7. Cyclotomic units and the plus class number
This chapter records the cyclotomic-unit part of the proof. The purpose is to
connect Bernoulli non-divisibility with the plus class number. Throughout this
chapter p is an odd prime, K is a field isomorphic to \mathbb{Q}(\zeta_p),
and K^+ = \mathbb{Q}(\zeta_p)^+ is its maximal real subfield. The group of real
units is E^+ := (\mathcal{O}_{K^+})^\times. Thus E^+ is the full unit group of
the maximal real subfield.