We construct static, spherically symmetric wormhole solutions with a nontrivial redshift function, inspired by noncommutative geometry, in which point sources are replaced by Gaussian smearing of minimal length, yielding a regular shape function. Within this framework, we derive model-independent relations that isolate the role of the redshift function in controlling the stress-energy components and the violation of the null energy condition (NEC). Negative or suitably tuned redshifts confine the exotic matter to a thin neighborhood of the throat. We then reformulate this redshift engineering in matter terms through a quasi-de Sitter equation of state (EOS) with localized Gaussian or Lorentzian perturbations, obtaining minimally exotic wormholes that are regular, horizon-free, and asymptotically flat. Finally, we extend the analysis to a Chaplygin-like EOS, introducing a nonlinear coupling between pressure and density that yields redshift wells with possible local blueshift regions and tunable anisotropies governed by a certain nonlinearity parameter. Together, these results provide a unified and physically transparent framework for constructing traversable noncommutative-geometry-inspired wormholes with controlled, spatially localized exotic matter content.
Some new class of Chaplygin wormholes are investigated in the framework of a Chaplygin gas with equation of state $ p = - \frac{A}ρ$, $A>0$. Since empty spacetime ($ p = ρ= 0 $) does not follow Chaplygin gas, so the interior Chaplygin wormhole solutions will never asymptotically flat. For this reason, we have to match our interior wormhole solution with an exterior vacuum solution i.e. Schwarzschild solution at some junction interface, say $ r = a $. We also discuss the total amount of matter characterized by Chaplygin gas that supplies fuel to construct a wormhole.
In this article, spherically symmetric thin-shell wormholes supported by a generalized Chaplygin gas are constructed and their stability under perturbations preserving the symmetry is studied. Wormholes with charge and with a cosmological constant are analyzed and the results are compared with those obtained for the original Chaplygin gas, which was considered in a previous work. For some values of the parameters, one stable configuration is also present and a new extra unstable solution is found.
When Morris and Thorne first proposed that traversable wormholes may be actual physical objects, they concentrated on the geometry by specifying the shape and redshift functions. This mathematical approach necessarily raises questins regarding the determination of the required stress-energy tensor. This paper discusses a natural way to obtain a complete wormhole solution by assuming that the wormhole (1) is supported by generalized Chaplygin gas and (2) admits conformal Killing vectors.
The modified Chaplygin gas (MCG) is a strong candidate for the unified model of dark matter and dark energy. The equation of state of this modified model is valid from the radiation era to the $Λ$CDM model. In early epoch (when $ρ$ was large), dark matter had the dominant role while at later stages (when $ρ$ is small), the MCG model behaves as dark energy. In this work, we have found exact solution of static spherically symmetric Einstein equations describing a wormhole for an inhomogeneous distribution of modified Chaplygin gas. For existence of wormhole solution, there are some restrictions …
This paper discusses a new variable equation of state parameter leading to exact solutions of the Einstein field equations describing traversable wormholes. In addition to generalizing the notion of phantom energy, the equation of state generates a mathematical model that combines the generalized phantom energy and the generalized Chaplygin gas models.
The purpose of this paper is to construct spherical thin-shell wormhole solutions through cut and paste technique and investigate the stability of these solutions in the vicinity of modified Chaplygin gas. The Darmois-Israel formalism is used to formulate the stresses of the surface concentrating the exotic matter. We explore the stability of the wormhole solutions by using the standard potential method. We conclude that there exist more stable as well as unstable solutions than the previous study with generalized Chaplygin gas \cite{15}.
We have examined the possible construction of a stationary, spherically symmetric and spatially inhomogeneous wormhole spacetime supported by the phantom energy. The later is supposed to be represented by the modified Chaplygin gas equation of state. The solutions so obtained satisfy the flare out and the asymptotic flatness conditions. It is also shown that the averaged null energy condition has to be violated for the existence of the wormhole.
