On Sizes of Hadrons

TL;DR

This paper examines different definitions of hadron sizes, such as charge and mass radii, analyzing their theoretical basis, physical interpretation, and conceptual challenges, especially concerning causality principles.

Contribution

It provides a detailed analysis of various hadron size definitions in terms of local field operators and discusses their conceptual and interpretational difficulties.

Findings

Different size definitions have complex relationships to physical sizes.

Conceptual difficulties arise related to causality principles.

The paper highlights the need for careful interpretation of size quantities.

Abstract

Recently, various types of "radii" have been intensively discussed in the literature: "charge", "mass", "mechanical", "gravitational", etc. In my report, I analyze the definitions of quantities of such type in terms of matrix elements of local field operators and their relationship to physical (geometric) size. I also try to find out possible (if any) interpretation of the mentioned quantities and point out some serious conceptual difficulties related to the causality principle.