Type Ia Supernovae in a High-Density Vacuum Cosmology: Revisiting the Chandrasekhar Limit and Distance Calibration

The gravitating vacuum model proposes that quantum vacuum energy density inside bound structures is approximately 800 times larger than the observed cosmological constant. This paper investigates whether such a dense vacuum affects the physics of Type Ia supernovae — the primary distance indicators of observational cosmology. We demonstrate that direct effects on white dwarf structure are negligible: the fractional change in the Chandrasekhar limit is ΔM_Ch/M_Ch ~ 10⁻²⁸, because the vacuum energy density (~10⁻²⁴ kg/m³) is 33 orders of magnitude below the white dwarf interior density (~10⁹ kg/m³). The carbon ignition conditions, detonation physics, and nickel-56 yield are all unaffected. We further show that the effective gravitational coupling G_eff = G(1 + 2α) does not modify the Chandrasekhar limit: the reclassification of ~5% of the nucleon mass as w = −1 vacuum energy (Paper #3a) does not change the total gravitating mass in the Newtonian limit relevant for white dwarf structure. Type Ia supernovae remain standard candles in this cosmology. We then identify indirect effects through progenitor evolution in the modified gravitational environment. The enhanced effective gravity accelerates stellar evolution timescales by ~1%, modifies the delay-time distribution, and introduces redshift-dependent correlations between host galaxy properties and Hubble diagram residuals. The predicted luminosity correction is of order ε ln(1 + z) with ε ~ 0.01–0.02 magnitudes — below the current systematic floor but within reach of combined LSST, Roman, and Euclid surveys (σ(ε) ~ 0.003 mag). The signal has a distinctive correlation structure: logarithmic in redshift, correlated with host stellar mass, and uncorrelated with color — distinguishable from dust evolution and other systematics. This paper closes a potential logical gap in the research programme: the cosmological parameters are calibrated using SNe Ia distances, and the demonstration that these distances are unmodified ensures the calibration is self-consistent. Keywords: Type Ia supernovae, Chandrasekhar limit, vacuum energy, distance calibration, Hubble diagram, standard candles, progenitor evolution, cosmological constant, dark energy, dark matter, gravitating vacuum Resource type: Preprint License: Creative Commons Attribution 4.0 International (CC BY 4.0) Related identifiers: Is part of the research programme "What If the Vacuum Gravitates Locally?" Is supplement to: Paper #3a (doi:10.5281/zenodo.19017167), Paper #8, Paper #9, Paper #12 References: Part of a 17-paper research programme. All completed preprints available at: https://interdisciplinary-research.institute/cosmology-and-theoretical-physics/ Authors: Kriger, Boris Affiliation: Institute of Integrative and Interdisciplinary Research, Department of Cosmology and Theoretical Physics ORCID: 0009-0001-0034-2903 Description: Paper #16 of the research programme "What If the Vacuum Gravitates Locally?"