Scalar‐isoscalar states, gravitational form factors, and dimension‐2 condensates in a large‐$Nc$ Regge approach

Scalar‐isoscalar states $(JPC = 0++)$ are analyzed within the large‐$Nc$ Regge approach. We find that the lightest $f0(600)$ scalar‐isoscalar state fits very well into the pattern of the radial Regge trajectory. We confirm the obtained mass values from an analysis of the pion and nucleon spin‐0 gravitational form factors, recently measured on the lattice. We find that a simple two‐state model suggests a meson nature of $f0(600),$ and a glueball nature of $f0(980),$ which naturally explains the ratios of various coupling constants. Finally, matching to the OPE requires a fine‐tuned mass condition of the vanishing dimension‐2 condensate in the Regge approach with infinitely many scalar‐isoscalar states.