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In recent years there has been a growing interest in the field of wormhole physics in the presence of Casimir effect. As this effect provides negative energy density, it can be utilized as an ideal candidate for the exotic matter required for creating a traversable wormhole. In the context of modified theories of gravity such as Brans–Dicke (BD) theory (Brans and Dicke 1961 Phys. Rev. 124 925), wormhole geometries have been vastly investigated. However, the scientific literature is silent on the issue of BD wormholes in the presence of Casimir energy. Our aim in the present study is to seek for static spherically symmetric solutions representing wormhole configurations in BD theory with Casimir energy as the supporting matter. The Casimir setup we assume comprises two electrically neutral, infinitely large parallel planes placed in a vacuum. We then consider the Casimir vacuum energy density of a scalar field in such a configuration with Dirichlet and mixed boundary conditions. In the former case the corresponding Casimir force is attractive and in the latter this force is repulsive. We present exact zero tidal force wormhole solutions as well as those with non vanishing redshift function for both types of Casimir energies. The conditions on wormhole solutions along with the weak (WEC) and null (NEC) energy conditions put constraints on the values of BD coupling parameter. These constraints are also subject to the value of BD scalar field at the throat and the throat radius. We therefore find that BD wormholes in the presence of Casimir energy can exist without violating NEC and WEC (for the repulsive Casimir force). Finally, we examine the equilibrium condition for stability of the obtained solutions using Tolman–Oppenheimer–Volkoff equation. [ABSTRACT FROM AUTHOR]

Wormhole solutions in General Relativity (GR) require exotic matter sources that violate the null energy condition (NEC), and it is well-known that higher-order modifications of GR and some alternative matter sources can support wormholes. In this study, we explore the possibility of formulating traversable wormholes in f(R) modified gravity, which is perhaps the most widely discussed modification of GR, with two approaches. First, to investigate the effects of geometrical constraints on the global characteristics, we gauge the TT-component of the metric tensor and employ Padè approximation to check whether a well-constrained shape function can be formulated in this manner. We then derive the field equations with a background of string cloud and numerically analyse the energy conditions, stability, and amount of exotic matter in this space-time. Next, as an alternative source in a simple f(R) gravity model, we use the background cloud of strings to estimate the wormhole shape function and analyse the relevant properties of the space-time. These results are then compared with those of wormholes threaded by normal matter in the simple f(R) gravity model considered. The results demonstrate that string cloud is a viable source for wormholes with NEC violations; however, the wormhole space-times in the simple f(R) gravity model considered in this study are unstable. [ABSTRACT FROM AUTHOR]

Acidization is a widely used stimulation technique for carbonate reservoirs aimed at removing formation damage, and if successful, can result in the creation of wormholes of specific lengths and conductivities around the wellbore. The formation of wormholes depends on the injection rate for a particular acid-mineral system and can be predicted through numerical simulations of the reactive phenomenon during acidization. In this paper, the commonly used two-scale continuum model is enhanced to encompass fractured-vuggy porous media. The fractures are characterized by a pseudo-fracture model, while vugs are represented by a cluster of anomalous matrices with high porosity. Moreover, a method for generating random pore-fracture-vuggy models is proposed. The governing equations are discretized by the finite volume method and are solved under three-dimensional linear and radial conditions. Sensitivity analysis of dissolution dynamics with respect to fracture and vug parameters is performed. The simulation results indicate that both fractures and vugs significantly impact wormhole development. Except for fractures perpendicular to the acid flow direction, fractures in other directions play a crucial role in determining the direction of wormhole growth. [ABSTRACT FROM AUTHOR]

In this work, we explore the wormhole physics in a modified gravitational theory, called the generalized Brans–Dicke theory (GBD). In order to solve the equations in this theory, the parameterized forms for the shape function and the scalar-field function are taken. With the help of selecting a specific form of state equation, i.e. considering a relation between the transverse pressure (not the total pressure) and the energy density for matter that threads wormhole: p t = α ρ = − ρ , we provide some special solutions of the traversable wormhole in GBD. Given that the violation of energy conditions (ECs) of matter often induces problems on the gravitational theory, it is important to inspect the ECs of matter in modified theories. In this GBD theory, we find that the weak energy condition, the null energy condition, the dominated energy condition and the strong energy condition could be satisfied for the matter near the throat of wormhole, depending on the parameterized models and the model-parameters values. Finally, using the classical reconstruction technique in the traversable wormhole physics, we derive a Lagrangian function of gravitational field for the GBD theory. [ABSTRACT FROM AUTHOR]

