Wormhole Geometry Research Articles

Gravitational Decoupling as a Generator of Curvature and Matter Distribution

AbstractIn this work, we generate curved Lorentzian manifolds from a flat Minkowskian space–time, through the Gravitational Decoupling by the Minimal Geometric Deformation method interpreting the decoupling sector as a generator of curvature and matter distribution. In particular, we obtain some new wormhole geometries by imposing either physically relevant equations of state or certain physically–motivated geometric constraints. These solutions are analyzed in detail. For all these solutions, we study the associated energy conditions, the geometric behavior and construct their embedding diagrams.

Traversable Wormhole in f(Q) Gravity Using Conformal Symmetry

In the current study, we investigate the possible existence of new wormhole solutions within f(Q) gravity by using the conformal symmetry, where Q is a non-metricity scalar. Modified versions of field equations within the scope of conformal symmetry with an anisotropic source of matter are calculated using the variational approach. We consider two distinct approaches, namely the linear equation of state and traceless fluid, in order to determine the exact form of the shape function for wormhole geometry. In the context of the f(Q) modified theory of gravity, we present a set of exact solutions for describing the existence of a relativistic wormhole. Further, the presence of dark matter is checked through make a use of energy conditions. In conclusion, it is interesting to mention that the presence of exotic matter is confirmed for both approaches, such as linear equation of state and traceless fluid.

Relativistic wormhole surrounded by dark matter halos in symmetric teleparallel gravity

AbstractIn this article we study the wormhole geometry in the galactic halo region under modified gravity, especially symmetric teleparallel gravity, where the nonmetricity scalar drives the gravitational interaction. The wormhole solutions for the assumed form have been presented, where α and β are the model parameters. The assumption of is based on the fact that its behavior should change with assumed parametric values of α as well as β within specific physical bounds. Two such models are presented based on the physically motivated shape function and energy conditions. We have elaborately shown, via mathematical calculations and graphical plots, the following features in our model: (i) energy conditions, especially NEC, which is very instructive in connection to energy violation in modified gravity theory, (ii) the wormhole solutions in the regime of Navarro‐Frenk‐White (NFW) density profiles for the galactic halo regions, (iii) treatment with particles moving in closed orbits around the wormholes which exhibit epicyclic frequencies, and (iv) the red‐blue shifts of the light coming from the wormhole throat in the vicinity of the dark matter halos. All the results and behaviors are satisfactory as well as interesting.

New wormhole solutions using dark matter profiles with the signature of observational data in teleparallel gravity

In this paper, we calculate a new class of wormhole solutions in the framework of teleparallel gravity. To obtain a characteristic wormhole solution, we use anisotropic matter distribution and a specific form of two dark matter profiles (URC profile and Quantum wave dark matter). As a general strategy, we create a relationship between calculated energy density and dark matter profiles for the system and investigate the physical properties of the wormhole geometry. A detailed analytical and graphical explanation of the matter contents via energy conditions is provided. The calculated shape functions of wormhole geometry meet the required conditions in both circumstances. Several intriguing features have emerged from the investigation, as have the properties of the exotic matter within the wormhole geometry. Finally, we have concluding remarks.

Traversable Wormhole Solutions Admitting Noether Symmetry in f(R,T2) Theory

This paper uses the Noether symmetry approach to examine the viable and stable traversable wormhole solutions in the framework of the f(R,T2) theory, where R is the Ricci scalar and T2=TμνTμν is the self-contraction of the stress–energy tensor. For this purpose, we consider a specific model of this modified theory to obtain the exact solutions of the Noether equations. Further, we formulate the generators of the Noether symmetry and first integrals of motion. We analyze the presence of viable and stable traversable wormhole solutions corresponding to different redshift functions. In order to determine whether this theory provides physically viable and stable wormhole geometry or not, we check the graphical behavior of the null energy constraint, causality condition and adiabatic index for an effective stress–energy tensor. It is found that viable and stable traversable wormhole solutions exist in this modified theory.

