We revisit the evolution of cosmic acceleration in a spatially flat $$w_0w_a$$ CDM universe, in which the equation of state of dark energy takes the CPL parametrization, using the latest baryon acoustic oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument (DESI), in combination with Planck cosmic microwave background (CMB) data and several type Ia supernova datasets, including PantheonPlus, Union3, and DESY5. We analyze the deceleration parameter $\textit{q}$($\textit{z}$) and the jerk parameter $\textit{j}$($\textit{z}$) and further validate our results using the $\textit{Om}$($\textit{z}$) diagnostic. Our findings indicate significant deviations from the predictions of the $$\Lambda $$ CDM model. Specifically, DESI BAO, DESI BAO + CMB, DESI BAO + CMB + Union3, and DESI BAO + CMB + DESY5 all provide strong evidence for a slowing down of cosmic acceleration at late times, as indicated by $$j(0) < 0$$ at more than 1 $$\sigma $$ confidence level, within the framework of $$w_0w_a$$ CDM model. These results suggest that in the $$w_0w_a$$ CDM universe cosmic acceleration has already peaked and is now in a phase of decline.

China

Jincheng Wang

Hongwei Yu

Puxun Wu

Revisiting cosmic acceleration with DESI BAO

Recently, DESI has released baryon acoustic oscillation (BAO) data, and DES has also published its 5-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 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, namely degenerate hierarchy (DH), normal hierarchy (NH), and inverted hierarchy (IH), as well as three dark energy models including $$\Lambda {\textrm{CDM}},$$ $$w{\textrm{CDM}},$$ and $$w_0w_a {\textrm{CDM}}$$ models. We find that cosmological data combined with the prior of particle physics experiments can provide strong to decisive evidence favoring the $$w_0w_a {{\textrm{CDM}}}+\sum m_\nu $$ model with NH. In the $$w_0w_a {\textrm{CDM}}$$ model, using the CMB+DESI+DESY5 data, we obtain constraints on the total neutrino mass, $$\sum m_\nu <0.171~{\textrm{eV}},\ 0.204~{\textrm{eV}},\ 0.220~{\textrm{eV}},$$ 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 $$\Lambda $$ CDM model for dark energy. The latter, in particular, exhibits a deviation at a confidence level that surpasses $$4\sigma .$$

Guo-Hong Du

Peng-Ju Wu

Tian-Nuo Li

Xin Zhang

Impacts of dark energy on weighing neutrinos after DESI BAO

In this work, we propose to utilize the observed ratio of spherically-averaged distance to the sound horizon scale from Baryon Acoustic Oscillation (BAO) data to test the cosmic distance duality relation (CDDR) by comparing the luminosity distances (LDs) obtained from Type Ia supernovae (SNIa) observations with angular diameter distances (ADDs) derived from these ratio measurements, using a cosmological-model-independent method. To match the LDs with the ADDs at the identical redshifts, we employ two methods: a compressed form of the Pantheon sample and a hybrid approach that combines the binning method with an artificial neural network (ANN). The Hubble parameter ( ) at any redshift is reconstructed from the observed Hubble parameter data with the ANN to derive the ADD. To avoid potential biases resulted from the specific prior values of the absolute magnitude $$M_{\textrm{B}}$$ of SNIa and the sound horizon scale $$r_{\textrm{d}}$$ from BAO measurements, we introduce the fiducial parameter $$\kappa \equiv 10^{M_{\textrm{B}} \over 5}\, r_{\textrm{d}}^{3 \over 2} $$ and marginalize their impacts by treating them as nuisance parameters with flat prior distributions in our statistical analysis. Subsequently, we update the measurements of ratio of the transverse comoving distance to the sound horizon scale from the latest BAO data released by the Dark Energy Spectroscopic Instrument (DESI) collaboration for CDDR testing. Our results indicate that BAO observation provides a powerful tool for testing the CDDR, independent of both the absolute magnitude $$M_{\textrm{B}}$$ and sound horizon scale $$r_{\textrm{d}}$$ , as well as any cosmological model.

Fan Yang

Xiangyun Fu

Bing Xu

Kaituo Zhang

Yang Huang

Ying Yang

Testing the cosmic distance duality relation using Type Ia supernovae and BAO observations

