arXiv subjects

Constantin Udriste

Publications and source records attributed to Constantin Udriste.

At least 19 recordsLinked to original sources

arXiv2019

Flatness produced by some geometric PDEs

This paper has several goals. The first idea is to study the geometric PDEs of connection-flatness, curvature-flatness, Ricci-flatness, scalar curvature-flatness in a modern and rigorous way. Although the idea is not new, our main Theorems about flatness introduce a different point of view in Differential Geometry. The second idea is to introduce and study the Euler-Lagrange prolongations of PDEs-flatness solutions via associated least squares Lagrangian densities and functionals on Riemannian manifolds. All geometric PDEs turned into one of the most intensively developing branches of modern differential geometry.

math.DG↗

arXiv2018

Phase Diagram for Roegenian Economics

We recall the similarities between the concepts and techniques of Thermodynamics and Roegenian Economics. The Phase Diagram for a Roegenian economic system highlights a triple point and a critical point, with related explanations. These ideas can be used to improve our knowledge and understanding of the nature of development and evolution of Roegenian economic systems.

q-fin.GN↗

arXiv2018

Economic Cycles of Carnot Type

Originally, the Carnot cycle is a theoretical thermodynamic cycle that provides an upper limit on the efficiency that any classical thermodynamic engine can achieve during the conversion of heat into work, or conversely, the efficiency of a refrigeration system in creating a temperature difference by the application of work to the system. The aim of this paper is to introduce and study the economic Carnot cycles into a Roegenian economy, using our Thermodynamic-Economic Dictionary. Of course, the most difficult questions are: what is the economic significance of such a cycle? Roegenian economics is acceptable or not, in terms of practical applications? Our answer is yes for both questions.

q-fin.GN↗

arXiv2018

Geobiodynamics and Roegenian Economic Systems

This mathematical essay brings together ideas from Economics, Geobiodynamics and Thermodynamics. Its purpose is to obtain real models of complex evolutionary systems. More specifically, the essay defines Roegenian Economy and links Geobiodynamics and Roegenian Economy. In this context, we discuss the isomorphism between the concepts and techniques of Thermodynamics and Economics. Then we describe a Roegenian economic system like a Carnot group. After we analyse the phase equilibrium for two heterogeneous economic systems. The European Union Economics appears like Cartesian product of Roegenian economic systems and its Balance is analysed in details. A Section at the end describes the "economic black holes" as small parts of a a global economic system in which national income is so great that it causes others poor enrichment. These ideas can be used to improve our knowledge and understanding of the nature of development and evolution of thermodynamic-economic systems.

q-fin.GN↗

arXiv2017

Optimal control on distributions

This paper studies (single-time and multitime) optimal control problems on a nonholonomic manifold (described either by the kernel of a Gibbs-Pfaff form or by the span of appropriate vector fields). For both descriptions we analyse: infinitesimal deformations and adjointness, single-time optimal control problems, multitime optimal control problem of maximizing a multiple integral functional, multitime optimal control problem of maximizing a curvilinear integral functional, Curvilinear functionals depending on curves, optimization of mechanical work on Riemannian manifolds. Also we prove that a nonholonomic system can be always controlled by uni-temporal or bi-temporal bang-bang controls.

math.OC↗

arXiv2017

Genome of Descartes Folium via Normalization

The Folium of Descartes in $\mathbb{K}\times\mathbb{K}$ carries group laws, defined entirely in terms of algebraic operations over the field $\mathbb{K}$. The problems discussed in this paper include: normalization of Descartes Folium, group laws and morphisms, exotic structures, exotic structures, second exotic structure, some topologies on Descartes Folium, differential structure on Descartes Folium, first isomorphism of algebraic Lie groups over $\mathbb{K}$, second isomorphism of algebraic Lie groups over $\mathbb{K}$, derived structures of algebraic Lie groups, a differential/complex analytic structure on Descartes Folium, Descartes Folium as a topological field, etc. For predicting these terms, we focus on methods that exploit diagram manipulation techniques (as alternatives to algebraic method of proofs). All our results confirm that the Descartes Folium stores natural group structures, unsuspected till now.

