## Is residual finiteness a quasi isometry invariant for f.g. groups?

A “residually finite group” is group for which the intersection of all finite index subgroups is trivial. Suppose $$G$$ and $$G’$$ are two quasi-isometric finitely generated groups. Does the residual finiteness of $$G$$ implies the same property for $$G’$$?

## How would I go about learning Quasi Crystal Mathematics?

I tried to find out a path to learn Quasi Crystam Mathematics? My math knowledge is only pretty basic however I am very much willing to work the way through up even undergrad parts and above if I can learn it through books or online.

What would it take to understand, use and work with Quasi Crystal Mathematics.