Wormhole Research Articles

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.

On the existence and stability of traversable wormhole solutions with novel shapefunctions in the framework of F(R,Lm) gravity

In this work, we have explored wormhole (WH) solutions in F(R,Lm) gravity by assuming the Morris–Thorne WH metric and F(R,Lm)=R2+(1+γR)Lm , where γ is the free model parameter. We determined the WH solutions by utilizing two newly developed shape functions (SF) that satisfy all basic conditions for a WH’s physical validity. We also observe that the null energy condition (NEC) behaves negatively. Finally, for both models, we use the volume integral quantifier ( VIQ ) and Tolman–Oppenheimer–Volkoff (TOV) equation to determine how much exotic matter is needed near the WH throat and the stability of the WH. The extensive detailed discussions of the matter components have been done via graphical analysis. The obtained WH geometries meet the physically acceptable conditions for a stable wormhole.

Some aspects of Morris-Thorne wormhole in gravity

The aim of this manuscript is to study traversable wormhole geometries in the non-metricity and matter coupling gravity. We investigate the Morris-Thorne wormhole metric within the framework of extended symmetric teleparallel gravity. With an anisotropic matter distribution, we explore two distinct wormhole models under two different scenarios. First, we consider the equations of state, and then we assume specific shape functions for each scenario. In both cases, the shape function satisfies all fundamental criteria for a traversable wormhole. We present our results through graphical representations and analyze the energy conditions. Furthermore, we examine the behavior of the wormhole through the anisotropic parameter. Finally, we present our conclusions based on the obtained results.

On possible traversable wormhole solutions supported by Karmarkar condition in [formula omitted]gravity within the [formula omitted]formalism

In their seminal work, Morris and Thorne (1988) introduced the concept of traversable wormholes (WHs), which are geometric structures serving as bridges to connect two distinct spacetimes or different points within the same spacetime. The properties of these WHs are determined by the choice of the shape function. Extensive research has been conducted in the literature on WHs within modified theories of gravity, considering various types of shape functions. In this paper, we focus on deriving the simplest solutions for traversable WHs within the framework of f(R,T) gravity. Our specific focus lies on the functional form f(R,T)=R+αR2+λT, where R represents the Ricci scalar and T denotes the trace of the energy–momentum tensor. By incorporating quadratic geometric and linear material corrections, we demonstrate that the matter content of WHs can obediently conform to the energy conditions (ECs). This study significantly advances our understanding of WHs within the context of modified gravity. Our findings shed new light on the behavior and properties of WHs, highlighting their compatibility with the f(R,T) gravity framework. By unveiling the ability of WHs to adhere to ECs through the inclusion of geometric and material corrections, we provide groundbreaking insights into these intriguing objects. Overall, our research contributes to the broader field of gravitational physics by presenting a unique perspective on WH modeling. By exploring WHs within the f(R,T) gravity framework and demonstrating their conformity to ECs, we expand our knowledge of these fascinating structures and pave the way for further investigations in this area.

Elliptical Space with the McVittie Metrics

The main feature of elliptical space—the topological identification of its antipodal points—could be fundamental for understanding the nature of the cosmological redshift. The physical interpretation of the mathematical (topological) structure of elliptical space is made by using physical connections in the form of Einstein-Rosen bridges (also called “wormholes”). The Schwarzschild metric of these structures embedded into a dynamic (expanding) spacetime corresponds to McVittie’s solution of Einstein’s field equations. The cosmological redshift of spectral lines of remote sources in this metric is a combination of gravitational redshift and the time-dependent scale factor of the Friedmann-Lemaitre-Robertson-Walker metric. I compare calculated distance moduli of type-Ia supernovae, which are commonly regarded as “standard candles” in cosmology, with the observational data published in the catalogue “Pantheon+”. The constraint based on these accurate data gives a much smaller expansion rate of the Universe than is currently assumed by modern cosmology, the major part of the cosmological redshift being gravitational by its nature. The estimated age of the Universe within the discussed model is 1.48·1012 yr, which is more than two orders of magnitude larger than the age assumed by using the standard cosmological model parameters.

Detection and prevention of sinkhole attacks in MANETS based routing protocol using hybrid AdaBoost-Random forest algorithm

