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I'm trying to understand the following construction:

Let $E$ a Banach lattice. Basically we want to construct for each $\nu \in E^*$ (A positive linear functional $\nu:E \rightarrow \mathbb{C})$, a real Banach lattice $F_\nu$.

So in $E$ we consider the (continuous)seminorm $p_\nu(x):= \nu(|x|) \, \, \forall x \in E$ (Why?). Let now $I_\nu := \{x \in E \, : \, p_\nu(x)=0\}$, this is a lattice ideal of $E$ (why?).

It is known (not to me) that the quotient space $E/I_\nu$, obtained in the usual way, is a vector lattice, and $p_\nu$ induces in $E/I_\nu$ a lattice norm $\tilde{p}_\nu(\hat{x}):=p_\nu(x) \,\,(x \in \hat{x}) \quad \forall \hat{x} \in E/I_\nu$. This comes from the fact that the canonical map $x \mapsto \hat{x}$ of $E$ into $E/I_\nu$ is a lattice homomorphism. Now let $F_\nu$ be the completion of vector lattice $E/I_\nu$ with the norm $\tilde{p}_\nu$. Then $F_\nu$ is a real Banach lattice and also a $AL-$ space, cause the norm is additive on the cone of positive elements. By the Kakutani representation theorem, $F_\nu$ as Banach lattice is isomorphic to some $L^1(\mu)$.

Really grateful to anyone giving me some background to understand this. (Even just the first part).

EDIT: As requested, I'm adding more informations to the question, adding the definition of Lattice Ideal:

A subset $S$ of a vector lattice $E$ is called solid if $x \in S$, $|y| \le |x|$ implies $y \in S$. A solid linear subspace of a vector lattice is called ideal. One could verify that a subspace $I$ of a Banach lattice $E$ is an ideal iif $$x \in I \Rightarrow x \in I \quad and \quad 0\le y \le x \in I \Rightarrow y \in I$$

James Arten
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  • Could you define the term "lattice ideal"? Wikipedia says that there are some nonequivalent definitions for this term used by different authors. – user754697 Feb 29 '20 at 12:26
  • I translated the term from German. Basically the original word is "Verbandsideal" where "Verband" is the german word for Lattice. I probably think that it must be intended as a standard ideal in Banach lattice $E$ thought as a Banach space. – James Arten Feb 29 '20 at 12:28
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    I don't think there is a "standard" lattice ideal. Wikipedia provides two definitions, and when I looked back at my honours thesis, I had seemingly a third definition that I don't think was equivalent to either. Does the text not define lattice ideals? – user754697 Feb 29 '20 at 12:31
  • Ok I found it.Just editing the question. Thank you for your interest – James Arten Feb 29 '20 at 13:26

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