I have been intrigued for a long time by the formal similarity of results from different areas of mathematics. Here are some examples.

**Set theory** Given a map $f:X\to Y$ and subsets $X' \subset X, Y'\subset Y$, we have $$f(f^{-1}(Y')\cap X')=Y'\cap f(X')$$

**Ringed spaces** Given a morphism of ringed spaces $f:X\to Y$, an $\mathcal O_X$-module $\mathcal F$ and a locally free module of finite type $\mathcal L$, we have
$$f_\ast(f^\ast{\mathcal L}\otimes_{\mathcal O_X} \mathcal F)=\mathcal L \otimes_{\mathcal O_Y} f_{\ast}\mathcal F$$

**Topology** Consider a proper continuous map of connected oriented manifolds $f:X\to Y$, then for $x\in H^\ast _c(X,\mathbb Z)$ and $y\in H^\ast _c(Y ,\mathbb Z)$ we have (Dold, p.314)

$$ f_!(f^\ast y . x)=y. f_!(x)$$

**Chow rings** Given a proper map $f:X\to Y$ between nonsingular algebraic varieties and cycle classes $a\in CH^\ast(X), \beta \in CH^\ast(Y)$ we have

$$ f_\ast(f^\ast \beta . \alpha)=\beta. f_\ast(\alpha) $$

**K-theory** Given a proper morphism of finite Tor dimension $f:X\to Y$ between schemes (and assuming $X$ and $Y$ have suitable ample line bundles), Quillen proved in his fundamental article on higher K-theory (Springer LNM 341, page 126) that for $x\in K_0(X)$ and $y\in K'_0(Y)$

$$f_\ast(f^\ast y . x)=y. f_\ast (x) $$

**Derived categories** Given a ring morphism $f:R\to S$, a bounded above complex $A$ of $R$-modules and a complex $B$ of $S$-modules we obtain in $\mathbb D(R)$ (Weibel, p.404)
$$ f_\ast(\mathbb L f^\ast( A) \otimes_S^{\mathbb L} B)=A \otimes_R^{\mathbb L} (f_\ast B)$$

**The question** Of course I'm well aware that there are strong links between say K-theory and Chow rings and that the examples of projection formulas are not independent. What I would like to know is whether there is some general context of which these examples could be said to be illustrations, even if not particular cases in the strict sense. An analogy would be that Grothendieck's Galois theory explains the similarity between the traditional Galois theory of fields and the theory of covering spaces although it is not true that the general theory of topologiclal coverings is a special case of Grothendieck's results.

**Edit** After seeing several comments and an answer, I'd like to clarify my question. It is not principally to find a general formulation of which all those results would be a special case (although that certainly would be nice). But rather to know if there is a powerful, presumably tough, result or theory which would imply a good deal of the examples mentioned above. Perhaps a bit like K-theory used for Riemann-Roch , Bott periodicity, classification of vector bundles...

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