Teplyakov, Alexander Sergeevich

Astashenok A.V., Tepliakov A.S.

Astashenok A.V., Baigashov A.S., Tepliakov A.S., Gusev K.P., Shamardina E.R.

Abstract We consider the important stage in evolution of close binary system namely common envelope phase in framework of various models of modified gravity. The comparison of results between calculations in Newtonian gravity and modified gravity allows to estimate possible observational imprints of modified gravity. Although declination from Newtonian gravity should be negligible we can propose that due to the long times some new effects can appear. We use the moving-mesh code AREPO for numerical simulation of binary system consisting of ∼ M ⊙ white dwarf and a red giant with mass ∼ 2M ⊙. For implementing modified gravity into AREPO code we apply the method of (pseudo)potential, assuming that modified gravity can be described by small corrections to usual Newtonian gravitational potential. As in Newtonian case initial orbit has to shrink due to the energy transfer to the envelope of a giant. We investigated evolution of common envelope in a case of simple model of modified gravity with various values of parameters and compared results with simulation in frames of Newtonian gravity.

Astashenok A.V., Tepliakov A.S.

We investigated evolution of metric and density perturbations for Tsallis model of holographic dark energy with energy density $\sim L^{2\gamma - 4}$, where $L$ is length of event horizon or inverse Hubble parameter and $\gamma$ is parameter of non-additivity close to $1$. Because holographic dark energy is not an ordinary cosmological fluid but a phenomena caused by boundaries of the universe, the ordinary analysis for perturbations is not suitable. One needs to consider perturbations of the future event horizon. For realistic values of parameters it was discovered that perturbations of dark energy don't grow infinitely but vanish or freeze. We also considered the case of realistic interaction between holographic dark energy and matter and showed that in this case perturbations also can asymptotically freeze with time.

Astashenok A.V., Tepliakov A.S.

The model of generalized Tsallis holographic dark energy (which is known to be particular representative of Nojiri–Odintsov HDE) with event horizon as cut-off is investigated using methods of dynamical analysis. We take into consideration possible interaction with dark energy and matter in various forms. Critical points are determined. Cosmological evolution of the universe depends from interaction parameters. If we use event horizon scale as cut-off quasi-de Sitter expansion is possible only for interaction of type [Formula: see text] (where [Formula: see text] is the Hubble parameter). For interactions [Formula: see text] and [Formula: see text] universe eventually stops ([Formula: see text]) or ends its existence in final singularity ([Formula: see text]). In the first case, fraction of dark energy tends to [Formula: see text] or constant value lesser than 1 because dynamical equilibrium between matter and dark energy is established on late times.

Astashenok A.V., Tepliakov A.S.

In this paper, we considered the Tsallis holographic dark energy model in frames of Nojiri–Odintsov gravity with [Formula: see text]. For IR, cutoff event horizon is taken. The cosmological evolution of such universe is investigated for various initial conditions and values of parameters. The dependence of the Hubble parameter [Formula: see text] from time in the future has an oscillation. It is shown that for [Formula: see text] appearance of singularities are typical and the time up to these singularities can be relatively small from cosmological viewpoint. The singularity is associated with the zero of second derivative of [Formula: see text] on [Formula: see text]. It is interesting to note that these models can describe observational data from Ia supernovae astrophysics and dependence of the Hubble parameter from redshift [Formula: see text] at least not worse than canonical [Formula: see text]CDM model.

Baigashov A.S., Nikitin M.A., Tepliakov A.S.

The possibility of correcting the trajectory of kilometer-long chondrite asteroids threatening the Earth with the help of nuclear explosions in near-Earth and distant outer space is assessed. It is shown that to put such asteroids on a safe trajectory requires nuclear explosions with a power of more than 100 Mt at distances of more than 100 million km from the Earth. It is also shown that at the found power it is impossible to preserve the integrity of kilometer-long asteroids because of their fragmentation. The latter circumstance makes the task of correcting the trajectories of such asteroids using nuclear explosions difficult to achieve because of the difficulties in predicting the trajectories of the fragments formed.

Astashenok A.V., Tepliakov A.

We consider a Tsallis holographic dark energy model with interaction between dark energy and matter. The density of dark energy is taken as ρd∼3C2/L4−2γ, where C, γ are constants. The event horizon is chosen as the characteristic scale L. The cosmological dynamics of the universe are analyzed, with special attention paid to the possibility of crossing the phantom line weff=−1. It is shown that for certain values of parameters this may occur not only once, but also twice.

Astashenok A.V., Odintsov S.D., Tepliakov A.S.

