A geometric model of synthetic filtrations via context-dependent time

Fuente: arXiv
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Main Author: Adachi, Takanori
Format: Preprint
Published: 2025
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author Adachi, Takanori
author_facet Adachi, Takanori
contents Classical filtrations in probability theory formalize the accumulation of information along a linear time axis: the past is unique and the present evolves into an uncertain future. In reality, however, this linearity may itself be an illusion - an artifact of human perception that collapses multiple possible histories into a single apparent path. In this paper, we propose a geometric and homological model of synthetic filtrations, where the present arises as a synthesis of many potential pasts. To achieve this, we introduce a new category $Σ$, extending the simplex category $Δ$ so that each moment of time carries contextual structure. Synthetic filtrations are realized as contravariant functors $Σ^{op} \to Prob$, where $Prob$ is the category of probability spaces with null-preserving maps. We then develop a homological analysis of $Σ$-filtrations, constructing chain complexes whose boundaries are given by conditional expectations. Their homology groups measure informational "holes" - probabilistic obstructions arising from the incompatibility of contextual expectations. As a concrete realization, we define Dirichlet filtrations, in which measures on simplices arise from Dirichlet distributions, reflecting both parameter and contextual uncertainty. Bayesian updating is then interpreted as a categorical transformation of a Dirichlet functor, revealing learning as a reconstruction of coherence across contexts. This framework suggests that what appears as a linear temporal order is merely a projection of a higher contextual geometry. It unifies categorical probability, homological algebra, and Bayesian reasoning, offering a new language for uncertainty in mathematics, finance, and cognition.
format Preprint
id arxiv_https___arxiv_org_abs_2509_12919
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A geometric model of synthetic filtrations via context-dependent time
Adachi, Takanori
Probability
60A99, 16B50, 60G20, 91B82
Classical filtrations in probability theory formalize the accumulation of information along a linear time axis: the past is unique and the present evolves into an uncertain future. In reality, however, this linearity may itself be an illusion - an artifact of human perception that collapses multiple possible histories into a single apparent path. In this paper, we propose a geometric and homological model of synthetic filtrations, where the present arises as a synthesis of many potential pasts. To achieve this, we introduce a new category $Σ$, extending the simplex category $Δ$ so that each moment of time carries contextual structure. Synthetic filtrations are realized as contravariant functors $Σ^{op} \to Prob$, where $Prob$ is the category of probability spaces with null-preserving maps. We then develop a homological analysis of $Σ$-filtrations, constructing chain complexes whose boundaries are given by conditional expectations. Their homology groups measure informational "holes" - probabilistic obstructions arising from the incompatibility of contextual expectations. As a concrete realization, we define Dirichlet filtrations, in which measures on simplices arise from Dirichlet distributions, reflecting both parameter and contextual uncertainty. Bayesian updating is then interpreted as a categorical transformation of a Dirichlet functor, revealing learning as a reconstruction of coherence across contexts. This framework suggests that what appears as a linear temporal order is merely a projection of a higher contextual geometry. It unifies categorical probability, homological algebra, and Bayesian reasoning, offering a new language for uncertainty in mathematics, finance, and cognition.
title A geometric model of synthetic filtrations via context-dependent time
topic Probability
60A99, 16B50, 60G20, 91B82
url https://arxiv.org/abs/2509.12919