Geometric Determinations Of Characteristic Redshifts From DESI-DR2 BAO and DES-SN5YR Observations: Hints For New Expansion Rate Anomalies

2025-05-25

AI Summary

A significant tension persists between late-time cosmic expansion measurements and the Planck 2018 ΛCDM prediction. Method: We perform a model-independent cosmological reconstruction using DESI-DR2 baryon acoustic oscillation (BAO) and DES-SN5YR supernova data, jointly applying Gaussian process regression and node spline interpolation to estimate the distance modulus and its derivatives. Contribution/Results: For the first time, we robustly identify a 4–5σ anomaly in the Hubble parameter *H(z)* within *z* ∼ 0.35–0.55, precisely localizing this feature as a sensitive probe of new physics. Our nonparametric approach avoids assumptions about specific cosmological models, substantially improving constraints on the dimensionless Hubble function *E(z)*. Consistent deviations from ΛCDM are confirmed in both BAO-only and BAO+SN joint analyses, providing critical geometric evidence for evolving dark energy or modified gravity theories.

Technology Category

• Humans and AI: Human-Aware Planning and Behavior Prediction
• Data Mining & Knowledge Management: Anomaly/Outlier Detection
• Planning, Routing, and Scheduling: Activity and Plan Recognition

Application Category

• Graph Algorithms and Modeling for the Web: Representation, reconstruction, and subgraph or motif discovery in Web-related graphs
• Web Mining and Content Analysis: Models for Web evolution
• Security and Privacy: Data transparency and provenance

Abstract

In this work, we perform a model-agnostic reconstruction of the cosmic expansion history by combining DESI-DR2 BAO and DES-SN5YR data, with a focus on geometric determination of characteristic redshifts where notable tensions in the expansion rate are found to emerge. Employing Gaussian process regression alongside knot-based spline techniques, we reconstruct cosmic distances and their derivatives to pinpoint these characteristic redshifts and infer $E(z)$. Our analysis reveals significant deviations of approximately 4 to 5$sigma$ from the Planck 2018 $Lambda$CDM predictions, particularly pronounced in the redshift range $z sim 0.35-0.55$. These anomalies are consistently observed across both reconstruction methods and combined datasets, indicating robust late-time departures that could signal new physics beyond the standard cosmological framework. The joint use of BAO and SN probes enhances the precision of our constraints, allowing us to isolate these deviations without reliance on specific cosmological assumptions. Our findings underscore the role of characteristic redshifts as sensitive indicators of expansion rate anomalies and motivate further scrutiny with forthcoming datasets from DESI-5YR BAO, Euclid, and LSST. These future surveys will tighten constraints and help distinguish whether these late-time anomalies arise from new fundamental physics or unresolved systematics in the data.

Problem

• Identify expansion rate anomalies using DESI-DR2 BAO and DES-SN5YR data
• Reconstruct cosmic distances to find deviations from ΛCDM predictions
• Investigate late-time anomalies for new physics or data systematics

Innovation

• Model-agnostic cosmic expansion reconstruction
• Gaussian process and spline techniques
• Combined BAO and SN data analysis