Testing cosmic acceleration from thermogravity without vacuum energy
Abstract
We present a first background-level observational test of a thermogravity theory in which the Einstein equations are clipped to a trace-free version, the cosmological constant Λ does not gravitate, and controlled violations of energy conservation obstruct the usual reinstatement of Λ as an integration constant. We therefore set Λ=0 and ask whether late-time acceleration can instead be generated solely by energy non-conservation, with no extra background parameter relative to flat ΛCDM. We contrast a minimal universal implementation with a model in which only CDM partakes in non-conservation. The universal model is strongly disfavored when combining Supernovae and BAO distances, with the inclusion of DESI BAO worsening the fit by Δχ2≃ 51 relative to ΛCDM, because matter creation ties the intermediate-redshift normalization of H(z) too rigidly to the present acceleration. This conclusion, however, should be interpreted with caution, since universal non-conservation would modify the observational dictionary itself. By contrast, restricting non-conservation to CDM leaves baryonic and photon observables unaffected at the background level and therefore allows a self-contained analysis. The resulting ξCDM model, which can be thought of as a one parameter extension of ΛCDM, provides an improved fit relative to ΛCDM for the background dataset combinations considered, with improvements reaching Δχ2=−4.85 and a maximum Bayesian preference of lnℬ=2.77. However, when the BAO ruler is calibrated using BBN or CMB information, the reduced effective early-time CDM density increases the sound horizon and drives H0 towards lower values, thereby increasing rather than alleviating the tension with the distance-ladder calibration.
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BibTeX
@misc{lee2026testing,
title = {{Testing cosmic acceleration from thermogravity without vacuum energy}},
author = {Dong Ha Lee and João Magueijo and Carsten van de Bruck and Eleonora Di Valentino},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.29206},
eprint = {2609.29206},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.29206},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Testing cosmic acceleration from thermogravity without vacuum energy
AU - Dong Ha Lee
AU - João Magueijo
AU - Carsten van de Bruck
AU - Eleonora Di Valentino
PY - 2026
DA - 2026/09/24
PB - arXiv
DO - 10.48550/arxiv.2609.29206
UR - https://arxiv.org/abs/2609.29206
AB - We present a first background-level observational test of a thermogravity theory in which the Einstein equations are clipped to a trace-free version, the cosmological constant Λ does not gravitate, and controlled violations of energy conservation obstruct the usual reinstatement of Λ as an integration constant. We therefore set Λ=0 and ask whether late-time acceleration can instead be generated solely by energy non-conservation, with no extra background parameter relative to flat ΛCDM. We contrast a minimal universal implementation with a model in which only CDM partakes in non-conservation. The universal model is strongly disfavored when combining Supernovae and BAO distances, with the inclusion of DESI BAO worsening the fit by Δχ^2≃ 51 relative to ΛCDM, because matter creation ties the intermediate-redshift normalization of H(z) too rigidly to the present acceleration. This conclusion, however, should be interpreted with caution, since universal non-conservation would modify the observational dictionary itself. By contrast, restricting non-conservation to CDM leaves baryonic and photon observables unaffected at the background level and therefore allows a self-contained analysis. The resulting ξCDM model, which can be thought of as a one parameter extension of ΛCDM, provides an improved fit relative to ΛCDM for the background dataset combinations considered, with improvements reaching Δχ^2=−4.85 and a maximum Bayesian preference of lnℬ=2.77. However, when the BAO ruler is calibrated using BBN or CMB information, the reduced effective early-time CDM density increases the sound horizon and drives H_0 towards lower values, thereby increasing rather than alleviating the tension with the distance-ladder calibration.
ER -