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Exploring new physics in the late Universe's expansion through non-parametric inference

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arxiv 2407.04223 v1 pith:JE7DV3TI submitted 2024-07-05 astro-ph.CO

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keywords lambdalesssimdeviationsexploringlatelesssim2phantomphysics
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abstract

In this study, we investigate deviations from the Planck-$\Lambda$CDM model in the late universe ($z \lesssim 2.5$) using the Gaussian Processes method, with minimal assumptions. Our goal is to understand where exploring new physics in the late universe is most relevant. We analyze recent Cosmic Chronometers (CC), Type Ia Supernovae (SN), and Baryon Acoustic Oscillations (BAO) data. By examining reconstructions of the dimensionless parameter $\delta(z)$, which measures deviations of the Hubble parameter from the Planck-$\Lambda$CDM predictions, we identify intriguing features at low ($z \lesssim 0.5$) and high ($z \gtrsim 2$) redshifts. Deviations from the Planck-$\Lambda$CDM model were not significant between $0.5\lesssim z \lesssim2$. Using the combined CC+SN+BAO dataset, we gain insights into dark energy (DE) dynamics, resembling characteristics of omnipotent DE, extending beyond quintessence and phantom models. DE exhibits n-quintessence traits for $z\gtrsim2$, transitioning with a singularity around $z\sim2$ to usual phantom traits in $1\lesssim z\lesssim2$. DE characteristics differ between scenarios ($H_0$-SH0ES and $H_0$-$\Lambda$\&CMB), with $H_0$-SH0ES leaning towards phantom traits and $H_0$-$\Lambda$\&CMB towards quintessence. We suggest exploring new physics at $z\lesssim0.5$ and $1.5\lesssim z\lesssim2.5$, particularly around $z = 2$, to understand cosmological tensions such as $H_0$ and $S_8$.

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Cited by 6 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Hubble tension: the shape wall

    astro-ph.CO 2026-07 accept novelty 6.0 of 10

    Late-time modifications to the expansion history can raise H0 by at most about 2% (conservative) to 3.7% (permissive) if the CMB acoustic scale is fixed.

  2. Defocusing dark energy: Raychaudhuri diagnostics beyond $w<-1/3$ and the phantom divide

    gr-qc 2026-07 accept novelty 6.0 of 10

    For sign-changing effective dark energy, smooth negative-to-positive density crossings make ρ+3p and ρ+p the correct diagnostics, give w=p/ρ a universal pole n(1+z†)/3, and force repulsion onset z_rep>z† while ρ<0.

  3. Alleviating the Hubble Tension with Smooth Sign-Switching Dark Energy: Full CMB Constraints with DESI and PantheonPlus

    astro-ph.CO 2026-07 conditional novelty 6.0 of 10

    Smooth ECDM dark energy remains compatible with Planck+ACT+SPT, DESI DR2 and Pantheon+/SH0ES while alleviating the Hubble tension through a controlled late-time density transition.

  4. Background-level reconstruction of scalar-field potentials from dark-energy histories and comparison with analytic potential families

    astro-ph.CO 2026-03 conditional novelty 5.5 of 10

    A background reconstruction maps prescribed ρ_de(z) histories to V(φ) and ranks analytic potentials by Bayesian evidence, with exponential preferred for CPL and shifted-tanh for sign-switching targets.

  5. Revisiting the temperature evolution law of the CMB with gaussian processes

    astro-ph.CO 2025-05 conditional novelty 5.0 of 10

    Gaussian Process reconstruction of CMB temperature data yields mild (~2 sigma) hints of deviation from T(z)=T0(1+z) at low redshift and a slight tension with COBE/FIRAS.

  6. Is $\omega_0 \omega_a$CDM a good model for the clumpy Universe?

    astro-ph.CO 2025-07 reject novelty 4.0 of 10

    Against a Gaussian-process reconstruction of 15 sigma8(z) measurements, the DESI w0waCDM model fits slightly better than LambdaCDM, but the difference is tiny and the comparison metric is biased.

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