We propose the unified description of the early acceleration (cosmological inflation) and the present epoch of so called "dark energy". The inflation can be described by cosmic fluid with van der Waals equation of state and with viscosity term. Viscosity leads to slow-roll inflation with the parameters such as the spectral index, and the tensor-to-scalar ratio in concordance with observational data. Our next step is to modify this equation of state (EoS) to describe the present accelerated expansion. One can add the term into EoS so that the contribution of which is small for inflation but crucial for late-time acceleration. The key point of the model is possible phase transition which leads to decrease of the viscosity. We show that proposed model describes observational data about standard "candles" and correct dependence of Hubble parameter from redshift. Moreover, we propose the possible scenario to resolve dark matter problem.

Astashenok A.V., Tepliakov A.S.

Some models of holographic dark energy for Randall–Sundrum brane are considered. For the first class of dark energy models, we take energy density in the form [Formula: see text], where [Formula: see text] is size of event horizon in universe and [Formula: see text] is parameter (Tsallis holographic energy). Analysis of observational data allows to define upper limit on value of [Formula: see text] ([Formula: see text] is current energy density in the universe and [Formula: see text] is brane tension). Then we investigate models for which dark energy density has the form [Formula: see text] where [Formula: see text] is Hubble parameter.

Astashenok A.V., Tepliakov A.S.

Saleem R., Rasool M.H., Aslam M.I., Shahid I.

Abstract This manuscript aims to study cosmic warm inflation (WI) in the framework of - gravity, where Q represents the nonmetricity (NM) scalar. To accomplish this task, we introduce the Tsallis, Renyi, and Barrow holographic dark energy (HDE) entropies into the standard Friedmann equations. Utilizing the slow-roll (SR) approximation, we find exact analytic solutions for the inflaton field, the effective potential necessary to produce inflation, and the scale factor for both low- and high-dissipative regimes. We calculate key parameters, including SR parameters, the number of e-folds, the scalar spectral index and its running, and finally tensor-to-scalar ratio to assess the accuracy of the chosen DE models in light of the published observational data. The allowed ranges of the involved free parameters are found from the limits on inflationary observables imposed by the Planck data. It is concluded that the obtained results are consistent with proposed theoretical predictions up to the confidence level.

Solanki R., Bhat A., Sahoo P.K.

Chokyi K.K., Chattopadhyay S., Tawfik A.N.

Abstract Within the framework of the Saez-Ballester theory, the Barrow Holographic Dark Energy (BHDE) has been reconstructed. This reconstruction was carried out in a homogeneous and anisotropic KS universe that was filled with BHDE. The study examined both non-interacting and interacting scenarios, with the future event horizon serving as the IR cut-off. The analysis focused on the evolution of the equation of State parameter for both cases, as well as the trajectories of w DE − w ′ DE . Additionally, the study investigated the inflation of the Universe filled with BHDE by plotting the slow-roll parameters. Furthermore, a connection between the canonical scalar field and BHDE was explored, as the presence of a scalar field is often associated with inflation. Finally, the tensor-to-scalar ratio r is plotted which seems to lie within the acceptable range.

Tyagi U.K., Haridasu S., Basak S.

Kundu R., Debnath U., Pradhan A.

Abstract The work explores the dynamics of a spherically symmetric perturbation of viscous modified Chaplygin gas (VMCG) in different gravity theories within the spherical top hat collapse framework (SC-TH). The study investigates the behaviour of perturbed quantities such as the δ, θ, w, w c , c s 2, c e 2, and h using numerical and graphical analysis. Our findings reveal that VMCG generates quintessential dark energy without crossing over to the phantom barrier in most of the gravity models considered here. Further, in all the gravity models considered here, VMCG remained classically stable. This research offers new insights into the evolution of VMCG in different gravitational contexts. In this paper, we have examined the collapse of viscous modified Chaplygin gas in the context of (i) Einstein’s gravity, (ii) Loop quantum cosmology, (iii) generalised Rastall gravity, and (iv) the fractal universe. We have also addressed their comparative analysis.

Rana D.S., Solanki R., Sahoo P.K.

AbstractIn this work, a power law model is explored, specifically, , along with viscous matter fluid having transport coefficient . The corresponding analytical solution is derived and then confronted with recent cosmic data. The Markov Chain Monte Carlo (MCMC) sampling technique is utilized to estimate the mean value of arbitrary parameters, by incorporating Cosmic Chronometers and recently published Pantheon+Analysis samples. In addition, some cosmological parameters are reconstructed by resampling the chains obtained by emcee, incorporating 6000 samples. It is found that the matter‐energy density depicts the expected positive behavior, whereas the effective pressure indicates the negative behavior that is leading the accelerating expansion, which is further predicted in the effective EoS parameter. Further, the asymptotic nature of the assumed model is investigated by invoking phase‐space analysis. It is concluded that the assumed viscous model successfully predicts an evolution of the universe from decelerated epoch to stable accelerated de‐Sitter epoch.

