Wormhole Model Research Articles

Wormhole geometries in f(Q) gravity and the energy conditions

Following the recent theory of f(Q) gravity, we continue to investigate the possible existence of wormhole geometries, where Q is the non-metricity scalar. Recently, the non-metricity scalar and the corresponding field equations have been studied for some spherically symmetric configurations in Mustafa (Phys Lett B 821:136612, 2021) and Lin and Zhai (Phys Rev D 103:124001, 2021). One can note that field equations are different in these two studies. Following Lin and Zhai (2021), we systematically study the field equations for wormhole solutions and found the violation of null energy conditions in the throat neighborhood. More specifically, considering specific choices for the f(Q) form and for constant redshift with different shape functions, we present a class of solutions for static and spherically symmetric wormholes. Our survey indicates that wormhole solutions could not exist for specific form function f(Q)= Q+ alpha Q^2. To summarize, exact wormhole models can be constructed with violation of the null energy condition throughout the spacetime while being rho ge 0 and vice versa.

Correspondence between quasinormal modes and the shadow radius in a wormhole spacetime

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 on the specific model, the typical shadow radius can increase or decrease and a reflecting point exists. Finally, we discuss whether a wormhole can mimic the black hole due to it's shadow. In the light of the EHT data, we find the upper and lower limits of the wormhole throat radius in the galactic center M87.

Traversable wormholes in the traceless f(R,T) gravity

Wormholes are tunnels connecting different regions in spacetime. They were obtained originally as a solution for Einstein’s General Theory of Relativity and according to this theory they need to be filled by an exotic kind of anisotropic matter. In the present sense, by “exotic matter” we mean matter that does not satisfy the energy conditions. In this paper, we propose the modeling of traversable wormholes (i.e. wormholes that can be safely crossed) within an alternative gravity theory that proposes an extra material (rather than geometrical) term in its gravitational action, namely the traceless [Formula: see text] theory of gravitation, with [Formula: see text] and [Formula: see text] being, respectively, the Ricci scalar and trace of the energy–momentum tensor. Our solutions are obtained from well-known particular cases of the wormhole metric potentials, namely redshift and shape functions. In possession of the solutions for the wormhole material content, we also apply the energy conditions to them. The features of those are carefully discussed.

Hydrodynamic models of astrophysical wormholes: The general concept

We study the amplification of shallow-water waves in the course of their propagation in a duct of a variable cross section with a spatially inhomogeneous flow. We derive the basic set of equations for the wave propagation and present the asymptotic analysis of solutions in the neighborhood of critical points where the wave speed coincides with the speed of the current. The considered model represents a kinematic analog of astrophysical event horizons occurring in the vicinity of the black holes (BH) or white holes (WH). We study then the wave propagation in the flow with two critical points (two horizons) when the flow transits first the BH horizon and then the WH one or vice versa. In the former case, the region between the critical points mimics a wormhole in general relativity. The theoretical results are illustrated by numerical calculations of wave propagation through the critical points. It is shown that the wave amplification after passing the active zone between the horizons takes place in BH–WH arrangements only and can occur for different relationships between the subcritical and supercritical flow velocities. The frequency dependence of the amplification factor is obtained and quantified in terms of the velocity ratio within and outside the “wormhole domain.”

Capacity of entanglement in local operators

We study the time evolution of the excess value of capacity of entanglement between a locally excited state and ground state in free, massless fermionic theory and free Yang-Mills theory in four spacetime dimensions. Capacity has non-trivial time evolution and is sensitive to the partial entanglement structure, and shows a universal peak at early times. We define a quantity, the normalized “Page time”, which measures the timescale when capacity reaches its peak. This quantity turns out to be a characteristic property of the inserted operator. This firmly establishes capacity as a valuable measure of entanglement structure of an operator, especially at early times similar in spirit to the Rényi entropies at late times. Interestingly, the time evolution of capacity closely resembles its evolution in microcanonical and canonical ensemble of the replica wormhole model in the context of the black hole information paradox.

Traversable Wormhole Geometries in Gravity

AbstractThe current interests in the universe motivate us to go beyond Einstein's General theory of relativity. One of the interesting proposals comes from a new class of teleparallel gravity named symmetric teleparallel gravity, i.e., gravity, where the non‐metricity term Q is accountable for fundamental interaction. These alternative modified theories of gravity's vital role are to deal with the recent interests and to present a realistic cosmological model. This manuscript's main objective is to study the traversable wormhole geometries in gravity. We construct the wormhole geometries for three cases: (i) by assuming a relation between the radial and lateral pressure, (ii) considering phantom energy equation of state (EoS), and (iii) for a specific shape function in the fundamental interaction of gravity (i.e. for linear form of ). Besides, we discuss two wormhole geometries for a general case of with two specific shape functions. Then, we discuss the viability of shape functions and the stability analysis of the wormhole solutions for each case. We have found that the null energy condition (NEC) violates each wormhole model which concluded that our outcomes are realistic and stable. Finally, we discuss the embedding diagrams and volume integral quantifier to have a complete view of wormhole geometries.