Acid enhanced oil recovery has been a focus of interest in the oil industry due to its significant results on improved recovery, especially in carbonate reservoirs. However, in carbonate reservoirs, highly conductive pathways called "wormholes" are created when acidic fluids are injected into carbonate rocks. Wormholes could jeopardize the enhanced oil recovery outcome and sweep efficiency leaving a substantial volume of oil in the reservoir unswept. This phenomenon has not been investigated yet. The main objective of this study is to identify the impact of these wormholes on the overall oil recovery during enhanced oil recovery practices. This was achieved by injecting acidic fluid into Indiana limestone at various injection rates to control the creation of wormholes. The injection rates were selected based on a proposed dimensionless phase space that predicts the wormholes development and dissolution phase. Our results show that wormholes have a significant impact on the enhanced oil recovery performance resulting in a decrease in the overall oil recovery by 9.6% for portions of the reservoir that experience wormholing. In real field applications, it is recommended to avoid creating wormholes over large portions of the reservoir affected by acid injection as it may jeopardize the field development outcome leaving an unspecified amount of oil in virgin regions in the reservoir which results in additional operational complications. Wormholes are only beneficial near the wellbore for wellbore cleanup and matrix treatment purposes thus providing easier access to the reservoir. However, care needs to be taken to constrain wormhole formation to skin factor reduction and avoid far-reaching wormholes in the reservoir. [ABSTRACT FROM AUTHOR]

Wormholes are hypothetical space-time tunnels with nontrivial topologies capable of connecting either two distant regions of the same universe or two different universes [[1], [3]]. The present Special Issue "Recent Advances in Wormhole Physics" is aimed at enlightening some recent results in selected areas of wormhole physics. At present, wormholes are extremely attractive and popular objects for research, it is sufficient to mention that the word "wormhole" is found in the titles of 1614 articles on the resource ArXiv.org for all years and 175 articles for the last 12 months (as of 19 January 2023). [Extracted from the article]

The Goheer–Kleban–Susskind no-go theorem says that the symmetry of de Sitter space is incompatible with finite entropy. The meaning and consequences of the theorem are discussed in light of recent developments in holography and gravitational path integrals. The relation between the GKS theorem, Boltzmann fluctuations, wormholes, and exponentially suppressed non-perturbative phenomena suggests that the classical symmetry between different static patches is broken and that eternal de Sitter space—if it exists at all—is an ensemble average. [ABSTRACT FROM AUTHOR]

We consider the generalized Tolman solution of general relativity, describing the evolution of a spherical dust cloud in the presence of an external electric or magnetic field. The solution contains three arbitrary functions f (R), F(R) and t0(R), where R is a radial coordinate in the comoving reference frame. The solution splits into three branches corresponding to hyperbolic ( f > 0), parabolic ( f = 0) and elliptic ( f < 0) types of motion. In such models, we study the possible existence of wormhole throats defined as spheres of minimum radius at a fixed time instant, and prove the existence of throats in the elliptic branch under certain conditions imposed on the arbitrary functions. It is further shown that the normal to a throat is a timelike vector (except for the instant of maximum expansion, when this vector is null), hence a throat is in general located in a T-region of space-time. Thus, if such a dust cloud is placed between two empty (Reissner--Nordström or Schwarzschild) space-time regions, the whole configuration is a black hole rather than a wormhole. However, dust clouds with throats can be inscribed into closed isotropic cosmological models filled with dust to form wormholes which exist for a finite period of time and experience expansion and contraction together with the corresponding cosmology. Explicit examples and numerical estimates are presented. The possible traversability of wormhole-like evolving dust layers is established by a numerical study of radial null geodesics. [ABSTRACT FROM AUTHOR]

The Euclidean path integral is well approximated by instantons. If instantons are dynamical, they will necessarily be complexified. Fuzzy instantons can have multiple physical applications. In slow-roll inflation models, fuzzy instantons can explain the probability distribution of the initial conditions of the universe. Although the potential shape does not satisfy the slow-roll conditions due to the swampland criteria, the fuzzy instantons can still explain the origin of the universe. If we extend the Euclidean path integral beyond the Hartle-Hawking no-boundary proposal, it becomes possible to examine fuzzy Euclidean wormholes that have multiple physical applications in cosmology and black hole physics. [ABSTRACT FROM AUTHOR]

