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Answering a question of Junker and Ziegler, we construct a countable first order structure which is not omega-categorical, but does not have any proper non-trivial reducts, in either of two senses (model-theoretic, and group-theoretic). We…

Logic · Mathematics 2015-02-27 Manuel Bodirsky , Dugald Macpherson

As artificial agents become increasingly capable, what internal structure is *necessary* for an agent to act competently under uncertainty? Classical results show that optimal control can be *implemented* using belief states or world…

Machine Learning · Computer Science 2026-04-03 Aran Nayebi

We study the (quantum) security of pseudorandom generators (PRGs) constructed from random oracles. We prove a "lifting theorem" showing, roughly, that if such a PRG is unconditionally secure against classical adversaries making polynomially…

Cryptography and Security · Computer Science 2025-06-02 Jonathan Katz , Ben Sela

We describe the basic theory of infinite time Turing machines and some recent developments, including the infinite time degree theory, infinite time complexity theory, and infinite time computable model theory. We focus particularly on the…

Logic · Mathematics 2019-08-16 Samuel Coskey , Joel David Hamkins

A locally-optimal structure is a combinatorial structure such as a maximal independent set that cannot be improved by certain (greedy) local moves, even though it may not be globally optimal. It is trivial to construct an independent set in…

Computational Complexity · Computer Science 2016-04-20 Leslie Ann Goldberg , Rob Gysel , John Lapinskas

Many high-stakes AI deployments proceed only if every stakeholder deems the system acceptable relative to their own minimum standard. With randomization over a finite menu of options, this becomes a feasibility question: does there exist a…

Computer Science and Game Theory · Computer Science 2026-04-21 Davin Choo , Paul W. Goldberg , Nicholas Teh

Knowing when a classifier's prediction can be trusted is useful in many applications and critical for safely using AI. While the bulk of the effort in machine learning research has been towards improving classifier performance,…

Machine Learning · Statistics 2018-10-30 Heinrich Jiang , Been Kim , Melody Y. Guan , Maya Gupta

Classical results of Bennett and Gill (1981) show that with probability 1, $P^A \neq NP^A$ relative to a random oracle $A$, and with probability 1, $P^\pi \neq NP^\pi \cap coNP^\pi$ relative to a random permutation $\pi$. Whether $P^A =…

Computational Complexity · Computer Science 2025-11-13 John M. Hitchcock , Adewale Sekoni , Hadi Shafei

Machine learning researchers and practitioners steadily enlarge the multitude of successful learning models. They achieve this through in-depth theoretical analyses and experiential heuristics. However, there is no known general-purpose…

Computational Complexity · Computer Science 2023-10-18 Matthias C. Caro

Recently we have introduced a new model of infinite computation by extending the operation of ordinary Turing machines into transfinite ordinal time. In this paper we will show that the infinite time Turing machine analogue of Post's…

Logic · Mathematics 2007-05-23 Joel David Hamkins , Andrew Lewis

Asking which sets are fixed-parameter tractable for a given parameterization constitutes much of the current research in parameterized complexity theory. This approach faces some of the core difficulties in complexity theory. By focussing…

Logic in Computer Science · Computer Science 2018-01-17 Jouke Witteveen , Leen Torenvliet

Evaluating conjunctive queries and solving constraint satisfaction problems are fundamental problems in database theory and artificial intelligence, respectively. These problems are NP-hard, so that several research efforts have been made…

Databases · Computer Science 2013-01-01 Gianluigi Greco , Francesco Scarcello

Computing reachability probabilities is a fundamental problem in the analysis of probabilistic programs. This paper aims at a comprehensive and comparative account on various martingale-based methods for over- and under-approximating…

Programming Languages · Computer Science 2018-11-16 Toru Takisaka , Yuichiro Oyabu , Natsuki Urabe , Ichiro Hasuo

We present a quantum algorithm which identifies with certainty a hidden subgroup of an arbitrary finite group G in only a polynomial (in log |G|) number of calls to the oracle. This is exponentially better than the best classical algorithm.…

Quantum Physics · Physics 2016-12-30 Mark Ettinger , Peter Hoyer , Emanuel Knill

Can a large system be fully characterized using its subsystems via inductive reasoning? Is it possible to completely reduce the behavior of a complex system to the behavior of its simplest "atoms"? In the following paper we answer these…

Quantum Physics · Physics 2018-11-19 Yakir Aharonov , Eliahu Cohen , Jeff Tollaksen

Even if Google AI's Sycamore processor is efficient for the particular task it has been designed for it fails to deliver universal computational capacity. Furthermore, even classical devices implementing transverse homoclinic orbits realize…

Quantum Physics · Physics 2019-11-05 Karl Svozil

We give a survey of the known connections between regularity conditions and amenability conditions in the setting of uniform algebras. For a uniform algebra $A$ we consider the set, $A_{lc}$, of functions in $A$ which are locally constant…

Functional Analysis · Mathematics 2014-12-25 M. J. Heath , J. F. Feinstein

The past decade has seen a significant interest in learning tractable probabilistic representations. Arithmetic circuits (ACs) were among the first proposed tractable representations, with some subsequent representations being instances of…

Artificial Intelligence · Computer Science 2017-08-25 Arthur Choi , Adnan Darwiche

While theoretical computer science primarily works with discrete models of computation, like the Turing machine and the wordRAM, there are many scenarios in which introducing real computation models is more adequate. We want to compare real…

Computational Complexity · Computer Science 2025-10-08 Thekla Hamm , Lucas Meijer , Tillmann Miltzow , Subhasree Patro

Hyperparameters play a critical role in machine learning. Hyperparameter tuning can make the difference between state-of-the-art and poor prediction performance for any algorithm, but it is particularly challenging for structure learning…

Machine Learning · Computer Science 2024-02-21 Damian Machlanski , Spyridon Samothrakis , Paul Clarke