Late-time Data Research Articles

Interacting models of dark energy and dark matter in Einstein scalar Gauss Bonnet gravity

We study the dynamics of the interacting models between the Gauss-Bonnet (GB) coupled scalar field and the dark matter fluid in a homogeneous and isotropic background. A key feature of GB coupling models is the varying speed of gravitational waves (GWs). We utilize recent constraints on the GW speed and conduct our analysis in two primary scenarios: model-dependent and model-independent. In the model-dependent scenario, where determining the GW speed requires a specific GB coupling functional form, we choose an exponential GB coupling. We adopt a dynamical system analysis to obtain the necessary constraints on the model parameters that describe different phases of the universe and produce a stable late-time accelerating solution following the GW constraint, and find that to satisfy all these constraints, fine-tuning of the free parameters involved in the models is often needed. In the model-independent scenario, the GW speed is fixed to one, and we construct the autonomous system to identify the late-time stable accelerating critical points. Furthermore, we adopt a Bayesian inference method using late-time observational data sets, including 31 data points from cosmic chronometer data (Hubble data) and 1701 data points from Pantheon+ and find that all the observational constraints can be satisfied without fine-tuning. In addition, we also utilize simulated binned Roman and LSST data to study the evolution of the universe in the model-independent scenario. We find that the model shows significant deviation at higher redshifts from ΛCDM and fits the current data much better than ΛCDM within the error bars.

Holographic and gravity-thermodynamic approaches in entropic cosmology: Bayesian assessment using late-time data

Holographic and gravity-thermodynamic approaches in entropic cosmology: Bayesian assessment using late-time data

[formula omitted]-Cosmological Boundary Flux Parameter

Efforts to explain the current accelerated expansion of the universe have prompted the investigation of different scenarios characterised by dark energy models. In this study, we explore an extended ωCBFP model, incorporating two commonly used parameterisations of ω(z) in terms of the redshift z: ω(z)=ω0 and ω(z)=ω0+ω1z/(1+z). In this context, the cosmological parameter Λ is directly linked to the dark matter component through a barotropic framework, where Λ acts as the source of ρcdm, characterised by a dimensionless constant λ, and directly dependent on Λω(z)CDM, which is fully defined by a specific ω(z) functional form. Through a statistical analysis, using late-time data of observational Hubble and type Ia Supernovae, we computed the joint best-fit value of the free parameters by means of the affine-invariant MCMC. On the one hand, the ω0CBFP instance shows an unexpected larger Ω0cdm contribution than the current Ω0Λ. Remarkably this outcome has not been previously reported (to our knowledge). On the other hand, in the ω0ω1CBFP example the dark energy component makes up nearly 60% of the total matter-energy at z=0, compared to just 36% for the cold dark matter contribution. This last result aligns more with the conventional ΛCDM model. In both instances there are unusual increases in Ωcdm(z) around z=1; however, these rises are offset by a decrease in Ωb(z).

Searching for late-time interaction signatures in Type Ia supernovae from the Zwicky Transient Facility

The nature of the progenitor systems and explosion mechanisms that give rise to Type Ia supernovae (SNe Ia) are still debated. The interaction signature of circumstellar material (CSM) being swept up by the expanding ejecta can constrain the type of system from which it was ejected. However, most previous studies have focussed on finding CSM ejected shortly before the SN Ia explosion, which still resides close to the explosion site resulting in short delay times until the interaction starts. We used a sample of 3\,627 SNe Ia from the Zwicky Transient Facility (ZTF) that were discovered between 2018 and 2020 and searched for interaction signatures greater than 100 days after peak brightness. By binning the late-time light curve data to push the detection limit as deep as possible, we identified potential late-time rebrightening in three SNe Ia (SN 2018grt, SN 2019dlf, and SN 2020tfc). The late-time optical detections occur between 550 and 1450\,d after peak brightness, have mean absolute r -band magnitudes of $-$16.4 to $-$16.8 mag, and last up to a few hundred days, which is significantly brighter than the late-time CSM interaction discovered in the prototype, SN 2015cp. The late-time detections in the three objects all occur within 0.8 kpc of the host nucleus and are not easily explained by nuclear activity, another transient at a similar sky position, or data quality issues. This is suggestive of environment or specific progenitor characteristics playing a role in the production of potential CSM signatures in these SNe Ia. Through simulating the ZTF survey, we estimate that $<$0.5 per cent of normal SNe Ia display a late-time ($>100$ d post peak) strong CSM interaction. This is equivalent to an absolute rate of $ to $54_ $ Gpc$^ $ yr$^ $ assuming a constant SN Ia rate of $2.4 $ Mpc$^ $ yr$^ $ for $z 0.1$. Weaker interaction signatures of emission, more similar to the strength seen in SN 2015cp, could be more common but are difficult to constrain with our survey depth.