Traversable wormhole solutions admitting Karmarkar condition in f(R, T) theory

In this paper, we evaluate traversable wormhole solutions through Karmarkar condition in f(R, T) theory, where T is the trace of the energy-momentum tensor and R represents the Ricci scalar. We develop a wormhole shape function for the static traversable wormhole geometry by using the embedding class-I technique. The resulting shape function is used to construct wormhole geometry that fulfills all the necessary conditions and joins the two asymptotically flat regions of the spacetime. We investigate the existence of viable traversable wormhole solutions for anisotropic matter configuration and examine the stable state of these solutions for different f(R, T) gravity models. We analyze the graphical behavior of null energy bound to examine the presence of physically viable wormhole geometry. It is found that viable and stable traversable wormhole solutions exist in this modified theory of gravity.

Imprints of dark matter on wormhole geometry in modified teleparallel gravity

Imprints of dark matter on wormhole geometry in modified teleparallel gravity

Factorization and global symmetries in holography

We consider toy models of holography arising from 3d Chern-Simons theory. In this context a duality to an ensemble average over 2d CFTs has been recently proposed. We put forward an alternative approach in which, rather than summing over bulk geometries, one gauges a one-form global symmetry of the bulk theory. This accomplishes two tasks: it ensures that the bulk theory has no global symmetries, as expected for a theory of quantum gravity, and it makes the partition function on spacetimes with boundaries coincide with that of a modular-invariant 2d CFT on the boundary. In particular, on wormhole geometries one finds a factorized answer for the partition function. In the case of non-Abelian Chern-Simons theories, the relevant one-form symmetry is non-invertible, and its “gauging” corresponds to the condensation of a Lagrangian anyon.

Some aspects of Morris–Thorne wormhole in Scalar–Tensor theory

In this work, we reach the equations of motion of Morris–Thorne wormhole geometry by means of the Einstein Field Equations and Klein–Gordon Equation of Scalar–Tensor Theory. We discuss the anisotropic matter energy distribution. We determine a relation between the radial and the transverse pressures. Hence, we express the anisotropic energy–momentum tensor in terms of one pressure class, by means of that relation. Besides that, we check the isotropic case and show that there is no traversable wormhole (WH), in the zero redshift function situation, if the energy–momentum distribution of the universe is isotropic. In addition, we represent the conditions in order that the Null Energy Condition (NEC) is satisfied in the zero redshift function case, for anisotropic distribution. We also propose a special class of traversable WH shape functions. We will be calling the WHs corresponding to that class of functions as the Yukawa Type WHs. We expressed the NEC for those WHs particularly. Furthermore, we determine the radial and the transverse pressures in zero redshift function situation.

Unitary symmetries in wormhole geometry and its thermodynamics

From a geometric point of view, we show that the unitary symmetries {{,textrm{U},}}(1) and {{,textrm{SU},}}(2) stem fundamentally from Schwarzschild and Reissner–Nordström wormhole geometry through spacetime complexification. Then, we develop quantum tunneling which makes these wormholes traversable for particles. Finally, this leads to wormhole thermodynamics.

Wormhole generating function in f(R,T) gravity

In this work, we have studied the traversable wormhole geometries in [Formula: see text] gravity theory, where [Formula: see text] denotes the Ricci scalar and [Formula: see text] is the trace of the energy–momentum tensor. Firstly, two new shape functions are obtained for some assumed generating function. Also, some new generating functions are obtained in wormhole geometry for some well-known shape functions and redshift functions. Energy conditions are examined in each wormhole solution and it is found that a particular type of wormhole satisfies all the energy conditions in a region.

