Representation Theorems for indefinite quadratic forms without spectral gap

Abstract

The First and Second Representation Theorem for sign-indefinite quadratic forms are extended. We include new cases of unbounded forms associated with operators that do not necessarily have a spectral gap around zero. The kernel of the associated operators is determined for special cases. This extends results by Grubišić, Kostrykin, Makarov and Veselić in [Mathematika 59 (2013), 169--189].

19 pages

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