What Powered the Kilonova-like Emission after GRB 230307A in the Framework of a Neutron Star–White Dwarf Merger?

The second brightest gamma-ray burst, GRB 230307A (with a duration T 90 ∼ 40 s), exhibited characteristics indicative of a magnetar engine during the prompt emission phase. Notably, a suspected kilonova was identified in its follow-up optical and infrared observations. Here we propose that the origin of GRB 230307A is a neutron star–white dwarf (NS–WD) merger as this could naturally explain the long duration and the large physical offset from the center of its host galaxy. In the framework of such an NS–WD merger event, the late-time kilonova-like emission is very likely to be powered by the spin-down of the magnetar and the radioactive decay of 56Ni, rather than by the decay of r-process elements as these heavy elements may not easily be synthesized in an NS-WD merger. It is demonstrated that the above scenario can be supported by our fit to the late-time observational data, where a mass of ∼10−3 M ⊙ 56Ni is involved in the ejecta of a mass of ∼0.1 M ⊙. Particularly, the magnetar parameters required by the fit are consistent with those derived from the early X-ray observation.

Beyond [formula omitted]CDM with [formula omitted]CDM: Criticalities and solutions of Padé Cosmography

Recently, cosmography emerged as a valuable tool to effectively describe the vast amount of astrophysical observations without relying on a specific cosmological model. Its model-independent nature ensures a faithful representation of data, free from theoretical biases. Indeed, the commonly assumed fiducial model, the ΛCDM, shows some shortcomings and tensions between data at late and early times that need to be further investigated. In this paper, we explore an extension of the standard cosmological model by adopting the f(z)CDM approach, where f(z) represents the cosmographic series characterizing the evolution of recent universe driven by dark energy. To construct f(z), we take into account the Padé series, since this rational polynomial approximation offers a better convergence at high redshifts than the standard Taylor series expansion. Several orders of such an approximant have been proposed in previous works, here we want to answer the questions: What is the impact of the cosmographic series choice on the parameter constraints? Which series is the best for the analysis? So, we analyze the most promising ones by identifying which order is preferred in terms of stability and goodness of fit. Theoretical predictions of the f(z)CDM model are obtained by the Boltzmann solver code and the posterior distributions of the cosmological and cosmographic parameters are constrained by a Monte Carlo Markov Chains analysis. We consider a joint data set of cosmic microwave background temperature measurements from the Planck collaboration, type Ia supernovae data from the latest Pantheon+ sample, baryonic acoustic oscillations and cosmic chronometers data. In conclusions, we state which series can be used when only late time data are used, while which orders has to be considered in order to achieve the necessary stability when large redshifts are considered.

Corrections to general relativity with higher-order invariants and cosmological applications

In this paper, we review the main features of modified theories of gravity containing higher-order curvature invariants in the action. After summarizing the main features of these theories, we consider their applications to cosmology, pointing out the differences with respect to general relativity that can eventually solve issues exhibited by the latter at low and high energy scales. Specifically, we explore a gravitational action that incorporates both the Ricci scalar [Formula: see text] and the topological Gauss–Bonnet term, denoted as [Formula: see text]. Our investigation revolves around the cosmological properties of a specific category of modified gravity theories, chosen upon symmetry considerations. Within the framework of a spatially flat, homogeneous and isotropic cosmic background, we demonstrate that it is possible to account for the presently observed acceleration of the Universe by means of the extra geometric terms carried by the selected [Formula: see text] model. This approach offers a way to address the issues associated with the cosmological constant. To achieve this, we first examine the energy conditions and find that, under certain choices for the values of the cosmographic parameters, these conditions are all violated. In the second part of the work, to assess the feasibility of the selected [Formula: see text] model, we place observational constraints on its free parameters through a Bayesian Monte Carlo technique applied to late-time cosmic data. Our findings reveal that the [Formula: see text] model can effectively reproduce observations at low redshifts, providing an alternative to the standard [Formula: see text]CDM scenario.

