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From the Obsidian Second Brain

Follow the connections.

146 public records, 14 topic maps, and six reading routes. Select an area, find a paper, or follow a documented reference. The topic hubs follow the layout of the vault’s Research Map.

PaperLarge circles: topics · lines: topic membership40 records shown
6Algebra and algebraicgeometry22Banach spaces andBanach lattices9Combinatorics and Ramseytheory9Geometric group theory7Groupoids and Cartanpairs46Homological algebra andderived limits1Ideals and convergence7Lattices and orderedalgebra10Measure and ergodictheory8Model theory anddefinability32Operator algebras16Ordered groups40Polish groups anddescriptive complexity33Topological dynamics andamenabilityThe noncommutative weak extension principle under OCAOrder, norming faces, and symmetries of Tursi's Banach latticeThe small index property for the random posetIsomorphism is strictly Borel reducible to quasi-isometry for finitely generated groupsIsomorphism and bi-embeddability of countable Archimedean ordered groupsBounded coordinate lengths and normal closures in Polish productsSpectral ranks and dynamical lengths of preliminary C*-algebrasSupport rings, Polishability, and the SIN propertyInjective and projective objects in categories of topological torsion Polish abelian groupsBounded geometry in Polish groups: locally compact models, amenability, and simple examplesExact boundedness exponents for permutation and automorphism groupsQuantitative boundedness in homeomorphism groupsFixed words, function groups, and exact odd boundedness exponentsFixed-exponent boundedness and cocompact permanence in Polish groupsSolution to Dixmier's Problem about spectra of C*-algebrasSharp Borel representation dimensions for compact arithmetic actionsArithmetic denominators and ordinary compact orbit comparisonsLocal swaps, Polish group topologies, and automorphisms of L¹ full groupsPolish topologies and coset obstructions for measurable transformation groupsLocal fields and ordinary affine Borel comparisonsPolishability from orbit reducibility of coset equivalence relationsInjective objects in the category of Polish abelian groupsProperty (OB) and the Coarse Geometry of Polish Groups --- Fixed Exponents, Permanence, and ApplicationsConvergence relations of pro-Lie Polish groupsRank-two and two-prime rigidity in Borel classification problemsNonabelian extensions of Solecki's coset dichotomyLoCoLoCo Polish subgroups and the non-Archimedean complexity spectrumJoint Euler-cocycle estimates and simplicial volume of surface bundlesMalliavin--Malliavin and whirly amenability: Borel observations, translation displacement, and total variationExactness of strong unitary groups associated with discrete groups with the approximation propertyBorel invariant means on countable inverse limits of amenable groupsBorel-definable homological algebra for locally compact Polish modules over rings of integersHomological algebra of pro-Lie Polish modules over rings of integersDescriptive classification of classes of C*-algebras and locally compact groupsThe franks of Moore groupsCorrigendum to "Complexity Classes of Polishable Subgroups"On the Borel complexity of operator imagesOn Niemiec's Universal Valued GroupsDerived limits and phantom filtrations for towers of locally compact Polish abelian groupsThe Descriptive Complexity of Nonabelian $\boldsymbol{\lim^1}$

Positions aid navigation; distance does not measure mathematical similarity. References were captured in the vault and are not proof dependencies.

Six routes through the archive

Read across the boundaries.

These are proposed syntheses from the Second Brain, not new results or established proof dependencies. Only papers already present in this public catalog are linked here.

Proposed reading route

Classification beyond fixed invariants

The fixed-invariant manuscript constructs E₀ classification inside families sharing a full Elliott invariant and comparison radius. The trace-dynamics manuscript codes homeomorphism conjugacy into cocycle conjugacy. Both illustrate the role of descriptive complexity after familiar invariants have been fixed.

Keep separate: E₀ bireducibility, universality for Polish group orbit relations, and failure of classification by countable structures are distinct claims. Fixed first-order theory is an additional assertion in the fixed-invariant family, not a consequence of every Borel coding.

2 additional source notes are outside this catalog edition.

Proposed reading route

Dynamical lengths, spectra, and Cartan pairs

The Cartan-pair draft organizes five length coordinates and their invariance properties. The AF-spectrum draft classifies realizable values and explicitly imports an exclusion theorem from a companion. The primitive-ideal and Fell–Pedersen drafts examine how topological and rank data constrain dynamical lengths.

Keep separate: Track absolute algebra invariants, pair invariants, and groupoid invariants separately. The Cartan abstract identifies a low-complexity case in which the twist can affect one coordinate. The earlier Fell/Pedersen rank paper and its dynamical-length companion have separate identities.

2 additional source notes are outside this catalog edition.

Proposed reading route

Ideals, bases, and reconstruction

The critical-ideal manuscript constructs ideals from errors of basis expansions. The convergence manuscript builds Polishable groups from ideals. The reconstruction paper asks what those groups remember about the starting ideal.

Keep separate: Keep equality, isomorphism of ideals, Rudin–Blass comparisons, and Katětov equivalence separate. The critical-ideal result up to isomorphism and the reconstruction result up to Katětov equivalence answer different questions.

2 additional source notes are outside this catalog edition.

Proposed reading route

Positive identities and order extension

These drafts connect positivity constraints with algebraic and algorithmic structure. The positive-normal-identity draft states undecidability in fixed free groups; the universal-subgroup draft transfers bi-order extension problems; the common-multiple draft gives a positive theorem for abelian-by-nilpotent groups.

Keep separate: The common-multiple theorem concerns nilpotent coefficient groups and nonnegative coefficients. It does not supply an algorithm for the free-group problems. Arithmetic interpretation in free lattice-ordered groups is another kind of definability statement.

2 additional source notes are outside this catalog edition.

Proposed reading route

Symmetry, concentration, and boundedness

The library contains concentration and Lévy stabilizer constructions, formulas for universal minimal flows, automatic continuity for a homogeneous poset, and a separate collection on quantitative boundedness of Polish groups. Their shared objects are symmetry groups with additional topological or metric structure.

Keep separate: Distinguish amenability, extreme amenability, whirly amenability, concentration, and Property (OB). Record the topology and whether an assertion concerns arbitrary abstract homomorphisms or only continuous actions.

Proposed reading route

Uniform lifting and perturbation

The completely positive correction draft controls a correction using a uniform defect. The recursive-subhomogeneous stability draft states a control function independent of pullback length and matrix sizes. The Banach-lattice semiprojectivity draft formulates almost contractive lifting through ideal quotients.

Keep separate: These are comparisons of proof organization across different categories. A Banach-lattice homomorphism and a C*-algebra *-homomorphism satisfy different requirements. Separate fixed parameters, uniform constants, and dependencies on domain or target.

1 additional source note is outside this catalog edition.

Source: uploaded Second Brain, checked 5 November 2026. 149 vault notes match the 146 public records; version duplicates are consolidated. Personal notes, local paths, and private manuscript links are not included.