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Homotopy theory, homological algebra, algebraic treatments of manifolds.

11 votes
1 answer
658 views

What are the homological properties of Young's lattice?

Young's lattice $Y$ is a graded poset and a distributive lattice whose elements are all the partitions of $n$ for $n \in \mathbb{N}$ with the poset relation coming from inclusion of Young diagrams. He …
10 votes
1 answer
370 views

Computing K-theory for cellular vector bundles

One of the most computationally convenient properties of singular cohomology $X \mapsto H^\bullet(X;\mathbb{Z})$ is the fact that one can extract it from a good cover $\{U_i\}$ of $X$ via Cech cohomol …
37 votes
Accepted

Reference on Persistent Homology

Since this area is developing rather quickly, there is a dearth of canonical references that would satisfy basic pedagogical requirements. If I were teaching a course on this material right now, I wou …
Vidit Nanda's user avatar
  • 15.5k
24 votes
4 answers
2k views

How many simplicial complexes on n vertices up to homotopy equivalence?

Fix a number $n$, and define $\gamma(n)$ to be the number of simplicial complexes on $n$ unlabeled vertices up to homotopy equivalence. It is unlikely that an explicit formula exists, but what is know …
10 votes
Accepted

Persistent homology over the integers

As mentioned in Carlsson and Zomorodian's paper (to which you have linked), the problem of computing persistence barcodes with coefficients in a ring $R$ relies essentially on classifying graded modul …
Vidit Nanda's user avatar
  • 15.5k
5 votes
Accepted

Simplicial complex construction from given Betti numbers?

One way to make things "minimal" (given the lack of any further information) is to construct a simplicial complex whose cup products are all trivial, so the (co)homology generators don't interact with …
Vidit Nanda's user avatar
  • 15.5k
5 votes
Accepted

What functions have the same persistence diagrams?

Your question is precisely the subject of Justin Curry's recent preprint. Bottom line: if you agree to identify functions $f,g:[0,1] \to \mathbb{R}$ whenever they have the same merge-tree, then ther …
Vidit Nanda's user avatar
  • 15.5k
7 votes

Discrete Morse theory: how do zig-zag paths determine homotopy type?

Thanks to Cosheaf Overlord Justin Curry for bringing this question to my attention. I'm only going to address the first question here, and I think with some computations (whose complexity depends on y …
Community's user avatar
  • 1
78 votes
1 answer
5k views

The topology of Arithmetic Progressions of primes

The primary motivation for this question is the following: I would like to extract some topological statistics which capture how arithmetic progressions of prime numbers "fit together" in a manner tha …
7 votes
0 answers
653 views

Is there an obstruction which classifies "quasi-isomorphism but not chain equivalence"?

Fix a ring $R$ and let $C_\bullet$, $D_\bullet$ be (possibly unbounded) chain complexes of $R$-modules. Assume that $f_\bullet:C_\bullet \to D_\bullet$ is a quasi-isomorphism: that is to say, $f$ is a …
12 votes

Inference using Topological Data Analysis: Is it worth it for a regular statistician to lear...

Update: There is a now a new paper by Otter et al which went through all the trouble of comparing many software packages for performance, memory, ease-of-use etc.: http://arxiv.org/abs/1506.08903 Thi …
Vidit Nanda's user avatar
  • 15.5k
22 votes
Accepted

fixed point property for maps of compacts

Lovely question! Sadly, the answer is "no" in the sense that the fixed point property is not homotopy-invariant even in the category of finite polyhedra. In fact, it is also not invariant under the op …
Vidit Nanda's user avatar
  • 15.5k
16 votes
1 answer
359 views

Moduli space of boundary maps with prescribed chain and homology groups?

Let $R$ be a reasonable ring (maybe I mean a PID, or $\mathbb{Z}$, and when sufficiently desperate, a field). Now consider fixed sequences $C_n$ and $H_n$ of $R$-modules, which are tame in every possi …
18 votes
Accepted

Persistence barcodes and spectral sequences

The answer to your question is no, nobody has used persistence to improve the algorithmic efficiency of computing differentials, although of course the relationship between persistence intervals of a …
Vidit Nanda's user avatar
  • 15.5k
3 votes

Classifying spaces for enriched categories

Edit: Modified in accordance with Tom Leinster's entirely reasonable objections. Sorry to exhume this question from 5+ years ago. In case someone is still looking for an answer, note that a very spec …
Vidit Nanda's user avatar
  • 15.5k

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