Neutrino-Exchange Interactions in 1-, 2-, and 3-Dimensions
  We examine several recent calculations of the self-energy of a neutron star arising from neutrino-exchange. It is shown that the results of Abada, et al. in 1+1 dimensions have no bearing on a 3-dimensional neutron star, since the criticality parameter (Gf N)/R^2 is always much smaller than unity in 1+1 dimensions. The calculation of Kiers and Tytgat in 3-dimensions is shown to disagree with the lowest order 2-body contribution, which is known exactly. This discrepancy raises the possibility that the description of a neutron star as a continuous medium may be inappropriate when calculating higher-order many-body effects. We conclude that none of the recent calculations contradict the earlier claims that the neutrino-exchange contributions to the self-energy of a neutron star are unphysically large, when calculated in the standard model. The implication of this result, that neutrinos must have a non-zero mass, m > 0.4 eV, remains intact. 
Ephraim Fischbach and Brian Woodahl (Purdue University)