We compare the cosmological kinematics obtained via our law of linearly varying deceleration parameter (LVDP) with the kinematics obtained in the ΛCDM model. We show that the LVDP model is almost indistinguishable from the ΛCDM model up to the near future of our universe as far as the current observations are concerned, though their predictions differ tremendously into the far future.
A type of exponential correction to General Relativity gives viable modified gravity model of dark energy. The model behaves as $R-2Λ$ at large curvature where an effective cosmological constant appears, but it becomes zero in flat space time. The cosmic evolution of the main density parameters is consistent with current observations. The thin shell conditions for the Solar system were analyzed. Apart from satisfying cosmological and local gravity restrictions, the model may also show measurable differences with $Λ$CDM at recent times. The current value of the deviation parameter $m$ for scale…
Since physics of the dark sector components of the Universe is not yet well-understood, the phenomenological studies of non-minimal interaction in the dark sector could possibly pave the way to theoretical and experimental progress in this direction. Therefore, in this work, we intend to explore some features and consequences of a phenomenological interaction in the dark sector. We use the Planck 2018, BAO, JLA, KiDS and HST data to investigate two extensions of the base $Λ$CDM model, viz., (i) we allow the interaction among vacuum energy and dark matter, namely the I$Λ$CDM model, wherein the …
In this work, which follows a series of studies on the higher-dimensional steady state universe idea and prepared for Professor Tekin Dereli's Festschrift, we show the influence of the dynamical internal (unobservable) space on the evolution of the possible anisotropy of the external (observable) space. We obtain mathematically exactly the same Friedmann equation of the standard $Λ$CDM model for the external space, but with some remarkable physical differences. In particular, the higher-dimensional negative cosmological constant plays the role of the four-dimensional positive cosmological cons…
Using the tilted flat-$Λ$CDM and the untilted non-flat $Λ$CDM inflation models to measure cosmological parameters from a compilation of observational data
We study the performance of three pairs of tilted $Λ$CDM cosmological models, two pairs allowing for non-flat spatial hypersurfaces with CMB temperature and polarization power spectrum data (P18) from Planck, P18 lensing (lensing), and non-CMB data (non-CMB). For the six models, we measure cosmological parameters and study whether or not pairs of the data sets are mutually consistent in these models. Half of these models allow the lensing consistency parameter $A_L$ to be an additional free parameter, while the other three have $A_L = 1$. The tilted spatially-flat models assume the usual primo…
We present an analysis of the Brans-Dicke cosmological model with a cosmological constant and cold dark matter (BD-$Λ$CDM). We find that the BD-$Λ$CDM is favored by the overall cosmological data (SNIa+BAO+$H(z)$+LSS+CMB) when it is compared with the standard model of cosmology. The BD-$Λ$CDM model can be viewed from the GR perspective as a Running Vacuum Model (RVM) with a time evolving vacuum energy density. Due to this fact and also to its time evolving effective gravitational coupling, the model can alleviate the $σ_8$ and the $H_0$ tensions at a time. We also present the results for differ…
In this study, we investigate the effect of the generalized uncertainty principle on the $Λ$CDM cosmological model. Using quantum corrected Unruh effect and Verlinde's entropic gravity idea, we find Planck-scale corrected Friedmann equations with a cosmological constant. These results modify the $Λ$CDM cosmology.
Constraining neutrino mass and extra relativistic degrees of freedom in dynamical dark energy models using Planck 2015 data in combination with low-redshift cosmological probes: basic extensions to $Λ$CDM cosmology
Tightening Cosmological Constraints Within and Beyond $Λ$CDM Using Gamma-Ray Bursts Calibrated with Type Ia Supernovae
INAF - Osservatorio Astronomico di Capodimonte(意大利国家天体物理研究所卡波迪蒙特天文台);Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University(北京师范大学前沿天文与天体物理研究院);Department of Astronomy, Beijing Normal University(北京师范大学天文系);INAF - Osservatorio Astronomico di Padova(意大利国家天体物理研究所帕多瓦天文台);Università di Camerino(卡梅里诺大学);INAF - Osservatorio Astronomico di Brera(意大利国家天体物理研究所布雷拉天文台);Istituto Nazionale di Fisica Nucleare, Sezione di Perugia(意大利国家核物理研究所佩鲁贾分部);SUNY Polytechnic(纽约州立理工大学);Al-Farabi Kazakh National University(阿里-法拉比哈萨克国立大学);ICRANet(国际相对论天体物理中心网络)
$Λ(t)$CDM Model: Cosmological Implications and Dynamical System Analysis
Babeș-Bolyai University(博拜什·鲍约伊大学);Khazar University(阿塞拜疆哈萨克斯坦大学);Indian Institute of Engineering Science and Technology, Shibpur(印度工程科学与技术学院(希布尔));Indian Institute of Astrophysics(印度天体物理研究所);Pondicherry University(本地治里大学)
We present a full-fledged analysis of Brans-Dicke cosmology with a cosmological constant and cold dark matter (BD-$Λ$CDM for short). We extend the scenarios where the current cosmological value of the BD-field is restricted by the local astrophysical domain to scenarios where that value is fixed only by the cosmological observations, which should be more natural in view of the possible existence of local screening mechanims. Our analysis includes both the background and perturbations equations in different gauges. We find that the BD-$Λ$CDM is favored by the overall cosmological data as compar…
Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens(雅典国家天文台天文学、天体物理学、空间应用与遥感研究所);Departamento de Matemáticas, Universidad Católica del Norte(北天主教学院数学系);CAS Key Laboratory for Research in Galaxies and Cosmology, School of Astronomy and Space Science, University of Science and Technology of China(中国科学院星系与宇宙学重点实验室,中国科学技术大学天文与空间科学学院)
In view of the recent measurement of $H_{0}$ from HST and SH0ES team, we explore the possibility of existence of a negative cosmological constant (AdS vacua in the dark energy sector) in the Universe. In this regard, we consider quintessence fields on top of a negative cosmological constant and compare such construction with $Λ$CDM model using a different combination of CMB, SnIa, BAO and $H_{0}$ data. Various model comparison estimators show that quintessence models with a negative $Λ$ is either preferred over $Λ$CDM or performs equally as $Λ$CDM model. This suggests that the presence of a ne…
In the paper, we consider two models in which dark energy is coupled with either dust matter or dark matter, and discuss the conditions that allow more time for structure formation to take place at high redshifts. These models are expected to have a larger age of the universe than that of $Λ$CDM [universe consists of cold dark matter (CDM) and dark energy (a cosmological constant, $Λ$)], so it can explain the formation of high redshift gravitationally bound systems which the $Λ$CDM model cannot interpret. We use the observational Hubble parameter data (OHD) and Hubble parameter obtained from c…