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arXiv2026

Categorical algebra of conditional probability

In the field of categorical probability, one uses concepts and techniques from category theory, such as monads and monoidal categories, to study the structures of probability and statistics. In this paper, we connect some ideas from categorical algebra, namely weakly cartesian functors and natural transformations, to the idea of conditioning in probability theory, using Markov categories and probability monads. First of all, we show that under some conditions, the monad associated to a Markov category with conditionals has a weakly cartesian functor and weakly cartesian multiplication. In particular, we show that this is the case for the Giry monad on standard Borel spaces. We then connect this theory to existing results on statistical experiments. We show that for deterministic statistical experiments, the so-called standard measure construction (which can be seen as a generalization of the ``hypernormalizations'' introduced by Jacobs) satisfies a universal property, allowing an equivalent definition which does not rely on the existence of conditionals.

math.CT↗

arXiv2026

A Dichotomy Theorem for Ordinal Ranks in MSO

We focus on formulae $\exists X.\, φ(\vec{Y}, X)$ of monadic second-order logic over the full binary tree, such that the witness $X$ is a well-founded set. The ordinal rank $\mathrm{rank}(X) < ω_1$ of such a set $X$ measures its depth and branching structure. We search for the least upper bound for these ranks, and discover the following dichotomy depending on the formula $φ$. Let $\mathrm{rank}(φ)$ be the minimal ordinal such that, whenever an instance $\vec{Y}$ satisfies the formula, there is a witness $X$ with $\mathrm{rank}(X) \leq \mathrm{rank}(φ)$. Then $\mathrm{rank}(φ)$ is either strictly smaller than $ω^2$ or it reaches the maximal possible value $ω_1$. Moreover, it is decidable which of the cases holds. The result has potential for applications in a variety of ordinal-related problems, in particular it entails a result about the closure ordinal of a fixed-point formula.

cs.LO↗

arXiv2026

On Good-for-MDPs Automata

Nondeterministic good-for-MDPs (GFM) automata are for MDP model checking and reinforcement learning what good-for-games (GFG) automata are for reactive synthesis: a more compact alternative to deterministic automata that displays nondeterminism, but only so much that it can be resolved locally, such that a syntactic product can be analysed. GFM has recently been introduced as a property for reinforcement learning, where the simpler Büchi acceptance conditions it allows to use is key. However, while there are classic and novel techniques to obtain automata that are GFM, there has not been a decision procedure for checking whether or not an automaton is GFM. We show that GFM-ness is decidable and provide an EXPTIME decision procedure as well as a PSPACE-hardness proof. We also compare the succinctness of GFM automata with other types of automata with restricted nondeterminism. The first natural comparison point are GFG automata. Deterministic automata are GFG, and GFG automata are GFM, but not vice versa. This raises the question of how these classes relate in terms of succinctness. GFG automata are known to be exponentially more succinct than deterministic automata, but the gap between GFM and GFG automata as well as the gap between ordinary nondeterministic automata and those that are GFM have been open. We establish that these gaps are exponential, and sharpen this result by showing that the latter gap remains exponential when restricting the nondeterministic automata to separating safety or unambiguous reachability automata.

cs.FL↗

arXiv2026

A categorical formulation of Kraus' paradox

We give a categorical formulation of Kraus' "magic trick" for recovering information from truncated types. Rather than type theory, we work in Van den Berg-Moerdijk path categories with a univalent universe, and rather than propositional truncation we work with arbitrary cofibrations, which includes truncation as a special case. We show, using Kraus' argument that any cofibration with homogeneous domain is a monomorphism. We give some simple concrete examples in groupoids to illustrate the interaction between homogeneous types, cofibrations and univalent fibrations.

math.CT↗

arXiv2026

On the Existential Theory of the Reals Enriched with Integer Powers of a Computable Number

