Who is Professor Hans Sedlmayr from Travels in Hyper Reality: Essays and what is their importance?

Hans Sedlmayr shares the focus of one of Eco's essays with McLuhan because he authored a book "Art in Crisis: The Lost Center", written in 1948. In this book, Sedlmayr, like McLuhan, is accused by Eco of not presenting the equations or formulas from which he draws his claims, a process that Eco refers to as Cogito Interruptus.