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While closed timelike curves (CTCs) are not known to exist, studying their consequences has led to nontrivial insights in general relativity, quantum information, and other areas. In this paper we show that if CTCs existed, then quantum…

Quantum Physics · Physics 2009-11-13 Scott Aaronson , John Watrous

Although the interpretation of complexity in extended theories of gravity is available in the literature, its illustration in $f(R,L_{m},\mathcal{T})$ theory is still ambiguous. The orthogonal decomposition of the Riemann tensor results in…

General Relativity and Quantum Cosmology · Physics 2025-06-23 A. Rehman , Tayyab Naseer , Nazek Alessa , Abdel-Haleem Abdel-Aty

We use the phenomenological approach to study properties of space-time in the vicinity of the Schwarzschild black-hole singularity. Requiring finiteness of the Schwarzschild-like metrics we come to the notion of integrable singularity that…

General Relativity and Quantum Cosmology · Physics 2013-01-24 Vladimir N. Lukash , Vladimir N. Strokov

Infinite time Turing machines are extended in several ways to allow for iterated oracle calls. The expressive power of these machines is discussed and in some cases determined.

Logic · Mathematics 2015-10-05 Robert Lubarsky

We discuss the question of time in a Bianchi I quantum cosmology in the framework of singularity avoidance. We show that time parameters fall into two distinct classes, that are such that the time development of the wave function either…

General Relativity and Quantum Cosmology · Physics 2020-02-18 Przemyslaw Malkiewicz , Patrick Peter , S. D. P. Vitenti

We propose a measure based upon the fundamental theoretical concept in algorithmic information theory that provides a natural approach to the problem of evaluating $n$-dimensional complexity by using an $n$-dimensional deterministic Turing…

Computational Complexity · Computer Science 2015-08-27 Hector Zenil , Fernando Soler-Toscano , Jean-Paul Delahaye , Nicolas Gauvrit

We consider the time and space required for quantum computers to solve a wide variety of problems involving matrices, many of which have only been analyzed classically in prior work. Our main results show that for a range of linear algebra…

Computational Complexity · Computer Science 2025-11-03 Paul Beame , Niels Kornerup , Michael Whitmeyer

There is an important and interesting open question in computational complexity on the relation between the complexity classes $\mathcal{NP}$ and $\mathcal{PSPACE}$. It is a widespread belief that $\mathcal{NP}\ne\mathcal{PSPACE}$. In this…

Computational Complexity · Computer Science 2025-04-02 Tianrong Lin

We investigate the minimum cases for realtime probabilistic machines that can define uncountably many languages with bounded error. We show that logarithmic space is enough for realtime PTMs on unary languages. On binary case, we follow the…

Computational Complexity · Computer Science 2017-05-05 Maksims Dimitrijevs , Abuzer Yakaryılmaz

In this paper we initiate the study of the computational complexity of learning linear temporal logic (LTL) formulas from examples. We construct approximation algorithms for fragments of LTL and prove hardness results; in particular we…

Formal Languages and Automata Theory · Computer Science 2021-02-02 Nathanaël Fijalkow , Guillaume Lagarde

This article expands our work in [Ca16]. By its reliance on Turing computability, the classical theory of effectivity, along with effective reducibility and Weihrauch reducibility, is only applicable to objects that are either countable or…

Logic · Mathematics 2026-05-19 Merlin Carl

We describe the Turing Machine, list some of its many influences on the theory of computation and complexity of computations, and illustrate its importance.

Computational Complexity · Computer Science 2013-08-26 P. M. B. Vitanyi

Quantum complexity measures the difficulty of obtaining a given state starting from a typically unentangled state. In this work, we show that complexity, when defined through the minimization of a Riemannian cost functional over the…

Quantum Physics · Physics 2025-06-05 Nadir Samos Sáenz de Buruaga

Interval Temporal Logic (ITL) is an established temporal formalism for reasoning about time periods. For over 25 years, it has been applied in a number of ways and several ITL variants, axiom systems and tools have been investigated. We…

Logic in Computer Science · Computer Science 2015-07-01 Ben Moszkowski

We consider dynamical systems for which the spatial extension plays an important role. For these systems, the notions of attractor, epsilon-entropy and topological entropy per unit time and volume have been introduced previously. In this…

Dynamical Systems · Mathematics 2009-11-11 Claudio Bonanno , Pierre Collet

We consider how changes in transfinite machine architecture can sometimes alter substantially their capabilities. We approach the subject by answering three open problems touching on: firstly differing halting time considerations for…

Logic · Mathematics 2020-12-16 Philip Welch

In this letter we briefly investigate the mathematical structure of space-time in the framework of discretization. It is shown that the discreteness of space-time may result in a new mechanical system which differ from the usual quantum…

Quantum Physics · Physics 2010-03-29 An-Wei Zhang

We revisit parallel-innermost term rewriting as a model of parallel computation on inductive data structures and provide a corresponding notion of runtime complexity parametric in the size of the start term. We propose automatic techniques…

Logic in Computer Science · Computer Science 2026-04-08 Thaïs Baudon , Carsten Fuhs , Laure Gonnord

Probabilistic Spacetime is a simple generalization of the classical model of spacetime in General Relativity, such that it allows to consider multiple metric field realizations endowed with probabilities. The motivation for such a…

General Relativity and Quantum Cosmology · Physics 2017-12-27 Jakub Káninský

The space-time foam formulas, quoted below in Eqs (1) and (3), express the minimal amount of quantum uncertainty to be introduced into the structure of the Einsteinian space-time in order to make that structure compatible with quantum…

Quantum Physics · Physics 2010-11-09 Andor Frenkel