De Finetti theorem on the infinite non-commutative torus

The set of spreadable states on an infinite non-commutative torus <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="double-struck upper A Subscript alpha Superscript double-struck upper Z"> <mml:semantics> <mml:msubsup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="double-struck">A</mml:mi> </mml:mrow> <mml:mi> α </mml:mi> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="double-struck">Z</mml:mi> </mml:mrow> </mml:msubsup> <mml:annotation encoding="application/x-tex">\mathbb {A}_\alpha ^\mathbb {Z}</mml:annotation> </mml:semantics> </mml:math> </inline-formula> is determined for all values of the deformation parameter <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="alpha"> <mml:semantics> <mml:mi> α </mml:mi> <mml:annotation encoding="application/x-tex">\alpha</mml:annotation> </mml:semantics> </mml:math> </inline-formula> . If <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartFraction alpha Over 2 pi EndFraction"> <mml:semantics> <mml:mfrac> <mml:mi> α </mml:mi> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi> π </mml:mi> </mml:mrow> </mml:mfrac> <mml:annotation encoding="application/x-tex">\frac {\alpha }{2\pi }</mml:annotation> </mml:semantics> </mml:math> </inline-formula> is irrational, the canonical trace is the only spreadable state. If <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartFraction alpha Over 2 pi EndFraction"> <mml:semantics> <mml:mfrac> <mml:mi> α </mml:mi> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi> π </mml:mi> </mml:mrow> </mml:mfrac> <mml:annotation encoding="application/x-tex">\frac {\alpha }{2\pi }</mml:annotation> </mml:semantics> </mml:math> </inline-formula> is rational, the set of all spreadable states is a Bauer simplex. Moreover, its boundary is the set of all infinite products of a single state on <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper C left-parenthesis double-struck upper T right-parenthesis"> <mml:semantics> <mml:mrow> <mml:mi>C</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="double-struck">T</mml:mi> </mml:mrow> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:annotation encoding="application/x-tex">C(\mathbb {T})</mml:annotation> </mml:semantics> </mml:math> </inline-formula> , which is invariant under all rotations by <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="n 0"> <mml:semantics> <mml:msub> <mml:mi>n</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:annotation encoding="application/x-tex">n_0</mml:annotation> </mml:semantics> </mml:math> </inline-formula> -th roots of unity, where <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="n 0 equals p 1 Superscript left-brace StartFraction m 1 Over 2 EndFraction right-brace Baseline ellipsis p Subscript r Superscript left-brace StartFraction m Super Subscript r Superscript Over 2 EndFraction right-brace"> <mml:semantics> <mml:mrow> <mml:msub> <mml:mi>n</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mi>p</mml:mi> <mml:mn>1</mml:mn> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo fence="false" stretchy="false">{</mml:mo> <mml:mfrac> <mml:msub> <mml:mi>m</mml:mi> <mml:mn>1</mml:mn> </mml:msub> <mml:mn>2</mml:mn> </mml:mfrac> <mml:mo fence="false" stretchy="false">}</mml:mo> </mml:mrow> </mml:msubsup> <mml:mo> … </mml:mo> <mml:msubsup> <mml:mi>p</mml:mi> <mml:mi>r</mml:mi> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo fence="false" stretchy="false">{</mml:mo> <mml:mfrac> <mml:msub> <mml:mi>m</mml:mi> <mml:mi>r</mml:mi> </mml:msub> <mml:mn>2</mml:mn> </mml:mfrac> <mml:mo fence="false" stretchy="false">}</mml:mo> </mml:mrow> </mml:msubsup> </mml:mrow> <mml:annotation encoding="application/x-tex">n_0=p_1^{\{\frac {m_1}{2}\}}\dots p_r^{\{\frac {m_r}{2}\}}</mml:annotation> </mml:semantics> </mml:math> </inline-formula> , with <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="left-brace StartFraction n Over 2 EndFraction right-brace"> <mml:semantics> <mml:mrow> <mml:mo fence="false" stretchy="false">{</mml:mo> <mml:mfrac> <mml:mi>n</mml:mi> <mml:mn>2</mml:mn> </mml:mfrac> <mml:mo fence="false" stretchy="false">}</mml:mo> </mml:mrow> <mml:annotation encoding="application/x-tex">\{\frac {n}{2}\}</mml:annotation> </mml:semantics> </mml:math> </inline-formula> being <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartFraction n Over 2 EndFraction"> <mml:semantics> <mml:mfrac> <mml:mi>n</mml:mi> <mml:mn>2</mml:mn> </mml:mfrac> <mml:annotation encoding="application/x-tex">\frac {n}{2}</mml:annotation> </mml:semantics> </mml:math> </inline-formula> for <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="n">

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Journal
Proceedings of the American Mathematical Society
Published
2025-12-09
DOI
https://doi.org/10.1090/proc/17490
Primary Topic
Advanced Operator Algebra Research
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article
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article

De Finetti theorem on the infinite non-commutative torus

Simone Del Vecchio, Stefano Rossi, Maria Elena Griseta, Vitonofrio Crismale
Proceedings of the American Mathematical Society
Advanced Operator Algebra Research
article