Acid stimulation in carbonates: A laboratory test of a wormhole model based on Damköhler and Péclet numbers

Acid stimulation has been used worldwide as a stimulation technique either by matrix acidizing to remove the near-wellbore permeability impairment which is referred to as formation damage or acid fracturing to enhance the connectivity between wells and reservoirs. Carbonate acid stimulation improves the near-wellbore permeability through the creation of deeply penetrating fluid pathways referred to as wormholes. The stimulation success depends on the length and width of these wormholes. Here, we test the results of a theoretical study which suggests that the effect of acid flow in a reactive porous medium can be fully defined by just two significant dimensionless numbers, the non-dimensional Damköhler and Péclet numbers. The approach was validated in an idealized numerical study and is here tested in a systematically controlled laboratory experiment for real carbonate rocks. In order to obtain statistically meaningful results, we pushed the envelope by testing the prediction of the critical point for the wormholing phenomenon in a difficult domain, where sufficient randomly distributed pathways exist such that the wormholing domain is rarely achieved. The result confirmed that for a randomly-structured highly porous media, the critical point for dissolution pattern formation including the wormholing phenomenon can be fully captured by a domain diagram of inverse Damköhler versus Péclet number as predicted by the theoretical model. The model also holds for moderately tight formations, however, breaks down when the natural permeability drops well below 100 mDarcy. We conclude that the result of this research can be applied to reliably predict the wormholes initiation and various dissolution structures under various injection rate and HCl-concentration.

Topological shadows and complexity of islands in multiboundary wormholes

Recently, remarkable progress in recovering the Page curve of an evaporating black hole (BH) in Jackiw-Teitelboim gravity has been achieved through use of Quantum Extremal surfaces (QES). Multi-boundary Wormhole (MbW) models have been crucial in parallel model building in three dimensions. Motivated by this we here use the latter models to compute the subregion complexity of the Hawking quanta of the evaporating BH in AdS3 and obtain the Page curve associated with this information theoretic measure. We use three- and n-boundary wormhole constructions to elucidate our computations of volumes below the Hubeny-Rangamani-Takayanagi (HRT) surfaces at different times. Time is represented by the growing length of the throat horizons corresponding to smaller exits of the multi-boundary wormhole and the evaporating bigger exit shrinks with evolving time. We track the change in choice of HRT surfaces with time and plot the volume with time. The smooth transition of Page curve is realized by a discontinuous jump at Page time in volume subregion complexity plots and the usual Page transition is realized as a phase transition due to the inclusion of the island in this context. We discuss mathematical intricacies and physical insights regarding the inclusion of the extra volume at Page time. The analysis is backed by calculations and lessons from kinematic space and tensor networks.

Stable wormhole models in general relativity under conformal symmetry

In this study, we shall explore conformal symmetry to examine the wormhole models by considering traceless fluid. In this regard, we shall take anisotropic fluid with spherically symmetric space-time. Further, we shall calculate the properties of shape-functions, which are necessary for the existence of wormhole geometry. The presence of exotic matter is confirmed in all the cases through the violation of the Null Energy Condition. Furthermore, we have discussed the stability of wormhole solutions through the Tolman–Oppenheimer–Volkoff (TOV) equation. It is observed that our acquired solutions are stable under the particular values of involved parameters in different cases in conformal symmetry.

Looking at Quantization of a Wave Function, from Weber (1961), to Signals from Wavefunctions at the Mouth of a Wormhole

We utilize how Weber in 1961 initiated the process of quantization of early universe fields to the problem of what may be emitted at the mouth of a wormhole. While the wormhole models are well developed, there is as of yet no consensus as to how, say GW or other signals from a wormhole mouth could be quantized or made to be in adherence to a procedure Weber cribbed from Feynman, in 1961. In addition, we utilize an approximation for the Hubble parameter parameterized from Temperature using Sarkar’s H ~ Temperature relations, as given in the text. Finally, after doing this, we go to the Energy as E also ~ Temperature, and from there use E (energy) as ~ signal frequency. This gives us an idea of how to estimate frequency generated at the mouth of a wormhole.

