A $w-M$ phantom transition at $z_t<0.1$ as a resolution of the Hubble tension
George Alestas, Lavrentios Kazantzidis, Leandros Perivolaropoulos
备注：
14 pages, 9 Figures. Accepted in Physical Review D (to appear). Typos corrected, a new figure and references added. The Mathematica files used for the construction of the figures may be downloaded from https://github.com/GeorgeAlestas/LwMPT
A rapid phantom transition of the dark energy equation of state parameter $w$ at a transition redshift $z_t<0.1$ of the form $w(z)=-1+Δw\;Θ(z_t-z)$ with $Δw<0$ can lead to a higher value of the Hubble constant while closely mimicking a Planck18/$Λ$CDM form of the comoving distance $r(z)=\int_0^z\frac{dz'}{H(z')}$ for $z>z_t$. Such a transition however would imply a significantly lower value of the SnIa absolute magnitude $M$ than the value $M_C$ imposed by local Cepheid calibrators at $z<0.01$. Thus, in order to resolve the $H_0$ tension it would need to be accompanied by a similar transition in the value of the SnIa absolute magnitude $M$ as $M(z)=M_C+ΔM \;Θ(z-z_t)$ with $ΔM<0$. This is a Late $w-M$ phantom transition ($LwMPT$). It may be achieved by a sudden reduction of the value of the normalized effective Newton constant $μ=G_{\rm{eff}}/G_{\rm{N}}$ by about $6\%$ assuming that the absolute luminosity of SnIa is proportional to the Chandrasekhar mass which varies as $μ^{-3/2}$. We demonstrate that such an ultra low $z$ abrupt feature of $w-M$ provides a better fit to cosmological data compared to smooth late time deformations of $H(z)$ that also address the Hubble tension. For $z_t=0.02$ we find $Δw\simeq -4$, $ΔM \simeq -0.1$. This model also addresses the growth tension due to the predicted lower value of $μ$ at $z>z_t$. A prior of $Δw=0$ (no $w$ transition) can still resolve the $H_0$ tension with a larger amplitude $M$ transition with $ΔM\simeq -0.2$ at $z_t\simeq 0.01$. This implies a larger reduction of $μ$ for $z>0.01$ (about $12\%$). The $LwMPT$ can be generically induced by a scalar field non-minimally coupled to gravity with no need of a screening mechanism since in this model $μ=1$ at $z<0.01$.
We consider a model with two real scalar fields which admits phantom domain wall solutions. We investigate the structure and evolution of these phantom domain walls in an expanding homogeneous and isotropic universe. In particular, we show that the increase of the tension of the domain walls with cosmic time, associated to the evolution of the phantom scalar field, is responsible for an additional damping term in their equations of motion. We describe the macroscopic dynamics of phantom domain walls, showing that extended phantom defects whose tension varies on a cosmological timescale cannot …
Braneworld models with induced gravity exhibit phantom-like behaviour of the effective equation of state of dark energy. They can, therefore, naturally accommodate higher values of $H_0$, preferred by recent local measurements, while satisfying the CMB constraints. We test the background evolution in such phantom braneworld scenarios with the current observational datasets. We find that the phantom braneworld prefers a higher value of $H_0$ even without the R19 prior, thereby providing a much better fit to the local measurements. Although this braneworld model cannot fully satisfy all combinat…
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A Friendly Phantom: Late-time AdS-to-dS transition and cosmological tensions
Istanbul Technical University（伊斯坦布尔理工大学）；University of Ioannina（约阿尼纳大学）；Deutsches Zentrum für Astrophysik（德国天体物理中心）；Odessa National University（敖德萨国立大学）
Phantom dark energy as a natural selection of evolutionary processes $\hat{\rm a}$ $\textit{la}$ $\textit{genetic algorithm}$ and cosmological tensions
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University of Trento（特伦托大学）；Université de Montpellier（蒙彼利埃大学）；Trento Institute for Fundamental Physics and Applications (TIFPA)-INFN（特伦托基础物理与应用研究所（TIFPA）-意大利国家核物理研究所）
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Recently, a low-$z$ measurement of the Hubble constant, $H_0 = 73.04 \pm 1.04 {\rm ~km/s/Mpc}$, was reported by the SH0ES Team. The long-standing Hubble tension, i.e. the difference between the Hubble constant from the local measurements and that inferred from the cosmic microwave background data based on the $Λ$CDM model, was further strengthened. There are many cosmological models modifying the cosmology after and around the recombination era to alleviate this tension. In fact, some of the models alter the small-scale fluctuation amplitude relative to larger scales, and thus require a signif…
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It has very recently been claimed that the neutrino-assisted early dark energy model -- a promising resolution of the Hubble tension that can ameliorate the theoretical fine-tuning and coincidence problems that plague other theories -- does not provide natural or cosmologically interesting results. In this short paper, we show that these conclusions are incorrect for three reasons. First, we identify errors in the calculations. Second, we dispute the definition in of what constitutes an 'interesting' and 'natural' model. Finally, we demonstrate that the conclusions of were arrived at without f…
The value of Hubble constant inferred from Planck measurements of anisotropies in the cosmic microwave background is at $4.4σ$ tension with direct astronomical measurements at low redshifts. Very recently, it has been conjectured that this discrepancy may be reconciled if a small fraction of the dark matter is described by three mutually orthogonal vector fields of the same mass. We study the thermal description of this model and use the observationally-inferred primordial fractions of baryonic mass in $^4{\rm He}$ to constrain its phase space. We show that while the sterile vector fields may …
