We model the nonlinear growth of cosmic structure in different dark energy models, using large volume N-body simulations. We consider a range of quintessence models which feature both rapidly and slowly varying dark energy equations of state, and compare the growth of structure to that in a universe with a cosmological constant. The adoption of a quintessence model changes the expansion history of the universe, the form of the linear theory power spectrum and can alter key observables, such as the horizon scale and the distance to last scattering. The difference in structure formation can be explained to first order by the difference in growth factor at a given epoch; this scaling also accounts for the nonlinear growth at the 15% level. We find that quintessence models which feature late $(z<2)$, rapid transitions towards $w=-1$ in the equation of state, can have identical baryonic acoustic oscillation (BAO) peak positions to those in $Λ$CDM, despite being very different from $Λ$CDM both today and at high redshifts $(z \sim 1000)$. We find that a second class of models which feature non-negligible amounts of dark energy at early times cannot be distinguished from $Λ$CDM using measurements of the mass function or the BAO. These results highlight the need to accurately model quintessence dark energy in N-body simulations when testing cosmological probes of dynamical dark energy.
In this work we investigate the possibility of constraining a thawing Quintessence scalar field model for dark energy. We propose using the imprint of baryon acoustic oscillation (BAO) on the cross-correlation of post-reionization 21-cm signal and galaxy weak lensing convergence field to tomographically measure the angular diameter distance $D_A(z)$ and the Hubble parameter $H(z)$. The projected errors in these quantities are then used to constrain the Quintessence model parameters. We find that independent $600$hrs radio interferometric observation at four observing frequencies $916 $MHz, $65…
We investigate the effects of the nonminimal coupling between the scalar field dark energy (quintessence) and the dark matter on the two- point correlation function. It is well known that this coupling shifts the turnover scale as well as suppresses the amplitude of the matter power spectrum. However, these effects are too small to be observed when we limit the coupling strength to be consistent with observations. Since the coupling of quintessence to baryons is strongly constrained, species dependent coupling may arise. This results in a baryon bias that is dif- ferent from unity. Thus, we lo…
Euclid is a future space-based mission that will constrain dark energy with unprecedented accuracy. Its photometric component is optimized for Weak Lensing studies, while the spectroscopic component is designed for Baryon Acoustic Oscillations (BAO) analysis. We use the Fisher matrix formalism to make forecasts on two quintessence dark energy models with a dynamical equation of state that leads to late-time oscillations in the expansion rate of the Universe. We find that Weak Lensing will place much stronger constraints than the BAO, being able to discriminate between oscillating models by mea…
From the analysis of Supernova Ia data alongwith Observational Hubble Data (OHD) and Baryon Acoustic Oscillation (BAO) data, we attempt to find out the nature of a scalar potential that may be responsible for the Dark Energy of the universe. We demonstrate that in order to explain the varying dark energy equation of state ($ω_X(z)$) as obtained in a model independent way from the analyses of observational data, we need to invoke a quintom scalar field having a "quintessence" part for $ω_X(z) > -1$ and a "phantom" part for $ω_X(z) < -1$. We consider a Gaussian type potential for these scalar fi…
Phantom-Crossing Dark Energy and the $Ω_m$ Tug-of-War
Princeton University（普林斯顿大学）；Laboratoire univers et particules de Montpellier (LUPM), Centre national de la recherche scientifique (CNRS) et Université de Montpellier（蒙彼利埃大学与法国国家科学研究中心联合宇宙与粒子物理实验室）
We study the nonlinear growth of cosmic structure in different dark energy models, using large volume N-body simulations. We consider a range of quintessence models which feature both rapidly and slowly varying dark energy equations of state, and compare the growth of structure to that in a universe with a cosmological constant. The adoption of a quintessence model changes the expansion history of the universe, the form of the linear theory power spectrum and can alter key observables, such as the horizon scale and the distance to last scattering. We incorporate these effects into our simulati…
