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Could We Be Fooled about Phantom Crossing?

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arxiv 2506.15091 v1 pith:MMTIB7DP submitted 2025-06-18 astro-ph.CO

Could We Be Fooled about Phantom Crossing?

classification astro-ph.CO
keywords dataphantombehaviorcrossingdarkdivideenergyline
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Recent data from DESI Year 2 BAO, Planck CMB, and various supernova compilations suggest a preference for evolving dark energy, with hints that the equation of state may cross the phantom divide line ($w = -1$). While this behavior is seen in both parametric and non-parametric reconstructions, comparing reconstructions that support such behavior (such as the best fit of CPL) with those that maintain $w>-1$ (like the best fit algebraic quintessence) is not straightforward, as they differ in flexibility and structure, and are not necessarily nested within one another. Thus, the question remains as to whether the crossing behavior that we observe, suggested by the data, truly represents a dark energy model that crosses the phantom divide line, or if it could instead be a result of data fluctuations and the way the data are distributed. We investigate the likelihood of this possibility. For this analysis we perform 1,000 Monte Carlo simulations based on a fiducial algebraic quintessence model. We find that in $3.2 \% $ of cases, CPL with phantom crossing not only fits better, but exceeds the real-data $\chi^2$ improvement. This Monte Carlo approach quantifies to what extent statistical fluctuations and the specific distribution of the data could fool us into thinking the phantom divide line is crossed, when it is not. Although evolving dark energy remains a robust signal, and crossing $w=-1$ a viable phenomenological solution that seems to be preferred by the data, its precise behavior requires deeper investigation with more precise data.

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Cited by 8 Pith papers

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

  1. Exploring the interplay of late-time dynamical dark energy and new physics before recombination

    astro-ph.CO 2026-03 conditional novelty 5.5

    Under standard recombination, phantom-crossing dynamical dark energy is preferred at ~97–98.5% probability; early-time fixes to the Hubble tension erase that preference while creating severe ω_m tension with CMB.

  2. Late-Time Oscillating Quintessence in Light of DESI

    astro-ph.CO 2026-06 unverdicted novelty 5.0

    A late-onset oscillating quintessence model improves the fit to DESI plus supernova and CMB data by Delta chi squared of about 9 over Lambda CDM, driven by background expansion.

  3. Reconstructing dark energy with fewer assumptions

    astro-ph.CO 2026-06 unverdicted novelty 5.0

    Bin-wise uncorrelated reconstruction from DESI/SDSS BAO and Pantheon+/Union3.1/DES-Dovekie supernovae yields dark energy density peaking then declining and equation of state oscillating with phantom crossing near z~0....

  4. Exploring the interplay of late-time dynamical dark energy and new physics before recombination

    astro-ph.CO 2026-03 unverdicted novelty 5.0

    Model-independent reconstruction finds 96.7-98.5% probability of phantom crossing if recombination is standard, but early new physics to ease Hubble tension weakens this preference while requiring unrealistically high...

  5. Constraints on Coupled Dark Energy in the DESI Era

    astro-ph.CO 2026-04 unverdicted novelty 4.0

    New cosmological data mildly favor a small coupling between dark matter and a scalar dark energy field at |β| ≈ 0.03 while allowing an effective phantom-crossing equation of state.

  6. Effective Phantom Dark Energy: What Cosmological Reconstruction Does and Does Not Imply

    astro-ph.CO 2026-05 unverdicted novelty 3.0

    Effective phantom dark energy is a background-level reconstruction that does not imply fundamental pathologies such as ghost instabilities or null energy condition violation by the underlying stress tensor.

  7. No evidence for phantom crossing: local goodness-of-fit improvements do not persist under global Bayesian model comparison

    astro-ph.CO 2026-05 unverdicted novelty 3.0

    Global Bayesian evidence shows no statistically significant support for dynamical dark energy or phantom crossing despite limited local fit improvements in the w0wa parametrization.

  8. No evidence for phantom crossing: local goodness-of-fit improvements do not persist under global Bayesian model comparison

    astro-ph.CO 2026-05 unverdicted novelty 3.0

    Local goodness-of-fit gains for w0wa and phantom crossing vanish under global Bayesian evidence, showing no statistically robust evidence for dynamical dark energy across datasets.