Uniformity of Space: Definition & Examples

  • Context: Graduate 
  • Thread starter Thread starter alexfloo
  • Start date Start date
  • Tags Tags
    Space Uniformity
Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
3 replies · 3K views
alexfloo
Messages
192
Reaction score
0
"Uniformity" of space

I have a question about terminology. Suppose we have a space X with the property that:

for all x, x' in X and neighborhood N of x, N is homeomorphic to some neighborhood N' of x'
OR
for all x, x' there exists a homeomorphism f:X→X s.t. f(x)=x'.

(I believe these are equivalent, but I haven't worked it out.) In some sense, these spaces are uniform (although I know that uniform space has its own meaning). There are no "distinguished" points, or different "types" of points. (Any open, simply-connected subset of Euclidean space has this property. Any closed subset of Euclidean space not equal to its boundary lacks it, since boundary points cannot be continuously mapped onto interior points.)

Is there a name for this?

EDIT: fixed an error.
 
Last edited:
Physics news on Phys.org


actually those 2 sentences are not equivalent since the continuous bijection doesn't guarantee the homeomorpic between neighborhood of x and x' , it must have continuous inverse to be homeomorphic
 


EDIT: You are correct. I'll add that in.
 


alexfloo said:
Continuous bijection should be sufficient:

Continuous X→Y means for each open OY subset of Y, f-1(OY)=OX is open in X. Bijection means that

f(OX)=f(f-1(OY))=OY,

so f-1 is also continuous.

Now you assume that all open sets are of the form [itex]f^{-1}(O_Y)[/itex]. This is not necessarily true.