In this paper,the thermodynamics of the Friedmann–Lemait re–Robertson–Walker universe have been explored in f(R)theories of gravity with arbitrary matter-geometry coupling.The equivalence between the modified Fried...In this paper,the thermodynamics of the Friedmann–Lemait re–Robertson–Walker universe have been explored in f(R)theories of gravity with arbitrary matter-geometry coupling.The equivalence between the modified Friedmann equations with any spatial curvature and the first law of thermodynamics is confirmed,where the assumption of the entropy plays a crucial role.Then laws of thermodynamics in our considering case are obtained.They can reduce to the ones given in Einstein's general theory of relativity under certain conditions.Moreover,a particular model is investigated through the obtained generalized second law of thermodynamics with observational results of cosmographic parameters.展开更多
We investigated the impact of f(R,L_(m),T)gravity on the internal structure of compact stars,expecting this theory to manifest prominently in the high-density cores of such stars.We considered the algebraic function,f...We investigated the impact of f(R,L_(m),T)gravity on the internal structure of compact stars,expecting this theory to manifest prominently in the high-density cores of such stars.We considered the algebraic function,f(R,L_(m),T)=R+αTL_(m),whereαrepresents the matter-geometry coupling constant.We specifically chose the matter Lagrangian density L_(m)=-ρto explore compact stars with anisotropic pressure.To this end,we employed the MIT bag model as an equation of state.Subsequently,we numerically solved the hydrostatic equilibrium equations to obtain mass-radius relations for quark stars(QSs),examining static stability criteria,adiabatic index,and speed of sound.Finally,we used recent astrophysical data to constrain the coupling parameterα,which may lead to either larger or smaller masses for QSs,compared to their counterparts in general relativity.展开更多
基金supported by the National Natural Science Foundation of China under Grant No.12165021Science Technology Department of Yunnan Province—Yunnan University Joint Funding(2019FY003005)。
文摘In this paper,the thermodynamics of the Friedmann–Lemait re–Robertson–Walker universe have been explored in f(R)theories of gravity with arbitrary matter-geometry coupling.The equivalence between the modified Friedmann equations with any spatial curvature and the first law of thermodynamics is confirmed,where the assumption of the entropy plays a crucial role.Then laws of thermodynamics in our considering case are obtained.They can reduce to the ones given in Einstein's general theory of relativity under certain conditions.Moreover,a particular model is investigated through the obtained generalized second law of thermodynamics with observational results of cosmographic parameters.
基金Supported by Walailak University under the New Researcher Development scheme(WU67268)A.Pradhan expresses gratitude to the IUCCA in Pune,India,for offering facilities under associateship programs.In addition,İzzet Sakallıthanks TÜBİTAK,ANKOS,and SCOAP3 for their contributions.Takol Tangphati andİzzet Sakallıalso appreciate COST Actions CA21106 and CA22113 for their networking support。
文摘We investigated the impact of f(R,L_(m),T)gravity on the internal structure of compact stars,expecting this theory to manifest prominently in the high-density cores of such stars.We considered the algebraic function,f(R,L_(m),T)=R+αTL_(m),whereαrepresents the matter-geometry coupling constant.We specifically chose the matter Lagrangian density L_(m)=-ρto explore compact stars with anisotropic pressure.To this end,we employed the MIT bag model as an equation of state.Subsequently,we numerically solved the hydrostatic equilibrium equations to obtain mass-radius relations for quark stars(QSs),examining static stability criteria,adiabatic index,and speed of sound.Finally,we used recent astrophysical data to constrain the coupling parameterα,which may lead to either larger or smaller masses for QSs,compared to their counterparts in general relativity.
