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Let $R$ be a commutative ring and $X$ a topological space. Define a sheafy cohomology theory (see here) to be a collection of functors $\mathrm{H}^q:\mathrm{Sh}(X;R\mathrm{Mod})\to R\mathrm{Mod}$ such that the following conditions are satisfied:

  • If $q<0$, then $\mathrm{H}^q(\mathscr{F})=0$. If $q=0$, then there is an isomorphism $\alpha_\mathscr{F}:\mathrm{H}^0(\mathscr{F})\to\mathscr{F}(X)$.

  • If $\mathscr{F}$ is flasque or fine, then $\mathrm{H}^q(\mathscr{F})=0$ for $q>0$.If $\mathscr{F}$ is flasque or fine, then $\mathrm{H}^q(\mathscr{F})=0$ for $q>0$.

  • If $0\to\mathscr{F}\to\mathscr{G}\to\mathscr{H}\to0$ is a short exact sequence of sheaves, then there is a long exact sequence: $$\cdots\to\mathrm{H}^q(\mathscr{F})\to\mathrm{H}^q(\mathscr{G})\to\mathrm{H}^q(\mathscr{H})\to\mathrm{H}^{q+1}(\mathscr{F})\to\cdots$$

My question is as follows: is ordinary sheaf cohomology $\mathrm{H}^q(X,\mathscr{F})$ the only sheafy cohomology theory (removing the flasque sheaf requirement)? If not, are there any other examples of a sheafy cohomology theory?

Let $R$ be a commutative ring and $X$ a topological space. Define a sheafy cohomology theory (see here) to be a collection of functors $\mathrm{H}^q:\mathrm{Sh}(X;R\mathrm{Mod})\to R\mathrm{Mod}$ such that the following conditions are satisfied:

  • If $q<0$, then $\mathrm{H}^q(\mathscr{F})=0$. If $q=0$, then there is an isomorphism $\alpha_\mathscr{F}:\mathrm{H}^0(\mathscr{F})\to\mathscr{F}(X)$.

  • If $\mathscr{F}$ is flasque or fine, then $\mathrm{H}^q(\mathscr{F})=0$ for $q>0$.

  • If $0\to\mathscr{F}\to\mathscr{G}\to\mathscr{H}\to0$ is a short exact sequence of sheaves, then there is a long exact sequence: $$\cdots\to\mathrm{H}^q(\mathscr{F})\to\mathrm{H}^q(\mathscr{G})\to\mathrm{H}^q(\mathscr{H})\to\mathrm{H}^{q+1}(\mathscr{F})\to\cdots$$

My question is as follows: is ordinary sheaf cohomology $\mathrm{H}^q(X,\mathscr{F})$ the only sheafy cohomology theory? If not, are there any other examples of a sheafy cohomology theory?

Let $R$ be a commutative ring and $X$ a topological space. Define a sheafy cohomology theory (see here) to be a collection of functors $\mathrm{H}^q:\mathrm{Sh}(X;R\mathrm{Mod})\to R\mathrm{Mod}$ such that the following conditions are satisfied:

  • If $q<0$, then $\mathrm{H}^q(\mathscr{F})=0$. If $q=0$, then there is an isomorphism $\alpha_\mathscr{F}:\mathrm{H}^0(\mathscr{F})\to\mathscr{F}(X)$.

  • If $\mathscr{F}$ is flasque or fine, then $\mathrm{H}^q(\mathscr{F})=0$ for $q>0$.

  • If $0\to\mathscr{F}\to\mathscr{G}\to\mathscr{H}\to0$ is a short exact sequence of sheaves, then there is a long exact sequence: $$\cdots\to\mathrm{H}^q(\mathscr{F})\to\mathrm{H}^q(\mathscr{G})\to\mathrm{H}^q(\mathscr{H})\to\mathrm{H}^{q+1}(\mathscr{F})\to\cdots$$

My question is as follows: is ordinary sheaf cohomology $\mathrm{H}^q(X,\mathscr{F})$ the only sheafy cohomology theory (removing the flasque sheaf requirement)? If not, are there any other examples of a sheafy cohomology theory?

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user62675
user62675

Axioms for sheaf cohomology

Let $R$ be a commutative ring and $X$ a topological space. Define a sheafy cohomology theory (see here) to be a collection of functors $\mathrm{H}^q:\mathrm{Sh}(X;R\mathrm{Mod})\to R\mathrm{Mod}$ such that the following conditions are satisfied:

  • If $q<0$, then $\mathrm{H}^q(\mathscr{F})=0$. If $q=0$, then there is an isomorphism $\alpha_\mathscr{F}:\mathrm{H}^0(\mathscr{F})\to\mathscr{F}(X)$.

  • If $\mathscr{F}$ is flasque or fine, then $\mathrm{H}^q(\mathscr{F})=0$ for $q>0$.

  • If $0\to\mathscr{F}\to\mathscr{G}\to\mathscr{H}\to0$ is a short exact sequence of sheaves, then there is a long exact sequence: $$\cdots\to\mathrm{H}^q(\mathscr{F})\to\mathrm{H}^q(\mathscr{G})\to\mathrm{H}^q(\mathscr{H})\to\mathrm{H}^{q+1}(\mathscr{F})\to\cdots$$

My question is as follows: is ordinary sheaf cohomology $\mathrm{H}^q(X,\mathscr{F})$ the only sheafy cohomology theory? If not, are there any other examples of a sheafy cohomology theory?