Hole Production In Particle Collisions Research Articles

Black hole production in particle collisions and higher curvature gravity

The problem of black hole production in trans-Planckian particle collisions is revisited, in the context of large extra dimensions scenarios of TeV-scale gravity. The validity of the standard description of this process (two colliding Aichelburg--Sexl shock waves in classical Einstein gravity) is questioned. It is observed that the classical spacetime has large curvature along the transverse collision plane, as signaled by the curvature invariant ${(R}_{\ensuremath{\mu}\ensuremath{\nu}\ensuremath{\lambda}\ensuremath{\sigma}}{)}^{2}.$ Thus quantum gravity effects, and in particular higher curvature corrections to the Einstein gravity, cannot be ignored. To give a specific example of what may happen, the collision is reanalyzed in the Einstein--Lanczos--Lovelock gravity theory, which modifies the Einstein--Hilbert Lagrangian by adding a particular ``Gauss--Bonnet'' combination of curvature squared terms. The analysis uses a series of approximations, which reduce the field equations to a tractable second order nonlinear PDE of the Monge--Amp\`ere type. It is found that the resulting spacetime is significantly different from the pure Einstein case in the future of the transverse collision plane. These considerations cast serious doubts on the geometric cross section estimate, which is based on the classical Einstein gravity description of the black hole production process.

Classical and quantum cross-section for black hole production in particle collisions

We suggest a simple model to study the problem of the black hole production in particle collisions. The cross-section for the classical and quantum production is analysed within this model. In particular, the possibility to form a black hole in collision of low energy particles (or at large impact parameter) via the quantum tunneling mechanism is pointed out. It is found that, in this model, the geometric cross-section gives a good estimate for the production at low and high energies. We also reconsider the arguments in favor of exponential suppression for the production of trans-Planckian black hole and conclude that no such suppression in fact appears. Analyzing the probability for the black hole production we point out on the importance of the back-reaction and reevaluate the contribution of the black hole formed in gravitational collapse to the Euclidean path integral.

More remarks on suppression of large black hole production in particle collisions

The problem of evaluating the cross section of production of large black holes in particle collisions at trans-Planckian energies is revisited. It is argued that the geometric cross section claimed in the literature would in fact lead to an exponentially growing with energy total cross section dominated by production of many “small” black holes. On the other hand, the semiclassical treatment of this problem, leading to an exponentially suppressed cross section for production of large black holes, requires that in the classical limit the cross section vanishes for massless colliding particles. The latter behavior can in principle be probed by numerical simulations in the classical general relativity.

Semiclassical suppression of black hole production in particle collisions

It is argued that the cross section for production of large black holes, for which a semiclassical description is applicable, cannot be given by the geometric area of the black hole horizon, as claimed recently in the literature. Rather the production cross section in a few-particle collision is suppressed by at least a factor exp(-I_E) with I_E being the Gibbons-Hawking (Euclidean) action for the black hole. Thus only essentially non-classical small black holes with mass of the order of the Planck mass can possibly be produced in few-particle collisions at trans-Planckian energies.