In a collisional Penrose process, two particles coming from the asymptotically flat region collide in the ergosphere of a compact object. The collision produces two new particles, one with positive energy and one with negative energy. When the particle with positive energy escapes to infinity, the process extracts energy from the compact object. In this paper, we study the collisional Penrose process in a rotating wormhole spacetime. We consider the simple case of a head-on collision at the throat of a Teo wormhole. We find that the process of energy extraction from a Teo wormhole can be substantially more efficient than the collisional Penrose process in the Kerr black hole spacetime.
The gravitational perturbation of the Morris-Thorne wormhole has been derived by using the Newman-Penrose formalism. We apply Teukolsky equation to the wormhole spacetime, compute the perturbed Weyl scalars, $Ψ_{4}^{(1)}$ and obtain its master equation, decomposed in spin weighted spherical harmonics with spin weight $-2$. For simplicity, we consider the perturbation provoked by a single gaussian pulse of pressureless dust matter.
In this work we study the problem of linear stability of gravitational perturbations in stationary and spherically symmetric wormholes. For this purpose, we employ the Newman-Penrose formalism which is well-suited for treating gravitational radiation in General Relativity, as well as the geometrical aspect of this theory. With this method we obtain a "master equation" that describes the behavior of gravitational perturbations that are of odd-parity in the Regge-Wheeler gauge. This equation is later applied to a specific class of Morris-Thorne wormholes and also to the metric of an asymptotical…
The Penrose process of an extremal braneworld black hole is studied. We analyze the Penrose process by two massive spinning particles collide near the horizon. By calculating the maximum energy extraction efficiency of this process, it turns out that the maximal efficiency increases as the tilde charge parameter $d$ of the braneworld blackhole decreases. Interestingly, for the negative value of $d$, the efficiency can be even larger than the Kerr case.
We study the collision of two uncharged spinning particles around an extreme Kerr-Sen black hole and calculate the maximal efficiency of the energy extraction from the Kerr-Sen black hole via super Penrose process. We consider the collision of two massive particles as well as collision of a massless particle with a massive particle. For all the cases, we find that the maximum efficiency decreases as the Kerr-Sen black hole's parameter($b=1-a$) increases.
We consider collision of particles in a wormhole near its throat. Particles come from the opposite mouths. If the lapse function is small enough there, the energy $E$ of debris at infinity grows unbounded, so we are faced with the so-called super-Penrose process. This requires the existence of the ergoregion, so a wormhole should be rotating.
The Penrose process in the vicinity of an extremal Banãdos-Teitelboim-Zanelli(BTZ) black hole is studied. Due to the existence of negative cosmological constant, only massless particles could escape to infinity. Hence we analyse the Penrose process by one massless particle collides with another massive particle near the horizon of BTZ black holes. Calculations of the maximum energy extraction efficiency of this process is carried out for both spinless and spinning particles. Our results show that the spinning particle have a higher energy extraction efficiency than the spinless particle. Moreo…
We investigate the power of a collisional Penrose process with an unbound energy extraction from an extreme Reissner-Nordström black hole. This process takes infinite time in a time coordinate at a constant radial coordinate outside of the black hole. For black holes as a power plant, the power of the process for an observer far away from the black hole can be useful. We define the power as energy gain from the extreme Reissner-Nordström black hole divided by the time interval of the process in a coordinate time; we estimate the upper bound of the power in a near-horizon limit, while the effic…
We analyze the collisional Penrose process between a particle on the ISCO orbit around an extreme Kerr black hole and a particle impinging from infinity. We consider both cases with non-spinning and spinning particles. We evaluate the maximal efficiency, $η_{\text{max}}=(\text{extracted energy})/(\text{input energy})$, for the elastic collision of two massive particles and for the photoemission process, in which the ISCO particle will escape to infinity after the collision with a massless impinging particle. For non-spinning particles, the maximum efficiency is $η_{\text{max}} \approx 2.562$ f…
We first study the escape probability of the spinning particle emitted from the Kerr black hole and find that the escape probability increases with the spin of the particle around the extreme Kerr black hole; in contrast, the escape probability decreases at the position near the horizon but increases at the position far away from the horizon with the increasing spin of the particle. We then probe the relation between the escape probabilities and the energy extraction efficiencies of collisional Penrose processes for the particles with varying spin. For the extreme Kerr black hole, the efficien…
We analyze collisional Penrose process of spinning test particles in an extreme Kerr black hole. We consider that two particles plunge into the black hole from infinity and collide near the black hole. For the collision of two massive particles, if the spins of particles are $s_1 \approx 0.01379μM$ and $s_2 \approx -0.2709μM$, we obtain the maximal efficiency is about $η_{max} = (\text{extracted energy})=(\text{input energy}) \approx 15.01$, which is more than twice as large as the case of the collision of non-spinning particles ($η_{max} \approx 6.32$). We also evaluate the collision of a mas…
In this paper we study a static cyclic symmetric traversable wormhole in $(2+1)-$dimensional gravity coupled to nonlinear electrodynamics in anti-de Sitter spacetime. The solution is characterized by three parameters: mass $M$, cosmological constant $Λ$ and one electromagnetic parameter, $q_α$. The causality of this spacetime is studied, determining its maximal extension and constructing then the corresponding Kruskal-Szekeres and Penrose diagrams. The quasinormal modes (QNMs) that result from considering a massive scalar test field in the wormhole background are determined by solving in exact…
We suggest two new scenarios of high-energy particle collisions in the background of a wormhole. In scenario 1 the novelty consists in that the effect does not require two particles coming from different mouths. Instead, all such scenarios of high energy collisions develop, when an experimenter sends particles towards a wormhole from the same side of the throat. For static wormholes, this approach leads to indefinitely large energy in the center of mass. For rotating wormholes, it makes possible the super-Penrose process (unbounded energies measured at infinity). In scenario 2, one of collidin…
This paper explores the neutral particle motion and collisional Penrose process in ergoregion of the braneworld Kerr black hole. We analyze the properties of event horizon, ergosphere and static limit. The particle collision in ergoregion via the Penrose process is investigated. Furthermore, we study the negative energy states and show that the sign of particle energy can be uniquely determined by the sign of angular momentum. In addition, we study the Wald inequality to determine the limits of energy extraction via the Penrose process and also find lower bound of the irreducible mass. The exp…
Violations of the null convergence condition in kinematical transitions between singular and regular black holes, horizonless compact objects, and bounces
Penrose and super-Penrose energy extraction from a Reissner-Nordström black hole spacetime with a cosmological constant through the BSW mechanism: Full story
The collisional Penrose process received much attention when Banados, Silk and West (BSW) pointed out the possibility of test-particle collisions with arbitrarily high center-of-mass energy in the vicinity of the horizon of an extremally rotating black hole. However, the energy that can be extracted from the black hole in this promising, if simplified, scenario, called the BSW effect, turned out to be subject to unconditional upper bounds. And although such bounds were not found for the electrostatic variant of the process, this version is also astrophysically unfeasible, since it requires a m…
