Products of mixed Hodge structures #
The product of two mixed Hodge structures has componentwise weight and Hodge filtrations. The product of their Deligne bigradings witnesses purity on the weight-graded pieces. The two inclusions and projections are mixed Hodge morphisms; their rational maps are the usual inclusions and projections of vector spaces. Their binary bicone is a bilimit, giving binary biproducts and, together with the zero object, finite products in the category of mixed Hodge structures.
References #
Deligne, Théorie de Hodge II, §2.3; Peters–Steenbrink, Mixed Hodge Structures, Ch. 3.
The product mixed Hodge structure, with componentwise weight and Hodge filtrations.
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The weight filtration of the product is the product of the weight filtrations.
The Hodge filtration of the product is the product of the Hodge filtrations.
The first projection from the product mixed Hodge structure.
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The second projection from the product mixed Hodge structure.
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The first inclusion into the product mixed Hodge structure.
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The second inclusion into the product mixed Hodge structure.
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The rational map of the first projection is the usual first projection of vector spaces.
The rational map of the second projection is the usual second projection of vector spaces.
The rational map of the first inclusion is the usual first inclusion of vector spaces.
The rational map of the second inclusion is the usual second inclusion of vector spaces.
The complex map of the first projection is the usual first projection of vector spaces.
The complex map of the second projection is the usual second projection of vector spaces.
The complex map of the first inclusion is the usual first inclusion of vector spaces.
The complex map of the second inclusion is the usual second inclusion of vector spaces.