In this work, we investigate three representative new-physics resonances that couple to Standard Model (SM) quarks through flavor-changing interactions involving the top quark. We identify the possible SMEFT operators at the electroweak scale and analyze their phenomenology.

China

Min Huang

Yandong Liu

Hao Zhang

Exploring new resonances with direct top flavor changing interactions * Min Huang and Hao Zhang is supported in part by the National Science Foundation of China (12575114, 12235001, 12075257)

We present a cosmological model-independent framework for testing general relativity (GR) on galactic scales by combining baryon acoustic oscillation (BAO) angular scale measurements with 120 galaxy-scale strong gravitational lensing systems. Using artificial neural networks (ANNs) and cubic spline reconstruction, we reconstruct the BAO angular scale from SDSS, BOSS, eBOSS, and DESI Data Release 2 (DR2), and infer the angular diameter distances to lenses and sources. Crucially, all the quantities used in the GR test are derived from observations and are independent of cosmological parameters such as the Hubble constant, the sound horizon, or the dark energy equation of state, minimizing potential biases from model-dependent distance priors. These distances are then incorporated into the strong lensing likelihood to constrain the parameterized post-Newtonian (PPN) parameter $$\gamma _\textrm{PPN}$$ under two lens mass models: a constant-density-slope model ( $$P_1$$ ) and a redshift-evolving model ( $$P_2$$ ). For the $$P_1$$ model, the ANN reconstruction yields $$\gamma _\textrm{PPN} = 1.102^{+0.148}_{-0.125}$$ , consistent with GR at $$1\sigma $$ confidence level, while the cubic spline gives $$\gamma _\textrm{PPN} = 1.150^{+0.139}_{-0.118}$$ , consistent with GR at $$2\sigma $$ confidence level. For the $$P_2$$ model, the ANN reconstruction gives $$\gamma _\textrm{PPN} = 1.315^{+0.181}_{-0.155}$$ , compatible with GR at $$2\sigma $$ , while the spline gives $$\gamma _\textrm{PPN} = 1.485^{+0.193}_{-0.168}$$ , showing mild tension at $$\sim 2.5\sigma $$ . The constraints exhibit a clear dependence on the adopted lens mass model, underscoring the critical role of lens modeling. No significant correlation is observed between $$\gamma _\textrm{PPN}$$ and the Einstein radius. Overall, current galaxy-scale observations are consistent with GR, providing no evidence for deviations from Einstein’s theory on kiloparsec scales.

Hengyu Wu

Tonghua Liu

Chenggang Shao

Testing general relativity on galactic scales via DESI-BAO and strong lensing: circumventing assumptions on the Hubble constant, sound horizon, and dark energy

We carry out a comparative analysis of the standard $$\Lambda $$ CDM cosmological model and the alternative $$R_h=ct$$ framework using recent observational data from cosmic chronometers (CC), Type Ia supernova, and baryon acoustic oscillations. The study evaluates the ability of each model to reproduce the observed expansion history of the Universe through a joint statistical assessment based on $$\chi ^2$$ statistics, Akaike Information Criterion ($\textit{AIC}$), Bayesian Information Criterion ($\textit{BIC}$), and Bayes factor. While both models yield acceptable fits, $$\Lambda $$ CDM consistently attains lower information-criterion values and higher likelihood, indicating a superior overall performance. An examination of the redshift evolution of the Hubble parameter $\textit{H}$($\textit{z}$) and the deceleration parameter $\textit{q}$($\textit{z}$) shows that $$\Lambda $$ CDM naturally captures the transition from early-time deceleration to late-time acceleration, whereas $$R_h=ct$$ predicts a strictly linear expansion. We also estimate the age of the Universe within both models, obtaining $$t_0^{\Lambda CDM}= 13.676_{-0.81}^{+0.92}$$ Gyr and $$t_0^{R_h=ct}= 16.035_{-0.98}^{+1.09}$$ Gyr. The posterior-derived age in the $$\Lambda $$ CDM framework is broadly consistent with the Planck 2018 CMB result. This agreement is interpreted as a validation of the analysis pipeline and the reliability of the DESI DR2, CC, and supernova constraints, rather than as a new result for $$\Lambda $$ CDM, and serves as a benchmark for assessing the viability of the $$R_h=ct$$ model. Recent JWST observations of unexpectedly mature high-redshift galaxies have renewed discussion regarding the timeline of early structure formation; although these results remain under active investigation, they underscore that fully resolving cosmic evolution may require refinements beyond the concordance paradigm.

