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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2508.00621 |
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| _version_ | 1866918235222310912 |
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| author | Gómez-Valent, Adrià González-Fuentes, Alex |
| author_facet | Gómez-Valent, Adrià González-Fuentes, Alex |
| contents | Cosmic microwave background data from the {\it Planck} satellite, combined with baryon acoustic oscillation measurements from the Dark Energy Spectroscopic Instrument and Type Ia supernovae from various samples, provide hints of dynamical dark energy (DE). These results indicate a peak in the DE density around $z\sim 0.4-0.5$, with the highest significance observed when using the supernovae from the Dark Energy Survey. In this {\it Letter}, we show that this peak does not necessarily imply a true crossing of the phantom divide if the measured effective DE is not a single component, but a combination of standard and negative quintessence. The latter is characterized by negative energy density and positive pressure, both decreasing in absolute value and tending to 0 in the future. For appropriate values of the parameters, negative quintessence is relevant at intermediate redshifts and becomes subdominant in front of standard quintessence around $z\sim 0.4-0.5$, giving rise to the aforementioned peak in the DE density. We find that our model is preferred over $Λ$CDM at a $3.26σ$ CL, which is comparable to the level of exclusion found with the Chevallier-Polarski-Linder parametrization. Our analysis leaves open the possibility of negative quintessence and other exotic fields existing in the low-energy universe, potentially playing a significant role in cosmic dynamics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2508_00621 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Effective Phantom Divide Crossing with Standard and Negative Quintessence Gómez-Valent, Adrià González-Fuentes, Alex Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology Cosmic microwave background data from the {\it Planck} satellite, combined with baryon acoustic oscillation measurements from the Dark Energy Spectroscopic Instrument and Type Ia supernovae from various samples, provide hints of dynamical dark energy (DE). These results indicate a peak in the DE density around $z\sim 0.4-0.5$, with the highest significance observed when using the supernovae from the Dark Energy Survey. In this {\it Letter}, we show that this peak does not necessarily imply a true crossing of the phantom divide if the measured effective DE is not a single component, but a combination of standard and negative quintessence. The latter is characterized by negative energy density and positive pressure, both decreasing in absolute value and tending to 0 in the future. For appropriate values of the parameters, negative quintessence is relevant at intermediate redshifts and becomes subdominant in front of standard quintessence around $z\sim 0.4-0.5$, giving rise to the aforementioned peak in the DE density. We find that our model is preferred over $Λ$CDM at a $3.26σ$ CL, which is comparable to the level of exclusion found with the Chevallier-Polarski-Linder parametrization. Our analysis leaves open the possibility of negative quintessence and other exotic fields existing in the low-energy universe, potentially playing a significant role in cosmic dynamics. |
| title | Effective Phantom Divide Crossing with Standard and Negative Quintessence |
| topic | Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2508.00621 |