Computation of several cyclotomic Swan subgroups

نویسندگان

  • Timothy Kohl
  • Daniel R. Replogle
چکیده

Let Cl(OK [G]) denote the locally free class group, that is the group of stable isomorphism classes of locally free OK [G]-modules, where OK is the ring of algebraic integers in the number field K and G is a finite group. We show how to compute the Swan subgroup, T (OK [G]), of Cl(OK [G]) when K = Q(ζp), ζp a primitive p-th root of unity, G = C2, where p is an odd (rational) prime so that hp = 1 and 2 is inert in K/Q. We show that, under these hypotheses, this calculation reduces to computing a quotient ring of a polynomial ring; we do the computations obtaining for several primes p a nontrivial divisor of Cl(Z[ζp]C2). These calculations give an alternative proof that the fields Q(ζp) for p=11, 13, 19, 29, 37, 53, 59, and 61 are not HilbertSpeiser.

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عنوان ژورنال:
  • Math. Comput.

دوره 71  شماره 

صفحات  -

تاریخ انتشار 2002