MAGIC detection of GRB 201216C atz = 1.1

ABSTRACTGamma-ray bursts (GRBs) are explosive transient events occurring at cosmological distances, releasing a large amount of energy as electromagnetic radiation over several energy bands. We report the detection of the long GRB 201216C by the MAGIC telescopes. The source is located at z = 1.1 and thus it is the farthest one detected at very high energies. The emission above 70 GeV of GRB 201216C is modelled together with multiwavelength data within a synchrotron and synchrotron self-Compton (SSC) scenario. We find that SSC can explain the broad-band data well from the optical to the very-high-energy band. For the late-time radio data, a different component is needed to account for the observed emission. Differently from previous GRBs detected in the very-high-energy range, the model for GRB 201216C strongly favours a wind-like medium. The model parameters have values similar to those found in past studies of the afterglows of GRBs detected up to GeV energies.

Proton Synchrotron Origin of the Very-high-energy Emission of GRB 190114C

We consider here a proton-synchrotron model to explain the MAGIC observation of GRB 190114C afterglow in the energy band of 0.2–1 TeV, while the X-ray spectra are explained by electron-synchrotron emission. Given the uncertainty of the particle acceleration process, we consider several variations of the model, and show that they all match the data very well. We find that the values of the uncertain model parameters are reasonable: isotropic explosion energy ∼1054.5 erg, ambient density ∼10–100 cm−3, and the fraction of electrons/protons accelerated to a high-energy power law is of a few percent. All these values are directly derived from the observed teraelectronvolt and X-ray fluxes. The model also requires that protons be accelerated to observed energies as high as a few 1020 eV. Further, assuming that the jet break takes place after 106 s gives the beaming-corrected energy of the burst to be ≈1053 erg, which is one to two orders of magnitude higher than usually inferred, because of the small fraction of electrons accelerated. Our modeling is consistent with both late time data at all bands, from optical to X-rays, and with numerical models of particle acceleration. Our results thus demonstrate the relevance of proton-synchrotron emission to the high-energy observations of gamma-ray bursts during their afterglow phase.

Systematic comparison of advanced models of two- and three-parameter equations to model the imbibition recovery profiles in naturally fractured reservoirs

AbstractThe imbibition process can be considered one of the most important mechanisms during the production of naturally fractured formations. In this process, the hydrocarbon production in the matrix blocks surrounded by water-filled fractures can be described by a recovery curve. Different equations have been proposed to describe the recovery process during the imbibition. This work presents a detailed analysis of the performance of two- and three-parameter models including Weibull, Probit, Logit-Hill, one-hit-multi-target (1HMT), and all-hit-multi-target (AHMT). These models were tested against different experimental and numerical simulation data in a wide range of rock and fluid properties and matrix dimensions. Particularly, the functionality of these models was examined in early, mid, and late times. It should be highlighted that the three-parameter models (1HMT and AHMT) have not been used previously to describe the imbibition data. The results show that the three-parameter models are more accurate to describe the imbibition recovery trends compared to the two-parameter models. Moreover, the analysis revealed that the AHMT model is better for the early-time data (Error = 0.5), the Logit-Hill model is more accurate for the mid-time data (Error = 0.075), and the Weibull model can best fit the late-time imbibition data (Error = 0.04). Finally, the best model for predicting the recovery factor in fractured reservoirs is model 1HMT because the lowest average RMSE (Root-Mean-Square Error) value of 0.0165 was obtained. The findings of this work can be used to more precisely select the model to curve fit the imbibition data.

Constraints on f(T) cosmology with Pantheon+

ABSTRACT f(T) cosmology has shown promise in explaining aspects of cosmic evolution. In this work, we analyse constraints on leading models of f(T) gravity in the context of the recently released Pantheon+ data set, together with comparisons with previous releases. We also consider other late time data sets including cosmic chronometers and baryonic acoustic oscillation data. Our main result is that we find that the different f(T) models under investigation connect to a variety of Hubble constant, which may help alleviate the cosmic tension on this parameter.

F(T,B) Gravity in the late Universe in the context of local measurements

We explore the viability of three models in $f(T,B)$ gravity using data from recent surveys based on cosmic chronometers, the Pantheon data set, and baryonic acoustic oscillation data. We also assess the consistency of these models and data set combinations with two important priors on the Hubble constant coming from the SH0ES Team and measurements using the tip of the red giant branch respectively. These give the highest and lowest values of the Hubble constant coming from cosmology independent studies. In general, our analysis does provide a more consistent fit for the late time data being analyzed. However, each model does include an additional model parameter in comparison with the concordance model. We close the analysis with a comparative analysis in which each model, data set and Hubble constant prior combination are cross-analyzed against each other.

