Some Identities for the Quantum Measure and its Generalizations

After a brief review of classical probability theory (measure theory), we present an observation (due to Sorkin) concerning an aspect of probability in quantum mechanics. Following Sorkin, we introduce a generalized measure theory based on a hierarchy of ``sum-rules.'' The first sum-rule yields classical probability theory, and the second yields a generalized probability theory that includes quantum mechanics as a special case. We present some algebraic relations involving these sum-rules. This may be useful for the study of the higher-order sum-rules and possible generalizations of quantum mechanics. We conclude with some open questions and suggestions for further work.Comment: (v1) 19 pages, LaTeX. (v2) 18 pages, LaTeX: minor corrections, simplified proof of lemma

How Many Undocumented: The Numbers Behind the U.S.-Mexico Migration Talks

Presents estimates of the undocumented migrant population in the U.S., broken down into the categories that were most relevant to the migration proposals under consideration by the U.S. and Mexican governments, prior to the March 2002 migration talks

New Lows From New Highs: Latino Economic Losses in the Current Recession

Assesses the recession's impact on the Latino population and the likely long-term effects of unemployment on Hispanic communities. Examines recession-related job losses for Hispanics and forecasts their prospects for economic recovery

The cosmological evolution of the QSO luminosity density and of the star formation rate

We demonstrate that the evolution of the QSO luminosity density with epoch displays a striking similarity to the cosmological evolution of the field galaxy star formation rate, recently derived from a number of independent surveys. The QSO luminosity density at 2800A is approximately one-fortieth that implied by the star formation rate in galaxies throughout the past 11 Gigayears (z<4). This similarity suggests that a substantial fraction of the QSO luminosity may be closely linked to the star formation process and its evolution with cosmic time.Comment: 3 pages, TeX, 1 figure, MNRAS in pres