This work studies the theoretical construction of charged quintessence thin-shell wormholes using Israel thin-shell approach. The stability of these wormhole solutions is investigated by taking linear, logarithmic and Chaplygin gas models as a constituent of exotic matter at thin-shell. The presence of wormhole stability regions particularly relies on the physically justifiable values of charge and quintessence parameter. It is noted that the increasing value of charge seems as an effective component for stable regions while the rise in negativity of the quintessence parameter gives more stable wormhole configurations. [ABSTRACT FROM AUTHOR]

In this review, we go over the bases of quantum teleportation, ER bridges in Genera! relativity, and the foundational work on the hypothesis ER=EPR and summarize the resulting wormhole teleportation protocol. Wethen discuss that -- resulting from ER=EPR -- certain wormholes have to be either traversable or at the very least let information permeate, resulting in the exploration of the possibility that incoming matter might change the metric outside of wormhole throats. In this study, made in the Schwarzschild metric with the original coordinate system, we managed to find a non-zero energy-momentum tensor produced by a particular solution of the electromagnetic wave equation in curved spacetime, implying a change in the overall metric by Einstein's Equation. [ABSTRACT FROM AUTHOR]

This paper explores the stable configuration of thin-shell wormholes constructed from two regular black holes (modified Hayward and four parametric) by using Visser cut and paste approach. The components of stress-energy tensor are evaluated through the Lanczos equations. We analyze the stability of thin-shell by using radial perturbation preserving its symmetries about equilibrium static solution. It is found that modified Hayward wormholes are more stable than the Hayward wormholes. Further, the stable regions of four parametric regular wormholes are larger than the Schwarzschild, Reissner–Nordström and Ayón–Beato–García wormholes. We conclude that stable region decreases for highly charged thin-shell wormholes. [ABSTRACT FROM AUTHOR]

Predicting the instabilities that occur during the chemical reaction between a percolating fluid and a soluble rock leading to the development of macroscopic channels called wormholes is a key for understanding many geological processes. Their shape and their spatial distribution depend on two dimensionless numbers, namely Damköhler (Da) and Péclet (Pe) numbers. Although the dissolution phenomenon has been extensively studied both in the context of acid stimulation of oil wells in carbonate rocks and carbon capture and storage, few works have focused on the influence of the physical properties of fluids on wormhole patterns. Consequently, through interpretation of images acquired during the injection of pure water into a 2‐D reconstituted salt massif and considering different configurations of injection, we illustrate the buoyancy effects on wormhole formation. Contrarily to observation in fractures, experimental results suggest that dissolution regimes can still be described by the classical dimensionless numbers Da and Pe. As for the regime diagram, it remains practically unchanged for strong Péclet and weak Damköhler and undergoes a slowdown of the propagation of the dissolution front when the number of Richardson's increases. Analysis of morphological descriptors such as area, interface, and tortuosity shows that density contrast has an influence on intermediate‐ to high‐Richardson dissolution regimes that may be explained by the existence of buoyancy effects. Key Points: Use of a laboratory physical model and morphological descriptors to study the influence of density contrast on dissolution regimesNo additional pattern was observed but displacement of transition between patterns toward higher Péclet/lower Damköhler induced by buoyancyA modification of interface morphology, with larger roughness, has been highlighted for high Richardson number [ABSTRACT FROM AUTHOR]

On a nanosecond time scale, solid insulators abnormally fail in bulk rather than on surface, which is termed as the 'worm-hole' effect. By using a generator with adjustable output pulse width and dozens of organic glass (PMMA) and polystyrene (PS) samples, experiments to verify this effect are conducted. The results show that under short pulses of 10 ns, all the samples fail due to bulk breakdown, whereas when the pulse width is tuned to a long pulse of 7 μs, the samples fail as a result of surface flashover. The experimental results are interpreted by analyzing the conditions for the bulk breakdown and the surface flashover. It is found that under short pulses, the flashover threshold would be as high as the bulk breakdown strength (EBD) and the flashover time delay (td) would be longer than the pulse width (τ), both of which make the dielectrics' cumulative breakdown occur easily; whereas under long pulses, that Ef is much lower than EBD and td is smaller than τ is advantageous to the occurrence of the surface flashover. In addition, a general principle on solid insulation design under short pulse condition is proposed based on the experimental results and the theoretical analysis. [ABSTRACT FROM AUTHOR]

We show that the scattering of radiation on a traversable wormhole forms a vortex in the radiation energy flux. Then, if the wormhole possesses also a magnetic fields, the vortex accelerates charged particles along the magnetic lines and such a system works as an accelerator. If the vortex is small, the system reaches the stationary state, when the income of the kinetic energy reradiates completely in the form of the synchrotron radiation. Such a mechanism allows us to relate a part of observed sources of the synchrotron radiation to magnetic wormholes. [ABSTRACT FROM AUTHOR]