BAO C., LI Z., GAO Y., WANG J.

近地小行星防御问题研究意义深远,不仅涉及到地球生态系统稳定与物种多样性保护,更与人类文明安危直接相关。动能撞击是对近地小行星进行防御的一种有效方案,大部分现有研究主要集中于从地球表面发射防御卫星进行小行星拦截。本文关注天基防御方案,即在地球高轨道有针对性地部署防御卫星,以对潜在威胁地球的近地小行星实施紧急动能撞击。基于此方案,本文深入探讨不同轨道特性对防御系统的有效防御范围的影响。以防御卫星轨控发动机的最大变轨能力为约束,通过求解二体模型中的Lambert问题,探究卫星轨道的不同半长轴、偏心率和倾角对防御范围的影响。研究结果发现,卫星轨道的有效防御范围会随着半长轴的增大而扩大,偏心率增加则会导致防御范围缩小,而轨道倾角的增大初始会使防御范围减小,随后逐渐增大,并在倾角达到90°时触达最小值。本研究致力于全面理解天基防御系统的性能特点,并提出优化防御卫星轨道配置的有效建议,旨在进一步提高近地小行星紧急防御的整体效能。

Astashenok A.V., Tepliakov A.S.

We investigated evolution of metric and density perturbations for Tsallis model of holographic dark energy with energy density $\sim L^{2\gamma - 4}$, where $L$ is length of event horizon or inverse Hubble parameter and $\gamma$ is parameter of non-additivity close to $1$. Because holographic dark energy is not an ordinary cosmological fluid but a phenomena caused by boundaries of the universe, the ordinary analysis for perturbations is not suitable. One needs to consider perturbations of the future event horizon. For realistic values of parameters it was discovered that perturbations of dark energy don't grow infinitely but vanish or freeze. We also considered the case of realistic interaction between holographic dark energy and matter and showed that in this case perturbations also can asymptotically freeze with time.

Paliathanasis A.

We explore the impact of the chameleon mechanism in scalar field Einstein–Gauss–Bonnet gravity on the dynamics of cosmological parameters. Conducting a thorough analysis of the phase space, we identify conditions under which the future attractor does not depict a singular universe. Our conclusion is that although Einstein–Gauss–Bonnet scalar field gravity offers an inflationary solution as a future attractor, it is unable to account for the late-time acceleration of the universe and it can not describe a universe similar to that provide by the $$\Lambda $$ CDM model. On the other hand, when the matter source is described by a massless scalar field, then the de Sitter universe is a future attractor. However, the hyperbolic inflationary solution provided by the two scalar fields does not exist.

Rana D.S., Sahoo P.K.

In this study, we explore the accelerated expansion of the universe within the framework of modified f(Q) gravity. The investigation focus on the role of bulk viscosity in understanding the universe’s accelerated expansion. Specifically, a bulk viscous matter-dominated cosmological model is considered, with the bulk viscosity coefficient expressed as $$\zeta = \zeta _0 \rho H^{-1} + \zeta _1 H $$ . We consider the power law f(Q) function $$f(Q)=\alpha Q^n $$ , where $$\alpha $$ and n are arbitrary constants and derive the analytical solutions for the field equations corresponding to a flat FLRW metric. Subsequently, we used the combined Cosmic Chronometers (CC)+Pantheon+SH0ES sample to estimate the free parameters of the obtained analytic solution. We conduct Bayesian statistical analysis to estimate the posterior probability by employing the likelihood function and the MCMC random sampling technique, along with the AIC and BIC statistical assessment criteria. In addition, we explore the evolutionary behavior of significant cosmological parameters. The effective equation of state (EOS) parameter predicts the accelerating behavior of the cosmic expansion phase. Further, by the statefinder and Om(z) diagnostic test, we found that our viscous model favors quintessence-type behavior and can successfully describe the late-time scenario.

Bekkhozhayev S., Zhadyranova A., Zhumabekova V.

In modified gravity theories, such as f(Q,T) gravity, the concept of dark energy arises from alterations to the gravitational field equations, often manifesting as purely geometrical effects. This perspective opens up intriguing possibilities, suggesting that a universe undergoing cosmic acceleration could be explained by a bulk viscous fluid coupled with a modified gravity theory. In this paper, we introduce a model describing the LRS Bianchi type-I spacetime filled with a viscous fluid within the framework of f(Q,T) gravity. By assuming that the universe is dominated by non-relativistic viscous matter, we derive an exact solution to the field equations for the Hubble parameter H(z) as a function of redshift z. We assess the viability of the proposed f(Q,T) model by fitting it to observational datasets and explore several key physical properties of our cosmological model, including the deceleration parameter, jerk parameter, anisotropy parameter, and Om(z) diagnostics. For the present-day values of the parameters, we obtain: zt=0.80−0.003+0.004, q0=−0.45±0.01, j0=0.63±0.12, and Δ=0.38±0.09 at the 1−σ confidence level. In addition, our findings indicate that our f(Q,T) model, dominated by bulk viscous dark energy, displays quintessence-like behavior according to the Om(z) diagnostic, with a negative slope across all redshift values. We conclude that our study contributes to a deeper understanding of cosmic dynamics and the role of viscosity in cosmological models.

