Reputation
4,358
Next privilege 5,000 Rep.
Approve tag wiki edits
Badges
1 17 39
Newest
 Inquisitive
Impact
~94k people reached

15m
asked Surniversal spaces
11h
comment Snake-like continua and universal images
My general comment addressed to the whole MO: let's make MO posts more self-contained, let them include explicit definitions.
2d
comment Can you write $\mathbb R^2$ as a disjoint union of two totally disconnected sets?
Dear @LasseRempe-Gillen, it's Janiszewski. Yes, I'll try to find your answer to the q. referenced by Kristal.
Apr
24
comment Applications of space filling curves
I applied, during the first half of 1985, the Hilbert curve to the image compression.
Apr
23
comment is there any more odd near-perfect number?
I am enthusiastic about almost nearly quasi sub-perfect pseudointegers.
Apr
23
comment is there any more odd near-perfect number?
=== Definition? ===
Apr
23
answered What is the correct term for “co-covering” designs
Apr
18
comment Do Peano curves provide a counterargument to Grothendieck's critique?
"...regarded as exhibiting the naturality of phenomena..." ?
Apr
9
comment Are there only finitely many near-perfect numbers with more than 4 distinct prime divisors?
I don't see any argument against the value of the q.f.'s question. Thus, I'd like to keep it open.
Mar
24
comment No matter how many algebraic invariants we attach to topological spaces, there will always be nonhomeomorphic spaces agreeing on all their invariants
@HJRW -- thank you for correcting me. My vague recollection was wrong in two directions. Let me repeat after you, yes, it was Markov and 4-dimensional manifolds.
Mar
23
comment No matter how many algebraic invariants we attach to topological spaces, there will always be nonhomeomorphic spaces agreeing on all their invariants
@SebastianGoette - actually, I applied Wall's homotopic example to obtain analogous example for compact spaces in the shape theory, it was simple (however, two guys had stolen my result in a broad daylight; I guess they needed their tenure bad or something like this).
Mar
23
comment No matter how many algebraic invariants we attach to topological spaces, there will always be nonhomeomorphic spaces agreeing on all their invariants
@AlexDegtyarev, I remember an old similar result by a Soviet mathematician (I think that it was Malcev, the father) for 3-dimensional manifolds.
Mar
23
comment No matter how many algebraic invariants we attach to topological spaces, there will always be nonhomeomorphic spaces agreeing on all their invariants
The proper (so-to-speak) version of the problem is: *** there doesn't exist any algorithm which decides about two spaces whether or not they are homeomorphic. *** Here we can actually restrict our attention to finite polyhedra only.
Mar
14
comment Primary structures in $\mathbb Q$
Emil, thank you for your answer. And let's still hope for more.
Mar
14
revised Primary structures in $\mathbb Q$
cosmetic
Mar
14
revised Primary structures in $\mathbb Q$
accidental word omission corrected
Mar
8
comment If all balls around fixed basepoints are isometric, are the spaces as well (length spaces)?
I feel that it would not hurt to add a definition (rather than a link) of "proper length".
Mar
2
revised Does element-wise concavity guarantee joint concavity?
Further possibilities. (Earlier my additional statement got accidentally erased).
Mar
2
revised Does element-wise concavity guarantee joint concavity?
Further possibilities.
Mar
2
answered Does element-wise concavity guarantee joint concavity?