Positivity of Fock Toeplitz operators via the Berezin transform

Abstract

This paper deals with the relationship between the positivity of the Fock Toeplitz operators and their Berezin transforms. The author considers the special case of the bounded radial function \(\varphi \left( z \right) = a + b{e^{ - \alpha {{\left| z \right|}^2}}} + c{e^{ - \beta {{\left| z \right|}^2}}}\), where a, b, c are real numbers and α, β are positive numbers. For this type of φ, one can choose these parameters such that the Berezin transform of φ is a nonnegative function on the complex plane, but the corresponding Toeplitz operator Tφ is not positive on the Fock space.