Dr. Pietro Paparella presented a talk entitled "The converse of the Cowling–Obrechkoff–Thron theorem" at ILAS Special Session on Spectral and combinatorial problems for nonnegative matrices and their generalizations, Joint Mathematics Meetings, San Francisco, CA on January 2024.

Abstract: The converse of the Cowling–Obrechkoff–Thron theorem is given. In addition to its theoretical interest, the result fills a gap in the proof of Kellogg’s celebrated eigenvalue inequality for P and P0 matrices.