Cosmic acceleration in f(Q) gravity: a nonlinear equation of state approach.
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| Title: | Cosmic acceleration in f(Q) gravity: a nonlinear equation of state approach. |
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| Authors: | Özansoy, Mehmet1 (AUTHOR) ozansoy.mhmt@gmail.com, Shukla, Bhupendra Kumar2 (AUTHOR) bhupendrashukla695@gmail.com, Sofuoğlu, Değer3 (AUTHOR) degers@istanbul.edu.tr, Beesham, Aroonkumar4,5,6,7 (AUTHOR) abeesham@yahoo.com, Tripathi, Rajnee8 (AUTHOR) rajneetripathi@hotmail.com |
| Source: | European Physical Journal C -- Particles & Fields. Feb2026, Vol. 86 Issue 2, p1-17. 17p. |
| Subjects: | Equations of state, Expanding universe, Physical cosmology, Hubble constant, Markov chain Monte Carlo |
| Abstract: | We investigate late-time cosmic acceleration within the framework of f(Q) gravity supplemented by a phenomenological nonlinear equation of state of the form p = A ρ - B ρ. Adopting a power-law ansatz f (Q) = γ , (Q / Q 0) n , we derive analytic expressions for the energy density and Hubble function and confront the model with a combined dataset consisting of CC, SNIa, BAO, quasar, and GRB observations covering 0.106 < z < 2.33. A Bayesian MCMC analysis constrains the parameter set H 0 , A , B , c , n and yields H 0 ≃ 71. 6 - 1.9 + 1.0 km s - 1 Mpc - 1 for the joint sample, together with a transition redshift z tr ≈ 0.68. Cosmographic diagnostics indicate a present-day deceleration parameter q 0 ≈ - 0.59 , with mild deviations of the jerk and snap parameters from their Λ CDM values at low redshift. Thermodynamic and causal consistency is ensured by the condition 0 ≤ c s 2 (z) ≤ 1 , while the matter-sector energy conditions remain satisfied up to z ∼ O (1). A statistical comparison with the concordance model shows that the proposed f (Q) + nEoS scenario achieves a goodness of fit comparable to Λ CDM over the same dataset, with χ 2 min model = 255.93 versus χ 2 min Λ CDM = 260.5 and χ red 2 ≈ 0.96 for both cases. The Akaike Information Criterion yields Δ AIC ≈ 1.4 , indicating statistical equivalence with a mild preference for Λ CDM due to its smaller parameter space. Therefore, the model provides a viable description of the late-time expansion history, allowing controlled deviations from Λ CDM that modestly alleviate, though do not resolve, the H 0 tension. Several other interesting properties of a nEoS are also elucidated upon. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | We investigate late-time cosmic acceleration within the framework of f(Q) gravity supplemented by a phenomenological nonlinear equation of state of the form p = A ρ - B ρ. Adopting a power-law ansatz f (Q) = γ , (Q / Q 0) n , we derive analytic expressions for the energy density and Hubble function and confront the model with a combined dataset consisting of CC, SNIa, BAO, quasar, and GRB observations covering 0.106 < z < 2.33. A Bayesian MCMC analysis constrains the parameter set H 0 , A , B , c , n and yields H 0 ≃ 71. 6 - 1.9 + 1.0 km s - 1 Mpc - 1 for the joint sample, together with a transition redshift z tr ≈ 0.68. Cosmographic diagnostics indicate a present-day deceleration parameter q 0 ≈ - 0.59 , with mild deviations of the jerk and snap parameters from their Λ CDM values at low redshift. Thermodynamic and causal consistency is ensured by the condition 0 ≤ c s 2 (z) ≤ 1 , while the matter-sector energy conditions remain satisfied up to z ∼ O (1). A statistical comparison with the concordance model shows that the proposed f (Q) + nEoS scenario achieves a goodness of fit comparable to Λ CDM over the same dataset, with χ 2 min model = 255.93 versus χ 2 min Λ CDM = 260.5 and χ red 2 ≈ 0.96 for both cases. The Akaike Information Criterion yields Δ AIC ≈ 1.4 , indicating statistical equivalence with a mild preference for Λ CDM due to its smaller parameter space. Therefore, the model provides a viable description of the late-time expansion history, allowing controlled deviations from Λ CDM that modestly alleviate, though do not resolve, the H 0 tension. Several other interesting properties of a nEoS are also elucidated upon. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 14346044 |
| DOI: | 10.1140/epjc/s10052-026-15310-1 |
