## A simple example concerning the upper box-counting dimension of a Cartesian product.(English)Zbl 1384.28008

The authors provide an example of two countable sets $$X$$ and $$Y$$ on the real axis such that the upper box-counting dimension of $$X\times Y$$ is strictly lesser than the sum of their upper box-counting dimensions.

### MSC:

 28A75 Length, area, volume, other geometric measure theory 28A80 Fractals
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