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<p>We investigate the cosmological implications of a tanh-parametrized scalar field model in the framework of modified <InlineEquation ID="IEq2"> <EquationSource Format="MATHML"><math> <mi>f</mi> <mo stretchy="false">(</mo> <mi>Q</mi> <mo>,</mo> <msub> <mi>L</mi> <mi>m</mi> </msub> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$f(Q, L_{m})$</EquationSource> </InlineEquation> gravity by adopting the form <InlineEquation ID="IEq3"> <EquationSource Format="MATHML"><math> <mi>f</mi> <mo stretchy="false">(</mo> <mi>Q</mi> <mo>,</mo> <msub> <mi>L</mi> <mi>m</mi> </msub> <mo stretchy="false">)</mo> <mo>=</mo> <mi>β</mi> <mi>Q</mi> <mo>+</mo> <mi>δ</mi> <msub> <mi>L</mi> <mi>m</mi> </msub> </math></EquationSource> <EquationSource Format="TEX">$f(Q, L_{m})=\beta Q+\delta L_{m}$</EquationSource> </InlineEquation> along with a scalar field energy density <InlineEquation ID="IEq4"> <EquationSource Format="MATHML"><math> <msub> <mi>ρ</mi> <mi>ϕ</mi> </msub> <mo>=</mo> <msub> <mi>ρ</mi> <mrow> <mi>c</mi> <mn>0</mn> </mrow> </msub> <mo>tanh</mo> <mo stretchy="false">(</mo> <mi>A</mi> <mo>+</mo> <mi>B</mi> <mi>z</mi> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$\rho _{\phi }= \rho _{c0} \tanh (A + Bz)$</EquationSource> </InlineEquation>. Using MCMC methods and combining 31 cosmic chronometer data points, 15 BAO, DESI DR2 BAO and 1701 Pantheon+ samples, we constrain the model parameters and obtain <InlineEquation ID="IEq5"> <EquationSource Format="MATHML"><math> <msub> <mi>H</mi> <mn>0</mn> </msub> <mo>=</mo> <msubsup> <mn>74.284</mn> <mrow> <mo>−</mo> <mn>4.275</mn> </mrow> <mrow> <mo>+</mo> <mn>4.155</mn> </mrow> </msubsup> </math></EquationSource> <EquationSource Format="TEX">$H_{0}=74.284^{+4.155}_{-4.275}$</EquationSource> </InlineEquation>, <InlineEquation ID="IEq6"> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="normal">Ω</mi> <mrow> <mi>m</mi> <mn>0</mn> </mrow> </msub> <mo>=</mo> <msubsup> <mn>0.326</mn> <mrow> <mo>−</mo> <mn>0.072</mn> </mrow> <mrow> <mo>+</mo> <mn>0.093</mn> </mrow> </msubsup> </math></EquationSource> <EquationSource Format="TEX">$\Omega _{m0}=0.326^{+0.093}_{-0.072}$</EquationSource> </InlineEquation> and <InlineEquation ID="IEq7"> <EquationSource Format="MATHML"><math> <mi>B</mi> <mo>=</mo> <mo>−</mo> <msubsup> <mn>0.001</mn> <mrow> <mo>−</mo> <mn>0.030</mn> </mrow> <mrow> <mo>+</mo> <mn>0.030</mn> </mrow> </msubsup> </math></EquationSource> <EquationSource Format="TEX">$B=-0.001^{+0.030}_{-0.030}$</EquationSource> </InlineEquation>. The model predicts a transition redshift <InlineEquation ID="IEq8"> <EquationSource Format="MATHML"><math> <msub> <mi>z</mi> <mrow> <mi>t</mi> <mi>r</mi> </mrow> </msub> <mo>=</mo> <mn>0.5914</mn> </math></EquationSource> <EquationSource Format="TEX">$z_{tr}=0.5914$</EquationSource> </InlineEquation> and a present deceleration parameter <InlineEquation ID="IEq9"> <EquationSource Format="MATHML"><math> <msub> <mi>q</mi> <mn>0</mn> </msub> <mo>=</mo> <mo>−</mo> <mn>0.5167</mn> </math></EquationSource> <EquationSource Format="TEX">$q_{0}=-0.5167$</EquationSource> </InlineEquation>, consistent with a Universe transitioning from deceleration to acceleration. We further analyze the evolution of the EoS parameter, density components and statefinder diagnostics in which all parameters show asymptotic convergence to a de Sitter phase. Additionally, we study black hole mass accretion within an effective framework, showing its dependence on the scalar field dynamics governed by the cosmological evolution. This work highlights the compatibility of tanh-scalar field forms with <InlineEquation ID="IEq10"> <EquationSource Format="MATHML"><math> <mi>f</mi> <mo stretchy="false">(</mo> <mi>Q</mi> <mo>,</mo> <msub> <mi>L</mi> <mi>m</mi> </msub> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$f(Q, L_{m})$</EquationSource> </InlineEquation> gravity in describing cosmic acceleration and gravitational phenomena.</p>

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Observational signatures of scalar field dynamics in modified \(f(Q, L_{m})\) gravity

  • 期刊论文

  • 发表日期：

    2026年5月13日

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  • Amit Samaddar,
  • S. Surendra Singh

摘要

We investigate the cosmological implications of a tanh-parametrized scalar field model in the framework of modified f ( Q , L m ) $f(Q, L_{m})$ gravity by adopting the form f ( Q , L m ) = β Q + δ L m $f(Q, L_{m})=\beta Q+\delta L_{m}$ along with a scalar field energy density ρ ϕ = ρ c 0 tanh ( A + B z ) $\rho _{\phi }= \rho _{c0} \tanh (A + Bz)$ . Using MCMC methods and combining 31 cosmic chronometer data points, 15 BAO, DESI DR2 BAO and 1701 Pantheon+ samples, we constrain the model parameters and obtain H 0 = 74.284 − 4.275 + 4.155 $H_{0}=74.284^{+4.155}_{-4.275}$ , Ω m 0 = 0.326 − 0.072 + 0.093 $\Omega _{m0}=0.326^{+0.093}_{-0.072}$ and B = − 0.001 − 0.030 + 0.030 $B=-0.001^{+0.030}_{-0.030}$ . The model predicts a transition redshift z t r = 0.5914 $z_{tr}=0.5914$ and a present deceleration parameter q 0 = − 0.5167 $q_{0}=-0.5167$ , consistent with a Universe transitioning from deceleration to acceleration. We further analyze the evolution of the EoS parameter, density components and statefinder diagnostics in which all parameters show asymptotic convergence to a de Sitter phase. Additionally, we study black hole mass accretion within an effective framework, showing its dependence on the scalar field dynamics governed by the cosmological evolution. This work highlights the compatibility of tanh-scalar field forms with f ( Q , L m ) $f(Q, L_{m})$ gravity in describing cosmic acceleration and gravitational phenomena.