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The recent results from the first-year baryon acoustic oscillations (BAO) data released by the Dark Energy Spectroscopic Instrument (DESI), combined with cosmic microwave background (CMB) and Type Ia supernova (SN) data, have shown a detection of significant deviation from a cosmological constant for dark energy. In this work, we utilize the latest DESI BAO data in combination with the SN data from the full 5 yr observations of the Dark Energy Survey and the CMB data from the Planck satellite to explore potential interactions between dark energy and dark matter. We consider four typical forms of the interaction term Q. Our findings suggest that interacting dark energy (IDE) models with Q ∝ ρ de support the presence of an interaction where dark energy decays into dark matter. Specifically, the deviation from ΛCDM for the IDE model with Q = β H 0 ρ de reaches the 3 σ level. These models yield a lower value of Akaike information criterion than the ΛCDM model, indicating a preference for these IDE models based on the current observational data. For IDE models with Q ∝ ρ c, the existence of interaction depends on the form of the proportionality coefficient Γ. The IDE model with Q = β H ρ c yields β = 0.0003 ± 0.0011, which essentially does not support the presence of the interaction. In general, whether the observational data support the existence of interaction is closely related to the model. Our analysis helps to elucidate which type of IDE model can better explain the current observational data. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) have been found in great numbers, but the physical mechanism of these sources is still a mystery. The redshift evolutions of the FRB energy distribution function and the volumetric rate shed light on the origin of FRBs. However, such estimations rely on the dispersion measurement (DM)–redshift (z) relationship. A few FRBs that have been detected recently show large excess DMs beyond the expectation from the cosmological and Milky Way contributions, which indicates large spread of DMs from their host galaxies. In this work, we adopt two lognormal-distributed DM host models and estimate the energy function using the non-repeating FRBs selected from the Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB Catalog 1. By comparing the lognormal-distributed DM host models to a constant DM host model, the FRB energy function results are consistent within the measurement uncertainty. We also estimate the volumetric rate of the non-repeating FRBs in three different redshift bins. The volumetric rate shows that the trend is consistent with the stellar-mass density redshift evolution. Since the lognormal-distributed DM host model increases the measurement errors, the inference of FRBs tracking the stellar-mass density is nonetheless undermined. [ABSTRACT FROM AUTHOR]

Neutral hydrogen (H  i) intensity-mapping (IM) surveys are considered a promising tool for investigating the expansion history of the Universe. In this work, we explore the potential of MeerKAT H  i IM observations in interferometer mode to estimate the power spectrum and constrain cosmological parameters within typical dark-energy models. We employ an approach called the 'delay spectrum', which allows us to separate the weak H  i signal from foreground contamination in the frequency domain. Our findings indicate that the choice of survey fields significantly impacts the fractional errors on the power spectrum (Δ P / P) within a limited observational time of 10 h. As the integration time increases from 10–10 000 h, Δ P / P progressively decreases until cosmic variance begins to dominate. For a total observation time of 10 000 h, the lowest Δ P / P at low k can be achieved by tracking 100 points for the MeerKAT L band (900–1200 MHz) and 10 points for the MeerKAT UHF band (580–1000 MHz). Next, we assess the performance of H  i IM in constraining typical dark-energy models. We find that the MeerKAT H  i IM survey in interferometer mode demonstrates limited capability in constraining the dark-energy equation of state, even when combined with Planck data. Our analysis serves as a valuable guide for future MeerKAT observations in H  i IM surveys. [ABSTRACT FROM AUTHOR]

Although the cosmic curvature has been tightly constrained in the standard cosmological model using observations of cosmic microwave background anisotropies, it is still of great importance to independently measure this key parameter using only late-Universe observations in a cosmological model-independent way. The distance sum rule in strong gravitational lensing (SGL) provides such a way, provided that the three distances in the sum rule can be calibrated by other observations. In this paper, we propose that gravitational waves (GWs) can be used to provide the distance calibration in the SGL method, which can avoid the dependence on distance ladder and cover a wider redshift range. Using the simulated GW standard siren observation by the Einstein Telescope as an example, we show that this scheme is feasible and advantageous. We find that ΔΩ k ≃ 0.17 with the current SGL data, which is slightly more precise than the case of using SN to calibrate. Furthermore, we consider the forthcoming LSST survey that is expected to observe many SGL systems, and we find that about 104 SGL data could provide the precise measurement of ΔΩ k ≃ 10−2 with the help of GWs. In addition, our results confirm that this method of constraining Ω k is strongly dependent on lens models. However, obtaining a more accurate phenomenological model for lens galaxies is highly predictable as future massive surveys observe more and more SGL samples, which will significantly improve the constraint of cosmic curvature. [ABSTRACT FROM AUTHOR]

