Effective $\Lambda$CDM model emerging from $f(Q,T)$ under a special EOS limit in symmetric cosmology with Bayesian and ANN observational constraints

Abstract

In this work, we investigate the cosmological consequences of an effective $\Lambda$CDM model emerging from the more general $f(Q,T)$ gravity theory under the special equation-of-state condition $\rho +p=0$. Under this limit, the field equations yield the constraint $F(Q,T)H(t)=C$, implying that the function $F=f_Q$ becomes purely dependent on the non-metricity scalar $Q$, and the background evolution mimics that of the standard $\Lambda$CDM model. We derive the resulting functional forms of $f(Q)$, obtain the corresponding effective cosmological constant, and analyze the physical nature of this reduction. To test the model against observations, we perform a background-level parameter estimation for $H_0$ and ${\Omega }_m$, and evaluate the derived parameter $S_8$ (anchored to the Planck baseline ${\sigma }_8$) using cosmic chronometers (CC), baryon acoustic oscillations (BAO), and Pantheon+ SN Ia datasets. A dual-pipeline analysis is carried out using conventional Bayesian Markov Chain Monte Carlo (MCMC) sampling alongside a machine-learning based Artificial Neural Network (ANN) emulator deployed as a complementary consistency check. We demonstrate that the ANN approach successfully emulates the continuous parameter space with high computational efficiency, yielding results in close agreement with the standard MCMC likelihood framework. Because the background evolution strictly mimics the standard $\Lambda$CDM paradigm, the model successfully reproduces recent observational trends and recovers standard parameter constraints without dynamically resolving the baseline $H_0$ and $S_8$ tensions. Our results indicate that effective $\Lambda$CDM scenarios derived from $f(Q,T)$ gravity provide a viable and consistent with recent observational data.

18 Pages, 10 Figures

References in corpus (46)

• Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
• Measurements of Omega and Lambda from 42 High-Redshift Supernovae
• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters
• Detection of the Baryon Acoustic Peak in the Large-Scale Correlation Function of SDSS Luminous Red Galaxies
• f(R) Theories Of Gravity
• Cosmological parameters from SDSS and WMAP
• f(R) theories
• Cosmological Constant - the Weight of the Vacuum
• The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological analysis of the DR12 galaxy sample
• f(R,T) gravity
• The Case for a Positive Cosmological Lambda-term
• The Complete Light-curve Sample of Spectroscopically Confirmed Type Ia Supernovae from Pan-STARRS1 and Cosmological Constraints from The Combined Pantheon Sample
• The 6dF Galaxy Survey: Baryon Acoustic Oscillations and the Local Hubble Constant
• The Cosmological Constant
• A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km/s/Mpc Uncertainty from the Hubble Space Telescope and the SH0ES Team
• Baryon Acoustic Oscillations in the Sloan Digital Sky Survey Data Release 7 Galaxy Sample
• f(T) teleparallel gravity and cosmology
• The Pantheon+ Analysis: Cosmological Constraints
• Dark torsion as the cosmic speed-up
• A 6% measurement of the Hubble parameter at $z\sim 0.45$: direct evidence of the epoch of cosmic re-acceleration
• Information criteria for astrophysical model selection
• Improved constraints on the expansion rate of the Universe up to z~1.1 from the spectroscopic evolution of cosmic chronometers
• The WiggleZ Dark Energy Survey: mapping the distance-redshift relation with baryon acoustic oscillations
• Coincident General Relativity
• Dark energy in modified Gauss-Bonnet gravity: late-time acceleration and the hierarchy problem
• KiDS-1000 Cosmology: Multi-probe weak gravitational lensing and spectroscopic galaxy clustering constraints
• $f(Q,T)$ gravity
• Observational constraints of $f(Q)$ gravity
• A systematic approach to generalisations of General Relativity and their cosmological implications
• Cosmological solutions and growth index of matter perturbations in $f(Q)$ gravity
• Cosmography of f(R) gravity
• From cosmic deceleration to acceleration: new constraints from SN Ia and BAO/CMB
• Static Spherically Symmetric Wormholes in $f(R,T)$ Gravity
• Cosmological Solutions of $f(T)$ Gravity
• Thermodynamics of cosmological horizons in $f(T)$ gravity
• The Pantheon+ Analysis: SuperCal-Fragilistic Cross Calibration, Retrained SALT2 Light Curve Model, and Calibration Systematic Uncertainty
• Cosmic acceleration with bulk viscosity in modified $f(Q)$ gravity
• $f(Q,T)$ gravity models with observational constraints
• Constraining $f(Q,T)$ gravity from energy conditions
• Cosmological viable models in $f(T,B)$ gravity as solutions to the $H_0$ tension
• Does the entropy of the Universe tend to a maximum?
• Late time cosmological approach in mimetic $f(R,T)$ gravity
• Geometrically deformed charged anisotropic models in $f(Q,T)$ gravity
• Impact of dark matter galactic halo models on wormhole geometry within $f(Q,T)$ gravity
• Conformally symmetric wormhole solutions supported by non-commutative geometries in the context of $f(Q,T)$ gravity
• Composite nature of $Z_b$ states from data analysis