Several studies in the literature have found a disagreement between compressed data on Baryon Acoustic Oscillations (BAO) derived using two distinct methodologies: the two-dimensional (2D, transverse or angular) BAO, which extracts the BAO signal from the analysis of the angular two-point correlation function; and the three-dimensional (3D or anisotropic) BAO, which also exploits the radial clustering signal imprinted on the large-scale structure of the universe. This discrepancy is worrisome, since many of the points contained in these data sets are obtained from the same parent catalogs of tracers and, therefore, we would expect them to be consistent. Since BAO measurements play a pivotal role in the building of the inverse distance ladder, this mismatch impacts the discourse on the Hubble tension and the study of theoretical solutions to the latter. So far, the discrepancy between 2D and 3D BAO has been only pointed out in the context of fitting analyses of cosmological models or parametrizations that, in practice, involve the choice of a concrete calibration of the comoving sound horizon at the baryon-drag epoch. In this Letter, for the first time, we quantify the tension in a much cleaner way, with the aid of apparent magnitudes of supernovae of Type Ia (SNIa) and excluding the radial component of the 3D BAO. We avoid the use of any calibration and cosmological model in the process. At this point we assume that the Etherington (a.k.a distance duality) relation holds. We use state-of-the-art measurements in our analysis, and study how the results change when the angular components of the 3D BAO data from BOSS/eBOSS are substituted by the recent data from DESI Y1. We find the tension to exist at the level of <math><mo>∼</mo><mn>2</mn><mi>σ</mi></math> and <math><mo>∼</mo><mn>2.5</mn><mi>σ</mi></math>, respectively, when the SNIa of the Pantheon+ compilation are used, and at <math><mo>∼</mo><mn>4.6</mn><mi>σ</mi></math> when the latter are replaced with those of DES Y5. In view of these results, we then apply a calibrator-independent method to investigate the robustness of the distance duality relation when analyzed not only with 3D BAO measurements, but also with 2D BAO. This is a test of fundamental physics, which covers, among other aspects, variations of the speed of light with the cosmic expansion or possible interactions between the dark and electromagnetic sectors. We do not find any significant hint for a violation of the cosmic distance duality relation in any of the considered data sets.

Italy

Spain

Arianna Favale

Adrià Gómez-Valent

Marina Migliaccio

Quantification of 2D vs 3D BAO tension using SNIa as a redshift interpolator and test of the Etherington relation

In this work, we test the cosmic distance duality relation (CDDR) by comparing the angular diameter distance (ADD) derived from the transverse Baryon Acoustic Oscillations (BAO) data with the luminosity distance (LD) from the Pantheon type Ia supernova (SNIa) sample. The binning method and Gaussian process are employed to match ADD data with LD data at the same redshift. First, we use nonparametric and parametric methods to investigate the impact of the specific prior values of the absolute magnitude  $$M_\textrm{B}$$  <math> <msub> <mi>M</mi> <mtext>B</mtext> </msub> </math>   from SNIa observations and the sound horizon scale  $$r_\textrm{s}$$  <math> <msub> <mi>r</mi> <mtext>s</mtext> </msub> </math>   from transverse BAO measurements on the CDDR tests. The results obtained from the parametric and non-parametric methods indicate that specific prior values of  $$M_\textrm{B}$$  <math> <msub> <mi>M</mi> <mtext>B</mtext> </msub> </math>   and  $$r_\textrm{s}$$  <math> <msub> <mi>r</mi> <mtext>s</mtext> </msub> </math>   lead to significant biases on the CDDR test. Then, to avoid these biases, we propose a method independent of  $$M_\textrm{B}$$  <math> <msub> <mi>M</mi> <mtext>B</mtext> </msub> </math>   and  $$r_\textrm{s}$$  <math> <msub> <mi>r</mi> <mtext>s</mtext> </msub> </math>   to test CDDR by considering the fiducial value of  $$\kappa \equiv 10^{M_\textrm{B} \over 5}r_\textrm{s}$$  <math> <mrow> <mi>κ</mi> <mo>≡</mo> <msup> <mn>10</mn> <mfrac> <msub> <mi>M</mi> <mtext>B</mtext> </msub> <mn>5</mn> </mfrac> </msup> <msub> <mi>r</mi> <mtext>s</mtext> </msub> </mrow> </math>   as a nuisance parameter and then marginalizing its influence with a flat prior in the analysis. No violation of the CDDR is found, and the transverse BAO measurement can be used as a powerful tool to verify the validity of CDDR in the cosmological-model-independent method.

Min Wang

Zhenyan Lu

Testing the cosmic distance duality relation with Type Ia supernova and transverse BAO measurements

The recent local measurements of the Hubble constant <math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math>, indicate a significant discrepancy of over 5σ compared to the value inferred from Planck observations of the cosmic microwave background (CMB). In this paper, we try to test the standard cosmological model ΛCDM by testing the consistency of early and late cosmological parameters in the same observed data. In practice, we simultaneously derive the early and late parameters using baryon acoustic oscillation (BAO) measurements, which provide both low and high-redshift information. CMB data are also included in the analysis as a “distance prior”, which tracks the same BAO feature and resolve parameter degeneracy. By using the parameter <math><msub><mrow><mi>ω</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>=</mo><msub><mrow><mi>Ω</mi></mrow><mrow><mi>m</mi></mrow></msub><msup><mrow><mi>h</mi></mrow><mrow><mn>2</mn></mrow></msup></math>, we introduce <math><mrow><mi>ratio</mi></mrow><mo>(</mo><msub><mrow><mi>ω</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>)</mo></math>, defined as the ratio of <math><msub><mrow><mi>ω</mi></mrow><mrow><mi>m</mi></mrow></msub></math> which are constrained from high and low-redshift measurements respectively, to quantify the consistency between early and late parameters. We obtained a value of <math><mrow><mi>ratio</mi></mrow><mo>(</mo><msub><mrow><mi>ω</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>)</mo><mo>=</mo><mn>1.0069</mn><mo>±</mo><mn>0.0070</mn></math>, indicating there is no tension between early parameters and late parameters in the framework of ΛCDM model. As a result, our test does not expose the defects of the ΛCDM model. In addition, we forecast the future BAO measurements of <math><mrow><mi>ratio</mi></mrow><mo>(</mo><msub><mrow><mi>ω</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>)</mo></math>, using several galaxy redshift surveys and 21 cm intensity mapping surveys, and find that these measurements can significantly improve the precision of cosmological parameters.

