title: A trigonometric sum relevant to the nonrelativistic theory of atoms.
abstract: We extend Van der Corput's method for exponential sums to study an oscillatory term appearing in the quantum theory of large atoms. We obtain an interpretation in terms of classical dynamics and we produce sharp asymptotic upper and lower bounds for the oscillations.
authors.affiliation: Departamento de Matemáticas, Universidad Autónoma de Madrid, Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Córdoba
authors.forename: C
authors.initials: C
authors.lastname: Fefferman
authors.forename: L
authors.initials: L
authors.lastname: Seco