In this article, we construct spherical thin-shell wormholes with charge in dilaton gravity. The exotic matter required for the construction is provided by a generalized Chaplygin gas. We study the stability under perturbations preserving the symmetry. We find that the increase of the coupling between the dilaton and the electromagnetic fields reduces the range of the parameters for which stable configurations are possible.
The present paper deals with some wormhole solutions which are obtained by taking two different shape functions along with zero tidal force. For obtaining wormhole solutions, anisotropic fluid and a equation of state $p_t=-\frac{a}ρ$ related by Chaplygin gas are considered where $ρ$ is the energy density, $p_t$ is tangential pressure and $a$ is positive constant. Energy conditions are examined for two different models, and it is found that a major energy conditions are satisfied in a region.
We study the stability of thin-shell wormholes in Einstein-Maxwell-Gauss-Bonnet gravity. The equation of state of the thin shell wormhole is considered first to obey a generalized Chaplygin gas and then we generalize it to an arbitrary state function which covers all known cases studied so far. In particular we study the modified Chaplygin gas and give an assessment for a general parotropic fluid. Our study is in d-dimensions and with numerical analysis in d=5 we show the effect of the GB parameter in the stability of thin-shell wormholes against the radial perturbations.
In this paper we construct spherical thin-shell wormholes supported by a Chaplygin gas. For a rather general class of geometries we introduce a new approach for the stability analysis of static solutions under perturbations preserving the symmetry. We apply this to wormholes constructed from Schwarzschild, Schwarzschild-de Sitter, Schwarzschild-anti de Sitter and Reissner-Nordstrom metrics. In the last two cases, we find that there are values of the parameters for which stable static solutions exist.
The purpose of this paper is to examine the possible existence or construction of traversable wormholes supported by generalized Chaplygin gas (GCG) by starting with a general line element and the Einstein tensor, together with the equation of state, thereby continuing an earlier study by the author of wormholes supported by phantom energy. Numerical techniques are used to demonstrate the existence of wormhole spacetimes that (1) meet the flare-out conditions at the throat, (2) are traversable by humanoid travelers, thanks to low tidal forces and short proper distances near the throat, and (3)…
We construct spherically symmetric thin-shell wormholes supported by a generalized Chaplygin gas in Born-Infeld electrodynamics coupled to Einstein gravity, and we analyze their stability under radial perturbations. For different values of the Born-Infeld parameter and the charge, we compare the results with those obtained in a previous work for Maxwell electrodynamics. The stability region in the parameter space reduces and then disappears as the value of the Born-Infeld parameter is modified in the sense of a larger departure from Maxwell theory.
Chaplygin anisotropic matter governing the cosmological evolution in two identical universes with an intermediate static spherically symmetric region is considered. The static region contains a wormhole allowing one to pass etween two horizons. The metric in the non-static region represents a kind of an anisotropic Kantowski-Sachs cosmological model starting from a horizon instead the initial singularity. A classification of the cosmologies with a monotonic late stage is presented. It is shown that only one scenario can involve a de Sitter regime. The scales in the de Sitter phase allows one t…
In this paper, we construct thin-shell wormholes from regular Ayon-Beato and Garcia black hole by employing cut and paste formalism and examine their stability. We analyze attractive and repulsive characteristics of wormholes corresponding to outward and inward-directed acceleration components, respectively. A general equation of state is assumed as a linear perturbation to explore stability of these constructed wormholes with and without cosmological constant. We consider linear, logarithmic and Chaplygin gas models for exotic matter and evaluate stability regions for different values of char…
We construct thin shell wormholes in the magnetic Melvin universe. It is shown that in order to make a TSW in the Melvin spacetime the radius of the throat can not be larger than $\frac{2}{B_{0}}$ in which $B_{0}$ is the magnetic field constant. We also analyze the stability of the constructed wormhole in terms of a linear perturbation around the equilibrium point. In our stability analysis we scan a full set of the Equation of States such as Linear Gas, Chaplygin Gas, Generalized Chaplygin Gas, Modified Generalized Chaplygin Gas and Logarithmic Gas. Finally we extend our study to the wormhole…
We present some exact solutions of the Einstein equations with an anisotropic fluid exploiting the Chaplygin equation of state. The solutions describe spacetimes with two identical T regions and an intermediate static spherically symmetric R region containing a wormhole. The metric in the T region represents an anisotropic Kantowski-Sachs cosmological model. Its evolution starts from an event horizon and develops according to different scenarios including eternal expansion, contraction and also a finite universe lifetime.
