A CD is clearly homotopic to a torus, though…
And the walls of a straw do have thickness…
A straw goes:
Gas - solid - gas - solid - gas
Comment on Baldur's Gayte
iAvicenna@lemmy.world 10 months ago
a torus is not homotopic to a straw though unless you take the straw and glue it at its ends
Semjaza@lemmynsfw.com 10 months ago
iAvicenna@lemmy.world 10 months ago
If solid torus yes, if just the regular torus (surface of the solid torus) no. CD is homotopic to a circle and so is a solid torus.
ytg@sopuli.xyz 10 months ago
Wouldn’t a straw be the product of a circle and a line?
iAvicenna@lemmy.world 10 months ago
What you said is stronger than being homotopic. homotopic is weaker, for instance a line is homotopic to a point, By taking the straw (even if it has thickness) and just shrinking it along its longer axis you eventually arrive at a circle. If it has thickness you will arrive at a band and then you can also retract radially to arrive at a circle.
stevedice@sh.itjust.works 10 months ago
I think people don’t know a torus is hollow.