Casimir wormholes in modified symmetric teleparallel gravity

In recent years there has been a growing interest in the field of Casimir wormhole. In classical general relativity (GR), it is known that the null energy condition (NEC) has to be violated to have a wormhole to be stable. The Casimir effect is an experimentally verified effect that is caused due to the vacuum field fluctuations in quantum field theory. Since the Casimir effect provides the negative energy density, thus this act as an ideal candidate for the exotic matter needed for the stability of the wormhole. In this paper, we study the Casimir effect on the wormhole geometry in modified symmetric teleparallel gravity or f(Q) gravity, where the non-metricity scalar Q drives the gravitation interaction. We consider three systems of the Casimir effect such as (i) two parallel plates, (ii) two parallel cylindrical plates, and (iii) two-sphere separated by a large distance to make it more experimentally feasible. Further, we studied the obtained wormhole solutions for each case with energy conditions at the wormhole throat with radius r_0 and found that some arbitrary quantity violates the classical energy conditions at the wormhole throat. Furthermore, the behavior of the equation of state (EoS) is also analyzed for each case. Finally, we investigate the stability of the obtained Casimir effect wormhole solutions with the generalized Tolman–Oppenheimer–Volkoff (TOV) equation.

Echoes from braneworld wormholes

We have studied the stability of wormhole geometries, under massless scalar, electromagnetic and axial gravitational perturbations, in the context of higher dimensional spacetimes. Intriguingly, the construction of a wormhole spacetime in the presence of higher dimensions, known as braneworld wormholes, \emph{does not} require the existence of exotic matter fields, unlike the scenario in four spacetime dimensions. Being a nonvacuum spacetime, the effective potential experienced by the axial gravitational perturbation differs considerably from the scenarios involving black holes. In particular, the present work provides one of the first attempts to study the gravitational perturbations of the wormhole spacetimes. Our analysis, involving both analytical and numerical techniques, demonstrates that there are echoes in the time domain signal of all the perturbations and the echo time delay is intimately related to the parameters originating from higher dimensions. Thereby combining the attempt to search for wormholes and extra dimensions, with the existence of gravitational wave echoes. Implications and future directions have also been discussed.

Casimir traversable wormholes for GUP corrected energy densities in f (T) gravity

Traversable wormholes are always supported by negative energy and therefore an exotic matter source is required for their principle existence. In this work, we consider Casimir energy density as an exotic matter source in the framework of f (T) gravity. In this way, we examine the behavior of shape function, equation of state parameters, energy conditions and stability conditions for wormhole geometry in teleparallel and f (T) gravity. We also assume three different generalized uncertainty principle corrected Casimir wormhole models. We analyze the effect of the generalized uncertainty principle minimal parameter on the constructed wormhole properties in f (T) gravity.

Gravitational wave memory in wormhole spacetimes

Gravitational wave memory is studied in the context of a certain class of braneworld wormholes. Unlike other wormhole geometries, this novel class of wormholes do not require any exotic matter fields for its traversability. First, we study geodesics in this wormhole spacetime, in the presence of a gravitational wave pulse. The resulting evolution of the geodesic separation shows the presence of displacement and velocity memory effects. Motivated by the same, we study the memory effects at null infinity using the Bondi-Sachs formalism, adapted for braneworld wormhole. Our analysis provides a non-trivial change of the Bondi mass after the passage of a burst of gravitational radiation and hence manifests the memory effect at null infinity. In both of these exercises, the presence of extra dimension and the wormhole nature of the spacetime geometry gets imprinted in the memory effect. Since future gravitational wave detectors will be able to probe the memory effect, the present work provides another avenue to search for compact objects other than black holes.

Weak gravitational lensing in dark matter and plasma mediums for wormhole-like static aether solution

In this paper, we study the deflection angle for wormhole-like static aether solution by using Gibbons and Werner technique in non-plasma, plasma, and dark matter mediums. For this purpose, we use optical spacetime geometry to calculate the Gaussian optical curvature, then implement the Gauss–Bonnet theorem in weak field limits. Moreover, we compute the deflection angle by using a technique known as Keeton and Petters technique. Furthermore, we analyze the graphical behavior of the bending angle psi with respect to the impact parameter b, mass m as an integration constant, and parameter q in non-plasma and plasma mediums. We examine that the deflection angle is exponentially increasing as direct with charge. Also, we observe that for small values of b, psi increases, and for large values of b the angle decreases. We also considered analysis to the shadow cast of the wormhole relative to an observer at various locations. Comparing it the Schwarzschild shadow, shadow cast is possible for wormhole as r<2m. At r>2m, the Schwarzschild is larger. As rrightarrow infty , we have seen that the behavior of the shadow, as well as the weak deflection angle, approaches that of the Schwarzschild black hole. Overall, the effect of plasma tends to decrease the value of the observables due to the wormhole geometry.