Asghari M., Allahyari A., Mota D.F.

Abstract We study the Barrow cosmological model, which proposes that quantum gravity effects create a complex, fractal structure for the universe's apparent horizon. We leverage the thermodynamics-gravity conjecture. By applying the Clausius relation to the apparent horizon of the Friedmann-Lemaître-Robertson-Walker universe within this framework, we derive modified field equations where the Barrow entropy is linked to the horizon. We assess the Barrow cosmology against current observations — cosmic microwave background, supernovae, and baryon acoustic oscillations data — and include projections for future Laser Interferometer Space Antenna (LISA) standard sirens (SS). Our numerical results suggest a modest improvement in the Hubble tension for Barrow cosmology with phantom dark energy behavior, compared to the standard cosmological model. Furthermore, incorporating simulated LISA SS data alongside existing observational constraints tightens the limitations on cosmological parameters, particularly the deformation exponent.

Rana D.S., Solanki R., Sahoo P.K.

In this article, we consider a newly proposed parameterization of the viscosity coefficient ζ, specifically ζ=ζ̄0ΩmsH, where ζ̄0=ζ0Ωm0s within the coincident f(Q) gravity formalism. We consider a non-linear function f(Q)=−Q+αQn, where α and n are arbitrary model parameters, which is a power-law correction to the STEGR scenario. We find an autonomous system by invoking the dimensionless density parameters as the governing phase-space variables. We discuss the physical significance of the model corresponding to the parameter choices n=−1 and n=2 along with the exponent choices s=0,0.5, and 1.05. We find that model I shows the stable de-Sitter type or stable phantom type (depending on the choice of exponent s) behavior with no transition epoch, whereas model II shows the evolutionary phase from the radiation epoch to the accelerated de-Sitter epoch via passing through the matter-dominated epoch. Hence, we conclude that model I provides a good description of the late-time cosmology but fails to describe the transition epoch, whereas model II modifies the description in the context of the early universe and provides a good description of the matter and radiation era along with the transition phase.

Chanda A., Mitra A.K., Dey S., Ghose S., Paul B.C.

Abstract Cosmological features of barrow holographic dark energy (BHDE), a recent generalization of original Holographic dark energy (DE) with a richer structure, are studied in the context of Dvali–Gabadadze–Porrati (DGP) brane, Randall and Sundrum (RS II) brane-world, and the cyclic Universe. It is found that a flat FRW scenario with pressure less dust and a DE component described as BHDE can accommodate late time acceleration with Hubble horizon considered as infrared cut off even in the absence of interaction between the dark sectors. Statefinder diagnostic reveals that these model resemble Λ C D M cosmology in future. It is found that BHDE parameter Δ, despite its theoretically constrained range of values, is significant in describing the evolution of the Universe, however, a classically stable cosmological model cannot be obtained in the RS-II and DGP brane. Viability of the models is also probed with observed Hubble data.

Mendoza-Martínez M.L., Cervantes-Contreras A., Trejo-Alonso J.J., Hernandez-Almada A.

AbstractRecently Tsallis cosmology has been presented as a novel proposal for alleviating both $$H_0$$ H 0 and $$\sigma _8$$ σ 8 tensions. Hence a universe filled with matter and radiation as perfect fluids and considering the Tsallis entropy is confronted using recent cosmological measurements coming from cosmic chronometers, type Ia supernovae, hydrogen II galaxies, quasars, and baryon acoustic oscillations. Following a Bayesian Markov Chain Monte Carlo analysis and combining the samples, we constrain the main characteristic parameters $$\alpha = 1.031^{+0.054}_{-0.051}$$ α = 1 . 031 - 0.051 + 0.054 and $$\delta = 1.005^{+0.001}_{-0.001}$$ δ = 1 . 005 - 0.001 + 0.001 where the uncertainties are $$1\sigma $$ 1 σ confidence level. Additionally, we estimate the current deceleration parameter $$q_0=-0.530^{+0.018}_{-0.017}$$ q 0 = - 0 . 530 - 0.017 + 0.018 , the deceleration-acceleration transition redshift $$z_T=0.632^{+0.028}_{-0.028}$$ z T = 0 . 632 - 0.028 + 0.028 and the age of the universe $$\tau _U = 12.637^{+0.067}_{-0.066}\,\textrm{Gyrs}$$ τ U = 12 . 637 - 0.066 + 0.067 Gyrs which are in agreement with the standard cosmology ($$\Lambda $$ Λ CDM) within $$1.5\sigma $$ 1.5 σ . Furthermore, we find that the dark energy equation of state is consistent with both phantom and quintessence behaviors within $$1\sigma $$ 1 σ in the past and converging to $$\Lambda $$ Λ CDM in the future. Additionally, we find agreement values of $$H_0$$ H 0 within $$1\sigma $$ 1 σ with the SH0ES values when the CMB distance priors are added to the analysis, suggesting that $$H_0$$ H 0 tension could be alleviated. Finally, Tsallis cosmology is preferred over $$\Lambda $$ Λ CDM by the combined data that motives further studies at the perturbation level.