This paper investigates $\exists\mathbb{R}(r^{\mathbb{Z}})$, that is the extension of the existential theory of the reals by an additional unary predicate $r^{\mathbb{Z}}$ for the integer powers of a fixed computable real number $r > 0$. If all we have access to is a Turing machine computing $r$, it is not possible to decide whether an input formula from this theory satisfiable. However, we show an algorithm to decide this problem when: 1. $r$ is known to be transcendental, or 2. $r$ is a root of some given integer polynomial (that is, $r$ is algebraic). In other words, knowing the algebraicity of $r$ suffices to circumvent undecidability. Furthermore, we establish complexity results under the proviso that $r$ enjoys what we call a polynomial root barrier. Using this notion, we show that the satisfiability problem of $\exists\mathbb{R}(r^{\mathbb{Z}})$ is 1. in NEXPTIME if $r$ is a natural number, 2. in EXPSPACE if $r$ is an algebraic number, and 3. in 3EXP if $r$ belongs to a family of transcendental numbers including $π$ and Euler's $e$. As a by-product of our results, we are able to remove the appeal to Schanuel's conjecture from the proof of decidability of the entropic risk threshold problem for stochastic games with rational probabilities, rewards and threshold [Baier et al., MFCS'23]: when the base of the entropic risk is Euler's $e$ and the aversion factor is a fixed algebraic number, the problem is in EXP.

cs.LO↗

arXiv2026

Proof-Carrying Analytic Approximation: Local-to-Global Evidence Transport at Encoding Cost

Under quasi-uniform refinement, bounded local-encoding hypotheses, and local $W^{r,2}$ approximation of order $r\ge 2$ in a rational piecewise-polynomial presentation of $W^{1,2}(0,1)$, carrying the complete proof genealogy up to the level required by an accuracy $\varepsilon$ costs the same asymptotic bit order as the finest-level conventional coefficient encoding. If $B_n=Θ(M_nβ_n)$ denotes that level-$n$ encoding size, our compiler transports supplied local approximation and overlap witnesses through exact partition-of-unity synthesis and geometric refinement to a represented limit with total certificate size $O(B_{m(\varepsilon)})$, where $m(\varepsilon)=O(\log(1/\varepsilon)/(r-1))$. The construction makes no oracle query to an independently supplied semantic target name ($Q_{\rm target}=0$). When $β_n=O(n+1)$, this becomes $O(\varepsilon^{-1/(r-1)}(1+\log(1/\varepsilon)))$. The surrounding framework is intentionally separated from this resource theorem. Every real computable Banach presentation admits a uniformly computable linear isometric embedding into standard computable $C([0,1])$, with computable inverse on its represented range. Complete metric evidence with rational strict slack collapses extensionally to the represented analytic metric once effective names are available, while chosen evidence transformations retain construction history and resource information. For the Lipschitz grammar used here, qualitative evidence-local lifting is canonical; the nontrivial question is therefore which evidence is retained and at what cost.

math.FA↗

arXiv2026

Essential Unitarity for Higher-Order Quantum Computation

We develop a boundary-centric semantic framework for higher-order quantum computation, building on the Kelly-Laplaza description of compact closure and Abramsky's execution account. In the semantic carrier Perm(C), morphisms are complex-linear combinations of polarized boundary linkings, composed by execution. Finite-family addresses provide coherent control over finite-level quantum registers (qudits) while retaining the multiplicative boundary structure. We identify essential unitarity, a boundary condition extending ordinary unitarity to higher-order interfaces. On positive qudit registers it coincides with ordinary matrix unitarity; at higher order it expresses preservation of information across the full polarized boundary. We define a unit-free coherent quantum core generated by multiplicative wiring, unitary gates on positive qudit registers, and contextual coherent control, and prove that every one of its morphisms is essentially unitary. The framework realizes an applied coherent quantum switch and the unitary stages of equal-ratio one-slot supermap dilations with explicit memory. An extended abstract of this work was accepted for QPL 2026 and is forthcoming in its proceedings.

