Back to tiny black holes

It's been ages since I searched arXiv for black hole papers.  But I did one today and found another paper on a favourite topic - micro black holes and whether they evaporate, and are a good candidate for dark matter.  The abstract:

The nature of dark matter is still an open problem. The simplest assumption is that gravity is the only force coupled certainly to dark matter and thus the micro blackholes could be a viable candidate. We investigated the possibility of direct detection of microblack holes with masses around and upward the Planck scale (10−5g), ensuring classical gravitational treatment of these objects in the next generation of huge LAr detectors. We show that the signals (ionization and scintillations) produced in LAr enable the discrimination between micro black holes or other particles. It is expected that the trajectories of these microblack holes will appear as crossing the whole active medium, in any direction, producing uniform ionization and scintillation on all the path.

I had to look up LAr - it's liquid argon.

The introduction section of the paper gives a good summary of the questions around evaporating black holes:

An important issue is to show that black holes do not radiate in some conditions and which are their characteristics, as an argument to explain that these relics objects can survive from early Universe. We would need to detect the black holes or to have strong indirect evidence of their existence, as well as to show that they do not radiate. At present we are far from doing this.

In a classical paper, Hawking [2] suggested that unidentified tracks in the photographs taken in old bubble chamber detectors could be explained as signals of gravitationally collapsed objects (μBH). The mechanism of black hole formation is well known. As a result of fluctuations in the early Universe, a large number of gravitationally collapsed objects can be formed with characteristics determined by the gravity and quantum behaviour. For masses above the Planck mass limit of10−5g quantum behaviour is prevented.The small black holes are expected to be unstable due to Hawking radiation, but the evaporation is not well-understood at masses of order of the Planck scale. Helfer [3] has shown that none of the derivations that have been given for the prediction of radiation from black holes is convincing. It argued that all involve, at some point, speculations on the physics at scales which are not merely orders of magnitude beyond any investigated experimentally(∼103GeV), but at scales increasing beyond the Planck scale (∼1019GeV), where essentially  quantum-gravitational effects are expected to be dominant and various derivations that havebeen put forward, not all are mutually consistent. 

Given the profound nature of the issues addressed, some disagreement and controversy exists over exactly what has been achieved. Balbinot [4] demonstrated that when a blackhole becomes more and more charged, the Hawking radiation decreases and in the limit of maximum charge containment there is no radiation. Certain inflation models naturally assume the formation of a large number of small black hole [5] and the GUP may indeed prevent total evaporation of small black holes by dynamics and not by symmetry, just like the prevention of hydrogen atom from collapse by the standard uncertainty principle [6].Chavda and Chavda [7] introduced a different idea: gravitationally bound black holes will not have Hawking radiation. They examine the range10−24kg≤MBH≤10−12kg where quantum aspects must be considered. These limits of masses are controversial regarding the stability of the black holes, see for example [8].