On the use of late-time drawdown in interpreting aquifer pumping test

The review aims to provide a common understanding of the use of late-time drawdown to interpret aquifer pumping tests. The first part of the review provides an overview of the use of the late-time drawdown in literature to illustrate where and how the term is being used. A discussion on the practical implications of using the term and its significance is then presented. The review shows the use of the late-time drawdown in three main ways: the application of the Cooper and Jacob time-drawdown method, the description of the third segment of the unconfined aquifer drawdown-time curve, and when trying to estimate representative/effective transmissivity parameters in heterogeneous aquifers. Unlike the other two situations, the use of late-time data in typical unconfined aquifers is supported by the groundwater flow principles and hence has a meaningful application. The aspects highlighted in this review are important to improve the theoretical and practical knowledge required for analysing and interpreting aquifer pumping test data.

Cosmological Boundary Flux Parameter

The {\it{Cosmological Boundary Flux Parameter}} is a novel proposal that attempts to explain the origin of the cosmological parameter $\Lambda$ purely by geometric nature. Then we implement this new approach to a flat FLRW universe along with a barotropic fluid. We present an ansatz in which $\Lambda$ is straightforwardly coupled to the matter sector; therefore, only one additional parameter was introduced: $\lambda$. Also, through a statistical analysis, using late-time data of observational Hubble and type Ia Supernovae, we computed the joint best-fit value of the free parameters by means of the affine-invariant MCMC. We want to emphasise that the joint analysis produces a smaller $H_{0}^{\rm CBFP}=69.80\rm\,\, Km \,s^{-1}\,Mpc^{-1}$ in contrast to the flat $\Lambda$CDM result $H_{0}^{\Lambda\rm CDM}=70.53\rm\,\, Km \,s^{-1}\,Mpc^{-1}$. The work presented here seeks to contribute to the discussion of the possible explanation for the cosmos' acceleration, together with tackling other important questions in modern cosmology.

Detailed analysis of excited-state systematics in a lattice QCD calculation of gA

Excited state contamination remains one of the most challenging sources of systematic uncertainty to control in lattice QCD calculations of nucleon matrix elements and form factors: early time separations are contaminated by excited states and late times suffer from an exponentially bad signal-to-noise problem. High-statistics calculations at large time separations $\gtrsim1$ fm are commonly used to combat these issues. In this work, focusing on $g_A$, we explore the alternative strategy of utilizing a large number of relatively low-statistics calculations at short to medium time separations (0.2--1 fm), combined with a multi-state analysis. On an ensemble with a pion mass of approximately 310 MeV and a lattice spacing of approximately 0.09 fm, we find this provides a more robust and economical method of quantifying and controlling the excited state systematic uncertainty. A quantitative separation of various types of excited states enables the identification of the transition matrix elements as the dominant contamination. The excited state contamination of the Feynman-Hellmann correlation function is found to reduce to the 1% level at approximately 1 fm while for the more standard three-point functions, this does not occur until after 2 fm. Critical to our findings is the use of a global minimization, rather than fixing the spectrum from the two-point functions and using them as input to the three-point analysis. We find that the ground state parameters determined in such a global analysis are stable against variations in the excited state model, the number of excited states, and the truncation of early-time or late-time numerical data.

Parametric and nonparametric methods hint dark energy evolution

We study dark energy through the viewpoints of parametric and nonparametric analyses of late-time cosmological data. We consider four Hubble parameter priors reflecting the Hubble tension and make use of two phenomenological functions, namely, a normalized dark energy density and a compactified dark energy equation of state. We predict the shape of both functions and present new constraints on the dark energy equation of state. The results hint at dark energy evolution regardless of the choice of the method and of the priors. The fact that similar evolutions for the dark energy densities are found through drastically different approaches suggests that the features found in this paper are driven by the data, and are not artifact of the reconstruction methods applied.

