# The Extremals of Minkowski's Quadratic Inequality

## TL;DR

This paper fully characterizes the extremals of Minkowski's quadratic inequality in convex geometry, confirming a longstanding conjecture using advanced operator theory and rigidity properties.

## Contribution

It provides a complete solution to the extremals problem for Minkowski's quadratic inequality, employing novel Dirichlet form representations and rigidity techniques.

## Key findings

- Confirmed the conjecture of R. Schneider on extremals.
- Represented mixed volumes via Dirichlet forms and elliptic operators.
- Established a quantitative rigidity property for these operators.

## Abstract

In a seminal paper "Volumen und Oberfl\"ache" (1903), Minkowski introduced the basic notion of mixed volumes and the corresponding inequalities that lie at the heart of convex geometry. The fundamental importance of characterizing the extremals of these inequalities was already emphasized by Minkowski himself, but has to date only been resolved in special cases. In this paper, we completely settle the extremals of Minkowski's quadratic inequality, confirming a conjecture of R. Schneider. Our proof is based on the representation of mixed volumes of arbitrary convex bodies as Dirichlet forms associated to certain highly degenerate elliptic operators. A key ingredient of the proof is a quantitative rigidity property associated to these operators.