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Homotopy theory, homological algebra, algebraic treatments of manifolds.

1 vote
1 answer
379 views

What is the pullback morphism on sheaf cohomology of local systems in terms of representatio...

Whenever we have a continuous map of topological spaces $f: X \to Y$ and a sheaf $\mathcal{F}$ on $Y$ (of abelian groups for example), we get an induced pullback map $$ H^n(Y, \mathcal{F}) \to H^n(X, …
Eduardo de Lorenzo's user avatar
2 votes
1 answer
286 views

Explicit generators from Serre spectral sequence

Let $p: E \to B$ be a locally trivial fibration with fiber $F$. If necessary, suppose that $B$ is simply connected. Suppose that the Serre spectral sequence leaves the term $H_p(B, H_q(F, \mathbb{Q})) …
Eduardo de Lorenzo's user avatar
3 votes
0 answers
204 views

Long exact sequence in Borel-Moore homology

The Wikipedia page for Borel-Moore homology states that for a locally compact set $X$ and a closed subset $Z$, if we write $U = X \setminus Z$ we have the following long exact sequence $$\cdots \to H^ …
Eduardo de Lorenzo's user avatar
3 votes
0 answers
243 views

Explicit description of the Leray spectral sequence with compact supports for a fibration

Consider a locally trivial fibration $f: E \to B$ with fiber $F = \mathbb{C}^n$. The Leray spectral sequence with compact supports is $$ E_2: H^p_c(B, \underline{H^q_c(F)}) \implies H^{p+q}_c(E). $$ S …
Eduardo de Lorenzo's user avatar
2 votes
1 answer
475 views

Higher direct image with compact support of a constant sheaf

Let $f: X \to Y$ be a locally trivial fibration between locally compact spaces with fiber $F$. It is well known that for a constant sheaf $A_X$ on $X$, the higher direct images $R^n f_* A_X$ are local …
Eduardo de Lorenzo's user avatar
1 vote
Accepted

Higher direct image with compact support of a constant sheaf

With the information added in the last update, the result is already proved once you realize that the unit of the adjunction $$ id \to a_{B,*} a_B^* $$ is actually an isomorphism on the category of ab …
Eduardo de Lorenzo's user avatar
5 votes
0 answers
694 views

Spectral sequence from a stratification by closed subvarieties

I am looking for a reference for the following result: If $X$ is an algebraic variety and $$X = T_n \supset T_{n-1} \supset \cdots \supset T_{-1} = \varnothing$$ is a stratification (edit: filtration) …
Eduardo de Lorenzo's user avatar
2 votes
1 answer
156 views

Pullback morphism of a hyperplane inclusion is zero in the derived category

Let $L \subset \mathbb{C}^n$ be a hyperplane and let $i:L \to \mathbb{C}^n$ be the inclusion. Since $i$ is proper, we have induced maps $i^*: H^k_c(\mathbb{C}^n) \to H^k_c(L)$, and these maps are zero …
Eduardo de Lorenzo's user avatar