Filling the gap in the table of smallest regulators up to degree 7

Abstract

In 2016 Astudillo, Diaz y Diaz and Friedman published sharp lower bounds for regulators of number fields of all signatures up to degree seven, except for fields of degree seven having five real places. We deal with this signature, proving that the field with the first discriminant has minimal regulator. The new element in the proof is an extension of Pohst's geometric method from the totally real case to fields having one complex place.