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

Abstract

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.

Ellis–Bronnikov Wormholes in Asymptotically Safe Gravity

“…Wormholes and their traversability are an object of intense discussion in the communities which study general relativity and it's extensions. By means of Einstein's theory, one shows [1][2][3][4] that the wormhole is traversable only with the presence of exotic matter, including Casimir energy [5][6][7][8][9], even being capable of mimicing the behavior of black holes [10][11][12]. Classically modified gravity theories involving wormholes (e.g., Einstein-Gauss-Bonett gravity [13], Lovelock gravity [14], Einstein-Born-Infeld gravity [15], and others [16][17][18][19]), as well as some quantum corrected ones [20], are also often discussed in the literature.…”

Constraining wormhole geometries using the orbit of S2 star and the Event Horizon Telescope

“…3r g 2r r and r 0 > 2r g , (15) yielding the following relation between the parameter M and mass of the WH is…”

“…For a BH, light moves around in a null circular geodesic constituting a photon sphere outside the event horizon, analogously a photon sphere is formed outside the WH's throat. In order to detect the shadows of any astrophysical WHs by an observer, an optically thin accretion disk of gas surrounding the WH is necessary [15]. However, due to weak gravitational field of WHs compared to BHs, the size of the shadow's boundary is expected to be smaller.…”

Accretion flows around exotic tidal wormholes I. Ray-tracing

“…Moreover, it was numerically shown in (Karimov et al 2019b) that Damour-Solodukhin wormholes are practically could not be distinguished from the Kerr back holes in terms of accretion. Finally, in (Karimov et al 2020) both naked singularity, wormhole and black hole were compared in the sense of accretion properties. Aforementioned studies could help us to discriminate black holes from other, more exotic objects of nonsingular nature.…”