quant-ph↗

arXiv2026

A homotopy-type-theoretic generalization of neurosymbolic inference

A wide range of neurosymbolic (NeSy) systems compute one functional: a belief-weighted sum of a logical quantity over a space of $σ$-structures, of which weighted model counting, fuzzy logic, and probabilistic logic are special cases. This account is built on sets, and a set deliberately forgets two things that are important for NeSy: when two $σ$-structures are the same up to a symmetry of the theory, and how many distinct proofs witness a query. Types, in the sense of homotopy type theory, preserve this information and turn the functional into a belief-weighted homotopy cardinality, a notion of size that counts each object in inverse proportion to its symmetries. We develop the framework from scratch for NeSy systems, prove a conservativity theorem that recovers the classical functional when symmetries are trivial, and show that the symmetry our framework exposes is exactly the one behind reasoning shortcuts. The payoff is concrete: the shortcut-aware concept posterior that recent methods reach by ensembling or expressive density estimation is the only symmetry-invariant point of the confusion-set simplex, computable in closed form by averaging a single model over the symmetry group. On MNIST reasoning-shortcut benchmarks this single-model wrapper is better calibrated than a diversity-trained ensemble, while leaving label accuracy and identifiable concepts untouched. Code is freely available at https://github.com/bio-ontology-research-group/hott-nesy.

cs.AI↗

arXiv2026

Prove2Me: An Open Collaborative Platform for Scaling Math Formalization

Proof assistants such as Lean 4 promise the paradigm of formally verified mathematics, but large-scale formalization projects have faced major barriers to entry, including the need for expertise in formal verification (as well as the underlying mathematics) and the significant time required for writing formal proofs. AI coding agents have dramatically reduced these barriers; human users can now use natural language to prompt agents to write complex proofs in Lean. This opens up the intriguing possibility of internet-scale mathematical collaboration involving both humans and AI agents, where correctness is machine-checked. To realize this possibility, we introduce Prove2Me (https://prove2.me), an open collaborative platform for formalizing mathematics. Users launch formalization "missions", to which AI agents contribute formal proofs toward completion. We designed mechanisms and a specialized harness in Prove2Me that enable large-scale collaboration so that agents can build on one another's work and freely reuse existing results. In doing so, Prove2Me aims to turn math formalization into a scalable, crowd-sourced effort open to anyone with an agent.

cs.AI↗

arXiv2026

Unary Functions, Automorphisms, and Unlabeled First-Order Model Counting

Every fixed first-order sentence $φ$ determines an enumerative sequence $n\mapsto\mathrm{FOMC}(φ,n)$, counting its models on the labeled domain $[n]$. We study the complexity of these sequences when logical specifications may use genuine unary function symbols and hence nested terms $x,f(x),f^2(x),\ldots$. We first prove that, for every fixed sentence $φ\in\mathrm{C}^1_{=}[f]$, with one unary function and an arbitrary finite relational vocabulary, $\mathrm{FOMC}(φ,n)$ is computable in time polynomial in $n$. By contrast, permitting either a second variable or a second unary function already yields hardness. Without counting quantifiers, there is a fixed sentence in $\mathrm{FO}^2_{=}[f]$ whose model-counting function is $\#\mathrm{P}_1$-complete. With one variable and two unary functions, there is a fixed constant-free universal sentence in $\mathrm{FO}^1_{=}[f,g]$, using only unary predicates besides $f$ and $g$, whose model-counting function is again $\#\mathrm{P}_1$-complete. We also relate labeled and unlabeled enumeration exactly. For every relational sentence $φ$, we construct an extension $φ_{\mathrm{aut}}$ in which a unary function records an automorphism and $\mathrm{FOMC}(φ_{\mathrm{aut}},n)=n!\cdot\mathrm{UFOMC}(φ,n)$, where $\mathrm{UFOMC}(φ,n)$ denotes the number of $n$-element models of $φ$ up to isomorphism. Thus automorphism marking gives a one-query exact reduction from unlabeled to labeled model counting at the same domain size. Over relational vocabularies of maximum arity at most $k$, where $k\geq2$, eliminating the auxiliary function yields single-query reductions from unlabeled $\mathrm{FO}^k_{=}$ and $\mathrm{C}^k$ model counting to labeled $\mathrm{FO}^{k+1}_{=}$ and $\mathrm{C}^{k+1}$ model counting, respectively.

