arXiv subjects

Peng-Ju Wu

Publications and source records attributed to Peng-Ju Wu.

At least 19 recordsLinked to original sources

arXiv2026

The open-Universe signal: A model artifact rather than genuine curvature

Recent late-Universe observations suggest an open Universe. If confirmed, such a departure from spatial flatness would carry profound implications for our understanding of cosmic inflation and the ultimate fate of the Universe. Motivated by this intriguing result and the release of new data, we revisit the question using baryon acoustic oscillation measurements from DESI DR2, multiple Type Ia supernova samples, refined strong gravitational lensing time-delay analyses, and the most up-to-date cosmic chronometer data. We find that within the $Λ$ cold dark matter ($Λ$CDM) paradigm, the combined data still prefer an open Universe with $Ω_K=0.049\pm0.037$. However, this preference vanishes in extensions to $Λ$CDM, where the data instead favor a flat Universe. The model comparison shows that for $Λ$CDM, introducing new physics is preferred over merely allowing spatial curvature, and flat $Λ$CDM extensions perform better than their curved counterparts. We therefore argue that the mild open-Universe signal is an artifact of limited model flexibility, rather than a genuine feature of late-Universe observations.

astro-ph.CO↗

arXiv2026

Simultaneous determination of Hubble constant and cosmic baryon density: Forecasts for the synergy between FRBs and emerging probes

Two of the most pressing challenges in cosmology are the persistent discrepancy in measurements of the Hubble constant, referred to as the Hubble tension, and the deficit of baryons in the local Universe, known as the missing baryon problem. Fast radio bursts (FRBs) provide a unique probe of both the Hubble constant $H_0$ and the cosmic baryon density $Ω_{\rm b}$. However, constraints from FRBs alone suffer from a severe $H_0$-$Ω_{\rm b}$ degeneracy that prevents them from resolving either problem. We show that this degeneracy can be broken by combining FRBs with other emerging probes whose degeneracy directions differ in the $H_0$-$Ω_{\rm b}$ plane. Specifically, we quantify three multi-messenger approaches: FRBs paired with gravitational wave (GW) standard sirens, strong gravitational lensing (SGL) time delays, and 21 cm intensity mapping (IM) surveys. The combinations FRB+GW, FRB+SGL, and FRB+21 cm IM each deliver simultaneous constraints on $H_0$ and $Ω_{\rm b}$ better than (1%, 1.5%) in the $Λ$CDM model, and when dynamical dark energy is introduced, the constraining precision degrades gracefully as model complexity increases. Furthermore, within a model-independent framework, both FRB+GW and FRB+SGL constrain $H_0$ and $Ω_{\rm b}$ to precisions better than (1.5%, 3%). These precision levels are based on nominal observational expectations and would improve significantly under optimistic observational scenarios.

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arXiv2026

How Dark Sector Equations of State Govern Interaction Signatures

Using late-Universe observations, we demonstrate that freeing dark energy and dark matter equations of state (EoS) dramatically alters the inferred strength and direction of their interactions. When dark sector EoS are fixed to $w_{\mathrm{de}}=-1$ and $w_{\mathrm{dm}}=0$, the data consistently favor an energy transfer from dark energy to dark matter across various interaction forms. This apparent evidence, however, proves highly sensitive to the EoS assumptions: treating $w_{\mathrm{de}}$ as a free parameter substantially weakens the evidence for interaction, with its value converging to the quintessence regime ($w_{\mathrm{de}}>-1$). In contrast, freeing $w_{\mathrm{dm}}$ maintains a preference for interaction, revealing a correlation where positive $w_{\mathrm{dm}}$ is associated with energy transfer from dark energy to dark matter, and negative $w_{\mathrm{dm}}$ with energy transfer from dark matter to dark energy. These findings caution against the simplistic assumption of $Λ$CDM EoS values when attempting to detect a possible interaction. Despite these fundamental degeneracies, model comparison indicates that interacting dark energy scenarios are positively to strongly supported by AIC and DIC, but only inconclusively to weakly supported by Bayesian evidence against the $Λ$CDM model.

astro-ph.CO↗

arXiv2026

Observational challenges to holographic and Ricci dark energy paradigms: Insights from ACT DR6 and DESI DR2

