We calculate the vacuum average value of the field square and the stress-energy tensor of a massive scalar field, with non-minimal coupling $ξ$ to the curvature in the short-throat flat-space wormhole background. The obtained results are not suitable for an analytical analysis and for this reason we provide a numerical analysis for different values of the coupling constant, $ξ$. It was shown that the vacuum polarization cannot self-consistently support the wormhole. Otherwise, the energy-momentum tensor does not violate the null energy condition near the throat.
In this paper we study the correspondence between the real part of quasinormal modes (QNMs) and the shadow radius in a wormhole spacetime. Firstly we consider the above correspondence in a static and spherically symmetric wormhole spacetime and then explore this correspondence numerically by considering different wormhole models having specific redshift functions. To this end, we generalize this correspondence to the rotation wormhole spacetime and calculate the typical shadow radius of the rotating wormhole when viewed from the equatorial plane. We argue that due to the rotation and depending…
We show that the violation of the null energy condition by matter, required by traversable wormholes, can be removed in spacetimes with torsion. In addition, we show that this violation can also be removed in the conformal frame obtained by a Weyl transformation. This comes about because both conformally transformed wormholes and wormholes in spacetimes with torsion become sustained thanks to a combination of 'normal' matter, that satisfies the null energy condition, and an induced 'geometric' energy-momentum tensor that is able to greatly violate the null energy condition.
Dynamics of test particles in thin-shell wormhole spacetimes
研究了Visser（1989 Nucl.Phys.B328203; 1995 Wormholes：from Einstein to Hawking（Woodbury，MN：American Institute of Physics））提出的剪切粘贴方法构造的可穿越Schwarzschild和Kerr薄壳虫洞中的测地线运动。轨道的椭圆函数计算精确，并与嵌入图的帮助下可视化。
The existence of charged black holes has suggested that wormholes may also be charged. The purpose of this paper is to construct a general model of a charged wormhole that proves to be a natural extension of the original Morris-Thorne wormhole. This goal is achieved by means of the classical embedding theory that has played a major role in the general theory of relativity.
The Carminati and McLenaghan (CM) curvature invariants are powerful tools for probing spacetimes. Henry et al. formulated a method of plotting the CM curvature invariants to study black holes. The CM curvature invariants are scalar functions of the underlying spacetime. Consequently, they are independent of the chosen coordinates and characterize the spacetime. For Class B1 spacetimes, there are four independent CM curvature invariants: R, r1, r2, and w2. Lorentzian traversable wormholes and warp drives are two theoretical solutions to Einstein's field equations, which allow faster-than-light …
In order to be traversable, the static Lorentzian wormhole must be made out of some exotic matter that violates the weak energy condition. The quantized fields are the natural candidates as their stress-energy tensor, in many cases, possesses desired properties. In this paper we construct and examine the stress-energy tensor of the quantized massive scalar, spinor and vector fields in six static wormhole spacetimes. We find that in all considered cases the quantum fields violate the Morris-Thorne conditions and do not have the form necessary to support the wormhole throat. This is in concord w…
In this work, we calculate the deflection angle of light in a spacetime that interpolates between regular black holes and traversable wormholes, depending on the free parameter of the metric. Afterwards, this angular deflection is substituted into the lens equations which allows to obtain physically measurable results, such as the position of the relativistic images and the magnifications.
This article deals with the study of the dynamics of particles in different wormhole geometries. Using the Jacobi metric approach we study the geodesic motion on the Morris-Thorne wormhole. We found the only stable circular orbit located at the throat. We show that the Gaussian curvature of the Jacobi metric is directly related with the wormhole flare-out condition. We provide a simple test for determining the existence of a throat in a spacetime by using the Gaussian curvature of the associated Jacobi metric only. We discuss about the trajectories in the Kepler problem in a wormhole backgroun…
We study the geometry of a wormhole spacetime filled with anisotropic matter in the context of general relativity. In the course of the study, new static and spherically symmetric solutions, analytic and numerical ones, are found. We specify the existence condition for a wormhole throat. We analyze properties of the solutions after categorizing them based on the spacetime regularity and the signature of energy density. The necessary conditions which allow a wormhole spacetime to be nonsingular are described.