cs.LO↗

arXiv2026

Computational free will as global selection: from sheaf-theoretic gluing to a conditional separation of P and NP

We formalise computational free will by separating locally constrained admissibility from the selection of one global continuation. Global sections of a finite choice presheaf form an admissible set, GLUE; SELECT singles out the continuation realised at a pre-identified occurrence. A uniform trace relation certifies that continuation efficiently after the act, although it is assumed not to be uniformly anticipable in polynomial time from the prior occurrence input. Under explicit uniformity, balance, historical-completeness, and unique-projection assumptions, this trace defines a total FNP search relation with no deterministic polynomial-time selector. Thus existence of computational free will in the stated sense implies a separation between polynomially verifiable and polynomially solvable search, and hence that P differs from NP. The result is conditional and gives no unconditional class separation.

cs.LO↗

arXiv2026

Schwarz: Solver-Aware Agentic Program Verification

Agentic verification systems can often generate source-level specifications that look plausible, but plausibility is not enough: the verifier must still turn those specifications into SMT obligations that the solver can prove. When this step fails, current LLM-driven loops usually expose only a coarse verifier error, timeout, or unknown solver result. The model cannot tell whether the specification is wrong, a helper lemma is missing, the proof context contains irrelevant facts, or the obligation needs a different theory view. This paper presents Schwarz, an agentic verification harness that makes SMT-backed proof failure local, checkable, and repairable. Schwarz turns failed verification into obligation-local repair tasks: program-point snapshots expose checked facts at a boundary, local lemmas let the agent propose missing proof steps, and theory-aware solver policies guide the agent toward solver-friendly formulations for numeric, quantified, memory, and floating-point obligations. We implement Schwarz for C and Rust/Verus and evaluate it on 1,475 tasks. On 475 benchmarks from recent agentic verification tools, Schwarz solves 95.2% of the tasks. On 1,000 tasks from the SV-COMP 2026 ReachSafety track, averaging 1,427 LOC, Schwarz solves 91.5% of the tasks, compared with 60.1% for CPAchecker. Ablations and comparison with a pure-agent baseline show that solver-aware repair is effective and scalable.

cs.LO↗

arXiv2026

A note on the reduction from LTLf to LTL

LTLf, a finite word variant of LTL, can be reduced to LTL by introducing a new atomic proposition indicating the prefix of the infinite words that correspond to the finite words that the original LTLf formula was considering. Such a reduction was originally proposed by De Giacomo and Vardi (IJCAI'13). However, while any LTL formula reduced from LTLf describes an obligation property in the hierarchy of Manna and Pnueli (PODC'90), the aforementioned reduction does not provide an LTL formula that belongs to the syntactic obligation fragment of LTL. This note shows how the reduction was fixed in Spot in order to ensure that the resulting LTL formula is always a syntactic obligation. Doing so allows algorithms specialized to syntactic obligation to be used on LTLf formulas. For instance, in previous work (CAV'26) we described a specialized translation from syntactic obligations to minimal, weak, deterministic Büchi automata that would not be usable with the original reduction.

cs.FL↗

arXiv2026

Exponential Gaps Between Intuitionistic Linear Extended Frege Systems

In this paper, we establish exponential separations between Extended Frege systems for a range of intuitionistic substructural and linear logics. More precisely, for any logic $L$ below the intuitionistic logic obtained by extending $\mathbf{ILL}$ with structural rules, and any logic $M$ not contained in $L$, we construct a family of $\mathsf{FL_e}$-provable formulas that have short proofs in $M$-Frege but require proofs of exponential size in $L$-Extended Frege. The same result holds in the $!$-free settings, using $\mathbf{IMALL}$ and $\mathbf{FL_e}$ in place of $\mathbf{ILL}$. The key ingredient in proving these separations is a variant of the feasible disjunction property for $L$-Frege, which may be of independent interest.

