Templatic Voynich generator

[Mauro]

Why we collapse sh with ch
sh and ch behave somehow as allomorphs: collapsing sh→ch reduces character bigram conditional entropy by 3.0-3.7% with zero change in stream length. The effect is consistent across both dialects and both stronger in H2 than in H1 (ratio 2.8-3.1x).

Collapsing all characters to X will reduce the entropy to zero with zero change in stream length. I'm not sure how this is an explanation for collapsing sh with ch. Also, isn't the problem with Voynichese that the conditional entropy is already too low?

Indeed. I have a better explanation: the distributions of characters preceding and following 'ch' and 'sh' are very similar. These are the geometric (root-mean-squares) distances of the Voynich characters ('ch' = C, 'sh' = S) according to the distributions of the previous and following character on the whole RF1a-n text (min possible value = 0, max possible value = sqrt(2)):

   

The distance between 'ch' and 'sh' according to the following character is 0.13, according to the previous character is 0.18, both low. There are other character couplets with lower distances, eg. 'm' and 'n' have a distance_following of 0.03 (they are both mostly followed by space), but none with a lower distance in both directions (i.e. 'm' and 'n' are 1.18 apart according to the previous character).

My conclusion is that this supports the idea that 'ch' and 'sh' might be the same character, but is far from proving it (and I'm actually not conmvinced by it). I'd be more confident to say that 'ch' and 'sh' have a very similar role, whichever that might be.

By the way, iirc the next most similar couplet is 'ckh' and 'cth' (K and T in the above diagrams), distance_following = 0.18 and distance_previous = 0.34