WSN (Wireless Sensor Network) is considered as one of the promising technologies which are utilized in various fields for various applications. Along with it, MANET (Mobile Ad Hoc Network) has attracted a distinct attention, as they serve communication means across innumerable domain. In recent years, due to the development of both wired and wireless technologies, attacks are becoming more frequent and these attacks can be in various form such as worm hole, black hole, grey-hole, sinkhole and others. These attacks can cause loss of security, increase the number of drop packets, decrease packet delivery ratio which result in poor routing performance. In order to overcome these issues, the proposed study employs PBCS (Particle Bee Colony Swarm) algorithm for finding the shortest path between the nodes, which helps in reducing the routing cost and makes the model more efficient and effective. In addition to this, Hybrid AdaBoost-Random forest algorithm is utilized in proposed model. This model helps in reducing the training time which makes the model more reliable and efficient than existing models. It can be implemented in huge dataset and in Hybrid AdaBoost-Random Forest algorithm, estimator of random forest is used, which result in high accuracy and low loss. AODV (Ad-Hoc on Demand Vector) protocol helps to identify the prevention of attack as this routing protocol perform better for longer and extensive duration of traffic than other protocols. The performance of the proposed model is evaluated using different metrics which includes accuracy, recall, precision, sensitivity and specificity. Besides, energy consumption, throughput, network lifetime, delay of the proposed model is also evaluated. The proposed model is then compared with various existing models in order to determine the efficiency and effectiveness of the proposed framework.

Casimir wormhole solutions in [formula omitted] gravity

In this paper, we study the Casimir effect on the wormhole geometry in f(R,Lm) gravity. We derive the field equations for the generic f(R,Lm) function by assuming static and spherically symmetric Morris–Thorne wormhole metric. Then we consider two non-linear f(R,Lm) models, specifically, f(R,Lm)=R2+Lmβ and f(R,Lm)=R2+(1+αLm)Lm where α and β are free parameters. We derive the shape functions for wormholes by utilizing the Casimir effect and examining their existence. Subsequently, we analyse the obtained wormhole solutions for each scenario, assessing the energy conditions at the wormhole throat with a radius of r0. Our findings reveal that for some arbitrary quantities, there is a violation of classical energy conditions at the wormhole throat. Additionally, we delve into the behaviour of the equation of state (EoS) for each case. Furthermore, we explore the stability of the Casimir effect wormhole solutions by employing the generalized Tolman–Oppenheimer–Volkoff (TOV) equation. Finally, we utilize the volume integral quantifier to determine the amount of exotic matter required near the wormhole throat for both models.

Non-commutative Wormhole geometries in presence of modified Chaplygin–Jacobi gas and Anton–Schmidt fluid

In this work, we have found Wormhole (WH) solutions in isotropic cosmology in the backdrop of general relativity while utilizing the “Modified Chaplygin–Jacobi Gas” and “Anton–Schmidt fluid” equations of state. As a starting point for our calculations, we have also considered two matter distributions, namely the Gaussian distribution and the Lorentzian distribution. All four energy conditions (i.e. strong, weak, null and dominant) are calculated, and their respective graphs are plotted as well. The shape function and redshift function associated with the wormhole structure are also derived and plotted graphically. After that, the embedding diagram of our wormhole models and proper radial distance are presented graphically. Finally, we have discussed the stability of the wormhole solutions obtained using the generalized Tolman–Oppenheimer–Volkov (TOV) equation and have examined the aspect of vanishing sound speed inside the wormhole throat to study the role of perturbations of the system.

Microscopic Origin of the Entropy of Black Holes in General Relativity

We construct an infinite family of microstates with geometric interiors for eternal black holes in general relativity with a negative cosmological constant in any dimension. Wormholes in the Euclidean path integral for gravity cause these states to have small, but nonzero, quantum mechanical overlaps that have a universal form. The overlaps have a dramatic consequence: The microstates span a Hilbert space of log dimension equal to the Bekenstein-Hawking entropy. The semiclassical microstates we construct contain Einstein-Rosen bridges of arbitrary size behind their horizons. Our results imply that all these bridges can be interpreted as quantum superpositions of wormholes of size at most exponential in the entropy. Published by the American Physical Society 2024

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

In this work, we construct three different models of static wormhole (WH) geometries within the realm of f(R,Lm) gravity theory. We start by deriving the corresponding field equations for the Morris–Thorne WH geometry in the context of anisotropic matter distribution under the generic form of f(R,Lm) gravity. By adequately specifying the key features of three different shape function models generated with different assumptions about their matter content, and assuming that WHs exert no tidal force by setting the gravitational redshift function to be a constant or φ′(r)=0, we disclose a variety of exact WH solutions in the theory. Our exact solutions for f(R,Lm) show that for all three classes of WHs found, the energy density is consistently positive in all spacetime, while the radial pressure is negative. This signifies that exotic matter is mandatory for the existence of WHs in f(R,Lm) gravity. We have also applied the energy conditions (ECs) for the WHs’ physical content and found that exact WH models are filled with exotic matter that violates the necessary ECs throughout spacetime and makes them compatible and traversable.