In the parallel paper by Li et al. (2019; https://doi.org/10.1029/2018JB017238), an effluent chemistry monitoring system was designed and used in core flood experiments to continuously measure the effluent concentration and study the evolution of the rock‐fluid system. In this study, the results from the parallel paper were used for interpretation and modeling of the dissolution and wormhole formation. Based on the behavior of the effluent concentration, two transient states and two quasi‐steady states were defined to describe the dissolution in the rock‐fluid system. Dimensional analysis was used to identify the controlling mechanisms of the dissolution and transport in the matrix and the wormholes. The dimensional analysis showed that the dissolution in the matrix was reaction controlled, while the dissolution in the wormholes was diffusion controlled. It also showed that the rock‐fluid system evolved from reaction‐controlled dissolution to diffusion‐controlled dissolution during the core flood tests. A continuum model and the extended Graetz solution were used to model the dissolution in the matrix and in the wormholes, respectively. In the continuum model, this study estimates the effective surface area as a function of the flow rate (injection flux), to account for the effect of flow conditions on dissolution. Finally, a semiempirical model combining the continuum model and the extended Graetz solution was developed to simulate the formation of wormholes and the evolution of the dissolution kinetics during core flood tests. Key Points: The continuous effluent concentration data were used to identify the four states of the dissolution processes during core flood testsThe dimensional analysis showed that the dissolution was reaction controlled in the matrix and diffusion controlled in the wormholesA semiempirical model was developed to simulate the formation of wormholes and the evolution of the dissolution kinetics [ABSTRACT FROM AUTHOR]

Core flood tests were conducted to study the effect of flow rate on the dissolution of the gypsum rock matrix and the formation of wormholes. An effluent chemistry monitoring system was designed and integrated into a triaxial system to provide continuous effluent concentration measurements, in addition to the pressure and flow measurements during the core flood tests. X‐ray computed tomography (CT) was used to study the geometry of the wormholes after the tests. The core flood tests showed agreement with experiments reported in the literature regarding permeability evolution and wormhole breakthrough. By continuously monitoring the effluent concentration, the effluent chemistry monitoring system advanced the experimental study by showing how the dissolution kinetics evolved with the formation of wormholes. Three‐dimensional topological and morphological algorithms were developed to analyze the CT data and provide quantitative descriptions for the wormhole geometry. The CT analysis showed that higher flow rates resulted in more complex wormhole geometries regarding the number of wormholes and branches. Key Points: A new device was introduced in core flood tests to study the evolution of the overall dissolution rate in the rock‐fluid systemThree‐dimensional topological and morphological algorithms were developed to analyze and compare the complex wormhole geometries quantitativelyWormhole growth rate and breakthrough pore volume as functions of the injection flow rate were compared with the relations in the literature [ABSTRACT FROM AUTHOR]

Highlights • An effective method for simulating wormhole in fractured formation was proposed. • The effects of three typical fractures on wormhole propagation were studied. • The local control domain around the fracture was found. • A step-by-step calculation method was proposed in this paper. Abstract Wormholes can effectively connect the fracture system as the dominant channels when carbonate matrix is acidified, thereby increasing the distance of acidification. It is critical to clarify the wormhole propagation law in carbonate reservoirs so as to optimize the acidification design. Previous studies highlight the influences of matrix as well as single simple fracture on wormhole propagation. However, the works characterizing impacts of single and multiple fractures with different geometry are insufficient. In this paper, the two-scale continuum model and pseudo-fracture model were combined to study the wormhole with different fractures. It was found that the fractures parallel to injection direction can concentrate fluids and thus accelerate the acid penetrating the formation, while the perpendicular ones will disperse fluids, thereby slowing down the breakthrough. The effect of straight fractures and arc fractures on wormholes are similar. When the inclination angle is less than 60°, straight fracture and arc fracture can be regarded as parallel fracture of corresponding length. When the inclination angle is greater than 60°, they can be regarded as superposition of parallel fracture and perpendicular fracture. As for the circular and polygonal fractures, only the parts near the outlet impact the subsequent wormhole propagation trajectories. The analysis of flow field shows that there is a control domain of about 3· L ·cos(θ) around the fractures. When there is no intersection of control domains of multiple fractures, there is no interference between them. There is no need to consider all fractures in the formation. Based on this, the step-by-step calculation method proposed in this paper is suitable for acidizing large-scale formation with complex fracture network. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we apply local discontinuous Galerkin methods to the compressible wormhole propagation. Optimal error estimates for the pressure, velocity, porosity and concentration in different norms are established on non-uniform grids. Numerical experiments are presented to verify the theoretical analysis and show the good performance of the LDG scheme for compressible wormhole propagation. [ABSTRACT FROM AUTHOR]