Asghari M., Allahyari A., Mota D.F.

Abstract We study the Barrow cosmological model, which proposes that quantum gravity effects create a complex, fractal structure for the universe's apparent horizon. We leverage the thermodynamics-gravity conjecture. By applying the Clausius relation to the apparent horizon of the Friedmann-Lemaître-Robertson-Walker universe within this framework, we derive modified field equations where the Barrow entropy is linked to the horizon. We assess the Barrow cosmology against current observations — cosmic microwave background, supernovae, and baryon acoustic oscillations data — and include projections for future Laser Interferometer Space Antenna (LISA) standard sirens (SS). Our numerical results suggest a modest improvement in the Hubble tension for Barrow cosmology with phantom dark energy behavior, compared to the standard cosmological model. Furthermore, incorporating simulated LISA SS data alongside existing observational constraints tightens the limitations on cosmological parameters, particularly the deformation exponent.

Basilakos S., Lymperis A., Petronikolou M., Saridakis E.N.

AbstractWe present how Tsallis cosmology can alleviate both $$H_0$$ H 0 and $$\sigma _8$$ σ 8 tensions simultaneously. Such a modified cosmological scenario is obtained by the application of the gravity-thermodynamics conjecture, but using the non-additive Tsallis entropy, instead of the standard Bekenstein–Hawking one. Hence, one obtains modified Friedmann equations, with extra terms that depend on the new Tsallis exponent $$\delta $$ δ that quantifies the departure from standard entropy. We show that for particular $$\delta $$ δ choices we can obtain a phantom effective dark energy, which is known to be one of the sufficient mechanisms that can alleviate $$H_0$$ H 0 tension. Additionally, for the same parameter choice we obtain an increased friction term and an effective Newton’s constant smaller than the usual one, and thus the $$\sigma _8$$ σ 8 tension is also solved. These features act as a significant advantage of Tsallis modified cosmology.

Rom B., Sari R., Lai D.

Abstract Many stellar-mass black holes (sBHs) are expected to orbit supermassive black holes at galactic centers. For galaxies with active galactic nuclei, it is likely that the sBHs reside in a disk. We study the formation of sBH binaries via gravitational-wave emission in such disks. We examine analytically the dynamics of two sBHs orbiting a supermassive black hole, estimate the capture cross section, and derive the eccentricity distribution of bound binaries at different frequency bands. We find that the majority of the merging sBH binaries, assembled in this manner, can be measured as highly eccentric, detectable in the LIGO-Virgo-KAGRA (LVK) band from their formation, with (1 − e) ≪ 1, through their circularization and up to their merger; the remaining binaries circularize to small eccentricities (e ≲ 0.3) before entering the LVK band. More eccentric mergers would be observed for sBHs with higher random velocities, closer to the supermassive black hole, or at lower observing frequency bands, as planned in future gravitational-wave detectors such as the Einstein Telescope and LISA.

Tomasetti E., Moresco M., Borghi N., Jiao K., Cimatti A., Pozzetti L., Carnall A.C., McLure R.J., Pentericci L.

