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The existence of traversable wormhole (TW) in the Einstein's general theory of relativity is explored with density profile obtained from modified Newtonian dynamics (MOND) with or without a scalar field. The shape functions for wormholes and the null energy conditions (NEC) of matter in the wormhole are determined with a constant redshift function. Wormholes are found to exist with MOND density profile in the presence of exotic matter and determine the mass of a asymptotic flat wormhole geometry. The addition of an extra massless scalar field with MOND density profile permits wormholes even when NEC is obeyed at the throat depending on the initial value of the scalar field. Considering a non-linear equation of state (EoS) , (where A, B and ρc are constants) in Einstein gravity we obtain TW. In this case new classes of TW solutions are determined which depends on the EoS parameters A and B. TW exists with normal matter when ρ(r0) ⩾ ρc and with exotic matter when ρ(r0) < ρc at the throat where. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study static spherically symmetric noncommutative F(T,TG) wormhole solutions along with Lorentzian distribution. Here, T and TG are torsion scalar and teleparallel equivalent Gauss-Bonnet term, respectively. We take a particular redshift function and two F(T,TG) models. We analyze the behavior of shape function and also examine null as well as weak energy conditions graphically. It is concluded that there exist realistic wormhole solutions for both models. We also studied the stability of these wormhole solutions through equilibrium condition and found them stable. [ABSTRACT FROM AUTHOR]

In the present paper a new model of a compact star is obtained by utilizing the Krori-Barua (KB) ansatz [Krori and Barua in J. Phys. A, Math. Gen. 8:508, ] in the presence of a quintessence field characterized by a parameter ω with $-1<\omega_{q}<-\frac{1}{3}$. The obtained model of strange stars is singularity free and satisfies all the physical requirements. Our model is stable as well as it is in static equilibrium. The numerical values of the mass of the strange stars 4U1820-30 (radius=10 km), SAX J1808.4-3658(SS1) (radius=7.07 km) and Her X-1 (radius=7.7 km) calculated from our model are very close to the standard data. The interior solution is matched to the exterior Schwarzschild spacetime in the presence of a thin shell where a negative surface pressure is needed to keep the thin shell from collapsing. [ABSTRACT FROM AUTHOR]

This paper discusses a new wormhole solution that admits conformal motion, given a noncommutative-geometry background. After a discussion of the wormhole geometry and the energy conditions, the analysis proceeds with the calculation of the active gravitational mass, a discussion of the TOV equation describing the equilibrium conditions, as well as the nature of the total gravitational energy. The wormhole spacetime is not asymptotically flat and is therefore cut off at some radial distance and joined to an exterior vacuum solution. [ABSTRACT FROM AUTHOR]

Much attention has been recently devoted to modified theories of gravity, the simplest models of which overcome General Relativity simply by replacing R with F(R) in the Einstein–Hilbert action. Unfortunately, such models typically lack most of the beautiful solutions discovered in Einstein’s gravity. Nonetheless, in F(R) gravity, it has been possible to get at least few black holes, but still we do not know any empty wormhole-like spacetime solution. This paper aims to explain why it is so hard to get such solutions (given that they exist!). Few solutions are derived in the simplest cases, while only an implicit form has been obtained in the non-trivial case. [ABSTRACT FROM AUTHOR]

Low energy limits of a string theory suggests that the gravity action should include quadratic and higher-order curvature terms, in the form of dimensionally continued Gauss–Bonnet densities. Einstein–Gauss–Bonnet is a natural extension of the general relativity to higher dimensions in which the first and second-order terms correspond, respectively, to general relativity and Einstein–Gauss–Bonnet gravity. We obtain five-dimensional (5D) black hole solutions, inspired by a noncommutative geometry, with a static spherically symmetric, Gaussian mass distribution as a source both in the general relativity and Einstein–Gauss–Bonnet gravity cases, and we also analyzes their thermodynamical properties. Owing the noncommutative corrected black hole, the thermodynamic quantities have also been modified, and phase transition is shown to be achievable. The phase transitions for the thermodynamic stability, in both the theories, are characterized by a discontinuity in the specific heat at , with the stable (unstable) branch for . The metric of the noncommutative inspired black holes smoothly goes over to the Boulware–Deser solution at large distance. The paper has been appended with a calculation of black hole mass using holographic renormalization. [ABSTRACT FROM AUTHOR]