Morris-Thorne wormholes in static pseudospherically symmetric spacetimes

In this paper we study static spherically symmetric wormhole solutions sustained by matter sources with isotropic pressure. We show that such spherical wormholes do not exist in the framework of zero-tidal-force wormholes. On the other hand, it is shown that for the often used power-law shape function there is no spherically symmetric traversable wormholes sustained by sources with a linear equation of state $p=\omega \rho$ for the isotropic pressure, independently of the form of the redshift function $\phi(r)$. We consider a solution obtained by Tolman at 1939 for describing static spheres of isotropic fluids, and show that it also may describe wormhole spacetimes with a power-law redshift function, which leads to a polynomial shape function, generalizing a power-law shape function, and inducing a solid angle deficit.

Exploring the applicability of traversable wormhole formation in [formula omitted] gravity

A possible candidate for the late time accelerated expanding universe is phantom energy, which possesses rather bizarre properties, such as the prediction of a Big Rip singularity and the violation of the null energy condition. The latter is a fundamental ingredient of traversable wormholes, and it has been shown that phantom energy may indeed sustain these exotic geometries. Inspired by the evolving dark energy parameter crossing the phantom divide, we consider in this work a varying equation of state parameter dependent on the radial coordinate, i.e., ω(r) = p(r)/ρ(r). We shall impose that phantom energy is concentrated in the neighbourhood of the throat, to ensure the flaring out condition, and several models are analysed. We shall also consider the possibility that these phantom wormholes be sustained by their own quantum fluctuations. The energy density of the graviton one-loop contribution to a classical energy in a phantom wormhole background and the finite one-loop energy density are considered as a self-consistent source for these wormhole geometries. The latter semi-classical approach prohibits solutions with a constant equation of state parameter, which further motivates the imposition of a radial dependent parameter, ω(r), and only permits solutions with a steep positive slope proportional to the radial derivative of the equation of state parameter, evaluated at the throat. The size of the wormhole throat as a function of the relevant parameters is also explored.

In this study, we search for a new class of wormhole solutions in the framework of Brans–Dicke (BD) theory in the presence of anisotropic matter distribution. Considering a linear equation of state (EoS) between radial pressure and energy density profile we find exact static spherically symmetric solutions to the BD field equations which represent wormhole configurations. The solutions we obtain include both cases with zero and nonzero redshift functions, for which, the conditions on wormhole geometry together with the weak (WEC) and null (NEC) energy conditions put constraints on model parameters such as, the BD coupling and EoS parameters. These constraints also depend on other model parameters such as, the value of BD scalar field and energy density at the wormhole throat. The regularity of the obtained solutions is verified by calculating the Kretschmann scalar in order to ensure that curvature singularities are absent in the wormhole spacetime. We then find that BD wormholes in the presence of anisotropic matter can exist without violating NEC and WEC, either at the throat or across the entire spacetime.

In this paper, we study the traversable wormhole solutions for a logarithmic corrected [Formula: see text] model by considering two different statements of shape [Formula: see text] and redshift [Formula: see text] functions. We calculate the parameters of the model including energy density [Formula: see text], tangential pressure [Formula: see text] and radial pressure [Formula: see text] for the corresponding forms of the functions. Then, we investigate different energy conditions such as null energy condition, weak energy condition, dominant energy condition and strong energy condition for our considered cases. Finally, we explain the satisfactory conditions of energy of the models by related plots.

This work emphasizes on the alteration in pile-soil interaction in case of geothermal energy piles during thermal cycle. The geothermal energy piles are investigated numerically using finite element software Abaqus. To simulate the soil mechanical and thermal response, two user defined material subroutines are used for the soil surrounding the piles. The behaviour of soil is reproduced using CASM; a soil constitutive model which is based on the concepts of critical state soil mechanics. To investigate the additional strains induced in the piles due to the thermal load, parametric analyses are carried out considering the effect of (i) different pile end restraints, (ii) relative densities of the soil, (iii) pile dimensions and (iv) lateral earth pressure coefficient. The analysis results indicate that the axial and radial strains are induced in the pile due to pile expansion during thermal loading. The increase in lateral earth pressure coefficient at interface of pile and soil can be correlated to the thermally induced radial strains. Moreover, the pile response to the thermal cycle can be considered to the governed by soil stiffness and the magnitude of thermal load applied on the pile. Analyses are also performed to investigate the influence of thermal parameters of soil and thermal load on the soil earth pressure coefficient at interface of pile and soil. The lateral earth pressure coefficient increases following the increase in magnitude of thermal load, however the effect of thermal conductivity of soil is not significant.KeywordsGeothermalAxial and radial strainsLateral earth pressure coefficient

In this paper we have studied the behavior of static spherically symmetric relativistic objects with locally anisotropic matter distribution considering the Tolman VII form for the gravitational potential $g_{rr}$ in curvature coordinates together with the linear relation between the energy density and the radial pressure. The interior spacetime has been matched continuously to the exterior Schwarzschild geometry. We have investigated and analyzed different physical properties of the stellar model and presented graphically.

