What Are 'M-M' and 'N-N' Circles in Russian Physics?

[nomadreid]

In a paper translated from the Russian, the author refers to "m-m" and "n-n" circles (including Minkowski circles) and orbits. When I first came across "n-n", I thought it was "non-negative" until I came across the "m-m". In one of the references I went to a diagram referred to, and saw an arc with "n" on each end of the arc referred to as an "n-n unit circle". I have no idea what he is talking about. Is this some standard notation I am unfamiliar with, or some notation perhaps peculiar to Russian?
In the same context, he has "m-m circles" with imaginary radii. I thought a radius was a distance, which is always real. ??
Thanks for guidance.

 

[nomather1471]

Can he talk about hyperboloid which is embedded in Minkowski, because hyperboloids can be thought as a sphere of imaginary radius...

 

[nomadreid]

thanks, nomather1471. Given the context of the paper, your suggestion makes sense. I stand corrected on my impression that radii were necessarily real.
In the meantime I asked a Russian physicist, who told me that this is not standard notation in Russian either. So my guess is that it is a bad translation, and that the "m-m" is merely a reference to the hyperboloid labeled with a couple of m's in one of his diagrams.