Reconstruction of finite Quasi-Probability and Probability from Principles: The Role of Syntactic Locality
Jacopo Surace
TL;DR
This work develops a principled reconstruction of quasi-probability theory from structural principles applied to finite Boolean algebras of statements. It introduces a Universal Valuation $V$ and the concept of Syntactic Locality to derive an additive representation of $V$ as a pre-probability $R=oldsymbol{\phi}\circ V$, unique up to additive regraduation. When a canonical reparametrisation is possible, quasi-probabilities emerge; probabilities arise as the subset stable under relativisation, and a coherent generalized Bayes' theorem applies to both pre-probabilities and quasi-probabilities. The framework clarifies conditioning in quasi-probability theory, resolves well-known conditioning issues, and reveals a rational versus irrational structure via semantic frames; holomorphic regularity collapses the gauge freedom to a global scalar, recovering standard probability theory within a broader algebraic setting. The results have foundational significance for quantum theory and probabilistic reasoning, offering a unifying account of additive representations, conditioning, and the emergence of classical probabilities from a more general quasi-probabilistic formalism.
Abstract
Quasi-probabilities appear across diverse areas of physics, but their conceptual foundations remain unclear: they are often treated merely as computational tools, and operations like conditioning and Bayes' theorem become ambiguous. We address both issues by developing a principled framework that derives quasi-probabilities and their conditional calculus from structural consistency requirements on how statements are valued across different universes of discourse, understood as finite Boolean algebras of statements.We begin with a universal valuation that assigns definite (possibly complex) values to all statements. The central concept is Syntactic Locality: every universe can be embedded within a larger ambient one, and the universal valuation must behave coherently under such embeddings and restrictions. From a set of structural principles, we prove a representation theorem showing that every admissible valuation can be re-expressed as a finitely additive measure on mutually exclusive statements, mirroring the usual probability sum rule. We call such additive representatives pre-probabilities. This representation is unique up to an additive regraduation freedom. When this freedom can be fixed canonically, pre-probabilities reduce to finite quasi-probabilities, thereby elevating quasi-probability theory from a computational device to a uniquely determined additive representation of universal valuations. Classical finite probabilities arise as the subclass of quasi-probabilities stable under relativisation, i.e., closed under restriction to sub-universes. Finally, the same framework enables us to define a coherent theory of conditionals, yielding a well-defined generalized Bayes' theorem applicable to both pre-probabilities and quasi-probabilities. We conclude by discussing additional regularity conditions, including the role of rational versus irrational probabilities in this setting.
