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

arXiv:2607.18008 · gr-qc, astro-ph.CO · Submitted 2026-07-20 · Read on arXiv

Özgür Akarsu, Antonio De Felice, N. Merve Uzun

gr-qc, astro-ph.CO

Submitted: 2026-07-20

Comments: 28 pages, 3 figures, 1 table

License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Terminology

• Quintessence — 13× in this paper · explained in 2 episodes
• Model-Agnostic — 5× in this paper · explained in 2 episodes
• Hubble Tension — 4× in this paper · explained in 9 episodes
• Bispectrum — 3× in this paper · explained in 3 episodes
• Consistency — 3× in this paper · explained in 3 episodes
• Matter Power Spectrum — 3× in this paper · explained in 2 episodes
• Anisotropy — 2× in this paper · explained in 3 episodes
• Degeneracy — 2× in this paper · explained in 3 episodes
• Inverse Problem — 2× in this paper · explained in 2 episodes
• Benchmark — 1× in this paper · explained in 2 episodes
• Clustering — 1× in this paper · explained in 2 episodes
• Cooperation — 1× in this paper · explained in 2 episodes
• Embeddings — 1× in this paper · explained in 2 episodes
• Equation of State (EoS) — 1× in this paper · explained in 4 episodes
• Generalization — 1× in this paper · explained in 13 episodes
• Gravitational Lensing — 1× in this paper · explained in 2 episodes
• Initial Data — 1× in this paper · explained in 2 episodes
• N-body simulations — 1× in this paper · explained in 2 episodes
• Trace — 1× in this paper · explained in 2 episodes
• World Model — 1× in this paper · explained in 7 episodes

Sources

• Dark Energy and the Accelerating Universe
• Mapping the Cosmological Expansion
• Revisiting a negative cosmological constant from low-redshift data
• Graduated dark energy: Observational hints of a spontaneous sign switch in the cosmological constant
• Negative cosmological constant in the dark sector?
• Do cosmological observations allow a negative $\Lambda$?
• On Redshift Evolution & Negative Dark Energy Density in Pantheon+ Supernovae
• Constraining the Cosmology of the Phantom Brane using Distance Measures
• Is the dark energy equation of state parameter singular?
• Do equation of state parametrizations of dark energy faithfully capture the dynamics of the late universe?
• Hints of sign-changing scalar field energy density and a transient acceleration phase at $z\sim 2$ from model-agnostic reconstructions
• Model-Independent Indication for a Localized Anomaly in the Late-Time Expansion History
• Background-level reconstruction of scalar-field potentials from dark-energy histories and comparison with analytic potential families
• Null Impact of the Null Energy Condition in Current Cosmology
• Effective Phantom Dark Energy: What Cosmological Reconstruction Does and Does Not Imply
• DESI 2024 VI: Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations
• DESI DR2 Results II: Measurements of Baryon Acoustic Oscillations and Cosmological Constraints
• Probing dynamical dark energy with late-time data: Evidence, tensions, and the limits of the $w_0w_a$CDM framework
• Dark Energy Crosses the Line: Quantifying and Testing the Evidence for Phantom Crossing
• Revisiting CPL with sign-switching density: To cross or not to cross the NECB

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