Resolving the Planck-DESI tension by nonminimally coupled quintessence
Institute of Theoretical Physics, Chinese Academy of Sciences (CAS)（中国科学院理论物理研究所）；University of Chinese Academy of Sciences (UCAS)（中国科学院大学）；Institute of Fundamental Physics and Quantum Technology, Ningbo University（宁波大学基础物理与量子技术学院）；School of Fundamental Physics and Mathematical Sciences, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences（中国科学院大学杭州高等研究院基础物理与数学科学学院）；Asia Pacific Center for Theoretical Physics (APCTP)（亚太理论物理中心）
We discuss some cosmological consequences of a general model of coupled quintessence in which the phenomenological coupling between the cold dark matter and dark energy is a function of the cosmic scale factor $ε(a)$. This class of models presents cosmological solutions in which the Universe is currently dominated by an exotic component, but will eventually be dominated by cold dark matter in the future. This dynamical behavior is considerably different from the standard $Λ$CDM evolution, and may alleviate some conflicts in reconciling the idea of the dark energy-dominated universe with observ…
Dynamical dark energy has been recently suggested as a promising and physical way to solve the 3.4 sigma tension on the value of the Hubble constant $H_0$ between the direct measurement of Riess et al. (2016) (R16, hereafter) and the indirect constraint from Cosmic Microwave Anisotropies obtained by the Planck satellite under the assumption of a $Λ$CDM model. In this paper, by parameterizing dark energy evolution using the $w_0$-$w_a$ approach, and considering a $12$ parameter extended scenario, we find that: a) the tension on the Hubble constant can indeed be solved with dynamical dark energy…
We study the nonlinear effects of the clustering and smooth quintessence. We present numerical and also approximate semi-analytical expressions of nonlinear power spectrum both for clustering and smooth dark energy models beyond the Baryon Acoustic Oscillations (BAO) scale. This approximation is motivated by the extension of the resummation method of Anselmi $\&$ Pietroni (J Cosmol Astro-Part Phys 12:13, 2012. \url{arXiv:1205.2235}) for the dark energy models with evolving equation of state. The results of this scheme allow us for the prediction of the nonlinear power spectrum in the mildly no…
In this work we propose a simple general parametrization scheme of the Hubble parameter for the scalar field dark energy models. In our approach it is possible to incorporate both the quintessence and phantom scalar field in a single analytical scheme and write down relevant cosmological parameters which are independent of the nature of the scalar field. A general condition for the phantom barrier crossing has also been obtained. To test this approach, a well behaved parametrization of the normalized Hubble parameter has been considered and a wide variety of observational data like CMB data, S…
We present a detailed and pedagogical analysis of recent cosmological data, including CMB, BAO, SnIa and the recent local measurement of $H_0$. We thus obtain constraints on the parameters of standard dark energy parameterizations, including $ΛCDM$, and $H(z)$ deformation models such as $wCDM$ (constant equation of state $w$ of dark energy), and the CPL model (corresponding to the evolving dark energy equation-of-state parameter $w(z) = w_0 + w_a \frac{z}{1+z}$). The fitted parameters include the dark matter density $Ω_{0m}$, the SnIa absolute magnitude $M$, the Hubble constant $H_0$ and the d…
Inspired by the string axiverse idea, it has been suggested that the recent transition from decelerated to accelerated cosmic expansion is driven by an axion-like quintessence field with a sub-Planckian decay constant. The scenario requires that the axion field be rather near the maximum of its potential, but is less finely tuned than other explanations of cosmic acceleration. The model is parametrized by an axion decay constant $f$, the axion mass $m$, and an initial misalignment angle $|θ_i|$ which is close to $π$. In order to determine the $m$ and $θ_{i}$ values consistent with observations…
We consider a quintessence model for dark energy interacting with dark matter via a Yukawa interaction. To put constraints on this model we use the CMB measurements from the Planck satellite together with BAO, SNIa and $H_0$ data. We conclude that this is a viable model and an appropriate scalar potential can favor the interacting scenario.