Recent studies suggest that dark energy may be dynamical rather than being a mere cosmological constant $Λ$. In this work, we examine the viability of two physically well-motivated dynamical dark energy models -- holographic dark energy (HDE) and Ricci dark energy (RDE) -- by confronting them with the latest observational data, including ACT cosmic microwave background anisotropies, DESI baryon acoustic oscillations, and DESY5 supernovae. Our analysis reveals a fundamental tension between early- and late-universe constraints within both frameworks: ACT favors a quintom scenario where the dark energy equation of state evolves from $w>-1$ at early times to $w<-1$ at late times, while DESI+DESY5 exhibits a distinct preference for quintessence where $w>-1$ across cosmic evolution. Critically, the RDE model fails to provide a coherent description of cosmic evolution, as it manifests severe tensions (exceeding $10σ$ significance) between early- and late-universe parameter reconstructions. In addition, Bayesian evidence disfavors both models relative to the $Λ$CDM model. Our findings statistically exclude the original HDE and RDE models and uncover a severe discrepancy between early- and late-universe observations described by them, leading to the conclusion that the HDE and RDE models can be ruled out by current observational data.

astro-ph.CO↗

arXiv2025

Cosmological search for sterile neutrinos after DESI 2024

The question of whether the massive sterile neutrinos exist remains a crucial unresolved issue in both particle physics and cosmology. We explore the cosmological constraints on the massive sterile neutrinos using the latest observational data, including the baryon acoustic oscillations data from DESI, the cosmic microwave background data from Planck satellite and ACT, and the 5-year Type Ia supernova data and the 3-year weak-lensing data from DES. We search for the massive sterile neutrinos within the $Λ$CDM, $w$CDM, and $w_0w_a$CDM models. Our analysis shows that when considering massive sterile neutrinos within the $w_0w_a\rm CDM$ model, the combined datasets allow us to infer a non-zero sterile neutrino mass at approximately $2σ$ confidence level. Specifically, in the $w_0w_a$CDM+Sterile model, the effective mass of sterile neutrinos and the effective number of relativistic species are constrained to be $m_{ν,\ \mathrm{sterile}}^{\mathrm{eff}} = 0.50^{+0.33}_{-0.27} \, \mathrm{eV}$ and $N_\mathrm{eff} = 3.076^{+0.011}_{-0.017}$, respectively. However, the $Λ$CDM+Sterile and $w$CDM+Sterile models could not provide evidence supporting the existence of massive sterile neutrinos.

astro-ph.CO↗

arXiv2025

Revisiting the phenomenologically emergent dark energy model: is non-zero equation of state of dark matter favored by DESI DR2?

The nature of dark matter remains one of the most fundamental and unresolved questions in modern cosmology. In most cosmological models, dark matter is typically modeled as pressureless dust with an equation of state (EoS) parameter $w_{\rm dm} = 0$. However, there is no fundamental theoretical reason to exclude the possibility of a non-zero dark matter EoS parameter. In this work, we explore the possibility of a non-zero dark matter EoS within the phenomenologically emergent dark energy (PEDE) model, given its simplicity and proven ability to alleviate the Hubble tension. We perform observational constraints by using the latest baryon acoustic oscillation data from DESI DR2, the cosmic microwave background (CMB) data from Planck, and the type Ia supernova data from DESY5 and PantheonPlus. From our analysis, we observe that a negative dark matter EoS parameter is preferred in all scenarios. Specifically, the CMB+DESI+DESY5 data yields $w_{\mathrm{dm}} = -0.00093 \pm 0.00032$, deviating from zero at approximately the $3σ$ level. However, this deviation is likely driven by unidentified systematics or inconsistencies in the DESY5 data, with the deviation decreasing to $2σ$ when using PantheonPlus data. Meanwhile, a negative $w_{\rm dm}$ would increase the Hubble tension due to the positive degeneracy between $w_{\rm dm}$ and $H_0$. Furthermore, Bayesian evidence suggests that the $Λ$CDM model is strongly preferred over the PEDE+$w_{\rm dm}$ model. These analyses illustrate that it is not possible to both support a non-cold dark matter component within the PEDE model and alleviate the Hubble tension simultaneously.

astro-ph.CO↗

arXiv2025

Testing the cosmic distance duality relation with baryon acoustic oscillations and supernovae data

