Wormhole Spacetime Research Articles

A five-dimensional vacuum-defect wormhole space-time

In this study, we present a novel extension to the Klinkhamer vacuum-defect model by incorporating a fifth spatial dimension. This modification results in the formulation of a comprehensive five-dimensional wormhole space-time. Crucially, this extension preserves its classification as a vacuum solution to the field equations, thereby automatically satisfying all energy conditions. We demonstrate that this five-dimensional vacuum-defect space-time can be expressed in a pure canonical form, and thus, locally reduces to five-dimensional Minkowski space. Finally, we explore the geodesic equations in the vicinity of this five-dimensional vacuum-defect wormhole, offering insights into its intriguing properties.

Comments on wormholes and factorization

In AdS/CFT partition functions of decoupled copies of the CFT factorize. In bulk computations of such quantities contributions from spacetime wormholes which link separate asymptotic boundaries threaten to spoil this property, leading to a “factorization puzzle.” Certain simple models like JT gravity have wormholes, but bulk computations in them correspond to averages over an ensemble of boundary systems. These averages need not factorize. We can formulate a toy version of the factorization puzzle in such models by focusing on a specific member of the ensemble where partition functions will again factorize.As Coleman and Giddings-Strominger pointed out in the 1980s, fixed members of ensembles are described in the bulk by “α-states” in a many-universe Hilbert space. In this paper we analyze in detail the bulk mechanism for factorization in such α-states in the topological model introduced by Marolf and Maxfield (the “MM model”) and in JT gravity. In these models geometric calculations in α states are poorly controlled. We circumvent this complication by working in approximate α states where bulk calculations just involve the simplest topologies: disks and cylinders.One of our main results is an effective description of the factorization mechanism. In this effective description the many-universe contributions from the full α state are replaced by a small number of effective boundaries. Our motivation in constructing this effective description, and more generally in studying these simple ensemble models, is that the lessons learned might have wider applicability. In fact the effective description lines up with a recent discussion of the SYK model with fixed couplings [1]. We conclude with some discussion about the possible applicability of this effective model in more general contexts.

Study of relativistic hot accretion flow around Kerr-like wormhole

We investigate the structure of relativistic, low-angular momentum, inviscid advective accretion flow in a stationary axisymmetric Kerr-like wormhole (WH) spacetime, characterized by the spin parameter (a k), the dimensionless parameter (β), and the source mass (M WH). In doing so, we self-consistently solve the set of governing equations describing the relativistic accretion flow around a Kerr-like WH in the steady state, and for the first time, we obtain all possible classes of global accretion solutions for transonic as well as subsonic flows. We study the properties of dynamical and thermodynamical flow variables and examine how the nature of the accretion solutions alters due to the change of the model parameters, namely energy (ℰ), angular momentum (λ), a k, and β. Further, we separate the parameter space in λ-ℰ plane according to the nature of the flow solutions, and study the modification of the parameter space by varying a k and β. Moreover, we retrace the parameter space in a k-β plane that allows accretion solutions containing multiple critical points. Finally, we calculate the disc luminosity (L) considering free-free emissions for transonic solutions as these solutions are astrophysically relevant and discuss the implication of this model formalism in the context of astrophysical applications.

Casimir wormholes with GUP correction in the Loop Quantum Cosmology

In this paper, we obtain novel traversable, static, and spherically symmetric wormhole solutions, derived from the effective energy density and isotropic pressure resulting from the Casimir effect, corrected by the Generalized Uncertainty Principle (GUP) within the framework of Loop Quantum Cosmology (LQC). The goal is to explore the interplay between competing quantum gravity effects and quantum vacuum phenomena in the emergence of non-trivial spacetime structures. We examine features such as traversability, embedding diagrams, energy conditions, curvature, and stability of the obtained solutions. Additionally, we analyze the junction conditions required to integrate the wormhole spacetime with an external Schwarzschild spacetime and calculate the amount of exotic matter needed to maintain the wormhole. Finally, we evaluate the conditions under which this latter remains visible or is hidden by the event horizon associated with the Schwarzschild spacetime.