Static and spherically symmetric wormholes in power-law [formula omitted] gravity model

By venturing into gravitational frameworks that extend beyond general relativity (GR), it becomes evident that traversable wormholes (WHs) can conceivably be constructed solely through gravitational means. In GR, the intrinsic degrees of freedom are insufficient for assembling these special kinds of objects without incorporating exotic matter forms. Nevertheless, by stretching gravity into altered frameworks, it becomes possible to satisfy the necessary stability and traversability conditions without relying on such exotic materials. The key concept lies in the view that WH solutions can appear as common features in gravity theories once extra geometrical degrees of freedom are incorporated. Interestingly, we investigate WH solutions in the context of f(R) gravity theory, using a spherically symmetric metric embracing three asymptotically flat regions. More precisely, we are focusing on f(R) gravitational theories formulated in metric formalism, presuming time-independent metric coefficients, and exploiting the well-established Morris–Thorne space–time framework. We thoroughly derived exact solutions for traversable WHs that graciously adhere to energy and pressure constraints, assuming a power-law form for f(R), denoted f(R)=αRn, where α is an arbitrary constant and n is the power-law exponent. Conclusively, our findings open up the possibility of constraining the parameters (α, n, r0) associated with WH solutions. Importantly, we found that the existence of exotic matter was necessary to satisfy the stability and traversability criteria for WHs in all the cases we analyzed.

Multi-localized time-symmetric initial data for the Einstein vacuum equations

Abstract We construct a class of time-symmetric initial data sets for the Einstein vacuum equations modeling elementary configurations of multiple almost isolated systems. Each such initial data set consists of a collection of several localized sources of gravitational radiation, and lies in a family of data sets which is closed under scaling out the distances between the systems by arbitrarily large amounts. This class contains data sets which are not asymptotically flat, but to which nonetheless a finite ADM mass can be ascribed. The construction proceeds by a gluing scheme using the Brill–Lindquist metric as a template. Such initial data are motivated in part by a desire to understand the dynamical interaction of distant systems in the context of general relativity. As a by-product of the construction, we produce families of complete, scalar-flat initial data with trivial topology and infinitely many minimal spheres, as well as families of initial data with infinitely many Einstein–Rosen bridges.

Internal structure of hairy rotating black holes in three dimensions

We construct hairy rotating black hole solutions in three dimensional Einstein gravity coupled to a complex scalar field. When we turn on a real and uniform source on the dual CFT, the black hole is stationary with two Killing vectors and we show that there is no inner horizon for the black hole and the system evolves smoothly into a Kasner universe. When we turn on a complex and periodic driving source on the dual CFT with a phase velocity equal to the angular velocity of the black hole, we have a time-dependent black hole with only one Killing vector. We show that inside the black hole, after a rapid collapse of the Einstein-Rosen bridge, oscillations of the scalar field follow. Then the system evolves into the Kasner epoch with possible Kasner inversion, which occurs in most of the parameter regimes. In both cases, one of the metric fields obeys a simple relation between its value at the horizon and in the Kasner epoch.

Solution of Weyl–Lanczos relations for Morris–Thorne wormhole

Solution of Weyl–Lanczos relations for Morris–Thorne wormhole

Exploring supersymmetric wormholes in N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 2 SYK with chords

A feature the N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 2 supersymmetric Sachdev-Ye-Kitaev (SYK) model shares with extremal black holes is an exponentially large number of ground states that preserve supersymmetry. In fact, the dimension of the ground state subsector is a finite fraction of the total dimension of the SYK Hilbert space. This fraction has a remarkably simple bulk interpretation as the probability that the zero-temperature wormhole — a supersymmetric Einstein-Rosen bridge — has vanishing length. Using chord techniques, we compute the zero-temperature Hartle-Hawking wavefunction; the results reproduce the ground state count obtained from boundary index computations, including non-perturbative corrections. Along the way, we improve the construction [1] of the super-chord Hilbert space and show that the transfer matrix of the empty wormhole enjoys an enhanced N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 4 supersymmetry. We also obtain expressions for various two point functions at zero temperature. Finally, we find the expressions for the supercharges acting on more general wormholes with matter and present the superchord algebra.

Geodesic Structure of Generalized Vaidya Spacetime through the K-Essence

This article investigates the radial and non-radial geodesic structures of the generalized K-essence Vaidya spacetime. Within the framework of K-essence geometry, it is important to note that the metric does not possess conformal equivalence to the conventional gravitational metric. This study employs a non-canonical action of the Dirac–Born–Infeld kind. In this work, we categorize the generalized K-essence Vaidya mass function into two distinct forms. Both the forms of the mass functions have been extensively utilized to analyze the radial and non-radial time-like or null geodesics in great detail inside the comoving plane. Indications of the existence of wormholes can be noted during the extreme phases of spacetime, particularly in relation to black holes and white holes, which resemble the Einstein–Rosen bridge. In addition, we have also detected a distinctive indication of the quantum tunneling phenomenon around the singularity (r→0). Furthermore, we have found that for certain types of solutions, there exist circular orbits through the event horizon as well as quasicircular orbits. Also, we have noted that there is no central singularity in our spacetime where both r and t tend towards zero. The existence of a central singularity is essential for any generalized Vaidya spacetime. This indicates that spacetime can be geodesically complete, which correlates with the findings of Kerr’s recent work (2023).

