Shukla photonic field theory (SPFT 5) : SIPE as Atomic, Optical & Vacuum Stiffness substrate

We propose that the late-time accelerated expansion of the Universe is driven by Shukla Inherent Photonic Energy (SIPE) — a pervasive, non-radiative field of intrinsic photonic excitations. Even as photon radiative frequencies redshift nearly to zero, each retains its SIPE quantum, remaining gravitationally active.