Aims. We aim to derive a new constraint on the expansion history of the Universe by applying the cosmic chronometers method in the VANDELS survey, studying the age evolution of high-redshift galaxies with a full-spectral-fitting approach. Methods. We selected a sample of 39 massive (log(M⋆/M⊙) > 10.8) and passive (log(sSFR/yr−1) < −11) galaxies from the fourth data release of the VANDELS survey at 1 < z < 1.5. To minimise the potential contamination by star-forming outliers, we selected our sample by combining different selection criteria, considering both photometric and spectroscopic information. The analysis of the observed spectral features provides direct evidence of an age evolution with redshift and of mass-downsizing, with more massive galaxies presenting stronger age-related features. To estimate the physical properties of the sample, we performed full spectral fitting with the code BAGPIPES, jointly analysing spectra and photometry of our sources without any cosmological assumption regarding the age of the population. Results. The derived physical properties of the selected galaxies are characteristic of a passive population, with short star formation timescales (⟨τ⟩ = 0.28 ± 0.02 Gyr), low dust extinction (⟨AV, dust⟩ = 0.43 ± 0.02 mag), and sub-solar metallicities (⟨Z/Z⊙⟩ = 0.44 ± 0.01) compatible with other measurements of similar galaxies in this redshift range. The stellar ages, even if no cosmological constraint is assumed in the fit, show a decreasing trend compatible with a standard cosmological model, proving the robustness of the method in measuring the ageing of the population. Moreover, they show a distinctive mass-downsizing pattern, with more massive galaxies (⟨log(M⋆/M⊙)⟩ = 11.4) being older than less massive ones (⟨log(M⋆/M⊙)⟩ = 11.15) by ∼0.8 Gyr. We thoroughly tested the dependence of our results on the assumed SFH, finding a maximum 2% fluctuation on median results using models with significantly different functional forms. The derived ages are combined to build a median age–redshift relation, which we used to perform our cosmological analysis. Conclusions. By fitting the median age–redshift relation with a flat ΛCDM model, assuming a Gaussian prior on ΩM, 0 = 0.3 ± 0.02 from late-Universe cosmological probes, we obtain a new estimate of the Hubble constant H0 = 67−15+14 km s−1 Mpc−1. In the end, we derive a new estimate of the Hubble parameter by applying the cosmic chronometers method to this sample, deriving a value of H(z = 1.26) = 135 ± 65 km s−1 Mpc−1 considering both statistical and systematic errors. While the error budget in this analysis is dominated by the scarcity of the sample, this work demonstrates the potential strength of the cosmic chronometers approach up to z > 1, especially in view of the next incoming large spectroscopic surveys such as Euclid.

Jiao K., Borghi N., Moresco M., Zhang T.

Abstract In this work, we perform a full-spectrum fitting of 350 massive and passive galaxies selected as cosmic chronometers from the LEGA-C ESO public survey to derive their stellar ages, metallicities, and star formation histories. We extensively test our results by assessing their dependence on the possible contribution of dust, calibration of noise and signal, and use of photometric data in addition to spectral information; we also identify indicators of the correct convergence of the results, including the shape of the posterior distributions, the analysis of specific spectral features, and the correct reproduction of the observed spectrum. We derive a clear age–redshift trend compatible with the aging in a standard cosmological model showing a clear downsizing pattern, with more massive galaxies being formed at higher redshift (z f ∼ 2.5) with respect to less massive ones (z f ∼ 2). From these data, we measure the differential aging of this population of cosmic chronometers to derive a new measurement of the Hubble parameter, obtaining H ( z = 0.8 ) = 113.1 ± 15.1 ( stat . ) − 11.3 + 29.1 ( syst . ) . This analysis allows us to compare for the first time the differential ages of cosmic chronometers measured on the same sample with two completely different methods, the full-spectrum fit (this work) and the analysis of Lick indices, known to correlate with the age and metallicity of the stellar populations. Albeit an understood offset in the absolute ages, the differential ages have proven to be extremely compatible between the two methods, despite the very different data, assumptions, and models considered, demonstrating the robustness of the method.

Moresco M., Amati L., Amendola L., Birrer S., Blakeslee J.P., Cantiello M., Cimatti A., Darling J., Della Valle M., Fishbach M., Grillo C., Hamaus N., Holz D., Izzo L., Jimenez R., et. al.

AbstractThe detection of the accelerated expansion of the Universe has been one of the major breakthroughs in modern cosmology. Several cosmological probes (Cosmic Microwave Background, Supernovae Type Ia, Baryon Acoustic Oscillations) have been studied in depth to better understand the nature of the mechanism driving this acceleration, and they are being currently pushed to their limits, obtaining remarkable constraints that allowed us to shape the standard cosmological model. In parallel to that, however, the percent precision achieved has recently revealed apparent tensions between measurements obtained from different methods. These are either indicating some unaccounted systematic effects, or are pointing toward new physics. Following the development of CMB, SNe, and BAO cosmology, it is critical to extend our selection of cosmological probes. Novel probes can be exploited to validate results, control or mitigate systematic effects, and, most importantly, to increase the accuracy and robustness of our results. This review is meant to provide a state-of-art benchmark of the latest advances in emerging “beyond-standard” cosmological probes. We present how several different methods can become a key resource for observational cosmology. In particular, we review cosmic chronometers, quasars, gamma-ray bursts, standard sirens, lensing time-delay with galaxies and clusters, cosmic voids, neutral hydrogen intensity mapping, surface brightness fluctuations, stellar ages of the oldest objects, secular redshift drift, and clustering of standard candles. The review describes the method, systematics, and results of each probe in a homogeneous way, giving the reader a clear picture of the available innovative methods that have been introduced in recent years and how to apply them. The review also discusses the potential synergies and complementarities between the various probes, exploring how they will contribute to the future of modern cosmology.