A symmetry algebra in double-scaled SYK

The double-scaled limit of the Sachdev-Ye-Kitaev (SYK) model takes the number of fermions and their interaction number to infinity in a coordinated way. In this limit, two entangled copies of the SYK model have a bulk description of sorts known as the “chord Hilbert space”. We analyze a symmetry algebra acting on this Hilbert space, generated by the two Hamiltonians together with a two-sided operator known as the chord number. This algebra is a deformation of the JT gravitational algebra, and it contains a subalgebra that is a deformation of the \mathfrak{sl}_2𝔰𝔩2 near-horizon symmetries. The subalgebra has finite-dimensional unitary representations corresponding to matter moving around in a discrete Einstein-Rosen bridge. In a semiclassical limit the discreteness disappears and the subalgebra simplifies to \mathfrak{sl}_2𝔰𝔩2, but with a non-standard action on the boundary time coordinate. One can make the action of \mathfrak{sl}_2𝔰𝔩2 algebra more standard at the cost of extending the boundary circle to include some “fake” portions. Such fake portions also accommodate certain subtle states that survive the semi-classical limit, despite oscillating on the scale of discreteness. We discuss applications of this algebra, including sub-maximal chaos, the traversable wormhole protocol, and a two-sided OPE.

A study of wormhole solutions in f(Q,T) gravity using some viable shape functions

This article examines static spherically symmetric wormhole (WH) solutions in f(Q,T) theory of gravity where Q represents non-metricity (NM) scalar while T is the trace of the stress-energy tensor. An anisotropic fluid configuration is taken into account to fulfill the task along with the linear form of the f(Q,T) model. For two different choices of the redshift function that are φ(r)=constant, φ(r)=(r0r)12 and for the shape functions, b(r)=r0+r0((rr0)γ−1),b(r)=r0log⁡(r+1)log⁡(r0+1), we construct the corresponding WH solutions. We examine the graphical behavior of the chosen shape functions and analyze all necessary and sufficient conditions for the existence of WH. We investigate the stability of obtained solutions and analyze how the energy conditions behave. We found that the null energy condition (NEC) is violated in a few regions of spacetime which shows the existence of traversable WHs in these regions. It is concluded that our results are viable for the positive values of theory parameters and within a range 0<γ<1 (the parameter of the shape function).

Possible existence of traversable wormhole in Finsler–Randers geometry

In the present article, we have explored the possible existence of a traversable wormhole in the framework of Finsler–Randers (F–R) geometry. In order to achieve this goal, first, we have constructed gravitational field equations for static, spherically symmetric spacetime with anisotropic fluid distribution in F–R geometry. Next, we have written the deduced form of field equations in the background of Morris–Thorne wormhole geometry. To visualize the shape of the wormhole, we have selected exponential shape function b(r)=frac{r}{expleft( eta left( frac{r}{r_{0}} - 1right) right) } with the constant parameter eta and the throat radius r_{0} and depicted two-dimensional and three-dimensional embedding diagrams corresponding to some considered values of eta and r_{0}. Moreover, all essential requirements to build a wormhole shape have been examined for the reported shape function. Next, We have analyzed wormhole configuration for three cases (I, II, III) corresponding to three selected redshift functions. Furthermore, each case is analyzed by dividing it into two models such as (i) Model-1 (for general anisotropic EoS p_{t}=chi p_{r}) and (ii) Model-2 (for linear phantom-like EoS p_{r} + omega rho =0). In each model of three cases, we have verified the validity of the wormhole solution in F–R geometry by considering null, weak, strong and dominant energy conditions. Also, the total amount of averaged NEC-violating matter near the wormhole throat has been analyzed by computing volume integral quantifier.

Probing the Connection between Entangled Particles and Wormholes in General Relativity.

Maldacena and Susskind conjectured that two entangled particles, which can be thought of as forming an Einstein-Podolsky-Rosen (EPR) pair, are connected by a nontraversable wormhole or Einstein-Rosen (ER) bridge. They named their conjecture ER=EPR. We present a concrete quantitative model for ER=EPR, in which two spin-1/2 particles in a singlet state are connected by a nontraversable wormhole in asymptotically flat general relativity. In our model, the fermions are described by the charged Dirac equation minimally coupled to gravity. This system has static wormhole solutions. We use these solutions as initial data and numerically evolve them forward in time. Our simulations show that black holes form, which are connected by the wormhole and which render the wormhole nontraversable. We also find that the wormhole throat shrinks, which places the particles in close proximity to one another and suggests an explanation for how the wormhole facilitates the nonlocal communication required by entanglement.