A careful examination of the fundamentals of electromagnetic theory shows that due to the underlying mathematical assumptions required for Stokes' Theorem, global charge conservation cannot be guaranteed in topologically non-trivial spacetimes. However, in order to break the charge conservation mechanism we must also allow the electromagnetic excitation fields D , H to possess a gauge freedom, just as the electromagnetic scalar and vector potentials φ and A do. This has implications for the treatment of electromagnetism in spacetimes where black holes both form and then evaporate, as well as extending the possibilities for treating vacuum polarisation. Using this gauge freedom of D , H we also propose an alternative to the accepted notion that a charge passing through a wormhole necessarily leads to an additional (effective) charge on the wormhole's mouth. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract A classical origin for the Bohmian quantum potential, as that potential term arises in the quantum mechanical treatment of black holes and Einstein–Rosen (ER) bridges, can be based on 4th-order extensions of Einstein's equations. The required 4th-order extension of general relativity is given by adding quadratic curvature terms with coefficients that maintain a fixed ratio, as their magnitudes approach zero, with classical general relativity as a singular limit. If entangled particles are connected by a Planck-width ER bridge, as conjectured by Maldacena and Susskind, then a connection by a traversable Planck-scale wormhole, allowed in 4th-order gravity, describes such entanglement in the ontological interpretation. It is hypothesized that higher-derivative gravity can account for the nonlocal part of the quantum potential generally. Highlights • Quantum Einstein–Rosen (ER) bridges permit tunneling across space. • Deterministic quantum mechanics, a la Bohm, describes ER bridge tunneling. • Quantum bridge tunneling is mimicked in purely classical 4th-order gravity. • Infinitesimal modifications of classical general relativity give quantum tunneling. • Traversable wormholes can connect entangled particles and preserve causality. [ABSTRACT FROM AUTHOR]

Recently, the ultra-diffuse galaxy (UDG) Dragonfly 44 in the Coma Cluster was observed and observations of the rotational speed suggest that its mass is almost the same as the mass of the Milky Way. On the other hand, interestingly, the galaxy emits only 1% of the light emitted by the Milky Way. Thus, astronomers reported that Dragonfly 44 may be made almost entirely of dark matter. In this study we try to determine whether or not the dark matter that constitutes Dragonfly 44 can form a wormhole. Two possible dark matter profiles are used, namely, UDG King's model and generalized Navarro–Frenk–White (NFW) dark matter profile. We have shown that King's model dark matter profile does not manage to provide a wormhole whereas the generalized NFW dark matter profile manages to find wormholes. [ABSTRACT FROM AUTHOR]

Tsukamoto [N. Tsukamoto, Phys. Rev. D95, 064035 (2017)] developed a method, which is an improvement over that of Bozza [V. Bozza, Phys. Rev. D66, 103001 (2002)], for calculating light deflection angle in the strong gravity field of a spherically symmetric static spacetime. The method is directly applicable to the massless Ellis–Bronnikov wormhole (EBWH), while Bozza's method is not applicable. We wish to show that it is still possible to obtain the same deflection angle by applying Bozza's method but only in an indirect way, that is, first calculate the deflection by the parent massive EBWH and then take its massless limit. [ABSTRACT FROM AUTHOR]

Abstract Horizonless compact objects with light rings (or photon spheres) are becoming increasingly popular in recent years for several reasons. In this paper, we show that a horizonless object such as a wormhole of Morris–Thorne type can have two photon spheres. In particular, we show that, in addition to the one present outside a wormhole throat, the throat can itself act as an effective photon sphere. Such wormholes exhibit two sets of relativistic Einstein ring systems formed due to strong gravitational lensing. We consider a previously obtained wormhole solution as a specific example. If such type of wormhole casts a shadow at all, then the inner set of the relativistic Einstein rings will form the outer bright edge of the shadow. Such a novel lensing feature might serve as a distinguishing feature between wormholes and other celestial objects as far as gravitational lensing is concerned. [ABSTRACT FROM AUTHOR]