A comparative study of new generic wormhole models with stability analysis via thin-shell

This analysis is devoted to exploring the interesting aspects of wormhole geometry. The energy conditions are checked for two different new generic shape functions, which satisfy the required wormhole properties. The presence of exotic matter is confirmed due to the violation of the energy conditions in the background of f(R, T) gravity as well as in the general relativity case. The traversable wormholes respecting the null energy conditions can be realized in both considered frameworks. A thin-shell around a wormhole geometry with two different generic shape functions is obtained by using the cut and paste approach taking Schwarzschild spacetime as an exterior manifold. The stability of thin-shell is explored with linearized perturbation along the equilibrium shell radius. Stable regions and the position of the expected event horizon depend on the choice of physical parameters. It is concluded that the number of expected event horizons increases for the second shape function.

Galactic Wormhole under Lovelock Gravity

We explore wormhole geometry in spiral galaxies under the third order Lovelock gravity. Using the cubic spline interpolation technique, we find the rotational velocity of test particles in the halo region of our spiral galaxy from observed values of radial distances and rotational velocities. Taking this value of the rotational velocity, we are able to show that it is possible to present a mathematical model regarding viable existence of wormholes in the galactic halo region of the Milky Way under the Lovelock gravity. A very important result that we obtain from the present investigation is that galactic wormhole in the halo region can exist with normal matter as well as exotic matter.

Exploring existence of traversable wormhole solutions in the presence of some corrected Casimir energy models

In this paper, we explore the wormhole solutions (which are initially proposed by R. Garattini [Eur. Phys. J. C 79 (2019) 951] who take generalized uncertainty principle (GUP) with Casimir energy) in the framework of two well-known dark energy (DE) models, generalized Chaplygin gas (GCG) and polytropic gas. We consider the GUP corrected pressure (force per unit surface area) in the equation of state (EoS) of these DE models to construct the GCG corrected energy density and polytropic gas corrected energy density. Three models of redshift function are taken into account to construct shape function as well as wormhole geometry for both cases of corrected energy densities. We find the behavior of EoS parameters, redshift function for isotropic and anisotropic fluid, equilibrium conditions, null energy condition and exotic volume at the throat of the wormhole with radius [Formula: see text].

Extremal surfaces and thin-shell wormholes

We study extremal surfaces in a traversable wormhole geometry that connects two locally ${\mathrm{AdS}}_{5}$ asymptotic regions. In the context of the $\mathrm{AdS}/\mathrm{CFT}$ correspondence, we use these to compute the holographic entanglement entropy for different configurations: First, we consider an extremal surface anchored at the boundary on a spatial 2-sphere of radius $R$. The other scenario is a slab configuration which extends in two of the boundary spacelike directions while having a finite size $L$ in the third one. We show that in both cases the divergent and the finite pieces of the holographic entanglement entropy give results consistent with the holographic picture and this is used to explore the phase transitions that the dual theory undergoes. The geometries we consider here are stable thin-shell wormholes with flat codimension-one hypersurfaces at fixed radial coordinate. They appear as electrovacuum solutions of higher-curvature gravity theories coupled to Abelian gauge fields. The presence of the thin shells produces a refraction of the extremal surfaces in the bulk, leading to the presence of cusps in the phase space diagram. Further, the traversable wormhole captures a phase transition for the subsystems made up of a union of disconnected regions in different boundaries. We discuss these and other features of the phase diagram.