Quantum Black Holes and Effective Quantum Gravity Approaches

Abstract

One of the most exciting developments in theoretical physics in the last 20 years has been the realization that the scale of quantum gravity could be in the TeV region instead of the usually assumed 10 19 GeV. Indeed, the strength of gravity can be affected by the size of potential extra-dimensions [1][2][3][4] or the quantum fluctuations of a large hidden sector of particles [5]. A dramatic signal of quantum gravity in the TeV region would be the production of small black holes in high energy collisions of particles at colliders. The possibility of creating small black holes at colliders has led to some wonderful theoretical works on the formation of black holes in the collisions of particles.Long before studying the production of such black holes in the high energy collisions of particles became fashionable, in the 1970's Penrose proved that a closed trapped surface forms when two shockwaves traveling at energies much larger than the Planck scale even when the impact parameter is non-zero. Unfortunately, he never published his work. The result was independently rediscovered by Eardley and Giddings in 2002 [6] when the high energy community started to discuss the formation of black holes at colliders. Earlier estimate of the production cross section had been done using the hoop conjecture. Some did not trust the hoop conjecture, thinking that in the collision of particles the situation was too asymmetrical to trust this conjecture. The paper of Eardley and Giddings settled the issue. Proving the formation of a closed trapped surface is enough to establish gravitational collapse and hence the formation of a black hole. This work was extended by Hsu [7] into the semi-classical region using path integral methods. One could thus claim with confidence that black holes with masses 5 to 20 times the Planck scale, depending on the model of quantum gravity, could form in the collision of particles at the CERN LHC is the Planck scale was low enough. Early phenomenological studies can be found in [8][9][10][11][12][13][14].

The horizon of the lightest black hole

“…Obviously, quantum black holes are quantum gravitational objects, but while we are still far from having a theory of quantum gravity, effective field theory techniques can be reliably applied to general relativity coupled to matter at energy scales below the energy scale at which quantum gravitational effects become of the same magnitude as quantum effects generated by the other forces of nature [2][3][4][5]. The leading order terms of the effective field theory are given by a e-mail: x.calmet@sussex.ac.uk b e-mail: casadio@bo.infn.it…”

Dynamic Onset of Feynman Relation in the Phonon Regime

“…Nonlinear optics 3 , a completely non-related field of study, investigates a wide range of light-matter interactions from sub-atomic particles and condensed matter physics 4 5 6 , to astrophysical phenomena 3 7 . Although widely used in many fields of physical science, nonlinear optics usually only serves as an indispensable probe (especially when the light intensity is not very high) rather than a tool to actively and dynamically alter the fundamental properties of a material under investigation except the intensity-dependent effects induced by ultra-high power ultra-short-pulse lasers 3 8 .…”