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,…
We consider a non-static evolving version of the regular "black-bounce"/traversable wormhole geometry recently introduced in JCAP02(2019)042 [arXiv:1812.07114 [gr-qc]]. We first re-write the static metric using Eddington-Finkelstein coordinates, and then allow the mass parameter $m$ to depend on the null time coordinate (a la Vaidya). The spacetime metric is \[ ds^{2}=-\left(1-\frac{2m(w)}{\sqrt{r^{2}+a^{2}}}\right)dw^{2}-(\pm 2 \,dw \,dr) +\left(r^{2}+a^{2}\right)\left(dθ^{2}+\sin^{2}θ\;dϕ^{2}\right). \] Here $w=\{u,v\}$ denotes the $\{outgoing,ingoing\}$ null time coordinate; representing $\…
Morris-Thorne wormholes in static pseudo-spherically symmetric spacetimes
本文研究了具有伪球对称性的经典广义相对论静态虫孔位形。我们表明，除了Lobo和Mimoso在参考物理中讨论的双曲虫孔解之外，修订版本\ D { \bf 82}，044034（2010），存在另一种虫孔类，其是球形Morris-Thorne虫孔的真正伪球形对应物（与Lobo-Mimoso虫孔类相反），因为满足了最初由Morris和Thorne为球对称虫孔定义的所有约束。我们发现，对于这两类双曲虫孔的能量密度，在喉，总是负的，而径向压力是积极的，相反的球对称的莫里斯-索恩虫孔。具体的双曲虫孔的构造和讨论施加不同的条件的径向和侧向压力，或通过考虑有限的选择的红移和形状函数。特别是，我们表明，双曲虫洞不能持续在喉部的幻影能量，并有伪球对称的虫洞支持的物质与各向同性的压力，其特征在于空间部分的角度赤字（或过剩）。
We study the linear polarization from the accretion disk around a class of static traversable wormholes. Applying the simplified model of a magnetized fluid ring orbiting in the equatorial plane, we search for characteristic signatures, which could distinguish wormhole from black hole spacetimes by their polarization properties. For the purpose we analyse the direct polarized images for different inclination angles, the strongly lensed indirect images, and the polarized radiation which reaches the asymptotic observer through the wormhole throat, and compare to the Schwarzschild black hole. For…
We study the thermodynamic equilibrium of matter in a wormhole `station' which connects various distinct asymptotic regions of a spacetime. An example of the `station' is a traversable wormhole connecting two distant regions. The temperatures of matter in the `station' measured at various asymptotic regions are not necessarily the same. We propose a generalized `temperature' which characterizes the thermal equilibrium in the spacetime with the `station'. We additionally discuss how thermal `equilibrium' works for a multiply connected spacetime.
