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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.

Older Americans are now working longer than pre-1980s trends would have predicted. Given concerns about the traditional sources of retirement income (Social Security, employer pensions, and prior savings), older Americans may have to rely more on earnings. This article suggests that many are already doing so by moving to bridge jobs after leaving their career employment.