De Finetti theorem on the infinite non-commutative torus

Simone Del Vecchio, Stefano Rossi, Maria Elena Griseta, Vitonofrio Crismale
article en

Abstract

The set of spreadable states on an infinite non-commutative torus <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="double-struck upper A Subscript alpha Superscript double-struck upper Z"> <mml:semantics> <mml:msubsup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="double-struck">A</mml:mi> </mml:mrow> <mml:mi> α </mml:mi> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="double-struck">Z</mml:mi> </mml:mrow> </mml:msubsup> <mml:annotation encoding="application/x-tex">\mathbb {A}_\alpha ^\mathbb {Z}</mml:annotation> </mml:semantics> </mml:math> </inline-formula> is determined for all values of the deformation parameter <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="alpha"> <mml:semantics> <mml:mi> α </mml:mi> <mml:annotation encoding="application/x-tex">\alpha</mml:annotation> </mml:semantics> </mml:math> </inline-formula> . If <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartFraction alpha Over 2 pi EndFraction"> <mml:semantics> <mml:mfrac> <mml:mi> α </mml:mi> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi> π </mml:mi> </mml:mrow> </mml:mfrac> <mml:annotation encoding="application/x-tex">\frac {\alpha }{2\pi }</mml:annotation> </mml:semantics> </mml:math> </inline-formula> is irrational, the canonical trace is the only spreadable state. If <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartFraction alpha Over 2 pi EndFraction"> <mml:semantics> <mml:mfrac> <mml:mi> α </mml:mi> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi> π </mml:mi> </mml:mrow> </mml:mfrac> <mml:annotation encoding="application/x-tex">\frac {\alpha }{2\pi }</mml:annotation> </mml:semantics> </mml:math> </inline-formula> is rational, the set of all spreadable states is a Bauer simplex. Moreover, its boundary is the set of all infinite products of a single state on <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper C left-parenthesis double-struck upper T right-parenthesis"> <mml:semantics> <mml:mrow> <mml:mi>C</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="double-struck">T</mml:mi> </mml:mrow> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:annotation encoding="application/x-tex">C(\mathbb {T})</mml:annotation> </mml:semantics> </mml:math> </inline-formula> , which is invariant under all rotations by <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="n 0"> <mml:semantics> <mml:msub> <mml:mi>n</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:annotation encoding="application/x-tex">n_0</mml:annotation> </mml:semantics> </mml:math> </inline-formula> -th roots of unity, where <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="n 0 equals p 1 Superscript left-brace StartFraction m 1 Over 2 EndFraction right-brace Baseline ellipsis p Subscript r Superscript left-brace StartFraction m Super Subscript r Superscript Over 2 EndFraction right-brace"> <mml:semantics> <mml:mrow> <mml:msub> <mml:mi>n</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mi>p</mml:mi> <mml:mn>1</mml:mn> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo fence="false" stretchy="false">{</mml:mo> <mml:mfrac> <mml:msub> <mml:mi>m</mml:mi> <mml:mn>1</mml:mn> </mml:msub> <mml:mn>2</mml:mn> </mml:mfrac> <mml:mo fence="false" stretchy="false">}</mml:mo> </mml:mrow> </mml:msubsup> <mml:mo> … </mml:mo> <mml:msubsup> <mml:mi>p</mml:mi> <mml:mi>r</mml:mi> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo fence="false" stretchy="false">{</mml:mo> <mml:mfrac> <mml:msub> <mml:mi>m</mml:mi> <mml:mi>r</mml:mi> </mml:msub> <mml:mn>2</mml:mn> </mml:mfrac> <mml:mo fence="false" stretchy="false">}</mml:mo> </mml:mrow> </mml:msubsup> </mml:mrow> <mml:annotation encoding="application/x-tex">n_0=p_1^{\{\frac {m_1}{2}\}}\dots p_r^{\{\frac {m_r}{2}\}}</mml:annotation> </mml:semantics> </mml:math> </inline-formula> , with <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="left-brace StartFraction n Over 2 EndFraction right-brace"> <mml:semantics> <mml:mrow> <mml:mo fence="false" stretchy="false">{</mml:mo> <mml:mfrac> <mml:mi>n</mml:mi> <mml:mn>2</mml:mn> </mml:mfrac> <mml:mo fence="false" stretchy="false">}</mml:mo> </mml:mrow> <mml:annotation encoding="application/x-tex">\{\frac {n}{2}\}</mml:annotation> </mml:semantics> </mml:math> </inline-formula> being <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartFraction n Over 2 EndFraction"> <mml:semantics> <mml:mfrac> <mml:mi>n</mml:mi> <mml:mn>2</mml:mn> </mml:mfrac> <mml:annotation encoding="application/x-tex">\frac {n}{2}</mml:annotation> </mml:semantics> </mml:math> </inline-formula> for <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="n">

Proceedings of the American Mathematical SocietyVol. 154(2)
University of Bari Aldo Moro (IT)
Openalex Percentile: Top 56%
Advanced Operator Algebra Research
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