Hot QCD physics studies the nuclear strong force under extreme temperature and densities. Experimentally these conditions are achieved via high-energy collisions of heavy ions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). In the past decade, a unique and substantial suite of data was collected at RHIC and the LHC, probing hydrodynamics at the nucleon scale, the temperature dependence of the transport properties of quark-gluon plasma, the phase diagram of nuclear matter, the interaction of quarks and gluons at different scales and much more. This document, as part of the 2023 nuclear science long range planning process, was written to review the progress in hot QCD since the 2015 Long Range Plan for Nuclear Science, as well as highlight the realization of previous recommendations, and present opportunities for the next decade, building on the accomplishments and investments made in theoretical developments and the construction of new detectors. Furthermore, this document provides additional context to support the recommendations voted on at the Joint Hot and Cold QCD Town Hall Meeting, which are reported in a separate document.

Transition generalized parton distributions (GPDs) describe matrix elements of nonlocal partonic QCD operators between the ground and excited baryon states and provide new tools for quantifying and interpreting the structure of baryon resonances in QCD. We discuss a description of non-diagonal Deeply Virtual Compton Scattering process involving a transition between a nucleon and a nucleon resonance in the $\pi N$ system within the framework of transition GPDs. We address the physical content of $N \to N^*$ and $N \to \Delta$ transition GPDs, review the existing theoretical models and present theoretical estimates of related observables for the kinematic conditions corresponding to the experimental studies with JLab@12GeV. We also discuss the perspective of exploring resonance production with help of transition GPDs and consider the application of the Froissart-Gribov projections to study excitation of nucleon resonances by means of QCD probes with spin-$J$.