cs.LO↗

arXiv2026

Subgroup Accessibility in Group Order Logic

We investigate the expressive power of fixed-point logics (FP) and their extensions in defining generating sets for accessible subgroups of definable permutation groups. This operation, computable in polynomial time via the Schreier-Sims algorithm, plays a central role in the group-theoretic approach to Graph Isomorphism and Graph Canonisation. In particular, it underpins polynomial-time canonisation for bounded colour-class graphs--a class for which no natural logic capturing P is currently known. We first show that this operation cannot, in general, be expressed in any logic for P. This limitation arises from the fact that accessible subgroups need not admit symmetric generating sets of polynomial size. However, we prove that when the base group admits a definable ordered generating set, the accessible subgroup operation becomes definable in fixed-point logic with the group order operator (FP + ord). This is achieved by partially simulating the Schreier-Sims algorithm within FP + ord. As a corollary, we show that fixed-point logic with counting (FPC) can also define the operation when the base group is abelian. In particular, FPC can define the automorphism group of any graph with abelian colours--despite being unable to canonise such graphs.

cs.LO↗

arXiv2026

Outrunning Big KATs: Efficient Decision Procedures for Variants of GKAT

This paper presents several efficient decision procedures for trace equivalence of GKAT automata, which make use of on-the-fly symbolic techniques via SAT solvers. To demonstrate applicability of our algorithms, we designed symbolic derivatives for CF-GKAT, a practical system based on GKAT designed to validate control-flow transformations. We implemented the algorithms in Rust and evaluated them on both randomly generated benchmarks and real-world control-flow transformations. Indeed, we observed order-of-magnitude performance improvements against existing implementations for both KAT and CF-GKAT. Notably, our experiments also revealed a bug in Ghidra, an industry-standard decompiler, highlighting the practical viability of these systems.

cs.PL↗

arXiv2026

Implementing Grassroots Logic Programs with Multiagent Transition Systems and AI (Full Version)

Grassroots Logic Programs (GLP) is a concurrent logic programming language in which logic variables are partitioned into paired readers and writers. An assignment is produced at most once via a writer and consumed at most once via its paired reader, and may contain additional readers and/or writers. This enables the concise expression of rich multidirectional communication modalities. The language was introduced together with concurrent (cGLP) and multiagent (maGLP) operational semantics. Here, we derive from these (1) dGLP, a deterministic counterpart of cGLP, and (2) madGLP, a counterpart of maGLP in which deterministic agents communicate solely by asynchronous message passing, and prove them correct against their abstract counterparts. maGLP shared variable pairs spanning agents can be implemented by two local variable pairs joined by a \emph{global link}, with correctness following from disjoint substitution commutativity (a consequence of GLP's single-occurrence invariant). We further prove that madGLP is grassroots. Both dGLP and madGLP serve as formal specifications for an AI-driven implementation discipline (math $\to$ informal spec $\to$ Dart) employed and described here: from dGLP, AI (Claude) developed a workstation-based GLP implementation in Dart, and from madGLP it is developing a smartphone-based multiagent one.

cs.PL↗

arXiv2026

Taming the Search Space: Solving and Generating Hitori and Binairo Puzzles

This paper investigates solving and generation techniques for the logic puzzles Hitori and Binairo. Two solving paradigms are compared: backtracking with domain-specific optimizations, and SAT-based solving via conjunctive normal form encodings. An empirical evaluation analyzes runtime, explored search nodes, and branching factor across varying puzzle sizes. To support systematic benchmarking in the evaluation, generators capable of producing valid and uniquely solvable puzzle instances are developed. Results indicate that constraint propagation is the most effective backtracking optimization, substantially reducing the effective branching factor, search tree size, and thus runtime. Heuristic variable ordering and scoring strategies provide additional improvements. For Binairo, the SAT-based approach solves all evaluated instances within low runtime, while optimized backtracking fails to solve difficult puzzle instances within the timeout. For Hitori, propagation-based backtracking achieves the best results, while for the SAT-based approach the iterative connectivity check takes up the majority of the runtime, failing difficult puzzle instances.

cs.LO↗