Environmental Gravitational Bias in Cosmological Redshift Inference

Abstract

Precision cosmology interprets observed redshifts within homogeneous FLRW models, neglecting that observers and emitters reside in structured gravitational environments. Within general relativity, potential differences modify clock rates via the lapse function, introducing systematic gravitational redshift components. We develop a semi-quantitative framework estimating this environmental bias as zenv ∼ 10−5 and show that it can produce ∼ 1% corrections in luminosity distances at low redshifts. The framework predicts a correlation between SN Ia Hubble residuals and local galaxy density, which can be tested with existing survey data.

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