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tamnd's digital brain — notes, problems, research
43815 notes
Independence results in set theory, including the axiom of choice and the continuum hypothesis, and the methods used to establish independence.
The axiom of choice, choice functions, indexed families, and first consequences in axiomatic set theory.
Relative consistency, inner models, constructibility, and the role of consistency results in axiomatic set theory.
Equivalent forms of the axiom of choice, including Zorn's lemma, the well ordering theorem, maximal principles, and right inverses of surjections.
The constructible universe, definable subsets, the hierarchy L_alpha, and the axiom of constructibility.
Axiom of Choice, equivalent formulations, constructible universe, consistency results, and independence phenomena.
The axioms of Zermelo Fraenkel set theory, the role of choice, and the use of axioms as a foundation for mathematics.
Cardinal addition, multiplication, exponentiation, finite and infinite cardinal arithmetic, and basic comparison laws.
Basic set theoretic language, including sets, membership, subsets, operations, relations, equivalence relations, order relations, and functions.
Well ordered sets, order isomorphisms, ordinals, successor ordinals, limit ordinals, and transfinite induction.
Cardinality, finite and infinite sets, countable sets, uncountable sets, and Cantor diagonal arguments.
Basic set theoretic notions including sets, relations, functions, cardinality, ordinals, well ordering, cardinal arithmetic, and the ZF and ZFC axioms.
Definition of definable sets and functions in first order structures, with parameters, examples, closure properties, and proofs.
Saturated models, realization of types, and their role in controlling definability and extensions.
Detailed introduction to stability theory, counting types, order property, definability of types, and structural consequences.
Detailed overview of classification theory, dividing lines such as stability, simplicity, and NIP, and the structural analysis of first order theories.
Definition of complete and partial types, realization of types in structures, examples, consistency, and basic properties.
Definable sets, definable functions, types, realizations, saturated models, stability theory, and classification programs.
Expressive limitations of first order logic, including inexpressibility of finiteness and categoricity issues.
Construction and properties of nonstandard models using compactness and Lowenheim Skolem.
Applications of compactness and Lowenheim Skolem to algebraic structures and existence results.
Downward and upward Lowenheim Skolem theorems and their consequences for model sizes in first order logic.
Detailed development of the compactness theorem, its proof via completeness, and fundamental applications in model theory.
Compactness, completeness, Lowenheim-Skolem theorems, nonstandard models, and limitations of first order logic.
Examples of first order structures from algebra, order theory, graph theory, and geometry.
Isomorphisms of first order structures, structural invariants, and properties preserved by isomorphism.
Elementary equivalence, theories of structures, and preservation of first order sentences.
Substructures, generated substructures, homomorphisms, embeddings, and preservation of atomic formulas.
Formal languages, signatures, and symbols used to describe structures in first order logic.
Basic model theoretic notions including languages, signatures, substructures, embeddings, elementary equivalence, isomorphism, and examples.
The cut rule, its elimination, and consequences for consistency and normalization.
Transformations of proofs, normalization, and structural properties of derivations.
Introduction to natural deduction, inference rules, and structured proofs for propositional logic.
Formal systems for deriving logical conclusions including natural deduction, sequent calculus, Hilbert systems, and proof transformations.
Sequents, structural rules, and introduction rules for logical connectives in the sequent calculus.
Hilbert style proof systems, axioms, and derivations using a minimal set of inference rules.
Validity, semantic entailment, satisfiability, countermodels, and logical consequence in first order logic.
Satisfaction, truth in a structure, models of sentences, and theories in first order logic.
Structures, domains, and interpretations of symbols in first order logic.
Syntax of first order logic including terms, predicate symbols, and the formation of formulas.
Universal and existential quantifiers, scope, free variables, bound variables, and variable capture.
Soundness, completeness, and the relationship between semantic validity and formal provability.
Extension of propositional logic with terms, predicates, quantifiers, structures, satisfaction, models, validity, and entailment.
