Stability and instability of Ellis and phantom wormholes: Are there ghosts?

Nandi, K. K.; Potapov, Alexander A.; Izmailov, R. N.; Tamang, Amarjit; Evans, James

doi:10.1103/physrevd.93.104044

Cited by 37 publications

(26 citation statements)

References 64 publications

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“…Interestingly, the gravity fields of massless (M = 0) BNS and EBWH do not at all accrete matter since r ms is imaginary or infinitely large respectively, as is shown in Table 1, but both deflect light [see Eqs. (67) and (70)] since the Keplerian mass sensed by the photons is non-zero (m = 0, γ = 0). These cases are important since massless EBWH has actually been modeled as galactic halo objects in the Milky Way [79,80].…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, under a restricted class of scalar field perturbations that vanish at the throat, EBWH has been shown to be stable [66]. Another recent new idea is that, due to curved spacetime, observation of instability or otherwise of EBWH could be perception-dependent depending on the location of the observer -while one observer perceives instability, another observer might perceive stability and conversely (see, for details, [67]). In any case, we do not contend the conclusion of instability but, instead of summarily ruling out EBWH, we advocate that verifiable diagnostics such as the accretion profiles (dealt with here), emission of gravitational waves, strong field lensing etc should be treated as observable verifications of EBWH, if there exists any in the universe [42,46].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Can accretion properties distinguish between a naked singularity, wormhole and black hole?

Karimov¹,

Izmailov²,

Potapov

et al. 2020

Eur. Phys. J. C

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We first advance a mathematical novelty that the three geometrically and topologically distinct objects mentioned in the title can be exactly obtained from the Jordan frame vacuum Brans I solution by a combination of coordinate transformations, trigonometric identities and complex Wick rotation. Next, we study their respective accretion properties using the Page–Thorne model which studies accretion properties exclusively for $$r\ge r_{\text {ms}}$$ r ≥ r ms (the minimally stable radius of particle orbits), while the radii of singularity/throat/horizon $$r<r_{\text {ms}}$$ r < r ms . Also, its Page–Thorne efficiency $$\epsilon $$ ϵ is found to increase with decreasing $$r_{\text {ms}}$$ r ms and also yields $$\epsilon =0.0572$$ ϵ = 0.0572 for Schwarzschild black hole (SBH). But in the singular limit $$r\rightarrow r_{s}$$ r → r s (radius of singularity), we have $$\epsilon \rightarrow 1$$ ϵ → 1 giving rise to $$100 \%$$ 100 % efficiency in agreement with the efficiency of the naked singularity constructed in [10]. We show that the differential accretion luminosity $$\frac{d{\mathcal {L}}_{\infty }}{d\ln {r}}$$ d L ∞ d ln r of Buchdahl naked singularity (BNS) is always substantially larger than that of SBH, while Eddington luminosity at infinity $$L_{\text {Edd}}^{\infty }$$ L Edd ∞ for BNS could be arbitrarily large at $$r\rightarrow r_{s}$$ r → r s due to the scalar field $$\phi $$ ϕ that is defined in $$(r_{s}, \infty )$$ ( r s , ∞ ) . It is concluded that BNS accretion profiles can still be higher than those of regular objects in the universe.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Can accretion properties distinguish between a naked singularity, wormhole and black hole?

Karimov¹,

Izmailov²,

Potapov

et al. 2020

Eur. Phys. J. C

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show abstract

“…However, some time ago, the question of (in)stability was analyzed from a completely different standpoint based not on challenging the mechanism of instability but on exploiting the fact that, in general relativity, observations are dependent on the location of the observer. It was then shown that while some observers observe instability of EBWH, there is a nonzero probability that some other observers could observe its stability from different locations [17]. Therefore, the present accretion scenario is relevant only to the latter types of observers.…”

Section: Introductionmentioning

confidence: 89%

Accretion Flow onto Ellis–Bronnikov Wormhole

et al. 2021

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Study of accretion onto wormholes is rather rare compared to that onto black holes. In this paper, we consider accretion flow of cosmological dark energy modeled by barotropic fluid onto the celebrated Ellis–Bronnikov wormhole (EBWH) built by Einstein minimally coupled scalar field ϕ, violating the null energy condition. The accreting fluid is assumed to be phantom, quintessence, dust and stiff matter. We begin by first pointing out a mathematical novelty showing how the EBWH can lead to the Schwarzschild black hole under a complex Wick rotation. Then, we analyze the profiles of fluid radial velocity, density and the rate of mass variation of the EBWH due to accretion and compare the profiles with those of the Schwarzschild black hole. We also analyze accretion to the massless EBWH that has zero ADM mass but has what we call nonzero Wheelerian mass (“mass without mass”), composed of the non-trivial scalar field, that shows gravitational effects. Our conclusion is that the mass of SBH due to phantom accretion decreases consistently with known results, while, in contrast, the mass of EBWH increases. Exactly an opposite behavior emerges for non-phantom accretion to these two objects. Accretion to massless EBWH (i.e., to nonzero Wheelerian mass) shares the same patterns as those of the massive EBWH; hence there is no way to distinguish massive and massless cases by means of accretion flow. The contrasting mass variations due to phantom accretion could be a reflection of the distinct topology of the central objects.

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“…It can also have applications in the studies of Primordial Black Holes (PBHs) where the accretion during the radiation dominated era is fast and takes place (e. g. [27,28]). Another potential application is related to the accretion of exotic cosmic fields that violate the weak energy condition, including phantom fields [29,30].…”

Section: Conclusion and Final Commentsmentioning

confidence: 99%

Frequency shift of light emitted from growing and shrinking black holes

Guzman,

Alvarez-Rios,

Gonzalez

2021

Preprint

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In this paper we present a method to study the frequency shift of signals sent from near a Schwarzschild black hole that grows or shrinks through accretion. We construct the numerical solution of Einstein's equations sourced by a spherical shell of scalar field, with positive energy density to simulate the growth and with negative energy density to simulate the shrink of the black hole horizon. We launch a distribution of null rays at various time slices during the accretion and estimate their energy along their own trajectories. Spatially the bundles of photons are distributed according to the distribution of dust, whose dynamics obeys Euler equations in the test field limit during the evolution of the black hole. With these elements, we construct the frequency shift of photons during the accretion process of growth or contraction of the hole, which shows a variability that depends on the thickness of the scalar field shell or equivalently the time scale of the accretion.

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Stability and instability of Ellis and phantom wormholes: Are there ghosts?

Cited by 37 publications

References 64 publications

Can accretion properties distinguish between a naked singularity, wormhole and black hole?

Can accretion properties distinguish between a naked singularity, wormhole and black hole?

Accretion Flow onto Ellis–Bronnikov Wormhole

Frequency shift of light emitted from growing and shrinking black holes

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