When Dark Matter Heats Up: A Model-Independent Search for Non-Cold Behavior

Abstract

This article questions the common assumption of cold dark matter (DM) by exploring the possibility of a non-zero equation of state (EoS) without relying on any parametric approach. In standard cosmological analyses, DM is typically modeled as pressureless dust with $w_{\mathrm{DM}}=0$, an assumption that aligns with large-scale structure formation, supports the empirical success of the $\Lambda$CDM model, and simplifies cosmological modeling. However, there is no fundamental reason to exclude a non-zero $w_{\mathrm{DM}}$ from the cosmological framework. In this work, we explore this possibility through non-parametric and parametric reconstructions based on Gaussian Process Regression. The reconstructions use Hubble parameter measurements from Cosmic Chronometers (CC), the Pantheon+ sample of Type Ia supernovae, and Baryon Acoustic Oscillation (BAO) data from DESI DR1 and DR2. Our findings suggest that a dynamical EoS for DM, although only mildly supported statistically, cannot be conclusively ruled out. Notably, we observe a mild tendency ($\sim 1\sigma$) toward a negative $w_{\mathrm{DM}}$ at the present epoch, which is most likely due to inconsistencies between the BAO data from DESI and other datasets.

arXiv commentVersion 2, ~21 pages including references and appendices; 8 captioned figures, 6 tables; published in Phys. Rev. D

References in corpus (47)

• dynesty: A Dynamic Nested Sampling Package for Estimating Bayesian Posteriors and Evidences
• In the Realm of the Hubble tension $-$ a Review of Solutions
• The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological Implications from two Decades of Spectroscopic Surveys at the Apache Point observatory
• The Pantheon+ Analysis: Cosmological Constraints
• Constraints on the redshift dependence of the dark energy potential
• Tensions between the Early and the Late Universe
• A 6% measurement of the Hubble parameter at $z\sim 0.45$: direct evidence of the epoch of cosmic re-acceleration
• Cosmic Chronometers: Constraining the Equation of State of Dark Energy. I: H(z) Measurements
• DESI 2024 VI: Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations
• Raising the bar: new constraints on the Hubble parameter with cosmic chronometers at z$\sim$2
• Challenges for $\Lambda$CDM: An update
• Age-dating Luminous Red Galaxies observed with the Southern African Large Telescope
• Euclid. I. Overview of the Euclid mission
• Cosmology Intertwined II: The Hubble Constant Tension
• DESI DR2 Results II: Measurements of Baryon Acoustic Oscillations and Cosmological Constraints
• Constraints on the equation of state of dark energy and the Hubble constant from stellar ages and the CMB
• The $H_0$ Olympics: A fair ranking of proposed models
• Reconstruction of dark energy and expansion dynamics using Gaussian processes
• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• New constraints on cosmological parameters and neutrino properties using the expansion rate of the Universe to z~1.75
• "Non-cold" dark matter at small scales: a general approach
• New Observational $H(z)$ Data from Full-Spectrum Fitting of Cosmic Chronometers in the LEGA-C Survey
• Using non-DESI data to confirm and strengthen the DESI 2024 spatially-flat $w_0{w}_a$CDM cosmological parameterization result
• Constraining Non-Cold Dark Matter Models with the Global 21-cm Signal
• Decaying dark matter and the tension in ${\sigma }_8$
• Cosmic dissonance: new physics or systematics behind a short sound horizon?
• Novel constraints on non-cold (non-thermal) Dark Matter from Lyman-$\alpha$ forest data
• Observational constraints on variable equation of state parameters of dark matter and dark energy after Planck
• Cosmological bounds on the equation of state of dark matter
• Model-independent reconstruction of the Interacting Dark Energy Kernel: Binned and Gaussian process
• The Dark Matter equation of state through cosmic history
• How to use GP: Effects of the mean function and hyperparameter selection on Gaussian Process regression
• fgivenx: A Python package for functional posterior plotting
• Model-agnostic assessment of dark energy after DESI DR1 BAO
• How Cold is Cold Dark Matter?
• Dark Matter properties through cosmic history
• Reconstruction of the Dark Energy equation of state from latest data: the impact of theoretical priors
• Machine Learning the Cosmic Curvature in a Model-independent Way
• Cosmological searches for a non-cold dark matter component
• Non-parametric reconstruction of interaction in the cosmic dark sector
• IWDM: The fate of an interacting non-cold dark matter $-$ vacuum scenario
• Dark matter solution to the $H_0$ and $S_8$ tensions, and the integrated Sachs-Wolfe void anomaly
• Evolving Dark Energy or Evolving Dark Matter?
• Gaussian-process reconstructions and model building of quintom dark energy from latest cosmological observations
• Non-parametric reconstruction of cosmological observables using Gaussian Processes Regression
• Non-comoving Cold Dark Matter in a $\Lambda$CDM background
• Non-particle dark matter from Hubble parameter

Cited by in corpus (3)

• Dark Energy in the DESI Era: A Brief Review of Evidence, Beyond-$\Lambda$CDM Interpretations, and Tensions
• From Nonparametric Distance Reconstruction to Testing the Etherington Relation and Cosmic Curvature Using 2D and 3D BAO Measurements
• Accelerating scaling solutions from dark matter particle creation