One of the most fundamental relationships in modern cosmology is the cosmic distance duality relation (CDDR), which describes the relationship between the angular diameter distance ($D_{\rm A}$) and the luminosity distance ($D_{\rm L}$), and is expressed as: $η(z)=D_{\rm L}(z)(1+z)^{-2}/D_{\rm A}(z)=1$. In this work, we conduct a comprehensive test of the CDDR by combining baryon acoustic oscillation (BAO) data from the SDSS and DESI surveys with type Ia supernova (SN) data from PantheonPlus and DESY5. We utilize an artificial neural network approach to match the SN and BAO data at the same redshift. To explore potential violations of the CDDR, we consider three different parameterizations: (i) $η(z)=1+η_0z$; (ii) $η(z)=1+η_0z/(1+z)$; (iii) $η(z)=1+η_0\ln(1+z)$. Our results indicate that the calibration of the SN absolute magnitude $M_{\rm B}$ plays a crucial role in testing potential deviations from the CDDR, as there exists a significant negative correlation between $η_0$ and $M_{\rm B}$. For PantheonPlus analysis, when $M_{\rm B}$ is treated as a free parameter, no evidence of CDDR violation is found. In contrast, fixing $M_{\rm B}$ to the $M_{\rm B}^{\rm D20}$ prior with $-19.230\pm0.040$ mag leads to a deviation at approximately the $2σ$ level, while fixing $M_{\rm B}$ to the $M_{\rm B}^{\rm B23}$ prior with $-19.396\pm0.016$ mag remains in agreement with the CDDR. Furthermore, overall analyses based on the SDSS+DESY5 and DESI+DESY5 data consistently show no evidence of the deviation from the CDDR.

astro-ph.CO↗

arXiv2025

Probing the sign-changeable interaction between dark energy and dark matter with DESI baryon acoustic oscillations and DES supernovae data

There is a possibility of interaction between dark energy and dark matter, and this interaction may also undergo a sign change during the evolution of the universe. In this paper, we utilize the latest observational data to constrain models of a sign-changeable interaction. The data we employ, in addition to the cosmic microwave background data, also encompass the first-year baryon acoustic oscillation data from DESI and the type Ia supernova data of the full 5-year observation from DES. To achieve high generality, we investigate four interacting dark energy (IDE) models with different forms of the interaction term $Q$: (i) IDE1 with $Q = β(a)Hρ_{\rm de}$; (ii) IDE2 with $Q = β(a)Hρ_{\rm c}$; (iii) IDE3 with $Q = β(a)H_0ρ_{\rm de}$; (iv) IDE4 with $Q = β(a)H_0ρ_{\rm c}$. From the analysis, we observe that $β(z) > 0$ at early times and $β(z) < 0$ at late times, with the coupling $β(z)$ crossing the non-interacting line $β(z) = 0$ during cosmic evolution at the 2$σ$ confidence level for the IDE1, IDE3, and IDE4 models. However, for the IDE2 model, $β(z)$ remains consistently negative and does not cross $β(z) = 0$ at the 2$σ$ confidence level. Our findings indicate that the energy transfer is from dark matter to dark energy when dark matter dominates the universe, and from dark energy to dark matter when dark energy dominates, for the IDE1 and IDE3 models. Furthermore, Bayesian evidence suggests that the IDE1 and IDE3 models are moderately preferred over the $Λ$CDM model. The overall outcomes of this study clearly indicate that, based on current observational data, the sign-changeable IDE models are quite compelling and merit further attention.

astro-ph.CO↗

arXiv2025

Measuring cosmic curvature with non-CMB observations

The cosmic curvature $Ω_{K}$ is an important parameter related to the inflationary cosmology and the ultimate fate of the universe. In this work, we adopt the non-CMB observations to constrain $Ω_{K}$ in the $Λ$CDM model and its extensions. The DESI baryon acoustic oscillation, DES type Ia supernova, cosmic chronometer, and strong gravitational lensing time delay data are considered. We find that the data combination favors an open universe in the $Λ$CDM model, specifically $Ω_{K}=0.108\pm0.056$ at the $1σ$ confidence level, which is in $2.6σ$ tension with the Planck CMB result supporting our universe being slightly closed. In the $Λ$CDM extensions, the data combination is consistent with a spatially flat universe. However, the central value of $Ω_{K}$ is positive and has a significant deviation from zero. We adopt the Akaike information criterion to compare different cosmological models. The result shows that non-flat models fit the observational data better than the flat $Λ$CDM model, which adds evidence to the argument that flat $Λ$CDM is not the ultimate model of cosmology.

