Volume Polynomials and Log-concavity of the Characteristic Polynomials of Matroids

The Rota--Heron--Welsh conjecture (now a theorem of Adiprasito, Huh, and the author) asserts the log-concavity of the characteristic polynomial of matroids. We give an exposition of the Lorentzian polynomial proof following the work of Branden and Leake aimed at undergraduate and beginning graduate students.