اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدMinimally Modified Gravity fitting Planck data better than $Lambda$CDM
128
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We study the phenomenology of a class of minimally modified gravity theories called $f(mathcal{H})$ theories, in which the usual general relativistic Hamiltonian constraint is replaced by a free function of it. After reviewing the construction of the theory and a consistent matter coupling, we analyze the dynamics of cosmology at the levels of both background and perturbations, and present a concrete example of the theory with a $3$-parameter family of the function $f$. Finally, we compare this example model to Planck data as well as some later-time probes, showing that such a realization of $f(mathcal{H})$ theories fits the data significantly better than the standard $Lambda$CDM model, in particular by modifying gravity at intermediate redshifts, $zsimeq743$.
قيم البحث
اقرأ أيضاً
We propose a new cosmological framework in which the strength of the gravitational force acted on dark matter at late time can be weaker than that on the standard matter fields without introducing extra gravitational degrees of freedom. The framework
integrates dark matter into a type-II minimally modified gravity that was recently proposed as a dark energy mimicker. The idea that makes such a framework possible consists of coupling a dark matter Lagrangian and a cosmological constant to the metric in a canonically transformed frame of general relativity (GR). On imposing a gauge fixing constraint, which explicitly breaks the temporal diffeomorphism invariance, we keep the number of gravitational degrees of freedom to be two, as in GR. We then make the inverse canonical transformation to bring the theory back to the original frame, where one can add the standard matter fields. This framework contains two free functions of time which specify the generating functional of the above mentioned canonical transformation and which are then used in order to realize desired time evolutions of both the Hubble expansion rate $H(z)$ and the effective gravitational constant for dark matter $G_{rm eff}(z)$. The aim of this paper is therefore to provide a new framework to address the two puzzles present in todays cosmology, i.e. the $H_0$ tension and the $S_8$ tension, simultaneously. When the dark matter is cold in this framework, we dub the corresponding cosmological model the V Canonical Cold Dark Matter (VCCDM), as the cosmological constant $Lambda$ in the standard $Lambda$CDM is replaced by a function $V(phi)$ of an auxiliary field $phi$ and the CDM is minimally coupled to the metric in a canonically transformed frame.
We study observational constraints on the non-metricity $f(Q)$-gravity which reproduces an exact $Lambda$CDM background expansion history while modifying the evolution of linear perturbations. To this purpose we use Cosmic Microwave Background (CMB)
radiation, baryonic acoustic oscillations (BAO), redshift-space distortions (RSD), supernovae type Ia (SNIa), galaxy clustering (GC) and weak gravitational lensing (WL) measurements. We set stringent constraints on the parameter of the model controlling the modifications to the gravitational interaction at linear perturbation level. We find the model to be statistically preferred by data over the $Lambda$CDM according to the $chi^2$ and deviance information criterion statistics for the combination with CMB, BAO, RSD and SNIa. This is mostly associated to a better fit to the low-$ell$ tail of CMB temperature anisotropies.
We study Planck 2015 cosmic microwave background (CMB) anisotropy data using the energy density inhomogeneity power spectrum generated by quantum fluctuations during an early epoch of inflation in the non-flat $Lambda$CDM model. Unlike earlier analys
es of non-flat models, which assumed an inconsistent power-law power spectrum of energy density inhomogeneities, we find that the Planck 2015 data alone, and also in conjunction with baryon acoustic oscillation measurements, are reasonably well fit by a closed $Lambda$CDM model in which spatial curvature contributes a few percent of the current cosmological energy density budget. In this model, the measured Hubble constant and non-relativistic matter density parameter are in good agreement with values determined using most other data. Depending on parameter values, the closed $Lambda$CDM model has reduced power, relative to the tilted, spatially-flat $Lambda$CDM case, and can partially alleviate the low multipole CMB temperature anisotropy deficit and can help partially reconcile the CMB anisotropy and weak lensing $sigma_8$ constraints, at the expense of somewhat worsening the fit to higher multipole CMB temperature anisotropy data. Our results are interesting but tentative; a more thorough analysis is needed to properly gauge their significance.
We investigate the $H_0$ tension in a range of extended model frameworks beyond the standard $Lambda$CDM without the data from cosmic microwave background (CMB). Specifically, we adopt the data from baryon acoustic oscillation, big bang nucleosynthes
is and type Ia supernovae as indirect measurements of $H_0$ to study the tension. We show that the estimated value of $H_0$ from indirect measurements is overall lower than that from direct local ones regardless of the data sets and a range of extended models to be analyzed, which indicates that, although the significance of the tension varies depending on models, the $H_0$ tension persists in a broad framework beyond the standard $Lambda$CDM model even without CMB data.
A modification of the action of the general relativity produces a different pattern for the growth of the cosmic structures below a certain length-scale leaving an imprint on the cosmic microwave background (CMB) anisotropies. We re-examine the upper
limits on the length-scale parameter B0 of f (R) models using the recent data from the Planck satellite experiment. We also investigate the combined constraints obtained when including the Hubble Space Telescope H0 measurement and the baryon acoustic oscillations measurements from the SDSS, WiggleZ and BOSS surveys.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
