Teaching Innovations in An Introductory Physics Course for Non-Science Majors

I have made several innovations to Physics 114: Physics of Sound, a course for Communication Disorders and General Education students at the University of Massachusetts. These changes include the use of a network of wireless communication devices called a Personal Response System, on-line tutorials and classnotes, a collaborative discussion section, exam corrections, microthemes, extra-credit papers, group extra-credit projects, and the use of student teaching assistants

OAST space power technology program

The current research and technology (R and T) base program is first described, then special attention is directed toward outlining a new system technology specifically oriented toward providing the utility power plant technology base for semi-permanent earth orbital facilities expected to be needed in the middle to late 1980's. The R and T program involves five areas of research: (1) photovoltaic energy conversion; (2) chemical energy conversion and storage; (3) thermal-to-electric conversion; (4) environment interactions; and (5) power systems management and distribution. The general objectives and planned direction of efforts in each of these areas is summarized

Quantum-Monte-Carlo Calculations for Bosons in a Two-Dimensional Harmonic Trap

Path-Integral-Monte-Carlo simulation has been used to calculate the properties of a two-dimensional (2D) interacting Bose system. The bosons interact with hard-core potentials and are confined to a harmonic trap. Results for the density profiles, the condensate fraction, and the superfluid density are presented. By comparing with the ideal gas we easily observe the effects of finite size and the depletion of the condensate because of interactions. The system is known to have no phase transition to a Bose-Einstein condensation in 2D, but the finite system shows that a significant fraction of the particles are in the lowest state at low temperatures.Comment: six pages, two figures; Contribution to QFS98; To be published in Journ. Low. Temp. Phy

Quantum Statistics: Is there an effective fermion repulsion or boson attraction?

Physicists often claim that there is an effective repulsion between fermions, implied by the Pauli principle, and a corresponding effective attraction between bosons. We examine the origins of such exchange force ideas, the validity for them, and the areas where they are highly misleading. We propose that future explanations of quantum statistics should avoid the idea of a effective force completely and replace it with more appropriate physical insights, some of which are suggested here.Comment: 26 pages, 3 figures. Submitted to American Journal of Physic

Angular momentum conservation in measurements on spin Bose-Einstein condensates

We discuss a thought experiment where two operators, Alice and Bob, perform transverse spin measurements on a quantum system; this system is initially in a double Fock spin state, which extends over a large distance in space so that the two operators are far away from each other. Standard quantum mechanics predicts that, when Alice makes a few measurements, a large transverse component of the spin angular momentum may appear in Bob's laboratory. A paradox then arises since local angular momentum conservation seems to be violated. It has been suggested that this angular momentum may be provided by the interaction with the measurement apparatuses. We show that this solution of the paradox is not appropriate, so that another explanation must be sought. The general question is the retroaction of a quantum system onto a measurement apparatus. For instance, when the measured system is entangled with another quantum system, can its reaction on a measurement apparatus be completely changed? Is angular momentum conserved only on average over several measurements, but not during one realization of the experiment?Comment: 11 pages, 3 figure

Quantum properties of a single beam splitter

When a single beam-splitter receives two beams of bosons described by Fock states (Bose-Einstein condensates at very low temperatures), interesting generalizations of the two-photon Hong-Ou-Mandel effect take place for larger number of particles. The distributions of particles at two detectors behind the beam splitter can be understood as resulting from the combination of two effects, the spontaneous phase appearing during quantum measurement, and the quantum angle. The latter introduces quantum "population oscillations", which can be seen as a generalized Hong-Ou-Mandel effect, although they do not always correspond to even-odd oscillations.Comment: 14 pages, 11 figure

The Two-Dimensional Bose-Einstein Condensate

We study the Hartree-Fock-Bogoliubov mean-field theory as applied to a two-dimensional finite trapped Bose gas at low temperatures and find that, in the Hartree-Fock approximation, the system can be described either with or without the presence of a condensate; this is true in the thermodynamic limit as well. Of the two solutions, the one that includes a condensate has a lower free energy at all temperatures. However, the Hartree-Fock scheme neglects the presence of phonons within the system, and when we allow for the possibility of phonons we are unable to find condensed solutions; the uncondensed solutions, on the other hand, are valid also in the latter, more general scheme. Our results confirm that low-energy phonons destabilize the two-dimensional condensate.Comment: 8 pages, 3 figures, REVTeX 4. To appear in J. Low Temp. Phys. Corrected a mistake in a calculation and changed the conclusions accordingl

Beyond spontaneously broken symmetry in Bose-Einstein condensates

Spontaneous symmetry breaking (SSB) for Bose-Einstein condensates cannot treat phase off-diagonal effects, and thus not explain Bell inequality violations. We describe another situation that is beyond a SSB treatment: an experiment where particles from two (possibly macroscopic) condensate sources are used for conjugate measurements of the relative phase and populations. Off-diagonal phase effects are characterized by a "quantum angle" and observed via "population oscillations", signaling quantum interference of macroscopically distinct states (QIMDS).Comment: 10 pages 4 figure