math.AG↗

arXiv2015

Almost Coquaternion Structure

Our aim is to define and study a structure for some $(4n+3)$-dimensional manifolds which is named almost coquaternion structure. This structure is composed of three almost cocomplex structures $(ϕ_a, ξ_a, η_a)$, $a = 1,2,3$, which satisfy some relations and may be considered as analogous to the almost quaternion structure for $(4n+4)$-dimensional manifolds. The sphere $S^{4n+3}$ is a typical example of differentiable manifold which admits an almost coquaternion structure $(ϕ_a, ξ_a, η_a)$, $a = 1,2,3$. Using the 1-forms $η_a$ of the almost coquaternion structure of the sphere $S^{4n+3}$, C. Teleman defined and studied on $S^{4n+3}$ a nonholonomic manifold $V^{4n}_{4n+3}$ whose Riemannian metric is the one of a symmetric space of E. Cartan. Keeping in mind Teleman's idea, we observed that on an almost coquaternion manifold a nonholonomic (holonomic) manifold of codimension three can be defined and studied by nonintegrable (completely integrable) Pfaff's system $η_1 = 0$, $η_2 = 0$, $η_3 = 0$.

math.DG↗

arXiv2015

Lagrange and Wolf Dualities in Nonholonomic Optimization

This article deals with optimizing problems classified by the kinds of restrictions as required in differential geometry and in mechanics: holonomic and nonholonomic. The central issue relates to dual nonholonomic programs (what they mean and how they are solved?) when the nonholonomic constraints are given by Pfaff equations. The original results are surprising and include aspects derived from the Vranceanu theory of nonholonomic manifolds, from the geometric distributions theory and from Darboux's theorem on canonical coordinates in which we can express a Pfaff form. On these ways we get also an original Riemannian geometry attached to a given constrained optimization problem.

math.OC↗

arXiv2015

Periodic linear discrete multitime diagonal recurrence with application in economics

Floquet theory, first published in 1883 for periodic linear differential equations, is extended in this paper to multitime diagonal recurrences. We find explicitly a monodromy matrix, and we comment its eigenvalues (called Floquet multipliers). The Floquet point of view brings about an important simplification: the initial linear diagonal recurrence system is reduced to a linear recurrence system, with constant coefficients along "diagonal lines". The results are applied to the discrete multitime Samuelson-Hicks models, with constant, respectively multi-periodic, coefficients, in order to find bivariate sequences with economic meaning. For constant coefficients case, it was found also the generating function; for multi-periodic coefficients case, we determined the Floquet multipliers.

math.DS↗

arXiv2015

Efficiency for multitime vector variational problems on Riemannian manifolds involving geodesic quasiinvex functionals

We study the connection between a multitime scalar variational problem (SVP), a multitime vector variational problem (VVP) and a multitime vector fractional variational problem (VFP). For (SVP), we establish necessary optimality conditions. For both vector variational problems, we define the notions of Pareto efficient solution and of normal efficient solution and we establish necessary efficiency conditions for (VVP) and (VFP) using both notions. The main purpose of the paper is to establish sufficient efficiency conditions for the vector problems (VVP) and (VFP). Moreover, we obtain sufficient optimality conditions for (SVP). The sufficient conditions are based on our original notion of $(ρ,b)$-geodesic quasiinvexity.

math.OC↗

arXiv2015

Discrete diagonal recurrences and discrete minimal submanifolds

Our original results refer to multivariate recurrences: discrete multitime diagonal recurrence, bivariate recurrence, trivariate recurrence, solutions tailored to particular situations, second order multivariate recurrences, characteristic equation, and multivariate diagonal recurrences of superior order. We find the solutions, we clarify the structural background and provides short, conceptual proofs. The original results include a new point of view on discrete minimal submanifolds.

