Second central extension in Galilean covariant field theory

The second central extension of the planar Galilei group has been alleged to have its origin in the spin variable. This idea is explored here by considering local Galilean covariant field theory for free fields of arbitrary spin. It is shown that such systems generally display only a trivial realization of the second central extension. While it is possible to realize any desired value of the extension parameter by suitable redefinition of the boost operator, such an approach has no necessary connection to the spin of the basic underlying field.Comment: 6 pgs., late

Comment on Gauge-Independent Analysis of Chern-Simons Theory with Matter Coupling

It is shown that a recently proposed relativistic field theory of anyons is mathematically flawed and also does not satisfy reasonable criteria for such a theory.Comment: 4 page

Vanguard Concentration

The design, manufacture, and performance of a solar parabolic dish/stirling engine system are investigated. The commercialization of the system is discussed based on ease of fabrication, assembly, and cost effectiveness. The various components contributed from government and related industries are evaluated

Soluble field theory with a massless gauge invariant limit

It is shown that there exists a soluble four parameter model in (1+1) dimensions all of whose propagators can be determined in terms of the corresponding known propagators of the vector coupling theory. Unlike the latter case, however, the limit of zero bare mass is nonsingular and yields a nontrivial theory with a rigorously unbroken gauge invariance.Comment: 7 pages, revtex, no figure

The functions of postpartum depression

Evolutionary approaches to parental care suggest that parents will not automatically invest in all offspring, and should reduce or eliminate investment in their children if the costs outweigh the benefits. Lack of paternal or social support will increase the costs born by mothers, whereas infant health problems will reduce the evolutionary benefits to be gained. Numerous studies support the correlation between postpartum depression (PPD) and lack of social support or indicators of possible infant health and development problems. PPD may be an adaptation that informs mothers that they are suffering or have suffered a fitness cost, that motivates them to reduce or eliminate investment in offspring under certain circumstances, and that may help them negotiate greater levels of investment from others. PPD also appears to be a good model for depression in general