The resilience of the Etherington–Hubble relation

ABSTRACT The Etherington reciprocity theorem, or distance duality relation (DDR), relates the mutual scaling of cosmic distances in any metric theory of gravity where photons are massless and propagate on null geodesics. In this paper, we make use of the DDR to build a consistency check based on its degeneracy with the Hubble constant, H0. We parametrize the DDR using the form η(z) = 1 + ϵz, thus only allowing small deviations from its standard value. We use a combination of late-time observational data to provide the first joint constraints on the Hubble parameter and ϵ with percentage accuracy: H0 = 68.6 ± 2.5 km s−1 Mpc−1 and $\epsilon = 0.001^{+0.023}_{-0.026}$. We build our consistency check using these constraints and compare them with the results obtained in extended cosmological models using cosmic microwave background data. We find that extensions to Λ cold dark matter (ΛCDM) involving massive neutrinos and/or additional dark radiation are in perfect agreement with the DDR, while models with non-zero spatial curvature show a preference for DDR violation, i.e. ϵ ≠ 0 at the level of ∼1.5σ. Most importantly, we find a mild 2σ discrepancy between the validity of the DDR and the latest publicly available Cepheid-calibrated Type Ia supernova (SNIa) constraint on H0. We discuss the potential consequences of this for both the Etherington reciprocity theorem and the H0 tension.

Confronting quantum-corrected teleparallel cosmology with observations

It has been shown that at the semi-classical order, gravitational theories with quantum fluctuations can be effectively recast as modified theories of gravity with non-minimal gravity-matter couplings. We proceed from an observational perspective and see whether such quantum fluctuations can leave imprints on the late Universe. Within the teleparallel formulation, we investigate a representative model in this general class of modified gravitational theories inlaid with quantum fluctuations, and determine the cosmological parameters by using compiled late-time data sets. Furthermore, we assess the statistical significance of such quantum corrections compared to the standard cosmological model. The results mildly favor the inclusion of quantum corrections with a negative density parameter supporting a phantom-like dark energy. This edge is not sufficient to rule out either models but it supports the consideration of quantum corrections in a cosmological setting.

Cosmological Boundary Flux Parameter

The {\it{Cosmological Boundary Flux Parameter}} is a novel proposal that attempts to explain the origin of the cosmological parameter $\Lambda$ purely by geometric nature. Then we implement this new approach to a flat FLRW universe, along with a barotropic fluid. We present an ansatz in which $\Lambda$ couples straightforwardly to the matter sector; therefore only one extra parameter was introduced: $\lambda$. Also, through a statistical analysis, using late time data of Observational Hubble and type Ia Supernovae, we computed the best-fit value of the free parameters by means of the affine-invariant MCMC. We want to emphasize that the Joint analysis produces a smaller $H_{0}=71.51\rm\,\, Km \,s^{-1}\,Mpc^{-1}$ in contrast to the $\Lambda$CDM result $H_{0}=72.15\rm\,\, Km \,s^{-1}\,Mpc^{-1}$. Indeed, this outcome approaches more to the CMB value $H_{0}^{\rm CMB}=67.70\rm\,\, Km \,s^{-1}\,Mpc^{-1}$ (Planck + BAO). Thus, this might suggest that our propoal might be a good candidate to amend the $H_{0}$ tension. In spite of that, more statistical analysis needs to be done to be certain about this. The work here presented seeks to contribute to the discussion of the possible explanation for the cosmos' acceleration, together with tackling other important questions in modern cosmology.

The Panchromatic Afterglow of GW170817: The Full Uniform Data Set, Modeling, Comparison with Previous Results, and Implications

Abstract We present the full panchromatic afterglow light-curve data of GW170817, including new radio data as well as archival optical and X-ray data, between 0.5 and 940 days post-merger. By compiling all archival data and reprocessing a subset of it, we have evaluated the impact of differences in data processing or flux determination methods used by different groups and attempted to mitigate these differences to provide a more uniform data set. Simple power-law fits to the uniform afterglow light curve indicate a t 0.86±0.04 rise, a t −1.92±0.12 decline, and a peak occurring at 155 ± 4 days. The afterglow is optically thin throughout its evolution, consistent with a single spectral index (−0.584 ± 0.002) across all epochs. This gives a precise and updated estimate of the electron power-law index, p = 2.168 ± 0.004. By studying the diffuse X-ray emission from the host galaxy, we place a conservative upper limit on the hot ionized interstellar medium density, <0.01 cm−3, consistent with previous afterglow studies. Using the late-time afterglow data we rule out any long-lived neutron star remnant having a magnetic field strength between 1010.4 and 1016 G. Our fits to the afterglow data using an analytical model that includes Very Long Baseline Interferometry proper motion from Mooley et al., and a structured jet model that ignores the proper motion, indicates that the proper-motion measurement needs to be considered when seeking an accurate estimate of the viewing angle.