In order to test if there is energy transfer between dark energy and dark matter, we investigate cosmological constraints on two forms of nontrivial interaction between the dark matter sector and the sector responsible for the acceleration of the universe, in light of the newly revised observations including OHD, CMB, BAO and SNe Ia. More precisely, we find the same tendencies for both phenomenological forms of the interaction term $Q=3γHρ$, i.e., the parameter $γ$ to be a small number, $|γ|\approx 10^{-2}$. However, concerning the sign of the interaction parameter, we observe that $γ>0$ when …
Recently we proposed a new approach to the testing of dark energy models based on the observational data. In that work we focused particularly on quintessence models for demonstration and invoked a widely used parametrization of the dark energy equation of state. In this paper we take the more recent SN Ia, CMB and BAO data, invoke the same parametrization, and apply this method of consistency test to five categories of dark energy models, including the LCDM model, the generalized Chaplygin gas, and three quintessence models: exponential, power-law and inverse-exponential potentials. We find t…
We present a parametrization for the Dark Energy Equation of State "EoS" which has a rich structure. Our EoS has a transition at pivotal redshift $z_T$ between the present day value $w_0$ to an early time $w_i=w_a+w_0\equiv w(z>>0)$ and the steepness of this transition is given in terms of the $q$ parameter. The proposed parametrization is $w=w_0+w_a(z/z_T)^q/(1+(z/z_T))^q$, with $w_0$, $w_i$, $q $ and $z_T$ constant parameters. This transition is motivated by scalar field dynamics such as for example quintessence models. Our parametrization reduces to the widely used EoS $w=w_0+w_a(1-a)$ for …
We put forward a pressure-parametric model to study the tiny deviation from cosmological constant(CC) behavior of the dark sector accelerating the expansion of the Universe. Data from cosmic microwave background (CMB) anisotropies, baryonic acoustic oscillations (BAO), Type Ia supernovae (SN Ia) observation are applied to constrict the model parameters. The constraint results show that such model suffers with $H_0$ tension as well. To realize this model more physically, we reconstruct it with the quintessence and phantom scalar fields, and find out that although the model predicts a quintessen…
Reconstruction of the Quintessence Scalar Field Potential Using Gaussian Processes
Mohammed I University（穆罕默德一世大学）；Higher School of Education and Training, Mohammed I University（穆罕默德一世大学教育与培训高等学院）；Department of Physics and Astronomy, University of California, Irvine（加州大学尔湾分校物理与天文学系）；Korea Astronomy and Space Science Institute（韩国天文与空间科学研究所）
We present a general model-independent approach to study the coupled dark energy and the string Swampland criteria. We show how the dark sector interaction is degenerated with the equation of state of dark energy in the context of the expansion of the Universe. With priors for either of them, the dynamics of dark energy and the dark sector interactions can be reconstructed together with the bounds of the Swampland criteria. Combining cosmic chronometers, baryon acoustic oscillation (BAO), and Type Ia supernovae our results suggest a mild $1 σ$ significance of dark sector interactions at low re…
We study the possibility of explaining the late time acceleration with an axion field which is coupled with the dark matter sector of the energy budget of the Universe. The axion field arises from the Ramond-Ramond sector of the Type-IIB string theory. We study the background evolution of the Universe as well as the growth of the matter perturbation in the linear regime. We subsequently use the observational data from Sn-Ia, BAO measurements, measurements of the Hubble parameter as well as the observational data for the growth of the matter perturbation to constrain our model. Our results show…
We study the observational constraints for the axion models in string theory which can successfully act as quintessence. The evolution of the universe in this model is sensitive to the initial value of the axion field. This initial value of the axion field controls deviation of the cosmic evolution from the ΛCDM behaviour. We use the recent Union2 Supernova Type Ia dataset as well as the data from BAO measurements, the WMAP measurement of the shift parameter and the $H(z)$ measurements. Using these data, the reconstructed equation of state of the axion field has extremely small deviation from …
We look at observational constraints on the thawing class of scalar field models proposed to explain the late time acceleration of the universe. Using the recently introduced `Statefinder Hierarchy', we compare these thawing class of models with other widely studied dark energy (and modified gravity) models to check the underlying parameter degeneracies. We put constraints on the deviations of these thawing models from the canonical ΛCDM model using a large class of observational data, e.g, the Supernova Type Ia data, the BAO data, the CMB data and data from the measurements of the Hubble para…
Classification of dark energy models in the plane of w and w', where w is the dark energy equation of state and w' its time-derivative in units of the Hubble time, has been studied in the literature. We take the current SN Ia, CMB and BAO data, invoke a widely used parametrization of the dark energy equation of state, and obtain the constraints on the w -w' plane. We find that dark energy models including the cosmological constant, phantom, non-phantom barotropic fluids, and monotonic up-rolling quintessence are ruled out at the 68.3% confidence level based on the current observational data. D…