The combined action of self-gravitating magnetic and electric vortex fields and a self-gravitating scalar field is considered. The properties of wormholes formed as a result of such an interaction are investigated. It is shown that a change in the energy density of a massless scalar field can modify the topology of spacetime for the system of self-gravitating fields under consideration. [ABSTRACT FROM AUTHOR]

Traversable wormholes, tunnel-like structures introduced by Morris and Thorne [Am. J. Phys.56 (1988) 395], have a significant role in connection of two different spacetimes or two different parts of the same spacetime. The characteristics of these wormholes depend upon the redshift and shape functions which are defined in terms of radial coordinate. In literature, several shape functions are defined and wormholes are studied in f (R) gravity with respect to these shape functions [F. S. N. Lobo and M. A. Oliveira, Phys. Rev. D80 (2009) 104012; H. Saiedi and B. N. Esfahani, Mod. Phys. Lett. A26 (2011) 1211; S. Bahamonde, M. Jamil, P. Pavlovic and M. Sossich, Phys. Rev. D94 (2016) 044041]. In this paper, two shape functions (i) b (r) = r 0 log (r + 1) log (r 0 + 1) and (ii) b (r) = r 0 (r r 0 ) γ , 0 < γ < 1 , are considered. The first shape function is newly defined, however, the second one is collected from the literature [M. Cataldo, L. Liempi and P. Rodríguez, Eur. Phys. J. C77 (2017) 748]. The wormholes are investigated for each type of shape function in f (R) gravity with f (R) = R + α R m − β R − n , where m , n , α and β are real constants. Varying the parameter α or β , f (R) model is studied in five subcases for each type of shape function. In each case, the energy density, radial and tangential pressures, energy conditions that include null energy condition, weak energy condition, strong energy condition and dominated energy condition and anisotropic parameter are computed. The energy density is found to be positive and all energy conditions are obtained to be violated which support the existence of wormholes. Also, the equation-of-state parameter is obtained to possess values less than − 1 , that shows the presence of the phantom fluid and leads toward the expansion of the universe. [ABSTRACT FROM AUTHOR]

It is known that wormhole geometry could be found solving the Einstein field equations by tolerating the violation of null energy condition (NEC). Violation of NEC is not possible for the physical matter distributions, however, it can be achieved by considering distributions of "exotic matter". The main purpose of this work is to find generating functions comprising the wormhole-like geometry and discuss the nature of these generating functions. We have used the Herrera et al. [Phys. Rev. D77, 027502 (2008)] approaches of obtaining generating functions in the background of wormhole spacetime. Here we have adopted two approaches for solving the field equations to find wormhole geometry. In the first method, we have assumed the redshift function f(r) and the shape function b(r) and solve for the generating functions. In another attempt, we assume generating functions and redshift functions and then try to find shape functions of the wormholes. [ABSTRACT FROM AUTHOR]

Mazharimousavi and Halilsoy [S. H. Mazharimousavi and M. Halilsoy, Mod. Phys. Lett. A31, 1650192 (2016)] recently proposed wormhole solutions in f(R)-gravity that satisfy energy conditions but are unstable. We show here that stability could still be achieved for thin-shell wormholes obtained by gluing the wormholes in f(R)-gravity with the exterior Schwarzschild vacuum. Using the new geometrical constraints from thin-shell "mass" and from external "force" developed by Garcia, Lobo and Visser, we demarcate and analyze the stability regions. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates wormhole solutions of spherically symmetric spacetime via Noether symmetry approach in f (R , T) gravity. For this purpose, we choose f (R , T) models appreciating indirect curvature–matter coupling and examine symmetry generators with associated conserved quantities. We determine possible existence of realistic traversable wormhole solutions for both dust as well as non-dust distributions and also study stable behavior of these solutions. For both models, we use constant as well as variable forms of red-shift function. To analyze physical existence of wormhole solutions, we study the behavior of null/weak energy conditions with respect to ordinary as well as effective energy–momentum tensors. It is concluded that there exist physically viable traversable as well as stable wormhole solutions in most of the cases. [ABSTRACT FROM AUTHOR]

Abstract The study of shadow is quite prominent nowadays because of the ongoing Event Horizon Telescope 1 observations. We construct the shadow images of charged wormholes in Einstein–Maxwell–dilaton (EMD) theory. The spacetime metric of the charged wormholes contains three charges: magnetic charge P , electric charge Q , and dilaton charge Σ. We evaluate the photon geodesics around the charged wormholes. We also calculate the effective potential and discuss its behavior with angular momentum L and different values of charges P , Q , and Σ. A study of the shadow of charged wormholes reveals that the shadow has an effect of the charges P and Q. The radius of the shadow increases with the magnetic charge P as well as the electric charge Q. We also find that the dilaton charge does not affect the shadow of the charged wormholes. [ABSTRACT FROM AUTHOR]

