Early- and late-time constraints on Wald-Gauss-Bonnet topological dark energy and implications for the H0 and S8 tensions
Abstract
The persistent H0 and S8 tensions motivate the search for new dark-energy mechanisms capable of modifying the late-time expansion history while preserving the successful early-Universe predictions of ΛCDM scenario. Wald-Gauss-Bonnet (WGB) topological dark energy provides a physically motivated realization of this possibility, where the effective dark-energy sector emerges from cosmic horizon thermodynamics and the black-hole formation and merger history. We present the first early- and late-Universe analysis of WGB cosmology, implementing the model as an effective fluid in a modified \texttt{CLASS} solver and constraining it against CMB data from \textit{Planck}, ACT~DR6 and SPT-3G, DESI~DR2 BAO, and Pantheon+ supernovae. While late-time data alone are consistent with ΛCDM, the full dataset prefers a non-zero WGB contribution, Cn=0.387+0.118−0.072, corresponding to a >3σ phantom-like deviation and an improved fit (Δχ2=−10.3). The preferred solution raises H0 from $68.5$ to 69.8 kmsmpc, reducing the Hubble tension by ∼1σ, at the cost of a mild increase in S8. The reconstructed cosmological observables show that WGB leaves the primary CMB almost unchanged while enhancing lensing and small-scale clustering, revealing a characteristic H0-S8 trade-off. WGB dark energy therefore emerges as a physically motivated and observationally viable late-time mechanism for partially alleviating the Hubble tension without introducing new early-Universe physics.
Related
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BibTeX
@misc{tsilioukas2026early,
title = {{Early- and late-time constraints on Wald-Gauss-Bonnet topological dark energy and implications for the $H_0$ and $S_8$ tensions}},
author = {Stylianos A. Tsilioukas and Fotios K. Anagnostopoulos and Spyros Basilakos and Andronikos Paliathanasis and Emmanuel N. Saridakis},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.26101},
eprint = {2607.26101},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.26101},
}
RIS
TY - UNPB
TI - Early- and late-time constraints on Wald-Gauss-Bonnet topological dark energy and implications for the H_0 and S_8 tensions
AU - Stylianos A. Tsilioukas
AU - Fotios K. Anagnostopoulos
AU - Spyros Basilakos
AU - Andronikos Paliathanasis
AU - Emmanuel N. Saridakis
PY - 2026
DA - 2026/10/30
PB - arXiv
DO - 10.48550/arxiv.2607.26101
UR - https://arxiv.org/abs/2607.26101
AB - The persistent H_0 and S_8 tensions motivate the search for new dark-energy mechanisms capable of modifying the late-time expansion history while preserving the successful early-Universe predictions of ΛCDM scenario. Wald-Gauss-Bonnet (WGB) topological dark energy provides a physically motivated realization of this possibility, where the effective dark-energy sector emerges from cosmic horizon thermodynamics and the black-hole formation and merger history. We present the first early- and late-Universe analysis of WGB cosmology, implementing the model as an effective fluid in a modified \texttt{CLASS} solver and constraining it against CMB data from \textit{Planck}, ACT~DR6 and SPT-3G, DESI~DR2 BAO, and Pantheon+ supernovae. While late-time data alone are consistent with ΛCDM, the full dataset prefers a non-zero WGB contribution, Cn=0.387^+0.118_−0.072, corresponding to a >3σ phantom-like deviation and an improved fit (Δχ^2=−10.3). The preferred solution raises H_0 from $68.5$ to 69.8 kmsmpc, reducing the Hubble tension by ∼1σ, at the cost of a mild increase in S_8. The reconstructed cosmological observables show that WGB leaves the primary CMB almost unchanged while enhancing lensing and small-scale clustering, revealing a characteristic H_0-S_8 trade-off. WGB dark energy therefore emerges as a physically motivated and observationally viable late-time mechanism for partially alleviating the Hubble tension without introducing new early-Universe physics.
ER -