scholarly journals High energy particle collisions and geometry of horizon

2016 ◽  
Vol 25 (10) ◽  
pp. 1650095 ◽  
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Black Hole ◽  
Center Of Mass ◽  
Naked Singularity ◽  
High Energy ◽  
Fine Tuning ◽  
High Energy Particle ◽  
Axially Symmetric ◽  
Particle Collisions ◽  
Material Source ◽  
Mass Frame

We consider collision of two geodesic particles near the lightlike surface (black hole horizon or naked singularity) of such an axially symmetric rotating or static metric that the coefficient [Formula: see text] on this surface. It is shown that the energy in the center of mass frame [Formula: see text] is indefinitely large even without fine-tuning of particles’ parameters. Kinematically, this is the collision between two rapid particles that approach the horizon almost with the speed of light but at different angles (or they align along the normal to the horizon too slowly). The latter is the reason why the relative velocity tends to that of light, hence to high [Formula: see text]. Our approach is model-independent. It relies on general properties of geometry and is insensitive to the details of material source that supports the geometries of the type under consideration. For several particular models (the stringy black hole, the Brans–Dicke analogue of the Schwarzschild metric and the Janis–Newman–Winicour one) we recover the results found in literature previously.

scholarly journals Rotation as an origin of high energy particle collisions

2016 ◽  
Vol 31 (04) ◽  
pp. 1650029 ◽  
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Center Of Mass ◽  
High Energy ◽  
High Energy Particle ◽  
Particle Collisions ◽  
Energy Particle ◽  
Relativistic Stars ◽  
Mass Frame ◽  
Model Independent

We consider collision of two particles in rotating spacetimes without horizons. If the metric coefficient responsible for rotation of spacetime is big enough, the energy of collisions in the center of mass frame can be as large as one likes. This can happen in the ergoregion only. The results are model-independent and apply both to relativistic stars and wormholes.

scholarly journals High-energy collision of particles in the magnetic field far from black holes

2014 ◽  
Vol 29 (29) ◽  
pp. 1450151
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Center Of Mass ◽  
High Energy ◽  
Axially Symmetric ◽  
High Energy Collision ◽  
Mass Frame ◽  
Symmetric Black Hole ◽  
Rotating Star ◽  
The Magnetic Field

We consider collision of two particles in the axially symmetric black hole metric in the magnetic field. If the value of the angular momentum |L| of one particles grows unbound (but its Killing energy remains fixed) one can achieve unbound energy in the center-of-mass frame E c.m. In the absence of the magnetic field, collision of this kind is known to happen in the ergoregion. However, if the magnetic field strength B is also large, with the ratio |L|/B being finite, large E c.m. can be achieved even far from a black hole, in the almost flat region. Such an effect also occurs in the metric of a rotating star.

scholarly journals High-energy collisions inside black holes and their counterpart in flat spacetime

2014 ◽  
Vol 23 (05) ◽  
pp. 1450045 ◽  
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Black Hole ◽  
Center Of Mass ◽  
High Energy ◽  
General Character ◽  
Particle Collisions ◽  
Flat Spacetime ◽  
Mass Frame ◽  
High Energy Collisions ◽  
Horizon Geometry

Two particles can collide inside a nonextremal black hole in such a way that the energy E c.m. in their center-of-mass frame becomes as large as one likes. We show that this effect can be understood with the help of a simple analogy with particle collisions in flat spacetime. As the two-dimensional part of near-horizon geometry inside a black hole is described by the flat Milne metric, the results have a general character. Full classification of scenarios with unbound E c.m. is suggested. Some scenarios of this kind require proximity of collision to the bifurcation point, but for some other ones this is not necessary.

scholarly journals Kinematics of ultra-high energy particle collisions near black holes in the magnetic field

2015 ◽  
Vol 30 (06) ◽  
pp. 1550027 ◽  
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Center Of Mass ◽  
High Energy ◽  
High Energy Particle ◽  
Ultra High Energy ◽  
Particle Collisions ◽  
Mass Frame ◽  
Bsw Effect ◽  
The Magnetic Field