Recently, some authors have proposed a new model for the BIon which can be applied in both nanosystems and cosmology. A Bion is a configuration which has been constructed from two branes and a wormhole which connects them. In this paper, we consider the process of formation of a BIon by joining hexagonal accretion disks. These disks exchange gravitational waves with each other and produce some curvature. By increasing the number of connected disks and joining these waves, a wormhole emerges. [ABSTRACT FROM AUTHOR]

Taking into account various energy density models in the framework of torsion-based modified theory, some wormhole solutions are derived and studied. We use a non-minimal coupling between matter and torsion in order to construct the wormhole geometry for constant, exponential and Lorentzian energy density models. Two sets of torsion dependent models, including (i) teleparalell case with linear forms of torsion scalar and (ii) a ℱ (T) gravity with quadratic form of torsion scalar, have been considered throughout this paper. Our study shows that additional terms to the Einstein field equations, due to consider modified gravity, give us the opportunity of obtaining wormhole solutions which may be supported by baryonic sources. We also check the equilibrium phase of the wormhole solutions using anisotropic and hydrostatic forces. The details of the obtained results depend on the numerical values of the free parameters that the function ℱ (T) holds. [ABSTRACT FROM AUTHOR]

This paper explores static spherically symmetric wormhole solutions in the galatic halo region for f (𝒢 , T) gravity (𝒢 and T represent the Gauss–Bonnet invariant and trace of the energy–momentum tensor, respectively). We formulate the explicit expressions for matter variables and evaluate wormhole solutions either specifying f (𝒢 , T) model to construct shape function or taking specific form of the shape function to determine f (𝒢 , T) model. It is found that null energy condition for the effective energy–momentum tensor is violated throughout the evolution in both cases while physically acceptable wormhole solutions exist only for a considered f (𝒢 , T) model. [ABSTRACT FROM AUTHOR]

Wormholes are tunnels connecting different regions in spacetime. They were obtained originally as a solution for Einstein's General Relativity theory 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 wormholes within an alternative gravity theory that proposes an extra material (rather than geometrical) term in its gravitational action. Our solutions are obtained from well-known particular cases of the wormhole metric potentials, named redshift and shape functions, and yield the wormholes to be filled by a phantom fluid, that is, a fluid with equation of state parameter ω < − 1. 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. [ABSTRACT FROM AUTHOR]

Abstract Optimal injection conditions are important for carbonate acidizing design. Both experimental and theoretical work have been carried out for studying optimal injection rates, but rarely the optimal wormhole propagation velocities. In this study, we developed a mathematical model that can describe wormhole propagation at optimal conditions. This model incorporates rock pore size distribution and acid-rock reaction characteristics, which essentially includes every factor that affects optimal conditions. Before developing our model, we studied the static pressure and flow field when a wormhole propagates to a certain length in a core plug through numerical simulations. Also, we carried out lab acidizing coreflood experiments to explore wormhole propagation behavior. The results show that when a wormhole reaches a certain length, the wormhole propagation velocity keeps the same. This is because a stable fluid loss profile is established after this length. Based on this finding, we focus on the wormhole tip. By incorporating an optimal tip flux model to a mechanistic model of wormhole growth, our new propagation model presents more fundamental mechanisms. Our model shows that the wormhole propagation velocity depends on the rock pore size distribution and the overall reaction rate coefficient at optimal conditions. Particularly, if the reaction is fully diffusion-limited, it depends on the rock pore size distribution and the diffusion coefficient. These are verified by acidizing coreflood experiments at different acid concentrations and temperatures. The findings of this study illustrate the importance of the overall reaction rate and diffusion rate. This model can be incorporated into an acidizing simulator for engineering design. Highlights • Both experimental and numerical studies show that wormhole propagates at a constant rate after it reaches a certain length for acidizing in a linear core. • A new wormhole propagation model at optimal conditions is developed. It is a function of acid overall reaction rate coefficient and rock pore properties. • This model is verified by acidizing coreflood experimental data from perspectives of acid concentration and temperature. It is robust and can be easily incorporated into an acidizing simulator. [ABSTRACT FROM AUTHOR]

