Relativistic MOND Theory from Modified Entropic Gravity

TL;DR

This paper develops a relativistic version of MOND within entropic gravity, incorporating temperature effects on holographic screens, and demonstrates its consistency with galaxy rotation data, offering an alternative to dark matter.

Contribution

It introduces a relativistic MOND model derived from entropic gravity with temperature-dependent corrections, bridging phenomenology and relativistic gravity theories.

Findings

RMOND reproduces MOND-like behavior in low-acceleration regimes.

Both RMOND and dark-matter models fit galaxy rotation curves better than baryonic Newtonian predictions.

RMOND shows improved fit at large radii ($r\gtrsim 20$ kpc) compared to baryons-only models.

Abstract

We derive a relativistic extension of Modified Newtonian Dynamics (MOND) within the framework of entropic gravity by introducing temperature-dependent corrections to the equipartition law on a holographic screen. Starting from a Debye-like modification of the surface degrees of freedom and employing the Unruh relation between acceleration and temperature, we obtain modified Einstein equations in which the geometric sector acquires explicit thermal corrections. Solving these equations for a static, spherically symmetric spacetime in the weak-field, low-temperature regime yields a corrected metric that smoothly approaches Minkowski space at large radii and naturally contains a characteristic acceleration scale. In the very-low-acceleration regime, the model reproduces MOND-like deviations from Newtonian dynamics while providing a relativistic underpinning for that phenomenology. We confront the theory with rotation-curve data for NGC~3198 and perform a Bayesian parameter inference, comparing our relativistic MOND (RMOND) model with both a baryons-only Newtonian model and a dark-matter halo model. We find that RMOND and the dark-matter model both fit the data significantly better than the baryons-only Newtonian prediction, and that RMOND provides particularly improved agreement at $r\gtrsim 20\,\mathrm{kpc}$. These results suggest that temperature-corrected entropic gravity provides a viable relativistic framework for MOND phenomenology, motivating further observational tests, including gravitational lensing and extended galaxy samples.