Einstein–Yang–Mills Wormholes Haunted by a Phantom Field

In this article, we study wormhole spacetimes in the framework of the static spherically symmetric SU(2)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ extbf {SU}} (2)$$\\end{document} Einstein–Yang–Mills theory coupled to a phantom scalar field. We show rigorously the existence of an infinite sequence of symmetric wormhole solutions, labelled by the number of zeros of the Yang–Mills potential. These solutions have previously been discovered numerically. Mathematically, the problem resembles the pure Einstein–Yang–Mills system for black hole initial conditions, which was well-studied in the 90s. The main difference in the present work is that the coupling to the phantom field adds a non-trivial degree of complexity to the analysis. After proving the existence of the symmetric wormhole solutions, we also present numerical evidence for the existence of asymmetric ones.

Effects of torsion charge on optical appearance and additional photon rings of an asymmetric thin-shell wormhole

In this paper, we study the optical properties of asymmetric thin-shell wormholes (ATWs) under torsion charge. Utilizing the cut-and-paste method developed by Visser, we construct these wormholes and determine their key physical properties, such as the radius of the photon sphere and critical impact parameters, under different torsion charges. Furthermore, we investigate the effective potential and behavior of photon motion within the wormhole spacetime, identifying a relationship between photon trajectories and impact parameters. The study focuses on scenarios where thin accretion disks act as the primary light source. It reveals that the optical features of ATWs under torsion charge significantly differ from those of black holes (BHs). Notably, an increase in torsion charge leads to a reduction in the sizes of both extra photon rings and lensing bands, which serve as important markers for distinguishing and characterizing ATW spacetimes from those of BHs.

Gravitational Wormholes

Spacetime wormholes are evidently an essential component of the construction of a time machine. Within the context of general relativity, such objects require, for their formation, exotic matter—matter that violates at least one of the standard energy conditions. Here, we explore the possibility that higher-curvature gravity theories might permit the construction of a wormhole without any matter at all. In particular, we consider the simplest form of a generalized quasi topological theory in four spacetime dimensions, known as Einsteinian Cubic Gravity. This theory has a number of promising features that make it an interesting phenomenological competitor to general relativity, including having non-hairy generalizations of the Schwarzschild black hole and linearized equations of second order around maximally symmetric backgrounds. By matching series solutions near the horizon and at large distances, we find evidence that strong asymptotically AdS wormhole solutions can be constructed, with strong curvature effects ensuring that the wormhole throat can exist.

Black Holes, Wormholes and Entanglement: Researchers cracked a paradox by considering what happens when the insides of black holes are connected by spacetime wormholes.

Black Holes, Wormholes and Entanglement: Researchers cracked a paradox by considering what happens when the insides of black holes are connected by spacetime wormholes.

Propagation of gravitational waves in a dynamical wormhole background for two-scalar Einstein–Gauss–Bonnet theory

In this work, we propose a model of Einstein–Gauss–Bonnet gravity coupled with two scalar fields. The two scalar fields are considered to be “frozen” or they become non-dynamical by employing appropriate constraints in terms of Lagrange multiplier fields. We show that, even in the case that the arbitrary spherically symmetric spacetime is dynamical, we can construct a model where the wormhole spacetime is a stable solution in this framework. We especially concentrate on the model reproducing the dynamical wormhole, where the wormhole appears in a finite-time interval. We investigate the propagation of the gravitational wave in the wormhole spacetime background and we show that the propagation speed is different from that of light in general, and there is a difference in the speeds between the incoming propagating wave and the outgoing propagating gravitational wave. We need to stress that the wormhole model used for exploring gravitational wave propagation is not obtained by solving any equations but is essentially constructed by hand.

Observational signatures of charged rotating traversable wormhole: shadows and light rings with different accretions

In this work, we investigate the optical appearance of qualitatively new observational features of accretion disk images around the charged rotating traversable wormhole (TWH) space-time for different spin, throat, and charge values. To accomplish this, we first consider the Hamilton–Jacobi method to derive the geodesic equations for the motion of photons and study the effects of parameters on the photon orbit in the observer’s sky. We found that each parameter affects the size and shape of the wormhole (WH) shadow and flatness is observed in the shadow because of spin and other parameters. To produce shadow images of sufficient visual quality but within manageable computational times, we adopt the ray-trace procedure and characterize the significant features of light trajectories on the observer’s screen, depending on the interaction between the space-time structure and the accretion disk. In addition, we consider the static spherically symmetric accretion flow model to observe the specific intensity around the traversable WH space-time geometry. It is found that the intensity and positions of the photon ring vary with respect to the involved parameters. In future observation, this type of study may provide a fertile playground to test the nature of compact objects, specifically the WH in the strong-field regime.

