measurements than calculations based on the Hartree-Slater method.Comment: 8 pages, 21 figures and images, 3 tables, to appear in proceedings of the Nuclear Science Symposium and Medical Imaging Conference 2009, Orland