Conjunctive normal form, disjunctive normal form, and systematic conversion of propositional formulas.
Foundations of propositional logic including syntax, semantics, equivalence, normal forms, and proof systems.
Definition of propositional variables, logical connectives, and formation rules for well formed formulas.
Logical equivalence, truth preserving transformations, and basic laws for rewriting propositional formulas.
Truth values, valuations, and evaluation of propositional formulas using truth tables.
Overview of mathematical logic, its scope, and the structure of the book.
How numbers move from concrete counting to abstract ideas.
Purpose, scope, and approach of this volume on the history and biography of mathematics.
Common mistakes in mathematical writing and how to avoid them.
Early counting through marks, objects, and physical recording systems.
Practical rules for writing mathematics in a clear, consistent, and readable way.
How early humans developed counting, measurement, and basic mathematical thinking before formal notation.
How a mathematical paper or article is organized so that readers can follow the main ideas.
How definitions, theorems, and proofs work together in mathematical writing.
How to write mathematics with enough detail, few distractions, and clear logical structure.
How to make computational results repeatable, checkable, and trustworthy.
When to compute exact results and when to use approximations.
Understanding the difference between manipulating exact mathematical expressions and computing with numerical values.
Overview of how to write mathematical ideas clearly, precisely, and in a useful structure.
Understanding how the cost of an algorithm grows with input size.
How to think step by step and turn mathematical ideas into clear procedures.
Overview of algorithmic thinking, computational methods, complexity, approximation, and verification in mathematics.
Using failures, boundary conditions, and extreme cases to test, refine, and understand mathematical statements.
Using examples, informal rules, and exploratory computation to guide mathematical problem solving.
Using structural similarity between problems to move ideas, methods, and proofs across domains.
Expanding or restricting a problem to reveal structure and guide solution.
Overview of general methods used to approach, transform, and solve mathematical problems.
Solving a problem by converting it into a simpler, known, or more structured form.
Using counting, random choice, and finite structure to prove identities and existence statements.
Using base cases and step rules to prove statements about objects built recursively.
Proving existence by giving explicit witnesses, algorithms, or methods of construction.
Overview of the main methods used to prove mathematical statements.
Proving a statement by starting from its assumptions and deriving its conclusion step by step.
Proving a statement by assuming its negation and deriving an impossibility.
Defining objects step by step and proving properties by following the same construction.
How transformations preserve structure and how invariants record what remains unchanged.
Breaking complex objects into simpler parts and building larger structures from controlled combinations.
How mathematics studies small pieces first and then assembles them into statements about the whole.
Understanding how reversing structure reveals parallel theories and results.
Overview of recurring patterns such as duality, symmetry, local-to-global reasoning, decomposition, recursion, and induction.
Understanding the benefits and costs of abstraction, and choosing the right level for mathematical work.
Raising abstraction from objects and operations to maps, composition, and universal properties.
Studying mathematical systems themselves through languages, axioms, models, proofs, and interpretations.
Replacing concrete values with symbols and rules to express general patterns.
Working with explicit examples, calculations, and finite procedures as the base level of mathematical reasoning.
Concrete examples showing structural thinking across algebra, topology, and graph theory.
Overview of how mathematics moves from concrete computation to structural and higher-level reasoning.
How preserved quantities and properties support comparison, classification, and structural reasoning.
How isomorphism formalizes structural sameness and separates equality from equivalence.
Structure-preserving maps, their role in comparison, composition, and transport of mathematical information.
Distinguishing abstract structures from their concrete instances, and using that distinction to reason across examples.
How definitions introduce mathematical objects, fix meaning, and support reusable reasoning.
Viewing notation as a designed interface that exposes structure, supports composition, and enables efficient reasoning.
How formal precision and informal readability work together in mathematical writing.
Overview of structures, mappings, invariants, and classification in mathematics.
How mathematical symbols and notation are chosen, scoped, reused, and designed for precision and readability.
How mathematical writing balances exact statements with readable exposition.