There are different versions of collisions of two particles near black holes with unbound energy E cm in the center of mass frame. The so-called BSW effect arises when a slow fine-tuned "critical" particle hits a rapid "usual" one. We discuss a scenario of collision in the strong magnetic field for which explanation turns out to be different. Both particles are rapid but the nonzero angle between their velocities (which are both close to c, the speed of light) results in a relative velocity close to c and, hence, big E cm .

scholarly journals HIGH ENERGY PARTICLE COLLISIONS NEAR THE BIFURCATION SURFACE

2013 ◽  
Vol 22 (08) ◽  
pp. 1350044 ◽  
Author(s):  
OLEG B. ZASLAVSKII
Keyword(s):  
Center Of Mass ◽  
High Energy ◽  
Generic Property ◽  
High Energy Particle ◽  
De Sitter ◽  
Particle Collisions ◽  
Energy Particle ◽  
Mass Frame ◽  
Bifurcation Surface ◽  
De Sitter Metric

We consider generic nonextremal stationary dirty black holes. It is shown that in the vicinity of any bifurcation surface the energy of collision of two particles in the center of mass frame can grow unbound. This is a generic property that, in particular, includes collisions near the inner black hole horizon analyzed earlier by different methods. The similar results are also valid for cosmological horizons. The case of the de Sitter metric is discussed.

scholarly journals New Scenarios of High-Energy Particle Collisions Near Wormholes

Universe ◽  
2020 ◽  
Vol 6 (12) ◽  
pp. 227
Author(s):  
Oleg B. Zaslavskii
Keyword(s):  
Center Of Mass ◽  
High Energy ◽  
Large Energy ◽  
High Energy Particle ◽  
Particle Collisions ◽  
Energy Particle ◽  
Wormhole Throat ◽  
Penrose Process ◽  
High Energy Collisions

We suggest two new scenarios of high-energy particle collisions in the background of a wormhole. In scenario 1, the novelty consists of the fact 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 colliding particles oscillates near the wormhole throat from the very beginning. In this sense, scenario 2 is intermediate between the standard one and scenario 1 since the particle under discussion does not come from infinity at all.

ACCELERATION OF PARTICLES AS A UNIVERSAL PROPERTY OF ERGOSPHERE

2013 ◽  
Vol 28 (11) ◽  
pp. 1350037 ◽  
Author(s):  
O. B. ZASLAVSKII
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Recent Observation ◽  
Center Of Mass ◽  
Kerr Black Hole ◽  
Acceleration Of Particles ◽  
Axially Symmetric ◽  
Fixed Energy ◽  
Mass Frame

We show that recent observation made by Grib and Pavlov, [A. A. Grib and Yu. V. Pavlov, Europhys. Lett.101, 20004 (2013)] for the Kerr black hole is valid in the general case of rotating axially symmetric metric. Namely, collision of two particles in the ergosphere leads to indefinite growth of the energy in the center-of-mass frame, provided the angular momentum of one of the two particles is negative and increases without limit for a fixed energy at infinity. General approach enabled us to elucidate why the role of the ergosphere is crucial in this process.

scholarly journals Black hole with a scalar field as a particle accelerator

2017 ◽  
Vol 26 (10) ◽  
pp. 1750108 ◽  
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Center Of Mass ◽  
High Energy ◽  
Particle Accelerator ◽  
Particle Collision ◽  
Axially Symmetric ◽  
Speed Of Light ◽  
Test Particles ◽  
Energy Formula

We consider stationary axially symmetric black holes with the background scalar field and test particles that can interact with this field directly. Then, particle collision near a black hole can lead to the unbounded energy [Formula: see text] in the center of mass frame (contrary to some recent claims in literature). This happens always if one of the particles is neutral whereas another one has nonzero scalar charge. Kinematically, two cases occur here. (i) A neutral particle approaches the horizon with the speed of light while the velocity of the charged one remains separated from it (this is direct analogue of the situation with collision of geodesic particles.). (ii) Both particles approach the horizon with the speed almost equal to that of light but with different rates. As a result, in both cases the relative velocity also approaches the speed of light, so that [Formula: see text] becomes unbounded. We consider also a case when the metric coefficient [Formula: see text] near a black hole. Then, overlap between the geometric factor and the presence of the scalar field opens additional scenarios in which unbounded energy [Formula: see text] is possible as well. We give a full list of possible scenarios of high-energy collisions for the situations considered.

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