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In this paper we present two different problems within the framework of shift-invariant theory. First, we develop a triangular form for shift-preserving operators acting on finitely generated shift-invariant spaces. In case of the normal…

Functional Analysis · Mathematics 2026-01-12 Elona Agora , Jorge Antezana , Diana Carbajal

We consider a two-dimensional model of double-diffusive convection and its time discretisation using a second-order scheme which treat the nonlinear term explicitly (backward differentiation formula with a one-leg method). Uniform bounds on…

Numerical Analysis · Mathematics 2014-02-28 Florentina Tone , Xiaoming Wang , Djoko Wirosoetisno

We investigate the problem of estimating a smooth invertible transformation f when observing independent samples X_1, ..., X_n ~ P \circ f, where P is a known measure. We focus on the two dimensional case where P and f are defined on R^2.…

Methodology · Statistics 2008-07-16 Ethan Anderes , Marc Coram

This paper presents a sample-efficient, data-driven control framework for finite-horizon linear quadratic (LQ) control of linear time-varying (LTV) systems. In contrast to the time-invariant case, the time-varying LQ problem involves a…

Systems and Control · Electrical Eng. & Systems 2025-09-30 Sahel Vahedi Noori , Maryam Babazadeh

We propose a novel multilinear dynamical system (MLDS) in a transform domain, named $\mathcal{L}$-MLDS, to model tensor time series. With transformations applied to a tensor data, the latent multidimensional correlations among the frontal…

Machine Learning · Computer Science 2018-11-20 Weijun Lu , Xiao-Yang Liu , Qingwei Wu , Yue Sun , Anwar Walid

Space-like and time-like invariant space-time intervals are used to analyse measurements of spatial and temporal distances. The former are found to be Lorentz invariant --there is no `relativistic length contraction', whereas the latter…

General Physics · Physics 2009-09-01 J. H. Field

The covariant two-point functions, derived from Ward identities in direct space, can be affected by consistency problems and can become unbounded for large time- or space-separations. This difficulty arises for several extensions of…

Mathematical Physics · Physics 2016-11-11 Malte Henkel , Stoimen Stoimenov

We propose and analyze a class of adaptive sampling algorithms for multimodal distributions on a bounded domain, which share a structural resemblance to the classic overdamped Langevin dynamics. We first demonstrate that this class of…

Machine Learning · Computer Science 2024-11-26 Björn Engquist , Kui Ren , Yunan Yang

Computed Tomography (CT) is a widely utilized imaging modality in clinical settings. Using densely acquired rotational X-ray arrays, CT can capture 3D spatial features. However, it is confronted with challenged such as significant time…

Image and Video Processing · Electrical Eng. & Systems 2025-07-16 Duoyou Chen , Yunqing Chen , Can Zhang , Zhou Wang , Cheng Chen , Ruoxiu Xiao

In this paper, we study the problem of sampling from a graphical model when the model itself is changing dynamically with time. This problem derives its interest from a variety of inference, learning, and sampling settings in machine…

Data Structures and Algorithms · Computer Science 2018-11-15 Weiming Feng , Nisheeth K. Vishnoi , Yitong Yin

Large volumes of spatiotemporal data, characterized by high spatial and temporal variability, may experience structural changes over time. Unlike traditional change-point problems, each sequence in this context consists of function-valued…

Methodology · Statistics 2025-06-12 Fengyi Song , Decai Liang , Changliang Zou

Lagrangian coherent structures (LCSs) are material surfaces that shape finite-time tracer patterns in flows with arbitrary time dependence. Depending on their deformation properties, elliptic and hyperbolic LCSs have been identified from…

Dynamical Systems · Mathematics 2016-11-23 David Oettinger , George Haller

In this paper, we discuss to the nonuniform sampling problem in principal shift-invariant subspaces of mixed Lebesgue spaces. We proposed a fast reconstruction algorithm which allows to exactly reconstruct the functions in the principal…

Functional Analysis · Mathematics 2018-01-26 Qingyue Zhang

Quantum canonical transformations corresponding to time-dependent diffeomorphisms of the configuration space are studied. A special class of these transformations which correspond to time-dependent dilatations is used to identify a…

Quantum Physics · Physics 2008-11-26 Ali Mostafazadeh

In this paper we study the continuous dynamical sampling problem at infinite time in a complex Hilbert space $\mathcal{H}$. We find necessary and sufficient conditions on a bounded linear operator $A\in\mathcal{B}(\mathcal{H})$ and a set of…

Functional Analysis · Mathematics 2020-06-16 Rocío Díaz Martín , Ivan Medri , Ursula Molter

This article gives a synopsis on new developments in affine invariant tests for multivariate normality in an i.i.d.-setting, with special emphasis on asymptotic properties of several classes of weighted $L^2$-statistics. Since weighted…

Statistics Theory · Mathematics 2020-04-17 Bruno Ebner , Norbert Henze

Efficient sampling from high-dimensional distributions is a challenging issue which is encountered in many large data recovery problems involving Markov chain Monte Carlo schemes. In this context, sampling using Hamiltonian dynamics is one…

Methodology · Statistics 2015-02-02 Lotfi Chaari , Jean-Yves Tourneret , Caroline Chaux , Hadj Batatia

Extracting the true dynamical variables of a system from high-dimensional video is challenging due to distracting visual factors such as background motion, occlusions, and texture changes. We propose LyTimeT, a two-phase framework for…

Computer Vision and Pattern Recognition · Computer Science 2025-10-23 Kuai Yu , Crystal Su , Xiang Liu , Judah Goldfeder , Mingyuan Shao , Hod Lipson

Multidimensional cosmological models with $n (n > 1)$ spaces of constant curvature are discussed classically and with respect to canonical quantization. These models are integrable in the case of Ricci flat internal spaces. For positive…

General Relativity and Quantum Cosmology · Physics 2009-09-25 U. Bleyer , A. Zhuk

An exact invariant is derived for $n$-degree-of-freedom Hamiltonian systems with general time-dependent potentials. The invariant is worked out in two equivalent ways. In the first approach, we define a special {\it Ansatz\/} for the…

Classical Physics · Physics 2023-03-23 Jürgen Struckmeier , Claus Riedel
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