Defective dual varieties for real spectra
Jens Forsgård · Journal of Algebraic Combinatorics · 2018
We introduce an invariant of a finite point configuration $$A \subset \mathbb {R}^{1+n}$$ which we denote the cuspidal form of A. We use this invariant to extend Esterov’s characterization of dual-defective point configurations to exponential sums; the dual variety associated with A has codimension at least 2 if and only if A does not contain any iterated circuit.