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Pseudodifferential parabolic equations with an operator square root arise in wave propagation problems as a one-way counterpart of the Helmholtz equation. The expression under the square root usually involves a differential operator and a…

Atmospheric and Oceanic Physics · Physics 2025-11-21 Matthias Ehrhardt , Jochen Glück , Pavel Petrov , Stefan Tappe

A sequential quadratic programming method is designed for solving general smooth nonlinear stochastic optimization problems subject to expectation equality constraints. We consider the setting where the objective and constraint function…

Optimization and Control · Mathematics 2026-03-17 Haoming Shen , Yang Zeng , Baoyu Zhou

In this paper we describe a wide class of non-Volterra quadratic stochastic operators using N. Ganikhadjaev's construction of quadratic stochastic operators. By the construction these operators depend on a probability measure $\mu$ being…

Dynamical Systems · Mathematics 2007-05-23 U. A. Rozikov , N. B. Shamsiddinov

We survey results that have been obtained for self-adjoint operators, and especially Schr\"odinger operators, associated with mathematical models of quasicrystals. After presenting general results that hold in arbitrary dimensions, we focus…

Mathematical Physics · Physics 2016-04-22 David Damanik , Mark Embree , Anton Gorodetski

Bayesian quadrature is a probabilistic, model-based approach to numerical integration, the estimation of intractable integrals, or expectations. Although Bayesian quadrature was popularised already in the 1980s, no systematic and…

Machine Learning · Computer Science 2026-02-19 Maren Mahsereci , Toni Karvonen

In this paper we introduce the concept of quadratic operator perspective for a continuous function {\Phi} defined on the positive semi-axis of real numbers. This generalize the quadratic weighted operator geometric mean and the quadratic…

Functional Analysis · Mathematics 2016-09-29 Silvestru Sever Dragomir

The Spencer operator, introduced by D.C. Spencer fifty years ago, is rarely used in mathematics today and, up to our knowledge, has never been used in engineering applications or mathematical physics. The main purpose of this paper, an…

Analysis of PDEs · Mathematics 2011-10-13 Jean-François Pommaret

The theory of quaternionic operators has applications in several different fields such as quantum mechanics, fractional evolution problems, and quaternionic Schur analysis, just to name a few. The main difference between complex and…

Functional Analysis · Mathematics 2017-10-31 Paula Cerejeiras , Fabrizio Colombo , Uwe Kähler , Irene Sabadini

In this paper we present a historical and scientific account of the development of the theory of the L\"owner-Kufarev classical and stochastic equations spanning the 90-year period from the seminal paper by K.L\"owner in 1923 to recent…

Complex Variables · Mathematics 2013-09-26 Filippo Bracci , Manuel D. Contreras , Santiago Díaz-Madrigal , Alexander Vasil'ev

In this paper I will give a brief history of the discovery (Hamilton, 1843) of quaternions. I will address the issue of why a theory of triplets (the original goal of Hamilton) could not be developed. Finally, I will discuss briefly the…

History and Overview · Mathematics 2011-11-28 Amy Buchmann

In their textbook, Suzuki and Varga [Y. Suzuki and K. Varga, {\em Stochastic Variational Approach to Quantum-Mechanical Few-Body Problems} (Springer, Berlin, 1998)] present the stochastic variational method with the correlated Gaussian…

Computational Physics · Physics 2009-11-13 Bernard Silvestre-Brac , Vincent Mathieu

It is a longstanding unsolved problem to characterize the optimal feedbacks for general SLQs (i.e., stochastic linear quadratic control problems) with random coefficients in infinite dimensions; while the same problem but in finite…

Optimization and Control · Mathematics 2019-10-15 Qi Lu , Xu Zhang

It is a longstanding unsolved problem to characterize the optimal feedback controls for general linear quadratic optimal control problem of stochastic evolution equation with random coefficients. A solution to this problem is given in [21]…

Optimization and Control · Mathematics 2022-02-22 Qi Lü , Tianxiao Wang

This paper is a survey on the emerging theory of truncated Toeplitz operators. We begin with a brief introduction to the subject and then highlight the many recent developments in the field since Sarason's seminal paper in 2007.

Complex Variables · Mathematics 2012-06-25 Stephan Ramon Garcia , William T. Ross

The constraint operators belonging to a generally covariant system are found out within the framework of the BRST formalism. The result embraces quadratic Hamiltonian constraints whose potential can be factorized as a never null function…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Rafael Ferraro , Daniel M. Sforza

We show that the four-state problem for general linear differential operators is flexible. The only flexibility result available in this context is the one for the five-state problem for the curl operator due to B. Kirchheim and D. Preiss,…

Analysis of PDEs · Mathematics 2021-07-23 Massimo Sorella , Riccardo Tione

Recent experimental advances have inspired the development of theoretical tools to describe the non-equilibrium dynamics of quantum systems. Among them an exact representation of quantum spin systems in terms of classical stochastic…

Quantum Physics · Physics 2023-04-19 Gennaro Tucci , Stefano De Nicola , Sascha Wald , Andrea Gambassi

This paper first presents necessary and sufficient conditions for the solvability of discrete time, mean-field, stochastic linear-quadratic optimal control problems. Then, by introducing several sequences of bounded linear operators, the…

Optimization and Control · Mathematics 2016-07-25 Robert. J Elliott , Xun Li , Yuan-Hua Ni

Nonextensive Statistical Mechanics has developed into an important framework for modeling the thermodynamics of complex systems and the information of complex signals. Upon the 80th birthday of the field's founder, Constantino Tsallis, a…

Statistical Mechanics · Physics 2025-11-25 Kenric P. Nelson

The satisfactory development of Quaternionic Analysis has indicated new solutions for physical and mathematical problems. It is worth mentioning the fact that quaternions possess four dimensions, and in this way they may be considered as…

Mathematical Physics · Physics 2015-08-25 J. Marão