An expression for the subdifferential set of the joint numerical radius of a tuple of matrices is obtained. Its applications to the Birkhoff-James orthogonality in the space consisting of tuples of matrices equipped with the joint numerical radius norm are discussed. © 2022 Informa UK Limited, trading as Taylor & Francis Group.

Priyanka Grover

Mathematics

(SoNS) School of Natural Sciences

Singla S.

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