India

Amritansh Mehrotra

Azerbaijan

S. Pacif

Brazil

A. Santos

Joint constraints on $$R_h=ct$$ cosmology from DESI DR2 BAO, CC, and SN$\textit{Ia}$ Pantheon $$^+$$ sample

Evidences for evolving dark energy are shown using baryon acoustic oscillation measurements from the recent Dark Energy Spectroscopic Instrument Data Release 2, combined with different Type Ia supernova datasets (Pantheon $$^+$$ , DES-Dovekie, and Union3) and the CMB compressed likelihood. We examine several dark energy parameterizations, including the Logarithmic, Exponential, CPL, BA, JBP, Thawing, Mirage, and GEDE models. Analyzing the DESI DR2 measurements alone, we find that evidence for evolving dark energy is primarily driven by the LRG1-2 tracers, as their inclusion yields a preferred value of $$w_0 > -1$$ . However, as each tracer provides only limited observables, this preference can result in an underconstrained and potentially unstable inference. Further, we find that each dark energy model predicts values in the $$w_0 > -1$$ , $$w_a < 0$$ quadrant, a region characterized by the Quintom-B type dark energy scenario. The logarithmic bayes factor shows that, among all models, the Mirage model shows the inconclusive-to-moderate evidence across all dataset combinations. Consistently, the statistical significance remains modest, with $$N\sigma \sim 1.1$$ -2.3, and no model showing a robust preference for dynamical dark energy using late-time datasets alone. The evolution of $\textit{w}$($\textit{z}$) shows a phantom crossing around $$z \sim 0.5$$ in most dynamical dark energy models, and the evolution of $$f_{\textrm{DE}}(z)$$ converges to $$f_{\textrm{DE}}(0) = 1$$ in all dark energy models.

Romania

Himanshu Chaudhary

Italy

Salvatore Capozziello

Vipin Sharma

Switzerland

Isidro Gómez-Vargas

Thailand

G. Mustafa

Evidence for evolving dark energy from DESI DR2 BAO and Pantheon $$^+$$ , DES-Dovekie, and Union3

We perform a comprehensive observational test of a canonical quintessence model driven by an exponential potential, motivated by its emergence in higher-dimensional theories, string-inspired scenarios, and modified gravity. Using a Markov Chain Monte Carlo framework, we constrain the model with the latest high-precision observational datasets–Cosmic Chronometers, Baryon Acoustic Oscillation, Pantheon $$^+$$ , and DES-SN5YR Type Ia Supernovae. The combined data significantly tighten the parameter bounds on $$(H_0, \Omega _{m_0}, \eta _0, \gamma )$$ and yield predictions for the Hubble parameter $\textit{H}$($\textit{z}$), the distance modulus $$\mu (z)$$ , and the scaled comoving angular diameter distance that remain in excellent agreement with observations and closely follow the $$\Lambda $$ CDM baseline. In addition, an information-theoretic model comparison based on the Akaike Information Criterion shows that the exponential quintessence model remains statistically comparable with the $$\Lambda $$ CDM scenario, despite the penalty associated with its additional parameters. The model naturally reproduces the transition from matter domination to late-time acceleration, maintains total equation of state $$\omega _{\textrm{tot}} > -1$$ as expected for canonical scalar fields, and provides an age of the universe consistent with $\textit{Planck}$ 2018. The Statefinder diagnostics show trajectories approaching the $$\Lambda $$ CDM fixed point, while allowing small observable departures. Energy condition analysis confirms physical viability, with only the Strong Energy Condition violated at late times, as required for acceleration. Overall, our results show that quintessence with an exponential potential provides a stable, observationally consistent alternative to $$\Lambda $$ CDM. Using the latest high-precision datasets, we obtain some of the most stringent constraints on this exponential-potential quintessence model, reaffirming its viability as a compelling dynamical explanation for dark energy.

Sanjeeda Sultana

Surajit Chattopadhyay

Cosmological dynamics of exponential quintessence constrained by BAO, cosmic chronometers, and DES-SN5YR/Pantheon $$^+$$ data

In this work, we observationally constrain two phenomenological $\textit{f}$($\textit{G}$) gravity models at the background level using Type Ia supernovae from the Pantheon+ (PP) sample, cosmic chronometer (CC) measurements, and the recent Baryon Acoustic Oscillation (BAO) data released by DESI. The analysis is performed using two dataset combinations: (i) PP+CC and (ii) PP+CC+DESI BAO. The modified Friedmann equations are solved numerically for two functional forms of $\textit{f}$($\textit{G}$) gravity, namely the power-law and exponential models. The cosmological parameters are constrained through Markov Chain Monte Carlo simulations. To evaluate the statistical performance of the models, we compute the corrected Akaike Information Criterion (AIC $$_c)$$ and the Bayesian Information Criterion (BIC). Our results show that both $\textit{f}$($\textit{G}$) models provide background evolutions consistent with current observational data. While the AIC $$_c$$ criterion indicates that the models are statistically comparable to the $$\varLambda $$ CDM model, the BIC slightly favors the simpler $$\varLambda $$ CDM scenario due to its smaller number of free parameters. In addition, the exponential model predicts a distinctive future dynamical feature, namely an additional transition from accelerated to decelerated expansion at $$z \approx -0.086,$$ which is absent in both the power-law model and the $$\varLambda $$ CDM framework.

