ScalingStacks

Proposition 3.9 . [03BS]

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Proposition 3.9.

Let LL be a line bundle on a paracompact strictly KK-analytic space VV. Let x∈Vx\in V and let ∥⁣∥{\|\hskip 4.30554pt\|} be a piecewise ℚ{\mathbb{Q}}-linear metric on LL.

  • (a)

    The set of points in VV where ∥⁣∥{\|\hskip 4.30554pt\|} is semipositive is open in VV.

  • (b)

    The tensor product of two piecewise ℚ{\mathbb{Q}}-linear metrics which are semipositive in xx is again semipositive in xx.

  • (c)

    Let f:V′→Vf:V^{\prime}\to V be a morphism of paracompact strictly KK-analytic spaces. If ∥⁣∥{\|\hskip 4.30554pt\|} is semipositive in xx, then f∗∥∥f^{*}{\|\hskip 4.30554pt\|} is semipositive in any point of f−1​(x)f^{-1}(x).

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