Abstract Understanding acid reactive flow and the formation of wormholes in carbonate rocks is important for designing successful acidizing operations. Linear coreflooding experiments have been widely carried out to gain insights about the dissolution process for varying rock types and acid systems. However, carbonate reservoir stimulation is dictated by radial flow configuration. As such, it is critical to bridge the gap between linear acid injection and radial acid injection. In this work, a series of radial acid injection and linear acid flow experiments are conducted at various injection rates while maintaining the same operating conditions. The objective is to develop a better understanding of the acidizing process under radial flow conditions at larger scale while applying high confining stresses as only a limited number of radial flow experimental studies have been reported in the literature. This is expected to provide guidance for the optimization and control of the matrix acidizing process for the field operations. The radial acidizing tests are performed on rectangular block samples with dimensions of 20 × 16 × 16 in. We use a quantitative acidizing model to select few representative acid injection rates due to the complexity of the experiments and limited availability of large block samples. This model shows good predictive capability when compared to the experimental results. Pore volume to breakthrough (PVBT) and optimum injection rate are determined for both radial and linear acidizing experiments. Lower PVBT values are obtained for the radial acidizing case. This is mostly associated with the larger rock pore volume exposed to acid for the radial block in comparison to the linear cylindrical core. High-resolution CT scan images of the acidized radial carbonate blocks and cylindrical cores are generated and analyzed. The CT scan images show different wormhole morphology when varying the acid injection rates. Similar branching features are obtained for the optimal wormholes in linear and radial tests. Injecting the acid at the optimal rate leads to fewer transverse branches but thicker when compared to the experiment at higher injection rate that requires more acid volume to breakthrough. The low injection rate results in the largest diameter wormholes with high tortuosity. The high-resolution nondestructive imaging and analysis has enabled to gain insight on the interaction between the acid and the rock sample under radial flow conditions. This analysis has revealed that the wormhole propagation direction is not only governed by the effective stress differential but also can be aligned with the fabric layers due to the sedimentation conditions of the rock. Highlights • Design and implementation of large-scale radial acidizing experiments. • Comparison analysis of linear and radial acid injection for well stimulation applications. • Control and optimization of matrix acidizing. • Visualization and characterization of wormhole morphology using high-resolution 3D CT scans of large carbonate blocks. [ABSTRACT FROM AUTHOR]

We investigate the effect of a black hole as a nucleation site of a false vacuum bubble based on the Euclidean actions of relevant configurations. As a result we find a wormhole-like configuration may be spontaneously nucleated once the black hole mass falls below a critical value of order of the Hubble parameter corresponding to the false vacuum energy density. As the space beyond the wormhole throat can expand exponentially, this may be interpreted as creation of another inflationary universe in the final stage of the black hole evaporation. [ABSTRACT FROM AUTHOR]

The deformation retract is, by definition, a homotopy between a retraction and the identity map. We show that applying this topological concept to Ricci-flat wormholes/black holes implies that such objects can get deformed and reduced to lower dimensions. The homotopy theory can provide a rigorous proof to the existence of black holes/wormholes deformations and explain the topological origin. The current work discusses such possible deformations and dimensional reductions from a global topological point of view, it also represents a new application of the homotopy theory and deformation retract in astrophysics and quantum gravity. [ABSTRACT FROM AUTHOR]

Abstract At the intersection of the newly emerging fields of optoacoustic imaging and theranostic nanomedicine, promising clinical progress can be made in dismal prognosis of ovarian cancer. An acidic pH targeted wormhole mesoporous silica nanoparticle (V7-RUBY) was developed to serve as a novel tumor specific theranostic nanoparticle detectable using multispectral optoacoustic tomographic (MSOT) imaging. We report the synthesis of a small, < 40 nm, biocompatible asymmetric wormhole pore mesoporous silica core particle that has both large loading capacity and favorable release kinetics combined with tumor-specific targeting and gatekeeping. V7-RUBY exploits the acidic tumor microenvironment for tumor-specific targeting and tumor-specific release. In vitro, treatment with V7-RUBY containing either paclitaxel or carboplatin resulted in increased cell death at pH 6.6 in comparison to drug alone (p < 0.0001). In orthotopic ovarian xenograft mouse models, V7-RUBY containing IR780 was specifically detected within the tumor 7X and 4X higher than the liver and >10X higher than in the kidney using both multispectral optoacoustic tomography (MSOT) imaging with secondary confirmation using near infrared fluorescence imaging (p < 0.0004). The V7-RUBY system carrying a cargo of either contrast agent or an anti-neoplastic drug has the potential to become a theranostic nanoparticle which can improve both diagnosis and treatment of ovarian cancer. [ABSTRACT FROM AUTHOR]