Quasinormal modes and bound states of massive scalar fields in wormhole spacetimes

Quasinormal modes and bound states of massive scalar fields in wormhole spacetimes

Periapsis shift in spherically symmetric spacetimes and effects of electric interactions* *This work is partially Supported by the Wuhan University Research Development Fund

The periapsis shift of charged test particles in arbitrary static and spherically symmetric charged spacetimes are studied. Two perturbative methods, the near-circular approximation and post-Newtonian methods, are developed and shown to be very accurate when the results are determined to high orders. The near-circular approximation method is more precise when eccentricity e of the orbit is small, whereas the post-Newtonian method is more effective when orbit semilatus rectum p is large. Results from these two methods are shown to agree when both e is small and p is large. These results are then applied to the Reissner-Nordström spacetime, the Einstein-Maxwell-dilation gravity, and a charged wormhole spacetime. The effects of various parameters on the periapsis shift, particularly that of the electrostatic interaction, are carefully studied. The periapsis shift data of the solar-Mercury are then used to constrain the charges of the Sun and Mercury, and the data of the Sgr A*-S2 periapsis shift are used to determine, for the first time using this method, the constraints of the charges of Sgr A* and S2.

Study of boson stars with wormhole

In this paper, we study the mixed system of boson stars (BSs) with wormholes at their center. The boson star is obtained by employing a complex scalar field without self-interaction or a complex scalar field with quartic self-interaction and the wormhole is obtained by employing a phantom field. Utilizing the numerical method, we successfully obtain both symmetric and asymmetric solutions within the two asymptotically flat regions. The key focus of our study involves the systematic exploration of variations in results by varying the throat parameter η0, and the parameter c, representing the quartic term in potential. In the ground state, we find the mass M and Noether charge Q versus the scalar field frequencies ω are multi-valued curves when the η0 is small or the self-interaction is strong, the multi-valued curves will turn into single-valued curves as η0 or c increases. Furthermore, we observe that asymmetric solutions can transition into symmetric solutions at specific scalar field frequencies ω for certain settings of η0 and c. In addition, when it comes to the excited state, the properties of symmetric solutions remain akin to those in the ground state, while asymmetrical results display different characteristics from the ground state. We also present the wormhole spacetime geometry to investigate the properties of this model.

Tidal forces in the Simpson–Visser black-bounce and wormhole spacetimes

The concept of regular black holes has gained attention in recent years, especially in the context of quantum gravity theories. In these theories, the existence of singularities is paradoxical as they represent a breakdown of the laws of physics. Motivated by the recent developments in this area, we study the tidal force effects in one such family of regular geometries described by the Simpson–Visser metric. We find the radial and angular force profiles for a radially in-falling particle in this spacetime and calculate the variation of the geodesic separation vector with the radial coordinate using two different initial conditions. These results are then compared with that of Schwarzschild black hole spacetime. We show that for a regular black hole, both radial and angular tidal forces show a peak outside the horizon and then fall to ultimately switch their behavior from stretching to compression and vice-versa. Also, they are finite at r=0 unlike the Schwarzschild spacetime. It is also seen that the angular deviation profile shows an oscillating behavior for a particular initial condition. Our analysis can be used to distinguish between regular black hole, one-way and two-way wormholes and a singular black hole spacetimes.

Dirac stars in wormhole spacetime

In this paper, we study the spherically symmetric Dirac star model in the presence of a phantom field, obtaining a traversable wormhole solution in non-trivial topological spacetime. This solution exhibits asymmetry in both the field configuration and the metric and possesses a finite ADM mass M and Noether charge Q. Furthermore, due to a wormhole at the center, this solution exhibits many differences from the Dirac star under trivial spacetime. Notably, when the wormhole throat size is small, our numerical calculations indicate the emergence of an extremely approximate black hole solution on one side of the wormhole spacetime, a phenomenon unexplored. At this time, the Kretschmann scalar near the throat tends to infinity, indicating the wormhole becomes untraversable.

