Exploring physical features of anisotropic quark stars in Brans-Dicke theory with a massive scalar field via embedding approach

The main aim of this study is to explore the existence and salient features of spherically symmetric relativistic quark stars in the background of massive Brans-Dicke gravity.The exact solutions to the modified Einstein field equations are derived for specific forms of coupling and scalar field functions using the equation of state relating to the strange quark matter that stimulates the phenomenological MIT-Bag model as a free Fermi gas of quarks.We use a well-behaved function along with the Karmarkar condition for class-one embedding as well as junction conditions to determine the unknown metric tensors.The radii of strange compact stars viz.,PSR J1416-2230,PSR J1903+327,4U 1820-30,CenX-3,and EXO1785-248,are predicted via their observed mass for different values of the massive Brans-Dicke parameters.We explore the influences of the mass of scalar field m_(ϕ),coupling parameter ωBD,and bag constant B on state determinants and perform several tests on the viability and stability of the constructed stellar model.Conclusively,we find that our stellar system is physically viable and stable as it satisfies all the energy conditions and necessary stability criteria under the influence of a gravitational scalar field.

Exploring physical properties of compact stars in f(R,T)-gravity:An embedding approach

Solving field equations exactly in f(R,T)−gravity is a challenging task.To do so,many authors have adopted different methods such as assuming both the metric functions and an equation of state(EoS)and a metric function.However,such methods may not always lead to well-behaved solutions,and the solutions may even be rejected after complete calculations.Nevertheless,very recent studies on embedding class-one methods suggest that the chances of arriving at a well-behaved solution are very high,which is inspiring.In the class-one approach,one of the metric potentials is estimated and the other can be obtained using the Karmarkar condition.In this study,a new class-one solution is proposed that is well-behaved from all physical points of view.The nature of the solution is analyzed by tuning the f(R,T)−coupling parameterχ,and it is found that the solution leads to a stiffer EoS forχ=−1 than that forχ=1.This is because for small values ofχ,the velocity of sound is higher,leading to higher values of Mmax in the M−R curve and the EoS parameterω.The solution satisfies the causality condition and energy conditions and remains stable and static under radial perturbations(static stability criterion)and in equilibrium(modified TOV equation).The resulting M−R diagram is well-fitted with observed values from a few compact stars such as PSR J1614-2230,Vela X-1,Cen X-3,and SAX J1808.4-3658.Therefore,for different values ofχ,the corresponding radii and their respective moments of inertia have been predicted from the M−I curve.