We confront two types of phantom dark energy potential with observational data. The models we consider are the power-law potential, $V\propto ϕ^μ$, and the exponential potential, $V\propto \exp(λϕ/{M_P})$. We fit the models to the latest observations from SN-Ia, CMB and BAO, and obtain tight constraints on parameter spaces. Furthermore, we apply the goodness-of-fit and the information criteria to compare the fitting results from phantom models with that from the cosmological constant and the quintessence models presented in our previous work. The results show that the cosmological constant is …
We investigate the potential of large X-ray-selected AGN samples for detecting baryonic acoustic oscillations (BAO). Though AGN selection in X-ray band is very clean and efficient, it does not provide redshift information, and thus needs to be complemented with an optical follow-up. The main focus of this study is (i) to find the requirements needed for the quality of the optical follow-up and (ii) to formulate the optimal strategy of the X-ray survey, in order to detect the BAO. We demonstrate that redshift accuracy of $σ_0=10^{-2}$ at $z=1$ and the catastrophic failure rate of $f_{\rm fail}\…
We use the HII galaxies $L - σ$ relation and the resulting Hubble expansion cosmological probe of a sample of just 25 high-$z$ (up to $z \sim 2.33$) HII galaxies, in a joint likelihood analysis with other well tested cosmological probes (CMB, BAOs) in an attempt to constrain the dark energy equation of state (EoS). The constraints, although still weak, are in excellent agreement with those of a similar joint analysis using the well established SNIa Hubble expansion probe. Interestingly, even with the current small number of available high redshift HII galaxies, the HII/BAO/CMB joint analysis g…
Updated Constraints on Omnipotent Dark Energy: A Comprehensive Analysis with CMB and BAO Data
University of Sheffield（谢菲尔德大学）；UNAM（墨西哥国立自治大学）；Universidade Federal do Rio Grande do Sul（南里奥格兰德联邦大学）；Instituto Nacional de Pesquisas Espaciais（巴西国家空间研究所）；Istanbul Technical University（伊斯坦布尔理工大学）；Jamia Millia Islamia（贾米亚米里亚伊斯兰大学）
A New Window on Dynamical Dark Energy: Combining DESI-DR2 BAO with future Gravitational Wave Observations
Observatório Nacional（巴西国家天文台）；Presidency University（总统大学）；Institute of Systems Science, Durban University of Technology（德班理工大学系统科学研究所）；Liaoning Normal University（辽宁师范大学）；University of Sheffield（谢菲尔德大学）
Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK)（高能加速器研究机构粒子核研究所在）；The Graduate University for Advanced Studies (SOKENDAI)（综合研究大学院大学）；Department of Physics, College of Humanities and Sciences, Nihon University（日本大学文理学部物理学科）；Center for Gravitational Physics and Quantum Information, Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理研究所引力物理与量子信息研究中心）；Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University（名古屋大学小林-益川粒子宇宙起源研究所）
Recent re-calibration of the Type Ia supernova (SNe~Ia) magnitude-redshift relation combined with cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) data have provided excellent constraints on the standard cosmological model. Here, we examine particular classes of alternative cosmologies, motivated by various physical mechanisms, e.g. scalar fields, modified gravity and phase transitions to test their consistency with observations of SNe~Ia and the ratio of the angular diameter distances from the CMB and BAO. Using a model selection criterion for a relative comparison of t…
Local $H_0$ determinations currently fall in a window between $H_0 \sim 70$ km/s/Mpc (TRGB) and $H_0 \sim 76$ km/s/Mpc (Tully-Fisher). In contrast, BAO data calibrated in an early $Λ$CDM universe are largely consistent with Planck-$Λ$CDM, $H_0 \sim 67.5$ km/s/Mpc. Employing a generic two parameter family of evolving equations of state (EoS) for dark energy (DE) $w_{\textrm{DE}}(z)$ and mock BAO data, we demonstrate that if i) $w_{\textrm{DE}}(z=0) < -1$ and ii) integrated DE density less than $Λ$CDM, then $H_0$ increases. EoS that violate these conditions at best lead to modest $H_0$ increases…
Density-Shear Baryon Acoustic Oscillation as a Cosmological Consistency Check
School of Physics and Astronomy, Sun Yat-Sen University（中山大学物理学院）；CSST Science Center for the Guangdong-Hongkong-Macau Greater Bay Area, SYSU（粤港澳大湾区嫦娥探月科学中心，中山大学）；Department of Strategic & Advanced Interdisciplinary Research, Peng Cheng Laboratory（鹏城实验室战略与先进交叉研究部）；Department of Astrophysical Sciences, Princeton University（普林斯顿大学天体物理学系）
Institute for Astronomy, University of Edinburgh（爱丁堡大学天体物理研究所）；Higgs Centre for Theoretical Physics, School of Physics and Astronomy, The University of Edinburgh（爱丁堡大学物理与天文学院希格斯理论物理中心）
We apply the $Om$ diagnostic to models for dark energy based on scalar fields. In case of the power law potentials, we demonstrate the possibility of slowing down the expansion of the Universe around the present epoch for a specific range in the parameter space. For these models, we also examine the issues concerning the age of Universe. We use the $Om$ diagnostic to distinguish the $Λ$CDM model from non minimally coupled scalar field, phantom field and generic quintessence models. Our study shows that the $Om$ has zero, positive and negative curvatures for $Λ$CDM, phantom and quintessence mod…