The generalized Chaplygin gas (GCG) is a candidate for the unification of dark energy and dark matter, and is parametrized by an exotic equation of state given by $p_{ch}=-A/ρ_{ch}^α$, where $A$ is a positive constant and $0<α\leq 1$. In this paper, exact solutions of spherically symmetric traversable wormholes supported by the GCG are found, possibly arising from a density fluctuation in the GCG cosmological background. To be a solution of a wormhole, the GCG equation of state imposes the following generic restriction $A<(8πr_0^2)^{-(1+α)}$, where $r_0$ is the wormhole throat radius, conseque…
It has been shown that a noncommutative-geometry background may be able to support traversable wormholes. This paper discusses the possible detection of such wormholes in the outer regions of galactic halos by means of gravitational lensing. The procedure allows a comparison to other models such as the Navarro-Frenk-White model and f(R) modified gravity and is likely to favor a model based on noncommutative geometry.
Noncommutative geometry, an offshoot of string theory, replaces point-like objects by smeared objects. The resulting uncertainty may cause a black hole to be observationally indistinguishable from a traversable wormhole, while the latter, in turn, may become observationally indistinguishable from a gravastar. The same noncommutative-geometry background allows the theoretical construction of thin-shell wormholes from gravastars and may even serve as a model for dark energy.
This paper addresses the following issues: (1) the possible existence of macroscopic traversable wormholes, given a noncommutative-geometry background, and (2) the possibility of allowing zero tidal forces, given a known density. It is shown that whenever the energy density describes a classical wormhole, the resulting solution is incompatible with quantum field theory. If the energy density originates from noncommutative geometry, then zero tidal forces are allowed. Also attributable to the noncommutative geometry is the violation of the null energy condition. The wormhole geometry satisfies …
This paper discusses noncommutative-geometry wormholes in the context of a cosmological model due to Sung-Won Kim. An ansatz suggested by the Friedmann-Lemaitre-Robertson-Walker (FLRW) model leads to the assumption that the matter content can be divided into two parts, a cosmological part depending only on time and a wormhole part depending only on space. These assumptions are sufficient for deriving a complete zero-tidal force wormhole solution. The wormhole is evolving due to the scale factor in the FLRW model; it is restricted, however, to the curvature parameters $k=0$ and $k=-1$. Unlike p…
Noncommutative geometry, an offshoot of string theory, replaces point-like structures with smeared objects and has recently been extended to higher dimensions. The purpose of this letter is to obtain wormhole solutions with this extended noncommutative geometry as a background. It is found through this investigation that wormhole solutions exist in the usual four, as well as in five dimensions, but they do not exist in higher-dimensional spacetimes.
