Dark Energy Nature in Logarithmic f(R,T)f(R,T) Cosmology

The present research paper is an investigation of dark energy nature of logarithmic $f(R, T)$-gravity cosmology in a flat FLRW space-time universe. We have derived modified Einstein's field equations for the function $f(R, T)=R-16\pi G\alpha\ln(T)$ where $R$ is the Ricci scalar curvature, $T$ is the trace of the stress energy momentum tensor and $\alpha$ is a model parameter. We have solved field equations in the form of two fluid scenario as perfect-fluid and dark-fluid, where dark fluid term is derived in the form of perfect fluid source. We have made an observational constraints on the cosmological parameters $\Omega_{(m)}, \omega^{(de)}$ and $H_{0}$ using $\chi^{2}$ test with observational datasets like Pantheon sample of SNe Ia and $H(z)$. With these constraints we have discussed our model with deceleration parameter $q$, energy parameters $\Omega_{(m)}, \Omega_{(de)}$, EoS parameter $\omega^{(de)}$ etc. Also, we have done Om diagnostic analysis. The derived $f(R, T)$ model shows a quintessence dark energy model $\omega^{(de)}>-1$ and late-time universe approaches to $\Lambda$CDM model.Comment: 16 pages, 8 figure

Modeling Transit Dark Energy in f(R,Lm)f(R, L_m)-gravity

This research paper deals with a transit dark energy cosmological model in $f(R, L_{m})$-gravity with observational constraints. For this, we consider a flat FLRW space-time and have taken a cosmological cosntant-like parameter $\beta$ in our field equations. The model has two energy parameters~ $\Omega_{m0}~ and~ \Omega_{\beta0}$, which govern the mechanism of the universe, in particular its present accelerated phase. To make the model cope with the present observational scenario, we consider three types of observational data set: $46$ Hubble parameter data set, SNe Ia $715$ data sets of distance modulus and apparent magnitude, and $40$ datasets of SNe Ia Bined compilation in the redshift $0\leq z<1.7$. We have approximated the present values of the energy parameters by applying $R^{2}$ and $\chi^{2}$-test in the observational and theoretical values of Hubble, distance modulus, and apparent magnitude parameters. Also, we have measured the approximate present values of cosmographic coefficients $\{H_{0}, q_{0}, j_{0}, s_{0}, l_{0}, m_{0}\}$. It is found that our approximated value-based model fits best with the observational module. We have found that as $t\to\infty$ (or $z\to 0$) then $\{q, j, s, l, m\}\to\{-1, 1, 1, 1, 1\}$. The cosmic age of the present universe is also approximated and comes up to the expectation. Our model shows a transit phase of the present accelerating universe with a deceleration in the past and has a transition point.Comment: 22 pages, 17 figures

Transit cosmological models in F(R,Tˉ)F(R,{\bar{T}}) F ( R , T ¯ ) gravity theory

Abstract In the present paper, we investigate some exact cosmological models in $$F(R,{\bar{T}})$$ F ( R , T ¯ ) gravity theory. We have considered the arbitrary function $$F(R, {\bar{T}})=R+\lambda {\bar{T}}$$ F ( R , T ¯ ) = R + λ T ¯ where $$\lambda$$ λ is an arbitrary constant, $$R, {\bar{T}}$$ R , T ¯ are respectively, the Ricci-scalar curvature and the torsion. We have solved the field equations in a flat FLRW spacetime manifold for Hubble parameter and using the MCMC analysis, we have estimated the best fit values of model parameters with $$1-\sigma , 2-\sigma , 3-\sigma$$ 1 - σ , 2 - σ , 3 - σ regions, for two observational datasets like H(z) and Pantheon SNe Ia datasets. Using these best fit values of model parameters, we have done the result analysis and discussion of the model. We have found a transit phase decelerating-accelerating universe model with transition redshifts $$z_{t}=0.4438_{-0.0790}^{+0.1008}, 0.3651_{-0.0904}^{+0.1644}$$ z t = 0 . 4438 - 0.0790 + 0.1008 , 0 . 3651 - 0.0904 + 0.1644 . The effective dark energy equation of state varies as $$-1\le \omega _{de}\le -0.5176$$ - 1 ≤ ω de ≤ - 0.5176 and the present age of the universe is found as $$t_{0}=13.8486_{-0.0640}^{+0.1005}, 12.0135_{-0.2743}^{+0.6206}$$ t 0 = 13 . 8486 - 0.0640 + 0.1005 , 12 . 0135 - 0.2743 + 0.6206 Gyrs, respectively for two datasets

