Math of Transfinite Donuts in 3-D Space

  • Thread starter Thread starter HarryWertM
  • Start date Start date
  • Tags Tags
    Transfinite
HarryWertM
Messages
99
Reaction score
0
Has anyone ever developed any sort of math involving donuts with an infinite number of holes? By donut, I mean a two-dimensional closed surface, curved in 3-space, with one 'hole'. Are there any results, of any kind, for 2-D donuts in 3-D space, with infinite number of holes?
 
Physics news on Phys.org
I think they're about as well understood as the donut with one hole. Riemann surfaces are one of the most thoroughly understood branches of mathematics.
 
Could you construct a doughnut with uncountable many holes ? It would not be a paracompact manifold.
 
You mean something like S\times I, where S is the unit disk with the rational points inside a circle of radius 1/2 centered at the origin deleted?
 
Last edited:
Sine Nomine said:
You mean something like S\times I, where S is the unit disk with the rational points inside a circle of radius 1/2 centered at the origin deleted?

Not sure how that example is a torus.

I was thinking more of the long line Cartesian product the circle with uncountably many holes removed.
 
Hello! There is a simple line in the textbook. If ##S## is a manifold, an injectively immersed submanifold ##M## of ##S## is embedded if and only if ##M## is locally closed in ##S##. Recall the definition. M is locally closed if for each point ##x\in M## there open ##U\subset S## such that ##M\cap U## is closed in ##U##. Embedding to injective immesion is simple. The opposite direction is hard. Suppose I have ##N## as source manifold and ##f:N\rightarrow S## is the injective...
Back
Top