Formation of specific static wormhole models is discussed, by assuming an $f(\textit{R}, \textit{T}) = R + 2 λT$ extended theory of gravity, $T =- ρ+ P_{r} + 2P_{l}$ being the trace of the energy momentum tensor. In the first part, wormhole solutions are constructed imposing that the radial pressure admits an equation of state corresponding to a varying Chaplygin gas. Two forms for the varying Chaplygin gas are considered, namely $P_{r} = - B b(r)^{u}/ρ^α$ and $P_{r} = -B R(r)^{m}/ ρ^{α}$, respectively. In the second part, the wormhole models are constructed assuming that the radial pressure c…
We construct cylindrical, traversable wormholes with finite radii by taking into account the cut-and-paste procedure for the case of cosmic string manifolds with a positive cosmological constant. Under reasonable assumptions about the equation of state of the matter located at the shell, we find that the wormhole throat undergoes a monotonous evolution provided it moves at a constant velocity. In order to explore the dynamical nonlinear behaviour of the wormhole throat, we consider that the matter at the shell is supported by anisotropic Chaplygin gas, anti-Chaplygin gas, or a mixed of Chaplyg…
Noncommutative geometry, as conceptualized by Nicolini, Smailagic, and Spallucci, may be viewed as a slight modification of Einstein's theory. The same can be said for $f(R)$ modified gravity for an appropriate choice of the function $f(R)$. Since such an $f(R)$ could be determined from the noncommutative-geometry background, these gravitational theories make very similar predictions in the discussion of (a) dark matter and (b) traversable wormholes; they can therefore be taken as equally viable models.
The aim of this paper is to study static spherically symmetric noncommutative $F(T,T_G)$ wormhole solutions along with Lorentzian distribution. Here, $T$ and $T_G$ are torsion scalar and teleparallel equivalent Gauss-Bonnet term, respectively. We take a particular redshift function and two $F(T,T_G)$ models. We analyze the behavior of shape function and also examine null as well as weak energy conditions graphically. It is concluded that there exist realistic wormhole solutions for both models. We also study the stability of these wormhole solutions through equilibrium condition and found them…
A fundamental property of Morris-Thorne wormholes is the so-called flare-out condition that automatically results in a violation of the null energy condition (NEC) in classical general relativity. By contrast, in $f(R)$ modified gravity, the material threading the wormhole may actually satisfy the NEC, while, at the same time, the effective stress-energy tensor arising from the modified theory violates the NEC, thereby sustaining the wormhole. It is shown in this paper that noncommutative geometry, an offshoot of string theory, can be viewed as a special case of $f(R)$ gravity and can therefor…
In this paper, we study static spherically symmetric wormhole solutions in extended teleparallel gravity with the inclusion of noncommutative geometry under Lorentzian distribution. We obtain expressions of matter components for non-diagonal tetrad. The effective energy-momentum tensor leads to the violation of energy conditions which impose condition on the normal matter to satisfy these conditions. We explore the noncommutative wormhole solutions by assuming a viable power-law $f(T)$ and shape function models. For the first model, we discuss two cases in which one leads to teleparallel gravi…
When Morris and Thorne first proposed the possible existence of traversable wormholes, they adopted the following strategy: maintain complete control over the geometry, thereby leaving open the determination of the stress-energy tensor. In this paper we determine this tensor by starting with a noncommutative-geometry background and assuming that the static and spherically symmetric spacetime admits conformal motions. This had been established in a previous collaboration with Rahaman et al. using a slightly different approach. Accordingly, the main purpose of this paper is to show that the worm…
This paper discusses the possible existence of traversable wormholes in f(R) modified gravity while assuming a noncommutative-geometry background, as well as zero tidal forces. The first part of the paper aims for an overview via several shape functions by determining the corresponding wormhole solutions and their properties. The solutions are made complete by deriving the modified-gravity functions F(r) and f(R), where F=df/dR. It is subsequently shown that the violation of the null energy condition can be attributed to the combined effects of f(R) gravity and noncommutative geometry. The sec…
In this paper, we construct thin-shell wormholes in (2+1)-dimensions from noncommutative BTZ black hole by applying the cut-and-paste procedure implemented by Visser. We calculate the surface stresses localized at the wormhole throat by using the Darmois-Israel formalism, and we find that the wormholes are supported by matter violating the energy conditions. In order to explore the dynamical analysis of the wormhole throat, we consider that the matter at the shell is supported by dark energy equation of state P = wρwith w < 0. The stability analysis is carried out of these wormholes to lineari…
We explore the possibility that traversable wormholes be supported by specific equations of state responsible for the present accelerated expansion of the Universe, namely, phantom energy, the generalized Chaplygin gas, and the van der Waals quintessence equation of state.
