Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1008.4421

New mechanism to cross the phantom divide

Yunshuang Du·Hongsheng Zhang·Xin-Zhou Li
View original source ↗Read source document ↗Export metadata ↓

Abstract

Recently, type Ia supernovae data appear to support a dark energy whose equation of state $w$ crosses -1, which is a much more amazing problem than the acceleration of the universe. We show that it is possible for the equation of state to cross the phantom divide by a scalar field in the gravity with an additional inverse power-law term of Ricci scalar in the Lagrangian. The necessary and sufficient condition for a universe in which the dark energy can cross the phantom divide is obtained. Some analytical solutions with $w<-1$ or $w>-1$ are obtained. A minimal coupled scalar with different potentials, including quadratic, cubic, quantic, exponential and logarithmic potentials are investigated via numerical methods, respectively. All these potentials lead to the crossing behavior. We show that it is a robust result which is hardly dependent on the concrete form of the potential of the scalar.

Explore related subjects

astro-ph.COgr-qchep-phhep-th

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Yunshuang Du, Hongsheng Zhang, Xin-Zhou Li. 2011-07-01. New mechanism to cross the phantom divide. https://doi.org/10.1140/epjc%2Fs10052-011-1660-z

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

DESI-Like Hubble Expansion From Staged Symmetry Breaking: Constraints on Renormalizable Models

The Dark Energy Spectroscopic Instrument (DESI) second data release shows a moderate preference for dark energy with a time-varying equation of state parameter, suggesting that the standard $Λ$CDM model may need to be revised. In particular, DESI favors dark energy whose equation of state parameter can drop below $-1$, violating the null energy condition. Chen and Loeb have recently suggested that this violation may be avoided if a subcomponent of the dark matter possesses a time-dependent equation of state. In this work, we explore the space of possible models, in an effort to find a natural, renormalizable realization. We find that once one requires the model to be renormalizable, a construction that generates the desired expansion history is fairly broadly obstructed. While we are unable to produce a fully natural, renormalizable realization of their ideas, this work is valuable for constraining directions one might pursue for viable theoretical explanations of the DESI results. Our framework is also interesting for incorporating features that may be of interest for model building elsewhere, as our decay cascades enable decays that switch on at particular redshifts while also naturally incorporating a self-interacting dark matter candidate with a velocity-dependent cross section as a consequence of gauge invariance. The second feature is relevant for addressing tensions between $Λ$CDM and observations of small-scale structure, particularly the diversity of galactic rotation curves.

astro-ph.CO↗
arXiv2026

Partial Relief of the Hubble Tension and a Natural Self-Interacting Dark Matter Candidate From Staged Symmetry Breaking

The values of the Hubble constant ($\rm{H_0}$) inferred from the cosmic microwave background (CMB) and local measurements via the distance ladder exhibit a $\sim5σ$ tension. In this work we propose that the tension might be partially alleviated if a subcomponent of the dark matter undergoes decays triggered by spontaneous symmetry breaking in the dark sector, where dark energy couples to the daughter species, but not the parent. This then allows interactions between dark matter and dark energy to turn on at a particular redshift, which can reduce fifth-force constraints, since early time interactions are absent. We provide an example of such an effective field theory whose structure is partially motivated by the desire for a plausible UV completion. We find that such a construction can naturally incorporate a possible self-interacting dark matter candidate with a velocity-dependent scattering cross section as a by-product of gauge invariance, though this is not necessary for alleviating the Hubble tension. This is relevant for addressing tensions between $Λ$CDM and small-scale structure, such as the core-cusp problem.

astro-ph.CO↗
arXiv2026

Turbulent Transport of Galactic Magnetic Fields into Cosmic Voids: Insights from IllustrisTNG

Astrophysical processes associated with galaxies may contribute to the magnetization of cosmic voids. We investigate the diffusion of galactic magnetic fields in an expanding universe in the presence of turbulent magnetic diffusivity. To estimate the turbulent magnetic diffusivity, we analyze the TNG50-1 data set of the IllustrisTNG simulation and derive its redshift dependence from the characteristic turbulent velocity and turbulent scale of the intergalactic medium. Using the resulting diffusivity, we find a present-day magnetic screening length of $\sim 7\,{\rm Mpc}$, roughly twenty times larger than previous estimates based on a constant turbulent diffusivity due to the larger turbulent scale obtained in our analysis. This scale corresponds to a significant fraction of the characteristic size of cosmic voids and suggests that galactic magnetic fields can play a more important role in void magnetization than previously estimated.

astro-ph.CO↗