Modified Quantum Gravitational Theory Applied to The Rotation Curve of NGC 7793: A ‎Gas-Coupled Quantum Alternative Explaining The Bosma Effect

Abstract

The rotation curve of the flocculent late-type spiral NGC 7793 exhibits a slow, nearly linear ‎inner rise and an extended flat outer profile at ~110 km/s, exemplifying the Bosma effect – the ‎close correspondence between dynamical mass and the distribution of neutral hydrogen. ‎Building on previous applications of Quantum Gravitational Theory (QGT) to galaxies such as ‎NGC 6503, NGC 3198, NGC 2903, DDO 154, NGC 2841, DDO 53, NGC 925, and NGC ‎‎1569, we apply a Modified Quantum Gravitational Theory (MQGT) that introduces ‎gas-dependent extensions to the standard QGT framework. Using SPARC photometry ‎‎(distance 3.61 Mpc) and a scaled HI profile from Carignan & Puche (1990), we compute the ‎gravitational scale length ‎ ‎= 5.32 kpc from the baryonic mass distribution. The MQGT ‎includes a gas-fraction-dependent effective scale length, differential coupling for cold and warm ‎HI phases, and dust modulation of the graviton mean free path. With parameters α ≈ 0.438,‎ ‎  ≈ 1.05,‎ ‎  ≈ 1.62, γ ≈ 0.25, η ≈ 3.2, the model provides a good fit to the observed ‎rotation curve with an RMS residual of 1.42 km/s and a reduced ‎  ‎ of 1.59; all data points lie ‎within the 1σ observational uncertainties. Standard QGT (without gas coupling) gives a poorer ‎fit (RMS 8.7 km/s). The results suggest that a quantum gravitational amplification mechanism ‎preferentially coupled to the extended warm HI component can naturally produce Bosma-like ‎behaviour without invoking non- baryonic dark matter. However, the parameter values are ‎derived for a single galaxy, and their universality remains to be tested on larger samples. ‎MQGT provides a viable baryon-only framework for modelling rotation curves of gas-rich ‎late-type spirals, motivating further observational tests with THINGS, SPARC, and future HI ‎surveys‎.