Coulomb blockade of strongly coupled quantum dots studied via bosonization of a channel with a finite barrier

A pair of quantum dots, coupled through a point contact, can exhibit Coulomb blockade effects that reflect an oscillatory term in the dots' total energy whose value depends on whether the total number of electrons on the dots is even or odd. The effective energy associated with this even-odd alternation is reduced, relative to the bare Coulomb blockade energy for uncoupled dots, by a factor (1-f) that decreases as the interdot coupling is increased. When the transmission coefficient for interdot electronic motion is independent of energy and the same for all channels within the point contact (which are assumed uncoupled), the factor (1-f) takes on a universal value determined solely by the number of channels and the dimensionless conductance g of each individual channel. This paper studies corrections to the universal value of (1-f) that result when the transmission coefficent varies over energy scales of the size of the bare Coulomb blockade energy. We consider a model in which the point contact is described by a single orbital channel containing a parabolic barrier potential, and we calculate the leading correction to (1-f) for one-channel (spin-split) and two-channel (spin-degenerate) point contacts in the limit where the single orbital channel is almost completely open. By generalizing a previously used bosonization technique, we find that, for a given value of the dimensionless conductance g, the value of (1-f) is increased relative to its value for a zero-thickness barrier, but the absolute value of the increase is small in the region where our calculations apply.Comment: 13 pages, 3 Postscript figure

Origin and Evolution of Saturn's Ring System

The origin and long-term evolution of Saturn's rings is still an unsolved problem in modern planetary science. In this chapter we review the current state of our knowledge on this long-standing question for the main rings (A, Cassini Division, B, C), the F Ring, and the diffuse rings (E and G). During the Voyager era, models of evolutionary processes affecting the rings on long time scales (erosion, viscous spreading, accretion, ballistic transport, etc.) had suggested that Saturn's rings are not older than 100 My. In addition, Saturn's large system of diffuse rings has been thought to be the result of material loss from one or more of Saturn's satellites. In the Cassini era, high spatial and spectral resolution data have allowed progress to be made on some of these questions. Discoveries such as the ''propellers'' in the A ring, the shape of ring-embedded moonlets, the clumps in the F Ring, and Enceladus' plume provide new constraints on evolutionary processes in Saturn's rings. At the same time, advances in numerical simulations over the last 20 years have opened the way to realistic models of the rings's fine scale structure, and progress in our understanding of the formation of the Solar System provides a better-defined historical context in which to understand ring formation. All these elements have important implications for the origin and long-term evolution of Saturn's rings. They strengthen the idea that Saturn's rings are very dynamical and rapidly evolving, while new arguments suggest that the rings could be older than previously believed, provided that they are regularly renewed. Key evolutionary processes, timescales and possible scenarios for the rings's origin are reviewed in the light of tComment: Chapter 17 of the book ''Saturn After Cassini-Huygens'' Saturn from Cassini-Huygens, Dougherty, M.K.; Esposito, L.W.; Krimigis, S.M. (Ed.) (2009) 537-57

The value of children to parents in the United States

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43479/1/11111_2004_Article_BF01277597.pd

The influence of first generation fertility and economic status on second generation fertility

This paper examines the impact of parental economic status and family size on the actual and expected fertility of adult children using longitudinal data from two generations of families participating in the Panel Study of Income Dynamics. There was a modest positive relationship between first generation family size and second generation fertility. More importantly, the ideal family size of the parental family was more closely related to fertility behavior and plans in the second generation than was actual parental family size. In addition, the data revealed the hypothesized negative correlation between parental financial status and second generation fertility behavior and plans. Several mechanisms which could produce the correlation between parental characteristics and the fertility of their children are explored.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43511/1/11111_2005_Article_BF01253070.pd