Scolnic D., Brout D., Carr A., Riess A.G., Davis T.M., Dwomoh A., Jones D.O., Ali N., Charvu P., Chen R., Peterson E.R., Popovic B., Rose B.M., Wood C.M., Brown P.J., et. al.

Abstract Here we present 1701 light curves of 1550 unique, spectroscopically confirmed Type Ia supernovae (SNe Ia) that will be used to infer cosmological parameters as part of the Pantheon+ SN analysis and the Supernovae and H 0 for the Equation of State of dark energy distance-ladder analysis. This effort is one part of a series of works that perform an extensive review of redshifts, peculiar velocities, photometric calibration, and intrinsic-scatter models of SNe Ia. The total number of light curves, which are compiled across 18 different surveys, is a significant increase from the first Pantheon analysis (1048 SNe), particularly at low redshift (z). Furthermore, unlike in the Pantheon analysis, we include light curves for SNe with z < 0.01 such that SN systematic covariance can be included in a joint measurement of the Hubble constant (H 0) and the dark energy equation-of-state parameter (w). We use the large sample to compare properties of 151 SNe Ia observed by multiple surveys and 12 pairs/triplets of “SN siblings”—SNe found in the same host galaxy. Distance measurements, application of bias corrections, and inference of cosmological parameters are discussed in the companion paper by Brout et al., and the determination of H 0 is discussed by Riess et al. These analyses will measure w with ∼3% precision and H 0 with ∼1 km s−1 Mpc−1 precision.

Brout D., Scolnic D., Popovic B., Riess A.G., Carr A., Zuntz J., Kessler R., Davis T.M., Hinton S., Jones D., Kenworthy W.D., Peterson E.R., Said K., Taylor G., Ali N., et. al.

Abstract We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from z = 0.001 to 2.26. This work features an increased sample size from the addition of multiple cross-calibrated photometric systems of SNe covering an increased redshift span, and improved treatments of systematic uncertainties in comparison to the original Pantheon analysis, which together result in a factor of 2 improvement in cosmological constraining power. For a flat ΛCDM model, we find Ω M = 0.334 ± 0.018 from SNe Ia alone. For a flat w 0CDM model, we measure w 0 = −0.90 ± 0.14 from SNe Ia alone, H 0 = 73.5 ± 1.1 km s−1 Mpc−1 when including the Cepheid host distances and covariance (SH0ES), and w 0 = − 0.978 − 0.031 + 0.024 when combining the SN likelihood with Planck constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both w 0 values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a flat w 0 w a CDM universe, and measure w a = − 0.1 − 2.0 + 0.9 from Pantheon+ SNe Ia alone, H 0 = 73.3 ± 1.1 km s−1 Mpc−1 when including SH0ES Cepheid distances, and w a = − 0.65 − 0.32 + 0.28 when combining Pantheon+ SNe Ia with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one-third of the total uncertainty in the measurement of H 0 and cannot explain the present “Hubble tension” between local measurements and early universe predictions from the cosmological model.

Astashenok A.V., Tepliakov A.

We consider a Tsallis holographic dark energy model with interaction between dark energy and matter. The density of dark energy is taken as ρd∼3C2/L4−2γ, where C, γ are constants. The event horizon is chosen as the characteristic scale L. The cosmological dynamics of the universe are analyzed, with special attention paid to the possibility of crossing the phantom line weff=−1. It is shown that for certain values of parameters this may occur not only once, but also twice.

Borghi N., Moresco M., Cimatti A.

Abstract We analyze the stellar ages obtained from a combination of Lick indices in Borghi et al. for 140 massive and passive galaxies selected in the LEGA-C survey at 0.6 < z < 0.9. From their median age–redshift relation, we derive a new direct measurement of H(z) without any cosmological model assumption using the cosmic chronometer approach. We thoroughly study the main systematics involved in this analysis: the choice of the Lick indices combination, the binning method, the assumed stellar population model, and the adopted star formation history; these effects are included in the total error budget. We obtain H(z = 0.75) = 98.8 ± 33.6 km s−1 Mpc−1. In parallel, we also propose a simple framework based on a cosmological model to describe the age–redshift relations in the context of galaxy downsizing. This allows us to derive constraints on the Hubble constant H 0 and the typical galaxy formation time. This new H(z) measurement, whose accuracy is currently limited by the scarcity of the sample analyzed, paves the road for the joint study of the stellar populations of individual passive galaxies and the expansion history of the universe in light of future spectroscopic surveys.