astro-ph.CO↗

arXiv2025

Comparison of dark energy models using late-universe observations

In the framework of general relativity, dark energy was proposed to explain the cosmic acceleration. A pivotal inquiry in cosmology is to determine whether dark energy is the cosmological constant, and if not, the challenge lies in constraining how it evolves with time. In this paper, we utilize the latest observational data to constrain some typical dark energy models, and make a comparison for them according to their capabilities of fitting the current data. Our study is confined to late-universe observations, including the baryon acoustic oscillation, type Ia supernova, cosmic chronometer, and strong gravitational lensing time delay data. We employ the Akaike information criterion (AIC), deviance information criterion (DIC), and Bayesian information criterion (BIC) to assess the worth of models. The AIC and DIC analyses indicate that all dark energy models outperform the $Λ$CDM model. However, the BIC analysis leaves room for $Λ$CDM due to its heavier penalty on the model complexity. Compared to $Λ$CDM, most dark energy models are robustly supported by AIC and DIC while being explicitly disfavored by BIC. The models that are robustly favored by AIC and DIC and not explicitly disfavored by BIC include the $w$CDM, interacting dark energy, and Ricci dark energy models. Furthermore, we observe that an alternative modified gravity model exhibits superior performance when compared with $Λ$CDM across all information criteria.

astro-ph.CO↗

arXiv2025

Cosmological preference for a positive neutrino mass at 2.7$\sigma$: A joint analysis of DESI DR2, DESY5, and DESY1 data

Neutrinos and dark energy (DE) have entered a new era of investigation, as the latest DESI baryon acoustic oscillation measurements tighten the constraints on the neutrino mass and suggest that DE may be dynamical rather than a cosmological constant. In this work, we obtain a high-confidence measurement of the neutrino mass within a dynamical DE framework. A joint analysis of DESI DR2, cosmic microwave background, DESY5 supernova, and DESY1 weak lensing data yields a total neutrino mass of $\sum m_\nu = 0.098^{+0.016}_{-0.037}\,\mathrm{eV}$, indicating a measurement for a non-zero, positive neutrino mass at the $2.7\sigma$ level within the $w_0w_a$CDM framework. This high-confidence measurement is driven mainly by these factors: (i) the DESI's preference for a dynamical DE with its equation of state evolving from $w< -1$ at early times to $w> -1$ at late times, thus leading to a larger neutrino mass; (ii) treating $N_{\mathrm{eff}}$ as a free parameter together with the inclusion of weak lensing data, which likewise allows for an increased neutrino mass. In the future, even higher-confidence measurements of neutrino mass are expected with stronger preferences for dynamical DE in light of more complete DESI data releases.

astro-ph.CO↗

arXiv2025

Exploring non-cold dark matter in a scenario of dynamical dark energy with DESI DR2 data

Recent observations of DESI hint that dark matter (DM) may not be cold but have a non-zero equation of state (EoS) parameter, and that dark energy (DE) may not be a cosmological constant. In this work, we explore the possibility of a non-zero DM EoS parameter within the framework of dynamical DE. We perform analysis by using the latest baryon acoustic oscillation (BAO) data from DESI DR2, the cosmic microwave background (CMB) data from Planck, and the type Ia supernova (SN) data from DESY5 and PantheonPlus. When using the combination of CMB, BAO, and SN data, our results indicate a preference for a non-zero DM EoS parameter at the $2.8σ$ and $3.3σ$ level within the content of a constant DE EoS. In contrast, for a time-evolving DE EoS parameterized by $w_0$ and $w_a$, this preference decreases to $0.8σ$ and $1.1σ$. Furthermore, allowing a non-zero DM EoS yields best-fit values of $w_0$ and $w_a$ that exhibit smaller deviations from the $Λ$CDM expectations, and Bayesian evidence analysis shows a comparable preference for this model relative to $Λ$CDM. The overall results of this work indicate that a non-zero DM EoS parameter warrants further exploration and investigation.

