Energy momentum tensor and the D-term in the bag model

TL;DR

This paper investigates the energy-momentum tensor form factors and the D-term in the nucleon and other hadrons within the bag model, highlighting their physical interpretation and theoretical implications.

Contribution

It provides a comprehensive analysis of EMT form factors and densities in the bag model for arbitrary colors, including the study of D-terms for various hadrons and resonances.

Findings

Demonstrates the connection between EMT conservation, stability, and the D-term sign.

Shows the consistency of EMT form factors in the large-Nc limit within the bag model.

Explores the physical interpretation of the D-term in hadron structure.

Abstract

The energy-momentum tensor (EMT) form factors pave new ways for exploring hadron structure. Especially the D-term related to the EMT form factor D(t) has received a lot of attention due to its attractive physical interpretation in terms of mechanical properties. We study the nucleon EMT form factors and the associated densities in the bag model which we formulate for an arbitrary number of colors Nc and show that the EMT form factors are consistently described in this model in the large-Nc limit. The simplicity of the model allows us to test in a lucid way many theoretical concepts related to EMT form factors and densities including recently introduced concepts like normal and tangential forces, or monopole and quadrupole contributions to the angular momentum distribution. We also study the D-terms of rho-meson, Roper resonance, other N* states and Delta-resonances. Among the most interesting outcomes is the lucid demonstration of the deeper connection of EMT conservation, stability, the virial theorem and the negative sign of the D-term.