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On the homology groups of the Brauer complex for a triquadratic field extension
Abstract:The homology groups urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0001, urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0002, and urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0003 of the Brauer complex for a triquadratic field extension urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0004 are studied. In particular, given urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0005, we find equivalent conditions for the image of D in urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0006 to be zero. We consider as well the second divided power operation urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0007, and show that there are nonstandard elements with respect to γ2. Further, a natural transformation urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0008, which turns out to be nondegenerate on the left, is defined. As an application we construct a field extension urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0009 such that the cohomology group urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0010 of the Brauer complex contains the images of prescribed elements of urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0011, provided these elements satisfy a certain cohomological condition. At the final part of the paper examples of triquadratic extensions urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0012 with nontrivial urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0013 are given. As a consequence we show that the homology group urn:x-wiley:0025584X:media:mana201600022:mana201600022-math-0014 can be arbitrarily big.
Keywords:Brauer group  conic  cohomology group  field extension  11E04  11E81
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