Wormhole Models and Energy Conditions in f ℛ Gravity with the Hu–Sawicki Model

In this recent study, we shall investigate the wormhole models with a Hu–Sawicki model in the framework of f ℛ gravity. Spherically static symmetric space-time is considered to construct wormhole models with the anisotropic fluid distribution. The traceless matter is discussed by imposing a particular equation of state. To address the important conditions of the shape function of the wormhole geometry, we have used the particular values of the involved parameters. Furthermore, different energy conditions are discussed to check the nature of matter against two specific models. The null energy condition is observed to be violated for both of the models. It is mentioned that our inquired results are acceptable.

Spherically symmetric static wormhole models in the Einsteinian cubic gravity

Our aim is to discuss spherically symmetric static wormholes with the Lorentzian signature in the Einsteinian cubic gravity for two different models of pressure sources. First, we calculate the modified fields equations for the Einsteinian cubic gravity for the wormhole geometry under the anisotropic matter. Then we investigate the shape-function for two different models, which can be taken as a part of the general relation, namely, [Formula: see text]. We further study the energy conditions for both the models in the background of the Einsteinian cubic gravity. We show that our obtained shape-functions satisfy all the necessary conditions for the existence of wormhole solutions in the Einsteinian cubic gravity for some particular values of the different involved parameters. We also discuss the behavior of the energy conditions especially the null and the weak energy conditions for the wormhole models in the Einsteinian cubic gravity.

Novel shadows from the asymmetric thin-shell wormhole

For dark compact objects such as black holes or wormholes, the shadow size has long been thought to be determined by the unstable photon sphere (region). However, by considering the asymmetric thin-shell wormhole (ATSW) model, we find that the impact parameter of the null geodesics is discontinuous through the wormhole in general and hence we identify novel shadows whose sizes are dependent of the photon sphere in the other side of the spacetime. The novel shadows appear in three cases: (A2) The observer's spacetime contains a photon sphere and the mass parameter is smaller than that of the opposite side; (B1, B2) there' s no photon sphere no matter which mass parameter is bigger. In particular, comparing with the black hole, the wormhole shadow size is always smaller and their difference is significant in most cases, which provides a potential way to observe wormholes directly through Event Horizon Telescope with better detection capability in the future.

Reflected entropy for an evaporating black hole

We study reflected entropy as a mixed state correlation measure in black hole evaporation. As a measure for bipartite mixed states, reflected entropy can be computed between black hole and radiation, radiation and radiation, and even black hole and black hole. We compute reflected entropy curves in three different models: 3-side wormhole model, End-of-the-World (EOW) brane model in three dimensions and two-dimensional eternal black hole plus CFT model. For 3-side wormhole model, we find that reflected entropy is dual to island cross section. The reflected entropy between radiation and black hole increases at early time and then decreases to zero, similar to Page curve, but with a later transition time. The reflected entropy between radiation and radiation first increases and then saturates. For the EOW brane model, similar behaviors of reflected entropy are found.We propose a quantum extremal surface for reflected entropy, which we call quantum extremal cross section. In the eternal black hole plus CFT model, we find a generalized formula for reflected entropy with island cross section as its area term by considering the right half as the canonical purification of the left. Interestingly, the reflected entropy curve between the left black hole and the left radiation is nothing but the Page curve. We also find that reflected entropy between the left black hole and the right black hole decreases and goes to zero at late time. The reflected entropy between radiation and radiation increases at early time and saturates at late time.

Wormhole modeling in f(R,T) gravity with minimally-coupled massless scalar field

In this paper, the strong gravitational lensing is explored for traversable wormholes in [Formula: see text] theory of gravity with minimally-coupled massless scalar field. First, the effective wormhole solutions are obtained using the model [Formula: see text], where [Formula: see text] is constant, [Formula: see text] is scalar curvature and [Formula: see text] is the trace of stress-energy tensor. Furthermore, three different shape functions namely, [Formula: see text] (Ref. 36), [Formula: see text] (Refs. 35 and 37) and [Formula: see text], [Formula: see text] (Refs. 34, 35, 39, 73) are considered and studied their qualitative behavior for the construction of wormhole geometry respectively. Subsequently, gravitational lensing effect is implemented to detect the existence of photon spheres at or outside the throat of wormholes.