Praveen Dhankar

Morocco

Dalale Mhamdi

Rwanda

Albert Munyeshyaka

Darshan Kumar

Joseph Ntahompagaze

Taoufik Ouali

Testing Gauss–Bonnet gravity with DESI BAO data

The <italic>R</italic> 2 and the single-field-like regime of <italic>R</italic> 2-Higgs inflation are disfavored by the observed high spectral index <italic>n<inf>s</inf></italic> from the combined cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements at the &#8239;&#8764;&#8239;2 <italic>&#963;</italic> level. The addition of a dimension-six <italic>R</italic> 3 term in the action helps alleviate this tension. We show that the parameter space accounting for the observed high <italic>n<inf>s</inf></italic> also induces rapid Goldstone and Higgs preheating. The preheating, especially from Goldstone modes, helps match the CMB and inflationary scales, which in turn supports the observed <italic>n<inf>s</inf></italic>.

Tanmoy Modak

Echoes of <italic>R</italic> 3 modification and Goldstone preheating in the CMB-BAO landscape

We investigate and update observational constraints on cosmological parameters within the $$\Lambda $$ CDM and dynamical dark energy frameworks, using a new compilation of the transverse (or 2D) BAO data, measurements that provide a relatively model-independent estimate of the BAO angular scale at a given redshift. Firstly, we assess the consistency of this compilation with CMB-Planck data and recent BAO results from the DESI collaboration. After confirming minimal tension with CMB data, we perform a series of joint analyses combining CMB data with the 2D BAO compilation, as well as with several recent Type Ia supernova (SNIa) samples. In all cases, we compare the constraining power of the 2D BAO data with that of DESI DR2 data (3D BAO). Our results indicate that combining 2D BAO with CMB and SNIa data provides observational constraints that are in agreement with those obtained using DESI DR2 data. Although the precision of DESI DR2 results remains higher, as expected due to the more accurate 3D measurements, the 2D BAO compilation combined with other probes yields strong constraints. For example, in the $$\Lambda $$ CDM context, we find (CMB + 2D BAO): $$H_0 = 68.16^{+0.41}_{-0.37} \,\,\, \text {km s}^{-1}\,\text {Mpc}^{-1}$$ and $$\Sigma m_{\nu } < 0.081~\textrm{eV}$$ (95% CL). These results are consistent with analogous analyses using DESI DR2. Several other cases are investigated and discussed in the main text. Our results show that this new 2D BAO compilation is robust and delivers meaningful cosmological constraints. Parameters from 2D BAO alone agree with CMB-only results, with no significant tension. Overall, 2D and 3D BAO provide consistent and complementary information when combined with other probes.

Miguel Sabogal

Rafael Nunes

Felipe Avila

Armando Bernui

Updated cosmological constraints from 2D BAO measurements: a new compilation and comparison with DESI DR2

This work reexamines cosmological parameter constraints from the DESI Data Release 2 baryon acoustic oscillation (BAO) measurements using the distance-basis representation $$(D_V/r_d,\,D_M/D_H)$$ , which separates the isotropic BAO scale from the scale-free Alcock–Paczynski ratio. This work compares $$\Lambda $$ CDM, $$\omega \textrm{CDM}$$ , and $$\omega _{0}\omega _{a}\textrm{CDM}$$ models to evaluate how the choice of data basis and the width of the prior on $$\omega _a$$ affect dark-energy inference. Ratio-only fits ( $$D_M/D_H$$ ) amplify the $$(\omega _0,\,\omega _a)$$ degeneracy and can produce large apparent shifts in point estimates without genuine evidence for dynamical dark energy. Joint fits using $$(D_V/r_d, D_M/D_H)$$ restore parameter consistency and show that these shifts mainly trace the degeneracy ridge. The pivoted equation of state, $$\omega _p=\omega (a_p)\simeq -0.9\pm 0.1$$ at $$z_p\simeq 0.34$$ , remains stable and consistent with a cosmological constant within $$1\sigma $$ . Model-selection diagnostics (AIC, BIC, and Bayes factors) provide only moderate support for $$\Lambda $$ CDM, indicating no significant evidence for an evolving $$\omega (a)$$ . These findings clarify the interplay among basis choice, absolute-scale anchoring, and degeneracy geometry in BAO-only dark-energy analyses, providing a benchmark for future DESI and next-generation surveys.

South Korea

Seokcheon Lee

Assessing the robustness of the CPL parametrization to basis and prior variations: insights from DESI DR2 BAO data

Using the latest observational data, we constrain the inflationary dynamics and the subsequent reheating epoch. Predictions for both phases can be significantly improved by employing numerically computed results compared to the slow-roll approximations. These results enable a more accurate reassessment of the observational viability of inflationary models, provide tighter constraints on the reheating history, and help lift the degeneracies in the predictions of inflation and reheating dynamics. Given current observational bounds, this enables a more accurate understanding of the early universe physics.

Ying-Ying Ye

Bao-Min Gu

Confronting inflation and reheating with observations: Improved predictions