astro-ph.CO↗

arXiv2025

Revisiting holographic dark energy after DESI 2024

New insights from the Dark Energy Spectroscopic Instrument (DESI) 2024 baryon acoustic oscillations (BAO) data, in conjunction with cosmic microwave background (CMB) and Type Ia supernova (SN) data, suggest that dark energy may not be a cosmological constant. In this work, we investigate the cosmological implications of holographic dark energy (HDE) and interacting holographic dark energy (IHDE) models, utilizing CMB, DESI BAO, and SN data. By considering the combined DESI BAO and SN data, we determine that in the IHDE model, the parameter $c > 1$ and the dark-energy equation of state $w$ does not cross $-1$ at the $1σ$ confidence level, whereas in the HDE model, it marginally falls below this threshold. Upon incorporating CMB data, we observe that in the HDE model, the parameter $c < 1$ and $w$ crosses $-1$ at a level beyond $10σ$. Conversely, for the IHDE model, the likelihood of $w$ crossing $-1$ is considerably diminished, implying that the introduction of interaction within the HDE model could potentially resolve or mitigate the cosmic big rip conundrum. Furthermore, our analysis reveals that the HDE and IHDE models are statistically as viable as the $Λ$CDM model when assessing Bayesian evidence with DESI BAO data combined with SN data. However, when CMB data are added, the HDE and IHDE models are significantly less favored compared to the $Λ$CDM model. Our findings advocate for further exploration of the HDE and IHDE models using forthcoming, more precise late-universe observations.

astro-ph.CO↗

arXiv2025

Impacts of dark energy on weighing neutrinos after DESI BAO

Recently, DESI has released baryon acoustic oscillation (BAO) data, and DES has also published its five-year supernova (SN) data. These observations, combined with cosmic microwave background (CMB) data, support a dynamically evolving dark energy at a high confidence level. When using cosmological observations to weigh neutrinos, the results of weighing neutrinos will be significantly affected by the measurement of dark energy due to the degeneracy between neutrino mass and the dark-energy equation of state. Therefore, we need to understand how the dynamical evolution of dark energy in the current situation will affect the measurement of neutrino mass. In this work, we utilize these latest observations and other additional distance measurements to discuss the mutual influence between neutrinos and dark energy, then calculate the Bayes factor to compare models. We consider three neutrino mass hierarchies including degenerate hierarchy (DH), normal hierarchy (NH), and inverted hierarchy (IH), as well as three dark energy models including $Λ\rm CDM$, $w\rm CDM$, and $w_0w_a \rm CDM$ models. Cosmological data combined with the prior of particle physics experiments can provide strong to decisive evidence favoring the $w_0w_a {\rm CDM}+\sum m_ν$ model with NH. In the $w_0w_a \rm CDM$ model, using the CMB+DESI+DESY5 data, we obtain constraints on the total neutrino mass, $\sum m_ν<0.171\ \rm eV,\ 0.204\ \rm eV,\ 0.220\ \rm eV$, for DH, NH, and IH, respectively. Furthermore, taking into account the neutrino hierarchy or incorporating additional distance measurements results in a more pronounced deviation from the $Λ$CDM model for dark energy. The latter, particularly, exhibits a deviation at a confidence level that surpasses $4σ$.

astro-ph.CO↗

arXiv2024

Prospects for cosmological research with the FAST array: 21-cm intensity mapping survey observation strategies

Precise cosmological measurements are essential for understanding the evolution of the universe and the nature of dark energy. The Five-hundred-meter Aperture Spherical Telescope (FAST), the most sensitive single-dish radio telescope, has the potential to provide the precise cosmological measurements through neutral hydrogen 21-cm intensity mapping sky survey. This paper primarily explores the potential of technological upgrades for FAST in cosmology. The most crucial upgrade begins with equipping FAST with a wide-band receiver ($0 < z < 2.5$). This upgrade can enable FAST to achieve higher precision in cosmological parameter estimation than the Square Kilometre Array Phase-1 Mid frequency. On this basis, expanding to a FAST array (FASTA) consisting of six identical FASTs would offer significant improvements in precision compared to FAST. Additionally, compared with the current results from the data combination of cosmic microwave background, baryon acoustic oscillations (optical galaxy surveys), and type Ia supernovae, FASTA can provide comparable constraints. Specifically, for the dark-energy equation-of-state parameters, FASTA can achieve $σ(w_0) = 0.09$ and $σ(w_a) = 0.33$.