Nojiri S., Odintsov S.D., Paul T.

The holographic cut-off, in the formalism of generalized holographic dark energy (HDE), is generalized to depend on LIR=LIR(Lp,L˙p,L¨p,⋯,Lf,L˙f,⋯,a), where Lp and Lf are the particle horizon and future horizon respectively, and a is the scale factor of the universe. Based on such formalism, we showed that the Barrow entropic dark energy (DE) model is equivalent to the generalized HDE where the respective holographic cut-off is determined by two ways – (1) in terms of particle horizon and its derivative and (2) in terms of future horizon and its derivative. Interestingly, such cut-off turns out to depend up-to first order derivative of Lp or Lf respectively. Such equivalence between the Barrow entropic dark energy and the generalized HDE is extended to the scenario where the exponent of the Barrow entropy allows to vary with the cosmological expansion of the universe. In both the cases (whether the Barrow exponent is a constant or varies with the cosmological evolution), we determine effective equation of state (EoS) parameter from the generalized holographic point of view, which, by comparing with the Barrow DE EoS parameter, further ensures the equivalence between the Barrow entropic dark energy and the generalized HDE.

Nojiri S., Odintsov S.D., Paul T.

In the formalism of generalized holographic dark energy (HDE), the holographic cut-off is generalized to depend upon LIR=LIRLp,L˙p,L¨p,⋯,Lf,L˙f,⋯,a with Lp and Lf being the particle horizon and the future horizon, respectively (moreover, a is the scale factor of the Universe). Based on such formalism, in the present paper, we show that a wide class of dark energy (DE) models can be regarded as different candidates for the generalized HDE family, with respective cut-offs. This can be thought as a symmetry between the generalized HDE and different DE models. In this regard, we considered several entropic dark energy models—such as the Tsallis entropic DE, the Rényi entropic DE, and the Sharma–Mittal entropic DE—and found that they are indeed equivalent with the generalized HDE. Such equivalence between the entropic DE and the generalized HDE is extended to the scenario where the respective exponents of the entropy functions are allowed to vary with the expansion of the Universe. Besides the entropic DE models, the correspondence with the generalized HDE was also established for the quintessence and for the Ricci DE model. In all the above cases, the effective equation of state (EoS) parameter corresponding to the holographic energy density was determined, by which the equivalence of various DE models with the respective generalized HDE models was further confirmed. The equivalent holographic cut-offs were determined by two ways: (1) in terms of the particle horizon and its derivatives, (2) in terms of the future horizon horizon and its derivatives.

da Silva W.J., Silva R.

We investigate the Tsallis holographic dark energy (THDE) models in the context of perturbations’ growth. We assume the description of dark energy by considering the holographic principle and the nonadditive entropy to carry out this. We implement the perturbed relativistic equations to achieve the growth of matter fluctuations, being the growth rate of the cosmic structures is non-negligible at low redshifts. To constrain and compare the models, we carry out the Bayesian analysis using the recent geometrical and growth rate observational data. The main results are: (i) the models are compatible with cosmological observations, (ii) the cosmological constant recovered with a $$1\sigma $$ confidence level, furthermore (iii) they could cross the phantom barrier. Finally, the models can relieve $$\approx 1\sigma $$ the $$\sigma _8$$ tension in the non-clustered case and can alleviate in $$\approx 2.8\sigma $$ the $$H_0$$ tension. From the model selection viewpoint, the data discarded the THDE models.

Glanville A., Howlett C., Davis T.M.

ABSTRACT With the remarkable increase in scale and precision provided by upcoming galaxy redshift surveys, systematic errors that were previously negligible may become significant. In this paper, we explore the potential impact of low-magnitude systematic redshift offsets on measurements of the Baryon Acoustic Oscillation (BAO) feature, and the cosmological constraints recovered from such measurements. Using 500 mock galaxy redshift surveys as our baseline sample, we inject a series of systematic redshift biases (ranging from $\pm 0.2{{\ \rm per\ cent}}$ to $\pm 2{{\ \rm per\ cent}}$), and measure the resulting shift in the recovered isotropic BAO scale. When BAO measurements are combined with CMB constraints across a range of cosmological models, plausible systematics introduce a negligible offset on combined fits of H0 and Ωm, and systematics must be an order of magnitude greater than this plausible baseline to introduce a 1σ shift on such combined fits. We conclude that systematic redshift biases are very unlikely to bias constraints on parameters such as H0 provided by BAO cosmology, either now or in the near future. We also detail a theoretical model that predicts the impact of uniform redshift systematics on α, and show this model is in close alignment with the results of our mock survey analysis.