Mathematical fiction is tough, because of the problems with "mathematical counterfactuals". Why not go with mathematical poetry instead? There are nice sections of same in the Clifton Fadiman anthologies. The first of these is also from The Space Child's Mother Goose. (All from memory, so please pardon any errors.)
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Three jolly sailors from Blandon-on-Tyne
Went to sea in a bottle by Klein
They found the view exceedingly dull
For the sea was entirely contained in the hull.
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There was a young lady named Bright
Who traveled much faster than light
She departed one day
In a relative way
And returned the previous night.
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There once was a fencer named Fisk
Whose movements were agile and brisk
So quick was his action
The Lorentz contraction
Diminished his sword to a disk.
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(There's also a bawdy version of that somewhere, referring to a different "sword".)
"Very well. Let's have a love poem, lyrical, pastoral, and expressed in the language of pure mathematics. Tensor algebra mainly, with a little topology and higher calculus, if need be. But with feeling, you understand, and in the cybernetic spirit."
"Love and tensor algebra? Have you taken leave of your senses?" Trurl began, but stopped, for his electronic bard was already declaiming:
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Three jolly sailors from Blandon-on-Tyne
Went to sea in a bottle by Klein
They found the view exceedingly dull
For the sea was entirely contained in the hull.
---------------
There was a young lady named Bright
Who traveled much faster than light
She departed one day
In a relative way
And returned the previous night.
-------------
There once was a fencer named Fisk
Whose movements were agile and brisk
So quick was his action
The Lorentz contraction
Diminished his sword to a disk.
--------------
(There's also a bawdy version of that somewhere, referring to a different "sword".)