We consider [Formula: see text] corrected model, i.e. [Formula: see text], where [Formula: see text] is the Ricci scalar and [Formula: see text], [Formula: see text] are arbitrary constant values, to investigate some of the interior configurations of static anisotropic spherical charged stellar structures. The existence of electric charge and a strong electric field confirms due to the higher values of pressure distribution and energy density of the matter inside the stars. Furthermore, for compact star configurations, we also consider the simplified MIT bag model equation of state (EoS) given by [Formula: see text], where [Formula: see text] is radial pressure, [Formula: see text] is energy density and [Formula: see text] is bag constant. This approach allows to find electric charge from the Einstein–Maxwell field equations. We have extensively discussed the behavior of the electric charge and anisotropic fluid distribution factor for five different values of [Formula: see text]. Interestingly, it is noticed during this study, for smaller values of [Formula: see text] we get intensity in electric charge. The Tolman–Oppenheimer–Volkoff equation (TOV), is modified in order to carry electric charge. In particular, we model the compact star candidates SAXJ 1808.4–3658 and Vela X-1 and give graphical representation of some important properties such as equilibrium condition, mass-radius ratio and surface redshift. In the end, our calculated solutions provide strong evidences for more realistic and viable charged stellar model.

In this paper we will examine the consequence of a canonical theory of quantum dust collapse in 2+1 dimensions. The solution of the WDW equation describing the collapse indicates that collapsing shells outside the apparent horizon are accompanied by outgoing shells within the apparent horizon during their collapse phase and stop collapsing once they reach the apparent horizon. Taking this picture of quantum collapse seriously, we determine a static solution with energy density corresponding to a dust ball whose collapse has terminated at the apparent horizon. We show that the boundary radius of the ball is larger than the BTZ radius confirming that no event horizon is formed. The ball is sustained by radial pressure which we determine and which we attribute to the Unruh radiation within it.

The general theory of relativity has allowed a better understanding of the structure of universe. One of the fundamentals problems in the general relativity is finding exact solutions of the Einstein-Maxwell field equations. Some solutions found applications in astrophysics, cosmology and more recently in the developments inspired by string theory. In this paper, we presented a compact object model in the framework of Einstein-Gauss-Bonnet gravity (EGB) with a linear equation of state considering a metric potential proposed for Buchdahl (1959). The new obtained models satisfy all physical requirements of a physically reasonable stellar object. We analyzed the effect of the Gauss-Bonnet coupling constant α on the main physical characteristics of the model. We checked that the radial pressure, energy density and anisotropy are well defined and are regular in the interior of the star and are dependent of the values of the coupling constant.

New exact interior solutions to the Einstein field equations for anisotropic spheres are found. We utilise a procedure that necessitates a choice for the energy density and the radial pressure. This class contains the constant density model of Maharaj and Maartens (Gen. Rel. Grav. 21, 899–905 (1989)), and the variable density model of Gokhroo and Mehra (Gen. Rel. Grav. 26, 75–84 (1994)), as special cases. These anisotropic spheres match smoothly to the Schwarzschild exterior and gravitational potentials are well behaved in the interior. A graphical analysis of the matter variables is performed which points to a physically reasonable matter distribution.

This study investigates anisotropic compact star configurations within the framework of [Formula: see text] gravity, employing a conformal Killing vector approach to model ultra-dense strange quark stars. Adopting the MIT bag equation of state (EOS) for strange quark matter (SQM) and a linear relation between tangential pressure and energy density, we derive exact solutions to the Einstein field equations under the modified gravity formalism. Key parameters, including the coupling constant [Formula: see text], bag constant B and anisotropy coefficient [Formula: see text], are analyzed for the representative candidate [Formula: see text]. Our results confirm the absence of geometric singularities, with metric potentials exhibiting regular behavior. Effective energy density, radial pressure and tangential pressure peak at the stellar center and decline monotonically toward the surface, while anisotropy increases radially, reaching maxima at the boundary. The model satisfies all energy conditions and adheres to the Buchdahl limit. Mass–radius relations reveal proportional increases in total mass M and radius R with rising [Formula: see text], contrasting general relativity (GR) predictions. Stability analyses via the modified Tolman–Oppenheimer–Volkoff (TOV) equation demonstrate equilibrium through force balance, with an emergent repulsive force [Formula: see text] attributed to matter-geometry coupling. Stability is further validated by Herrera’s cracking criterion and adiabatic indices. Surface redshift decreases with [Formula: see text], while compactification factors remain consistent with ultra-dense characteristics. Tabulated results highlight decreasing central density, surface density and compactness ([Formula: see text]) with increasing [Formula: see text]. This work establishes a robust, singularity-free anisotropic stellar model in [Formula: see text] gravity, offering insights into the interplay of modified gravity, anisotropy and quark matter in describing compact astrophysical objects.

Minimally deformed regular Bardeen black hole solutions in Rastall theory

Anisotropic charged strange stars in Krori-Barua spacetime under [formula omitted] gravity

We present a new family of spherically symmetric, static solutions of the Einstein field equations in isotropic, comoving coordinates. The radial pressure at each interior point of these models vanishes yet equilibrium is still possible. The constant density Florides solution which describes the gravitational field inside an Einstein cluster is obtained as a special case of our solution-generating method. We show that our solutions can be utilized to model strange star candidates such as Her. X-1, SAX J1808.4-3658(SS2), SAX J1808.4-3658(SS1) and PSR J1614-2230.