In this paper, we construct thin-shell wormholes from charged black string through cut and paste procedure and investigate its stability. We assume modified generalized Chaplygin gas as a dark energy fluid (exotic matter) present in the thin layer of matter-shell. The stability of these constructed thin-shell wormholes is investigated in the scenario of linear perturbations. We conclude that static stable as well as unstable configurations are possible for cylindrical thin-shell wormholes.
We study static solutions of the Tolman--Oppenheimer--Volkoff equations for spherically symmetric objects (stars) living in a space filled with the Chaplygin gas. Two cases are considered. In the normal case all solutions (excluding the de Sitter one) realize a three-dimensional spheroidal geometry because the radial coordinate achieves a maximal value (the "equator"). After crossing the equator, three scenarios are possible: a closed spheroid having a Schwarzschild-type singularity with infinite blue-shift at the "south pole", a regular spheroid, and a truncated spheroid having a scalar curva…
We construct spherically symmetric thin-shell wormholes with a generalized Chaplygin gas at the throat, in Born-Infeld electrodynamics coupled to Einstein gravity. We analyze their stability under radial perturbations.
This study explores the Gaussian and the Lorentzian distributed spherically symmetric wormhole solutions in the $f(τ, T)$ gravity. The basic idea of the Gaussian and Lorentzian noncommutative geometries emerges as the physically acceptable and substantial notion in quantum physics. This idea of the noncommutative geometries with both the Gaussian and Lorentzian distributions becomes more striking when wormhole geometries in the modified theories of gravity are discussed. Here we consider a linear model within $f(τ,T)$ gravity to investigate traversable wormholes. In particular, we discuss the …
In this paper, we derive some new exact solutions of static wormholes in $f(R)$ gravity supported by the matter possesses Lorentizian density distribution of a particle-like gravitational source. We derive the wormhole's solutions in two possible schemes for a given Lorentzian distribution: assuming an astrophysically viable $F(R)$ function such as a power-law form and discuss several solutions corresponding to different values of the exponent (here $F =\frac{df}{dR}$). In the second scheme, we consider particular form of two shape functions and have reconstructed f(R) in both cases. We have d…
In the present work we search for a new wormhole solution inspired by noncommutative geometry with the additional condition of allowing conformal Killing vectors (CKV). A special aspect of noncommutative geometry is that it replaces point-like structures of gravitational sources with smeared objects under Gaussian distribution. However, the purpose of this paper is to obtain wormhole solutions with noncommutative geometry as a background where we consider a point-like structure of gravitational object without smearing effect. It is found through this investigation that wormhole solutions exist…
In this manuscript, we explore the existence of wormhole solutions exhibiting spherical symmetry in a modified gravity namely $f(R,T)$ theory by involving some aspects of non-commutative geometry. For this purpose, we consider the anisotropic matter contents along with the well-known Gaussian and Lorentizian distributions of string theory. For the sake of simplicity in analytic discussions, we take a specific form of $f(R,T)$ function given by $f(R,T)=R+λT$. For both these non-commutative distributions, we get exact solutions in terms of exponential and hypergeometric functions. By taking some…
Instituto Federal de Educação, Ciência e Tecnologia do Ceará (IFCE)（塞阿拉联邦教育、科学与技术学院）；Universidade Federal do Cariri (UFCA)（卡拉伊里联邦大学）；Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências da Universidade de Lisboa（里斯本大学理学院空间科学与天体物理研究所）；Departamento de Física, Faculdade de Ciências da Universidade de Lisboa（里斯本大学理学院物理学系）
The purpose of this paper is to show that wormholes in noncommutative geometry can be macroscopic, based in part on an earlier study. The necessary violation of the weak energy condition is attributable to the noncommutative-geometry background rather than to the use of "exotic matter." The zero tidal forces make the wormhole suitable for humanoid travelers. Also discussed is the stability to linearized radial perturbations.
