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The energy of interacting neutron matter with spin polarization is calculated in Hartree-Fock approximation by the method of unitary transformations for a hard core and a soft core potential. In addition the magnetic spin susceptibility is given and the possibility of a ferromagnetic transition investigated. It is shown that the effect of the nuclear forces for all densities considered depresses the magnetic spin susceptibility relative to that of the corresponding ideal Fermi gas.

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Sixty years ago, in 1949, Kurt Gödel published a paper dedicated to Albert Einstein on the occasion of his 70th birthday. Gödel presented a solution of Einstein's field equations for a rotating, homogeneous, stationary universe with negative cosmological constant. Among various surprising properties this universe allows closed timelike curves (CTC), i.e. travel into the past and into the future. Until today many papers have been published concerning physical, logical and philosophical consequences of these results and the existence of closed timelike worldlines in the General Theory of Relativity. Starting from a short survey on Gödel's work we proceed to elucidate more modern interpretations of the existence of CTCs.

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