The quantum mechanical theory of collisions

textLecture notes by Roy Glauber, Department of Physics, Harvard University. Cours professe a l'Ecole d'ete de physique theorique. Les Houches, Haute-Savoie, FranceEcole d'ete de physique theorique. Les Houches, Haute-Savoie, FrancePhysic

Involuntary Part-Time Employment: A Slow and Uneven Economic Recovery

In this brief, author Rebecca Glauber reports that, although unemployment overall has returned to its pre-recession level, involuntary part-time employment is still much higher than it was before the Great Recession began--a trend that raises questions about the continuing ability of the economy to deliver employment security to people willing and able to work. Involuntary part-time employment is down 34 percent since the Great Recession but is still above its pre-recession level. If the involuntary part-time employment rate continues this pace of decline, it will not return to its pre-recession level until 2018, a full nine years after the official end of the recession. Racial disparities persist. Since the recession, involuntary part-time employment declined by over 30 percent for white, Asian, and Hispanic workers but by less than 20 percent for black workers. Among workers with less than a high school degree, 9 percent work part time involuntarily, compared to just 2 percent of college graduates. Involuntary part-time workers are more than five times as likely as full-time workers to live in poverty. As the economy continues to recover, Glauber recommends that the complexities of involuntary part-time employment and disparities in the recovery are explored

Prospects for the U.S. Farm Economy in 2010

Agribusiness,

Coulomb-nuclear interference in pion-nucleus bremsstrahlung

Pion-nucleus bremsstrahlung offers a possibility of measuring the structure functions of pion-Compton scattering from a study of the small-momentum-transfer region where the bremsstrahlung reaction is dominated by the single-photon-exchange mechanism. The corresponding cross-section distribution is characterized by a sharp peak at small momentum transfers. But there is also a hadronic contribution which is smooth and constitutes an undesired background. In this communication the modification of the single-photon exchange amplitude by multiple-Coulomb scattering is investigated as well as the Coulomb-nuclear interference term.Comment: 21 pages, 5 figures. Eqs.(51,52) corrected; some new figure

A remark on the Primakoff effect

The coherent-nuclear reaction a + A -> a* + A is in the small-angle region dominated by the one-photon-exchange mechanism, often referred to as the Primakoff effect. In this region information about the electromagnetic decay a* -> a + gamma can be obtained. Well-known examples are the two-photon decays of the pi- and eta-mesons. Also decays of charged hadrons can be studied. For charged hadrons the one-photon-exchange amplitude comes with a Coulomb-phase factor and a Coulomb-form factor, which depend on the ratio between transverse- and logitudinal-momentum transfers, the latter being fixed. At the peak of the cross-section distribution, where the two momentum transfers are equal, the form factor could cut down the cross-section value by as much as 40 %. Consequently, a determination of a radiative-decay rate that relies on the peak value becomes sensitive to a proper treatment of the Coulomb-form factor.Comment: 5 pages, 2 figure

Acoustic interaction forces between small particles in an ideal fluid

We present a theoretical expression for the acoustic interaction force between small spherical particles suspended in an ideal fluid exposed to an external acoustic wave. The acoustic interaction force is the part of the acoustic radiation force on one given particle involving the scattered waves from the other particles. The particles, either compressible liquid droplets or elastic microspheres, are considered to be much smaller than the acoustic wavelength. In this so-called Rayleigh limit, the acoustic interaction forces between the particles are well approximated by gradients of pair-interaction potentials with no restriction on the inter-particle distance. The theory is applied to studies of the acoustic interaction force on a particle suspension in either standing or traveling plane waves. The results show aggregation regions along the wave propagation direction, while particles may attract or repel each other in the transverse direction. In addition, a mean-field approximation is developed to describe the acoustic interaction force in an emulsion of oil droplets in water.Comment: 11 pages, 5 eps figures, RevTex 4.

Parental Educational Investment and Children's Academic Risk: Estimates of the Impact of Sibship Size and Birth Order from Exogenous Variations in Fertility

The stylized fact that individuals who come from families with more children are disadvantaged in the schooling process has been one of the most robust effects in human capital and stratification research over the last few decades. For example, Featherman and Hauser (1978: 242-243) estimate that each additional brother or sister costs respondents on the order of a fifth of a year of schooling. However, more recent analyses suggest that the detrimental effects of sibship size on children's educational achievement might be spurious. We extend these recent analyses of spuriousness versus causality using a different method and a different set of outcome measures. We suggest an instrumental variable approach to estimate the effect of sibship size on children's private school attendance and on their likelihood of being held back in school. Specifically, we deploy the sex-mix instrument used by Angrist and Evans (1998). Analyses of educational data from the 1990 PUMS five percent sample reveal that children from larger families are less likely to attend private school and are more likely to be held back in school. Our estimates are smaller than traditional OLS estimates, but are nevertheless greater than zero. Most interesting is the fact that the effect of sibship size is uniformly strongest for latter-born children and zero for first born children.

The Motherhood Wage Penalty: High-Earning Women Are Doing Better Than Before

In this data snapshot, author Rebecca Glauber discusses her research on the motherhood wage penalty. In her study, she asked whether the motherhood wage penalty has declined over the past few decades. A decrease began in the 1990s but was most pronounced for high-earning women and smallest for lower-earning women. Median-earners fell somewhere in between. Today, high-earning women, or those who make close to $100,000 per year, no longer pay a motherhood penalty. But low earners, or those struggling on$15,000 per year, do

Density Operators for Fermions

The mathematical methods that have been used to analyze the statistical properties of boson fields, and in particular the coherence of photons in quantum optics, have their counterparts for Fermi fields. The coherent states, the displacement operators, the P-representation, and the other operator expansions all possess surprisingly close fermionic analogues. These methods for describing the statistical properties of fermions are based upon a practical calculus of anti-commuting variables. They are used to calculate correlation functions and counting distributions for general systems of fermions.Comment: 45 pages, late