Traversable wormhole modelling with exponential and hyperbolic shape functions in F(R,T) framework

The concept of traversable wormhole, a hypothetical tunnel-like structure is initially proposed by Morris and Thorne (Am. J. Phys. 56, 395 (1988)) by using Einstein’s general relativity theory. Harko et al. (Phys. Rev. D 84, 024020 (2011)) defined [Formula: see text] gravity as an extended gravitational theory having terms [Formula: see text] and [Formula: see text] as Ricci scalar and trace of energy momentum respectively. In this article, we explore wormhole models for the framework of [Formula: see text] gravity by using two different shape functions. The first shape function is [Formula: see text], [Formula: see text] (proposed by Mishra and Sharma, arXiv:2003.00298v1 , 2020) and second is a hyperbolic shape function which is of the form [Formula: see text]. Geometrical behavior of wormholes are discussed in anisotropic scenario by using equation of state [Formula: see text]. The stability of models are analyzed by using equilibrium condition and determining gravitational force, anisotropic force, hydrostatic force and force due to modified gravity. For the validation of null energy condition and weak energy condition, significant role of shape function is illustrated for the presence of nonexotic matter.

Wormhole models with exotic matter in Rastall gravity

In this paper, we examine the wormhole solutions by taking two different anisotropic models in Rastall gravity. For this purpose, we shall discuss anisotropic fluid to construct two different anisotropic models. Further, we shall employ two specific shape functions to calculate the behavior of energy conditions. The presence of exotic matter is confirmed in all the cases of this study due to the violation of the null energy condition. All the properties of shape function under both anisotropic models are fulfilled. It is noticed that wormhole solutions exist under the particular values of involved parameters in different cases in Rastall gravity.

Rotating Melvin-like Universes and Wormholes in General Relativity

We find a family of exact solutions to the Einstein–Maxwell equations for rotating cylindrically symmetric distributions of a perfect fluid with the equation of state p=wρ (|w|<1), carrying a circular electric current in the angular direction. This current creates a magnetic field along the z axis. Some of the solutions describe geometries resembling that of Melvin’s static magnetic universe and contain a regular symmetry axis, while some others (in the case w>0) describe traversable wormhole geometries which do not contain a symmetry axis. Unlike Melvin’s solution, those with rotation and a magnetic field cannot be vacuum and require a current. The wormhole solutions admit matching with flat-space regions on both sides of the throat, thus forming a cylindrical wormhole configuration potentially visible for distant observers residing in flat or weakly curved parts of space. The thin shells, located at junctions between the inner (wormhole) and outer (flat) regions, consist of matter satisfying the Weak Energy Condition under a proper choice of the free parameters of the model, which thus forms new examples of phantom-free wormhole models in general relativity. In the limit w→1, the magnetic field tends to zero, and the wormhole model tends to the one obtained previously, where the source of gravity is stiff matter with the equation of state p=ρ.

Non-commutative wormhole solutions in exponential gravity with matter coupling

In the present article, we use non-commutative geometry to investigate the wormhole solutions in modified f(R, T) theory of gravity. In particular, we consider Gaussian and Lorentzian source with f(R,T)=f1(R)+λT model to discuss the wormhole solutions existence. We choose two different models of f1(R) i.e. f1(R)=R−αγ(1−e−Rγ) known as exponential gravity model and f1(R)=R−αγtanh(Rγ) known as Tsujikawa model, where α, γ are model parameters. We explore the viable solutions for these models. Moreover, we discuss analytically as well as graphically, distinct properties of these model of wormholes by giving suitable values to the model parameters. Conclusively, we find that obtained wormhole solutions are stable and physically acceptable with the considered exponential and Tsujikawa gravity models.

Quantum chaos, thermodynamics and black hole microstates in the mass deformed SYK model

We study various aspects of the mass deformation of the SYK model which makes the black hole microstates escapable. SYK boundary states are given by a simple local boundary condition on the Majorana fermions and then evolved in Euclidean time in the SYK Hamiltonian. We study the ground state of this mass deformed SYK model in detail. We also use SYK boundary states as a variational approximation to the ground state of the mass deformed SYK model. We compare variational approximation with the exact ground state results and they showed a good agreement. We also study the time evolution of the mass deformed ground state under the SYK Hamiltonian. We give a gravity interpretation of the mass deformed ground state and its time evolutions. In gravity side, mass deformation gives a way to prepare black hole microstates that are similar to pure boundary state black holes. Escaping protocol on these ground states simply gives a global AdS2 with an IR end of the world brane. We also study the thermodynamics and quantum chaotic properties of this mass deformed SYK model. Interestingly, we do not observe the Hawking Page like phase transition in this model in spite of similarity of the Hamiltonian with eternal traversable wormhole model where we have the phase transition.