2nd Comment on “On the Klein–Gordon oscillator in topologically charged Ellis–Bronnikov type wormhole spacetime”

2nd Comment on “On the Klein–Gordon oscillator in topologically charged Ellis–Bronnikov type wormhole spacetime”

Observational appearance and extra photon rings of an asymmetric thin-shell wormhole with a Bardeen profile* *Supported by the National Natural Science Foundation of China (11903025), the Science and Technology Program of Sichuan Province, China(2023ZYD0023), and the starting fund of China West Normal University (18Q062)

In this work, the optical appearance of an asymmetric thin-shell wormhole with a Bardeen profile is studied. To initiate the process, we need to construct an asymmetric thin-shell wormhole utilizing the cut-and-paste technique proposed by Visser and subsequently ascertain its pertinent physical quantities such as the radius of the photon sphere and critical impact parameters for different values of magnetic charge g. Then, the effective potential and motion behavior of photons are also investigated within the framework of asymmetric thin-shell wormholes with a Bardeen profile. It can be found that the effective potential, ray trajectory, and azimuthal angle of the thin-shell wormhole exhibit a strong correlation with the mass ratio of black holes. By considering the accretion disk as the sole background light source, we observe additional photon rings and lensing bands in the optical appearance of the asymmetric thin-shell wormhole with a Bardeen profile compared to those exhibited by the Bardeen black hole. One can find that there is an increase in the size of the specific additional light bands with increasing magnetic charge g, which is different from the black hole case. These exceptionally luminous rings can serve as a robust criterion for the identification and characterization of the thin-shell wormhole spacetime.

Comment on “On the Klein–Gordon oscillator in topologically charged Ellis–Bronnikov-type wormhole spacetime”

Comment on “On the Klein–Gordon oscillator in topologically charged Ellis–Bronnikov-type wormhole spacetime”

Wilson loops and wormholes

We analyse the properties of Wilson loop observables for holographic gauge theories, when the dual bulk geometries have a single and/or multiple boundaries (Euclidean spacetime wormholes). Such observables lead to a generalisation and refinement of the characterisation in [1] based on the compressibility of cycles and the pinching limit of higher genus Riemann surfaces, since they carry information about the dynamics and phase structure of the dual gauge theory of an arbitrary dimensionality. Finally, we describe how backreacting correlated observables such as Wilson loops can lead to wormhole saddles in the dual gravitational path integral, by taking advantage of a representation theoretic entanglement structure proposed in [13, 15].

A study of an embedding class-I traversable wormhole in Galileon Gravity

In this article, we examine the possibility of the creation of a traversable wormhole geometry in Galileon Gravity (GG). In this gravity, the alternation of gravity is determined by an effective scalar field ϕ, treated as the Galileon field. From a mechanism perspective, GG is developed by covariantizing the decoupling Lagrangian of the DGP (Dvali-Gabadadze-Porrati) model. Now, to achieve our aim, gravitational field equations have been constructed corresponding to a line element, which represents a static and spherically symmetric spacetime. Next, we have modified these field equations in the context of a Morris-Thorne traversable wormhole spacetime. In particular, we have used the ‘Karmarkar condition’ to evaluate the wormhole solutions in a general sense. Further, for a better understanding of our obtained wormhole solutions, 2-dimensional and 3-dimensional diagrams have been displayed. Later, we scrutinized the possible creation of a traversable wormhole based on the essential requirements, that is, the infraction of energy conditions in the neighborhood of the throat region, especially the Null Energy Condition (NEC). For this purpose, we have discussed three cases like Case-I: without the necessity of dark energy (DE), Case-II: with support of phantom-like DE and Case-III: with the SFDM profile of a dark matter (DM) halo. Next, we have examined the hydrostatic equilibrium position corresponding to our obtained wormhole system in GG. Furthermore, to examine the small and sufficient quantity of exotic matter, the possible formation of a traversable wormhole has been explored by a volume integral quantifier. Lastly, we have shown the nature of active mass. Finally, we have concluded that traversable wormhole solutions can also be established in the presence of an effective scalar field without any essential support of exotic matter in the neighborhood of the throat region by GG.