We compare the effects of Noncommutative Geometry and Gravity's Rainbow on traversable wormholes which are sustained by their own gravitational quantum fluctuations. Fixing the geometry on a well tested model, we find that the final result shows that the wormhole is of the Planckian size. This means that the traversability of the wormhole is in principle, but not in practice.
In this work, we have studied accretion of the dark energies onto Morris-Thorne wormhole. For quintessence like dark energy, the mass of the wormhole decreases and phantom like dark energy, the mass of wormhole increases. We have assumed two types of dark energy like variable modified Chaplygin gas (VMCG) and generalized cosmic Chaplygin gas (GCCG). We have found the expression of wormhole mass in both cases. We have found the mass of the wormhole at late universe and this is finite. For our choices the parameters and the function $B(a)$, these models generate only quintessence dark energy (no…
It is generally agreed that the acceleration of the Universe can best be explained by the presence of dark or phantom energy. The equation of state of the latter shows that the null energy condition is violated. Such a violation is the primary ingredient for sustaining traversable wormholes. This paper discusses wormholes supported by a more general form called polytropic phantom energy. The equation of state results in significant generalizations of the phantom-energy and, in some cases, the generalized Chaplygin-gas wormhole models, both of which continue to receive considerable attention fr…
This paper discusses the stability to linearized radial perturbations of spherically symmetric thin-shell wormholes with a "phantom-like" equation of state for the exotic matter at the throat: $P=ωσ$, $ω<0$, where $σ$ is the energy-density of the shell and $P$ the surface pressure. This equation is analogous to the generalized Chaplygin-gas equation of state used by E.F. Eiroa. The analysis, which differes from Eiroa's in its basic approach, is carried out for wormholes constructed from the following spacetimes: Schwarzschild, de Sitter and anti de Sitter, Reissner-Nordstrom, and regular charg…
The strategy adopted in the original Morris-Thorne wormhole was to retain complete control over the geometry at the expense of certain engineering considerations. The purpose of this paper is to obtain several complete wormhole solutions by assuming a noncommutative-geometry background with a concomitant isotropic-pressure condition. This condition allows us to consider a cosmological setting with a perfect-fluid equation of state. An extended form of the equation generalizes the first solution and subsequently leads to the generalized Chaplygin-gas model and hence to a third solution. The sol…
It is a very well known fact that the energy conditions concerning Lorentzian wormhole (WH) solutions of Einstein equations are violated. Consequently, attempts to avoid the violation of the energy conditions constitutes one of the main areas of research in WH physics. On the other hand, the current literature show us that noncommutativity is one of the candidates to understand the physics of the early Universe. In this letter we show that the null and weak energy conditions violations do not happen when the WH background geometry is a noncommutative one. We also construct the shape function a…
In this paper, we construct generic, spherically symmetric thin-shell wormholes and check their stabilities using the unified dark sector, including dark energy and dark matter. We give a master equation, from which one can recover, as a special case, other stability solutions for generic spherically symmetric thin-shell wormholes. In this context, we consider a particular solution; namely we construct an effective thin-shell wormhole under Lorentz symmetry breaking. We explore stability analyses using different models of the modified Chaplygin gas with constraints from cosmological observatio…
We discuss how the assumption of variable equation of state (EoS) allows the elimination of the instability at equilibrium throat radius $a_0=3M$ featured by previous Schwarzschild thin-shell wormhole models. Unobstructed stability regions are found for three choices of variable EoS. Two of these EoS entail linear stability at every equilibrium radius. Particularly, the thin-shell remains stable as $a_0$ approaches the Schwarzschild radius $2M$. A perturbative analysis of the wormhole equation of motion is carried out in the case of variable Chaplygin EoS. The squared proper angular frequency …
