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We discuss the geometry of timelike surfaces (two-dimensional submanifolds) in a Lorentzian manifold and its interpretation in terms of general relativity. A classification of such surfaces is presented which distinguishes four cases of…

General Relativity and Quantum Cosmology · Physics 2008-06-27 Wolfgang Hasse , Volker Perlick

Four-dimensional manifolds with changing signature are obtained by taking the large $N$ limit of fuzzy $CP^2$ solutions to a Lorentzian matrix model. The regions of Lorentzian signature give toy models of closed universes which exhibit…

High Energy Physics - Theory · Physics 2017-02-08 A. Chaney , A. Stern

The Lorentzian metric structure used in any field theory allows one to implement the relativistic notion of causality and to define a notion of time dimension. This article investigates the possibility that at the microscopic level the…

High Energy Physics - Theory · Physics 2013-04-11 Shinji Mukohyama , Jean-Philippe Uzan

Let $BQP(n)$ be a boolean quadric polytope, $LOP(m)$ be a linear ordering polytope. It is shown that $BQP(n)$ is linearly isomorphic to a face of $LOP(2n)$.

Computational Complexity · Computer Science 2018-04-18 Aleksandr Maksimenko

For a toy version of a quantum system with a conscious observer, it is demonstrated that the many-worlds problem is solved by retreating into the conscious subspace of an entire observer history. In every step of a discretised time, the…

Quantum Physics · Physics 2014-05-27 Lutz Polley

Objects are represented in sensory systems by continuous manifolds due to sensitivity of neuronal responses to changes in physical features such as location, orientation, and intensity. What makes certain sensory representations better…

Disordered Systems and Neural Networks · Physics 2016-08-23 SueYeon Chung , Daniel D. Lee , Haim Sompolinsky

As autonomous systems are increasingly deployed in open and uncertain settings, there is a growing need for trustworthy world models that can reliably predict future high-dimensional observations. The learned latent representations in world…

Machine Learning · Computer Science 2025-06-04 Jordan Peper , Zhenjiang Mao , Yuang Geng , Siyuan Pan , Ivan Ruchkin

In this paper, we consider the problem of designing an asymptotic observer for a nonlin-ear dynamical system in discrete-time following Luenberger's original idea. This approach is a two-step design procedure. In a first step, the problem…

Optimization and Control · Mathematics 2020-02-10 Lucas Brivadis , Vincent Andrieu , Ulysse Serres

We consider spacetime to be a 4-dimensional differentiable manifold that can be split locally into time and space. No metric, no linear connection are assumed. Matter is described by classical fields/fluids. We distinguish electrically…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Friedrich W. Hehl , Yuri N. Obukhov

A novel method, connecting the space of solutions of a linear differential equation, of arbitrary order, to the space of monomials, is used for exploring the algebraic structure of the solution space. Apart from yielding new expressions for…

Mathematical Physics · Physics 2007-05-23 N. Gurappa , Prasanta K. Panigrahi , T. Shreecharan

This note investigates the distributed estimation problem for continuous-time linear time-invariant (LTI) systems observed by a network of observers. Each observer in the network has access to only part of the output of the observed system,…

Optimization and Control · Mathematics 2017-08-07 Weixin Han , Harry L. Trentelman , Zhenhua Wang , Yi Shen

Rational observers are to be constructed for rational systems while polynomial observers are to be constructed for polynomial systems. An observer synthesis procedure is formulated. First an output-based rational realization is synthesized…

Optimization and Control · Mathematics 2016-12-26 Jana Nemcova , Mihaly Petreczky , Jan H. van Schuppen

We live in a 3+1 space-time that is intended as a description of the universe with three space dimensions and one time dimension. Space-time dimensionality seems so natural that it is rarely criticized. Experiments and the highly successful…

General Physics · Physics 2009-11-10 Giorgio Fontana

A class of cosmological solutions of higher dimensional Einstein field equations with the energy-momentum tensor of a homogeneous, isotropic fluid as the source are considered with an anisotropic metric that includes the direct sum of a…

General Relativity and Quantum Cosmology · Physics 2013-10-24 Ozgur Akarsu , Tekin Dereli

Inferring universal laws of the environment is an important ability of human intelligence as well as a symbol of general AI. In this paper, we take a step toward this goal such that we introduce a new challenging problem of inferring…

Artificial Intelligence · Computer Science 2018-11-30 Siyu Huang , Zhi-Qi Cheng , Xi Li , Xiao Wu , Zhongfei Zhang , Alexander Hauptmann

We state sufficient conditions for the existence, on a given open set, of the extension, to nonlinear systems, of the Luenberger observer as it has been proposed by Kazantzis and Kravaris. We prove it is sufficient to choose the dimension…

Optimization and Control · Mathematics 2009-03-03 Vincent Andrieu , Laurent Praly

We consider an inverse variational problem for the lines of constant curvature in (pseudo-)Euclidean two-, three-, and four-dimensional spaces. The accumulated results are physically meaningful in the case of relativistic mechanics of…

Classical Analysis and ODEs · Mathematics 2022-02-17 R. Ya. Matsyuk

Several theories have been advanced recently which appear to offer a resolution to that portion of the measurement problem which previously dealt with a possible reduction of the state vector in a subjective fashion by the brain, mind or…

Quantum Physics · Physics 2007-05-23 Fred H. Thaheld

We develop a general theory of spatial solitons in a liquid crystalline medium exhibiting a nonlinearity with an arbitrary degree of effective nonlocality. The model accounts the observability of "accessible solitons" and establishes an…

Optics · Physics 2009-11-10 Claudio Conti , Marco Peccianti , Gaetano Assanto

The analysis of modern cosmological data is becoming an increasingly important task as the amount of data multiplies. An important goal is to extract geometric information, i.e. the metric of the cosmos, from observational data. The…

General Relativity and Quantum Cosmology · Physics 2009-02-20 Charles Hellaby , Alnadhief H. A. Alfedeel