A comparative study of 1959-60 referrals to the school adjustment counselling services of Malden and Needham

Thesis (M.S.)--Boston Universit

Performance of the Lester battery charger in electric vehicles

Tests are performed on an improved battery charger. The primary purpose of the testing is to develop test methodologies for battery charger evaluation. Tests are developed to characterize the charger in terms of its charge algorithm and to assess the effects of battery initial state of charge and temperature on charger and battery efficiency. Tests show this charger to be a considerable improvement in the state of the art for electric vehicle chargers

Absence of Landau-Peierls Instability in the Magnetic Dual Chiral Density Wave Phase of Dense QCD

We investigate the stability of the Magnetic Dual Chiral Density Wave (MDCDW) phase of cold and dense QCD against collective low-energy fluctuations of the order parameter. The appearance of additional structures in the system free-energy due to the explicit breaking of the rotational and isospin symmetries by the external magnetic field and the field-induced asymmetry of the lowest Landau level modes play a crucial role in the analysis. The new structures not only affect the condensate minimum equations, but also the spectrum of the thermal fluctuations, which lacks the transverse soft modes that typically affect single-modulated inhomogeneous phases in the absence of a magnetic field. Consequently, the long-range order of the MDCDW phase is preserved at finite temperature. The lack of Landau-Peierls instabilities in the MDCDW phase makes this inhomogeneous phase of dense quark matter particularly relevant for the physics of neutron stars.Comment: Typos corrected, new discussions adde

Yukawa Interactions and Dynamical Generation of Mass in an External Magnetic Field

In this work we study the dynamical generation of a fermion mass induced by a constant and uniform external magnetic field in an Abelian gauge model with a Yukawa term. We show that the Yukawa coupling not only enhances the dynamical generation of the mass, but it substantially decreases the magnetic field required for the mass to be generated at temperatures comparable to the electroweak critical temperature. These results indicate that if large enough primordial magnetic fields were present during the early universe evolution, the field-induced generation of fermion masses, which in turn corresponds to the generation of fermion bound states, may play an important role in the electroweak phase transition.Comment: Corrected mistake in last reference. Work presented at SILAFAE'98, 8 pages. To be published in the proceedings of SILAFAE'98, April 8-11, San Juan, Puerto Ric

Neutrinos under Strong Magnetic Fields

In this talk we review the results on neutrino propagation under external magnetic fields. We concentrate on the effects of strong magnetic fields $M_{W}^{2}\gg B\gg m_{e}^{2}$ in neutral media. It is shown that the neutrino energy density get a magnetic contribution in the strong-field, one-loop approximation, which is linear in the Fermi coupling constant as in the charged medium. It is analyzed how this correction produces a significant oscillation resonance between electron-neutrinos and the other two active flavors, as well as with sterile neutrinos. The found resonant level-crossing condition is highly anisotropic. Possible cosmological applications are discussed. Effects due to primordial hypermagnetic fields on neutrinos propagating in the symmetric phase of the electroweak model are also presented. At sufficiently strong hypermagnetic fields, $B\geq T^{2}$, the neutrino energy is found to be similar to that of a massless charged particle with one-degree of freedom.Comment: Talk given at the Fourth Tropical Workshop on Particle Physics and Cosmology, Cairns, Australia, June 9-13, 200

Neutrino Propagation and Oscillations in a Strong Magnetic Field

We review the results on neutrino propagation in neutral and charged media under strong magnetic fields $M_{W}^{2}\gg B\gg m_{e}^{2}$. It is shown that the neutrino energy density gets a magnetic contribution in both charged and neutral media, which is linear in the magnetic field, of first order in $G_{F}$, and independent of the charge density. This new term enters as a correction to the neutrino kinetic energy and produces an anisotropic contribution to the neutrino index of refraction. As a consequence, in a neutral medium a highly anisotropic resonant level-crossing condition takes place for the oscillation between electron-neutrinos and the other neutrino species. Possible cosmological applications are presented.Comment: Talk given at the Conference: MRST-2004: "From Quaks to Cosmology," Montreal, Canada, May 12-14, 200

Entanglement from density measurements: analytical density-functional for the entanglement of strongly correlated fermions

We derive an analytical density functional for the single-site entanglement of the one-dimensional homogeneous Hubbard model, by means of an approximation to the linear entropy. We show that this very simple density functional reproduces quantitatively the exact results. We then use this functional as input for a local density approximation to the single-site entanglement of inhomogeneous systems. We illustrate the power of this approach in a harmonically confined system, which could simulate recent experiments with ultracold atoms in optical lattices as well as in a superlattice and in an impurity system. The impressive quantitative agreement with numerical calculations -- which includes reproducing subtle signatures of the particle density stages -- shows that our density-functional can provide entanglement calculations for actual experiments via density measurements. Next we use our functional to calculate the entanglement in disordered systems. We find that, at contrast with the expectation that disorder destroys the entanglement, there exist regimes for which the entanglement remains almost unaffected by the presence of disordered impurities.Comment: 6 pages, 3 figure