Guanlin Liu

Yu Wang

Wen Zhao

Testing the consistency of early and late cosmological parameters with BAO and CMB data

In this work, we studied four types of cosmological models with different mechanisms driving the accelerated expansion of the universe, include Braneworld models, Chaplygin Gas models, Emergent Dark Energy models, and cosmological torsion models. Considering that the dynamics of these models at low redshifts are very similar and difficult to distinguish, we used the latest and largest UV and X-ray measurements of quasars (QSOs) observations covering the range of redshift  $$0.009&lt;z&lt;7.5$$  <math> <mrow> <mn>0.009</mn> <mo>&lt;</mo> <mi>z</mi> <mo>&lt;</mo> <mn>7.5</mn> </mrow> </math>  . However, the high intrinsic dispersion of this sample and the degeneracy between cosmological model parameters, we added 2D-BAO and 3D-BAO datasets to help us constrain the parameters of these cosmological models. Our results suggest that standard cold dark matter scenario may not be the best cosmological model preferred by the high-redshift observations. The Generalized Chaplygin Gas (GCG) and cosmological constant plus torsion (named Case II) models perform best by Akaike Information Criterion (AIC), but the  $$\Lambda $$  <math> <mi>Λ</mi> </math>  CDM is the best cosmological model preferred by Bayesian Information Criterion (BIC). Our work also supports that the Phenomenologically Emergent Dark Energy and cosmological torsion models may alleviate the Hubble tension, the reported value of the Hubble constant obtained from QSO+BAO datasets combination lies between Planck 2018 observations and local measurements from the SH0ES collaboration, while other cosmological models all support that the Hubble constant tends to be closer to recent Planck 2018 results, but these model are penalized by information criterion.

Ziqiang Liu

Tonghua Liu

Xinyi Zhong

Yifei Xu

Xiaogang Zheng

Constraining on the non-standard cosmological models combining the observations of high-redshift quasars and BAO

By taking advantage of the braneworld sum rules, we explore the feasibility of constructing a flat 3-brane scenario consisting solely of positive tension branes in a 5D extension of the Lorentz-violating massive gravity. It is found that the theory supports three distinct brane configurations, one of which is exactly what we expected, consisting solely of two positive tension branes. The cosmological problem of Randall-Sundrum-1 model and the gauge hierarchy problem can be solved in this model simultaneously. Furthermore, the analysis of linear perturbations reveals that the tensor, vector and scalar modes are all massive and share the same mass spectrum, except that the ground state of vector mode is absent. Moreover, the tensor and vector modes are robust, but the scalar mode is ghost-like. Interestingly, even though the Kaluza-Klein gravitons have an extremely small mass splitting scale, an estimation of the effective gravitational potential and production of these gravitons on the brane indicates that the phenomenology of the present model is equivalent to that of the 6D ADD model.

Ke Yang

Bao-Min Gu

Yi Zhong

Braneworld sum rules and positive tension branes in a massive gravity

It is believed that gravity can be considered as a quantum coherent mediator. In this study, we propose a plan to test the existence of extra dimensions using the quantum gravity induced entanglement of masses (QGEM) experiment. This experiment involves two freely falling test masses passing through a Stern–Gerlach-like device. We investigate the entanglement witness between these masses within the framework of the Randall–Sundrum II model (RS-II). Our findings indicate that the system reaches entanglement more rapidly in the presence of extra dimensions, particularly when the radius of the extra dimension is large.

Shuai Feng

Fu-Wen Shu

Quantum gravity induced entanglement of masses with extra dimensions

A Randall–Sundrum-like braneworld scenario is constructed in a 5D extension of the Lorentz-violating massive gravity. The gauge hierarchy problem is solved in current model. The linear perturbations are calculated, and it is found that the tensor and vector perturbations are robust and free from the ghost and tachyonic instabilities, however, the scalar perturbation is a ghost filed. After Kaluza–Klein reduction, all the tensor, vector and scalar modes are massive and possess the mass splitting of order of TeV in their respective mass spectra. The massive ground states of tensor and scalar modes propagate only along the brane, however, the vector ground state is absent in the mass spectrum. By introducing the Goldberger-Wise mechanism to stabilize the extra dimension, the 4D effective theory on the brane includes a nearly massless graviton plus three towers of very massive spin-2, spin-1 and ghost spin-0 particles.

Shi-Fa Guo

A braneworld model in a massive gravity