An $n$-dimensional Riemannian space is said to be of embedding class $m$ if $n+m$ is the lowest dimension of the flat space in which the given space can be embedded. A spherically symmetric spacetime of class two can be reduced to class one by a suitable transformation of coordinates. Applied to wormholes, given a well-defined shape function $b=b(r)$, the resulting wormhole has an event horizon and is therefore nontraversable. On a macroscopic scale, $b(r)$ can be replaced by $m(r)$, the effective mass of a spherical star of radius $r$ with $m(0)=0$, to yield a valid solution. Spacetimes of em…
Wormholes in Einstein-Dirac-Maxwell theory with identical spacetime asymptotics
Al-Farabi Kazakh National University（阿尔法拉比哈萨克国立大学）；Academician J. Jeenbaev Institute of Physics of the NAS of the Kyrgyz Republic（吉尔吉斯共和国国家科学院J. Jeenbaev院士物理研究所）
In this paper we derive new static phantom traversable wormholes by assuming a shape function with a quadratic dependence on the radial coordinate r. We mainly focus our study on wormholes sustained by exotic matter with positive energy density (as seen by any static observer) and a variable equation of state $p_r/ρ<-1$, dubbed phantom matter. Among phantom wormhole spacetimes extending to infinity, we show that a quadratic shape function allows us to construct static spacetimes of finite size, composed by a phantom wormhole connected to an anisotropic spherically symmetric distribution of dar…
Stability regions of glued wormholes with massless Kim-Lee backreacted spacetimes as interior
Zel’dovich International Center for Astrophysics, Bashkir State Pedagogical University（泽尔多维奇天体物理国际中心，巴什基尔国立师范大学）；Department of Mathematics, Kidderpore College（基德波尔学院数学系）
When bosonic matter in the form of a complex scalar field is added to Ellis wormholes, the phenomenon of spontaneous symmetry breaking is observed. Symmetric solutions possess full reflection symmetry with respect to the radial coordinate of the two asymptotically flat spacetime regions connected by the wormhole, whereas asymmetric solutions do not possess this symmetry. Depending on the size of the throat, at bifurcation points pairs of asymmetric solutions arise from or merge with the symmetric solutions. These asymmetric solutions are energetically favoured. When the backreaction of the bos…
The general parametrization for spacetimes of spherically symmetric Lorentzian, traversable wormholes in an arbitrary metric theory of gravity is presented. The parametrization is similar in spirit to the post-Newtonian parametrized formalism, but with validity that extends beyond the weak field region and covers the whole space. Our method is based on a continued-fraction expansion in terms of a compactified radial coordinate. Calculations of shadows and quasinormal modes for various examples of parametrization of known wormhole metrics that we have performed show that, for most cases, the pa…
The embedding of a curved spacetime in a higher-dimensional flat spacetime has continued to be a topic of interest in the general theory of relativity, as exemplified by the induced-matter theory. This paper deals with spacetimes of embedding class one, i.e., spacetimes that can be embedded in a five-dimensional flat spacetime. Einstein's theory allows the fifth dimension to be either spacelike or timelike. By assuming the latter, this paper addresses two fundamental issues concerning Morris-Thorne wormholes, the origin of exotic matter and the frequently inexplicable enormous radial tension a…
Spacetime wormholes in isotropic spacetimes are represented traditionally by embedding diagrams which were symmetric paraboloids. This mirror symmetry, however, can be broken by considering different sources on different sides of the throat. This gives rise to an asymmetric thin-shell wormhole, whose stability is studied here in the framework of the linear stability analysis. Having constructed a general formulation, using a variable equation of state and related junction conditions, the results are tested for some examples of diverse geometries such as the cosmic string, Schwarzschild, Reissn…
We investigate the role of a specifically warped extra dimension in constructing examples of higher dimensional spacetimes representing Lorentzian wormholes. The warping chosen is largely inspired by the well-known non-static Witten bubble of nothing, though our spacetimes are static and geometrically different. Vacuum solutions in $D\geq 5$ dimensions and others (non-asymptotically flat) with `perfectly normal' matter stress energy are interpreted as possible Lorentzian wormholes. Asymptotically flat wormholes in $D\geq 5$ with `exotic matter' and within this class of spacetimes also appear t…
In this paper, we investigate the role of gravito-inertial effects on the Casimir energy of a massless scalar field confined between two parallel plates orbiting a static and zero tidal Schwarzschild-like wormhole, at zero temperature. Firstly, we obtain the metric in isotropic coordinates, finding the allowed angular velocities and the circular orbit radii for a material particle as well as for the photon. Following, we compute the changes induced by both gravity and rotation of the plates in the energy density of the quantum vacuum fluctuations associated to the scalar field, in the zero tid…