Quintessence Behavior of an Anisotropic Bulk Viscous Cosmological Model in Modified f(Q)-Gravity

In this article, we consider an anisotropic viscous cosmological model having LRS Bianchi type I spacetime with f(Q) gravity. We investigate the modified f(Q) gravity with form f(Q)=&alpha;Q2+&beta;, where Q is the non-metricity scalar and &alpha;, &beta; are the positive constants. From the modified Einstein&rsquo;s field equation having the viscosity coefficient &xi;(t)=&xi;0H, the scale factor is derived as a(t)=2sinhm+26&xi;0&alpha;(2m+1)t. We apply the observational constraints on the apparent magnitude m(z) using the &chi;2 test formula with the observational data set such as JLA, Union 2.1 compilation and obtained the best approximate values of the model parameters m,&alpha;,H0,&xi;0. We find a transit universe which is accelerating at late times. We also examined the bulk viscosity equation of state (EoS) parameter &omega;v and derived its current value satisfying &omega;v&lt;&minus;1/3, which shows the dark energy dominating universe evolution having a cosmological constant, phantom, and super-phantom evolution stages. It tends to the &Lambda; cold dark matter (&Lambda;CDM) value (&omega;v=&minus;1) at late times. We also estimate the current age of the universe as t0&asymp;13.6 Gyrs and analyze the statefinder parameters with (s,r)&rarr;(0,1) as t&rarr;&infin;

Quintessence Behavior of an Anisotropic Bulk Viscous Cosmological Model in Modified <i>f</i>(<i>Q</i>)-Gravity

In this article, we consider an anisotropic viscous cosmological model having LRS Bianchi type I spacetime with f(Q) gravity. We investigate the modified f(Q) gravity with form f(Q)=αQ2+β, where Q is the non-metricity scalar and α, β are the positive constants. From the modified Einstein’s field equation having the viscosity coefficient ξ(t)=ξ0H, the scale factor is derived as a(t)=2sinhm+26ξ0α(2m+1)t. We apply the observational constraints on the apparent magnitude m(z) using the χ2 test formula with the observational data set such as JLA, Union 2.1 compilation and obtained the best approximate values of the model parameters m,α,H0,ξ0. We find a transit universe which is accelerating at late times. We also examined the bulk viscosity equation of state (EoS) parameter ωv and derived its current value satisfying ωv−1/3, which shows the dark energy dominating universe evolution having a cosmological constant, phantom, and super-phantom evolution stages. It tends to the Λ cold dark matter (ΛCDM) value (ωv=−1) at late times. We also estimate the current age of the universe as t0≈13.6 Gyrs and analyze the statefinder parameters with (s,r)→(0,1) as t→∞

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Revisiting the plant growth-promoting rhizobacteria: lessons from the past and objectives for the futurePlant beneficial rhizobacteria (PBR) is a group of naturally occurring rhizospheric microbes that enhance nutrient availability and induce biotic and abiotic stress tolerance through a wide array of mechanisms to enhance agricultural sustainability. Application of PBR has the potential to reduce worldwide requirement of agricultural chemicals and improve agro-ecological sustainability. The PBR exert their beneficial effects in three major ways; (1) fix atmospheric nitrogen and synthesize specific compounds to promote plant growth, (2) solubilize essential mineral nutrients in soils for plant uptake, and (3) produce antimicrobial substances and induce systemic resistance in host plants to protect them from biotic and abiotic stresses. Application of PBR as suitable inoculants appears to be a viable alternative technology to synthetic fertilizers and pesticides. Furthermore, PBR enhance nutrient and water use efficiency, influence dynamics of mineral recycling, and tolerance of plants to other environmental stresses by improving health of soils. This report provides comprehensive reviews and discusses beneficial effects of PBR on plant and soil health. Considering their multitude of functions to improve plant and soil health, we propose to call the plant growth-promoting bacteria (PGPR) as PBR.Not Availabl

Book of Abstracts of the 2nd International Conference on Applied Mathematics and Computational Sciences (ICAMCS-2022)

It is a great privilege for us to present the abstract book of ICAMCS-2022 to the authors and the delegates of the event. We hope that you will find it useful, valuable, aspiring, and inspiring. This book is a record of abstracts of the keynote talks, invited talks, and papers presented by the participants, which indicates the progress and state of development in research at the time of writing the research article. It is an invaluable asset to all researchers. The book provides a permanent record of this asset. Conference Title: 2nd International Conference on Applied Mathematics and Computational SciencesConference Acronym: ICAMCS-2022Conference Date: 12-14 October 2022Conference Organizers: DIT University, Dehradun, IndiaConference Mode: Online (Virtual