Constraining an Expanding Locally Anisotropic metric from the Pioneer anomaly

TL;DR

This paper explores how an Expanding Locally Anisotropic (ELA) metric can account for the Pioneer anomaly by combining local gravitational effects with cosmic expansion, providing bounds on the metric's parameters.

Contribution

It introduces a fine-tuneable ELA metric model that incorporates both local and cosmological effects, offering a new approach to explain the Pioneer anomaly.

Findings

Bounds on ELA metric parameters derived from Pioneer anomaly data

Estimated mass-energy density contributions compatible with Lambda-CDM

Quantified Doppler acceleration deviations within observational limits

Abstract

It is discussed the possibility of a fine-tuneable contribution to the two way Doppler acceleration either towards, either outwards the Sun for heliocentric distances above 20 AU by considering a background described by an Expanding Locally Anisotropic (ELA) metric. This metric encodes both the standard local Schwarzschild gravitational effects and the cosmological Universe expansion effects allowing simultaneously to fine-tune other gravitational effects at intermediate scales, which may be tentatively interpreted as a covariant parameterization of either cold dark matter either gravitational interaction corrections. Are derived bounds for the ELA metric functional parameter by considering the bounds on the deviation from standard General Relativity imposed by the current updated limits for the Pioneer anomaly, taking in consideration both the natural outgassing and on-board radiation pressure, resulting in an average Doppler acceleration outwards the Sun of a_p = +0.4^{+2.1}_{-2.0} x 10^{-10} (m/s^2). It is also computed the mass-energy density for the ELA metric within the bounds obtained and are discussed the respective contributions to the cosmological mass-energy density which, for compatibility with the Lambda-CDM model, are included in Omega_{CDM}.