Measurements of time-delay cosmography of lensed quasars can provide an independent probe to explore the expansion history of the late-time Universe. In this paper, we employ the time-delay cosmography measurements from seven lenses (here abbreviated as the TD data) to constrain interacting dark energy (IDE) models. We mainly focus on the scenario of vacuum energy (with w  = −1) interacting with cold dark matter, and consider four typical cases of the interaction form Q. When the TD data alone are employed, we find that the IDE models with Q  ∝ ρde seem to have an advantage in relieving the H 0 tension between the cosmic microwave background (CMB) and TD data. When the TD data are added to the CMB+BAO+SN+ H 0 data, we find that (i) the coupling parameter β in all the considered IDE models is positive within 1σ range, implying a mild preference for the case of cold dark matter decaying into dark energy; (ii) the IDE model with Q  = β H 0ρc slightly relieves the S 8 tension, but the other considered IDE models further aggravate this tension; (iii) the Akaike information criteria of the IDE models with Q  ∝ ρc are lower than that of the ΛCDM model, indicating that these IDE models are more preferred by the current mainstream data. We conclude that the considered IDE models have their own different advantages when the TD data are employed, and none of them can achieve good scores in all aspects. [ABSTRACT FROM AUTHOR]

The remarkable development of cosmology benefits from the increasingly improved measurements of cosmic distances, including absolute distances and relative distances. In recent years, however, the emerged cosmological tensions have motivated us to explore independent and precise late-universe probes. The two observational effects of strong gravitational lensing (SGL), the velocity dispersions of lens galaxies and the time delays between multiple images can provide measurements of relative and absolute distances, respectively, and their combination makes it possible to break the degeneracies between cosmological parameters and enable tight constraints on them. In this paper, we combine the observed 130 SGL systems with velocity-dispersion measurements and 7 SGL systems with time-delay measurements to constrain dark-energy cosmological models. It is found that the combination of the two effects does not significantly break the degeneracies between cosmological parameters as expected. However, with the simulations of 8000 SGL systems with well-measured velocity dispersions and 55 SGL systems with well-measured time delays based on the forthcoming LSST survey, we find that the combination of two effects can significantly break the parameter degeneracies, and make the constraint precision of cosmological parameters meet the standard of precision cosmology. We conclude that the observations of SGL will become a useful late-universe probe for precisely measuring cosmological parameters. [ABSTRACT FROM AUTHOR]

We forecast constraints on cosmological parameters in the interacting dark energy models using the mock data generated for neutral hydrogen intensity mapping (IM) experiments. In this work, we only consider the interacting dark energy models with energy transfer rate Q = βHρc and take BINGO, FAST, SKA1-MID, and Tianlai as typical examples of the 21 cm IM experiments. We find that the Tianlai cylinder array will play an important role in constraining the interacting dark energy model. Assuming perfect foreground removal and calibration and using the Tianlai-alone data, we obtain σ(H0) = 0.19 km s−1 Mpc−1, σ(Ωm) = 0.0033, and σ(σ8) = 0.0033 in the IΛCDM model, which are much better than the results of Planck+optical BAO (i.e., optical galaxy surveys). However, the Tianlai-alone data cannot provide a very tight constraint on the coupling parameter β compared with Planck+optical BAO, while the Planck+Tianlai data can give a rather tight constraint of σ(β) = 0.00023 due to the parameter degeneracies being well broken by the data combination. In the IwCDM model, we obtain σ(β) = 0.00079 and σ(w) = 0.013 from Planck+Tianlai. In addition, we also make a detailed comparison among BINGO, FAST, SKA1-MID, and Tianlai in constraining the interacting dark energy models. We show that future 21 cm IM experiments will provide a useful tool for exploring the nature of dark energy and play a significant role in measuring the coupling between dark energy and dark matter. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) are a mysterious astrophysical phenomenon of bright pulses emitted at radio frequencies, and they are expected to be frequently detected in the future. The dispersion measures of FRBs are related to cosmological parameters, thus FRBs have the potential to be developed into a new cosmological probe if their data can be largely accumulated in the future. In this work, we study the capability of future FRB data to improve cosmological parameter estimation in two dynamical dark energy models. We find that the simulated FRB data can break the parameter degeneracies inherent in the current cosmic microwave background (CMB) data. Therefore, the combination of CMB and FRB data can significantly improve the constraints on the Hubble constant and dark energy parameters, compared to those using CMB or FRB alone. If 10,000 FRB events with known redshifts are detected in the future, they would perform better than the baryon acoustic oscillation (BAO) data in breaking the parameter degeneracies inherent in the CMB data. We also find that the combination of FRB and gravitational-wave (GW) standard siren data provides an independent low-redshift probe to verify the results from the CMB and BAO data. For the data combination of CMB, GW, and FRB, it is found that the main contribution to the constraints comes from the CMB and GW data, but the inclusion of the FRB data still can evidently improve the constraint on the baryon density. [ABSTRACT FROM AUTHOR]