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PhyslibAlpha.ProbabilisticTheory.JordanOrderUnit.JBW.Basic

JBW-algebras

i. Overview

A JBW-algebra is a monotone-complete JB-algebra whose normal states separate points.

ii. Key results

  • `JBWAlgebra` : JBW-algebras.
  • `JBWAlgebra.eq_of_forall_normal_state_eq` : normal states separate points.

3 declarations

theorem

Normal states preserve suprema of bounded monotone sequences in JBW-algebras

Let EE be a JBW-algebra and ω\omega be a normal state on EE. If (xn)n∈N(x_n)_{n \in \mathbb{N}} is a monotone increasing sequence in EE that is bounded above, then there exists an element a∈Ea \in E such that aa is the least upper bound of the range of the sequence (a=sup⁡nxn)(a = \sup_{n} x_n), and ω(a)\omega(a) is the least upper bound of the set of values {ω(xn)∣n∈N}\{\omega(x_n) \mid n \in \mathbb{N}\} (i.e., ω(a)=sup⁡nω(xn)\omega(a) = \sup_{n} \omega(x_n)).

theorem

Normal states preserve the supremum of bounded monotone sequences in JBW-algebras

Let EE be a JBW-algebra and ω\omega be a normal state on EE. If (xn)n∈N(x_n)_{n \in \mathbb{N}} is a monotone increasing sequence in EE that is bounded above, then the value of the state applied to the supremum of the sequence, ω(sup⁡n∈Nxn)\omega(\sup_{n \in \mathbb{N}} x_n), is the least upper bound of the set of values {ω(xn)∣n∈N}\{\omega(x_n) \mid n \in \mathbb{N}\}.

theorem

Existence of a normal finite weight ww such that w(x)≠0w(x) \neq 0 for x>0x > 0

Let EE be a JBW-algebra. For any non-zero element xx in the positive cone of EE (that is, x≥0x \ge 0 and x≠0x \neq 0), there exists a normal finite weight ww on EE such that w(x)≠0w(x) \neq 0. Here, a weight is called finite if it maps all positive elements to finite values, and normal if it preserves the least upper bounds of monotone functions.