astro-ph.CO↗

arXiv2024

Constraints on Interacting Dark Energy Models from the DESI Baryon Acoustic Oscillation and DES Supernovae Data

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 five-year 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 $Q \propto ρ_{\rm de}$ support the presence of an interaction where dark energy decays into dark matter. Specifically, the deviation from $Λ$CDM for the IDE model with $Q=βH_0ρ_{\rm de}$ reaches the $3σ$ level. These models yield a lower value of Akaike information criterion than the $Λ$CDM model, indicating a preference for these IDE models based on the current observational data. For IDE models with $Q\proptoρ_{\rm c}$, the existence of interaction depends on the form of the proportionality coefficient $Γ$. The IDE model with $Q=βHρ_{\rm c}$ yields $β=0.0003\pm 0.0011$, 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.

astro-ph.CO↗

arXiv2023

A path to precision cosmology: synergy between four promising late-universe cosmological probes

In the next decades, it is necessary to forge new late-universe cosmological probes to precisely constrain the Hubble constant and the equation of state of dark energy simultaneously. In this work, we show that the four typical late-universe cosmological probes, the 21 cm intensity mapping (IM), fast radio burst (FRB), gravitational wave (GW) standard siren, and strong gravitational lensing (SGL), are expected to be forged into useful tools in solving the Hubble tension and exploring dark energy. We propose that the synergy of them is rather important in cosmology. We simulate the 21 cm IM, FRB, GW, and SGL data based on the hypothetical observations of the Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX), the Square Kilometre Array (SKA), the Einstein Telescope (ET), and the Large Synoptic Survey Telescope (LSST), respectively. We find that the four probes show obviously different parameter degeneracy orientations in cosmological constraints, so any combination of them can break the parameter degeneracies and thus significantly improve the constraint precision. The joint 21 cm IM+FRB+GW+SGL data can provide the constraint errors of $σ(Ω_{\rm m})=0.0022$ and $σ(H_0)=0.16\ \rm km\ s^{-1}\ Mpc^{-1}$ in the $Λ$CDM model, which meet the standard of precision cosmology, i.e., the constraint precision of parameters is better than 1%. In addition, the joint data give $σ(w)=0.020$ in the $w$CDM model, and $σ(w_0)=0.066$ and $σ(w_a)=0.25$ in the $w_0w_a$CDM model, which are all better than the constraints obtained by the CMB+BAO+SN data. We show that the synergy between the four late-universe cosmological probes has magnificent prospects.

astro-ph.CO↗

arXiv2023

Prospects for measuring dark energy with 21 cm intensity mapping experiments: A joint survey strategy

The 21 cm intensity mapping (IM) technique provides us with an efficient way to observe the cosmic large-scale structure (LSS). From the LSS data, one can use the baryon acoustic oscillation and redshift space distortion to trace the expansion and growth history of the universe, and thus measure the dark energy parameters. In this paper, we make a forecast for cosmological parameter estimation with the synergy of three 21 cm IM experiments. Specifically, we adopt a novel joint survey strategy, FAST ($0<z<0.35$)+SKA1-MID ($0.35<z<0.8$)+HIRAX ($0.8<z<2.5$), to measure dark energy. We simulate the 21 cm IM observations under the assumption of excellent foreground removal. We find that the synergy of three experiments could place quite tight constraints on cosmological parameters. For example, it provides $σ(Ω_{\rm m})=0.0039$ and $σ(H_0)=0.27\ \rm km\ s^{-1}\ Mpc^{-1}$ in the $Λ$CDM model. Notably, the synergy could break the cosmological parameter degeneracies when constraining the dynamical dark energy models. Concretely, the joint observation offers $σ(w)=0.019$ in the $w$CDM model, and $σ(w_0)=0.085$ and $σ(w_a)=0.32$ in the $w_0w_a$CDM model. These results are better than or equal to those given by CMB+BAO+SN. In addition, when the foreground removal efficiency is relatively low, the strategy still performs well. Therefore, the 21 cm IM joint survey strategy is promising and worth pursuing.

astro-ph.CO↗