math.DS↗

arXiv2015

Discrete linear multiple recurrence with multi-periodic coefficients

The aim of our paper is to formulate and solve problems concerning linear multiple periodic recurrence equations. Among other things, we discuss in detail the cases with periodic and multi-periodic coefficients, highlighting in particular the theorems of Floquet type. For this aim, we find specific forms for the fundamental matrix. Explicitly monodromy matrix is given, and its eigenvalues (called Floquet multipliers) are shown. The Floquet point of view brings about an important simplification: the initial linear multiple recurrence system is reduced to another linear multiple recurrence system, with constant coefficients along partial directions. The results are applied to the discrete multitime Samuelson-Hicks models with constant, respectively multi-periodic, coefficients, in order to find bivariate sequences with economic meaning.

math.DS↗

arXiv2015

Discrete multitime multiple recurrence

The aim of our paper is to formulate and solve problems concerning multitime multiple recurrence equations. We discuss in detail the generic properties and the existence and uniqueness of solutions. Among the general things, we discuss in detail the cases of autonomous and non-autonomous recurrences, highlighting in particular the theorems of existence and uniqueness of solutions. Finally, are given interesting examples which are the analogue of arithmetic progression and the analogue of geometric progression. The multitime multiple recurrences are required in analysis of algorithms, computational biology, information theory, queueing theory, filters theory, statistical physics etc. The theoretical part about them is little or not known, this being the first paper about the subject.

math.DS↗

arXiv2015

Linear discrete multitime multiple recurrence

The multitime multiple recurrences are common in analysis of algorithms, computational biology, information theory, queueing theory, filters theory, statistical physics etc. The theoretical part about them is little or not known. That is why, the aim of our paper is to formulate and solve problems concerning nonautonomous multitime multiple recurrence equations. Among other things, we discuss in detail the cases of linear recurrences with constant coefficients, highlighting in particular the theorems of existence and uniqueness of solutions.

math.DS↗

arXiv2012

Multitime Rayleigh Solitons

Multitime evolution PDEs for Rayleigh waves are considered, using geometrical ingredients capable to build an ultra-parabolic-hyperbolic differential operator. Their soliton solutions are found based on appropriate hypotheses and specific ODEs. These multitime solitons develop complex behavior of deformation phenomena. The original results include: the form of multitime Rayleigh PDEs, the construction of multitime Rayleigh solitons via some significant amounts of analysis and the stability of multitime Rayleigh solitons, which are stable enough to persist indefinitely. In this context we survey some of the highlights of multitime PDEs theory, from the more classical single-time case, to the more recent multitime case, as well as current developments in using this theory to rigorously prove the sense for several evolution variables and PDEs.

math-ph↗

arXiv2012

Riemann flow and Riemann wave via bialternate product Riemannian metric

We illustrate the flow or wave character of the metrics and curvatures of evolving manifolds, introducing the Riemann flow and the Riemann wave via the bialternate product Riemannian metric. This kind of evolutions are new and very natural to understand certain flow or wave phenomena in the nature as well as the geometry of evolving manifolds. It possesses many interesting properties from both mathematical and physical point of views. We reveal the novel features of Riemann flow and Riemann wave, as well as their versatility, by new original results. The main results refer to: (1) Riemann flow PDE, (3) connection between Ricci flow and Riemann flow,(4) the meaning of the Riemann flows on constant curvature manifolds, (5) the gradient Riemann solitons, (6) the infinitesimal deformations (linearizations) of Ricci flow and of Riemann flow PDEs, (7) the existence of Ricci or Riemann curvature blow-up at finite-time singularities of the flow, (8) the Riemann wave PDE and its meaning on constant curvature manifolds, (9) the existence of Ricci or Riemann curvature blow-up at finite-time singularities of the wave, (10) the general form of some essential PDE systems on Riemannian manifolds.

math.AP↗

arXiv2012

Riemannian optimal control

The aim of this paper is to adapt the general multitime maximum principle to a Riemannian setting. More precisely, we intend to study geometric optimal control problems constrained by the metric compatibility evolution PDE system; the evolution ("multitime") variables are the local coordinates on a Riemannian manifold, the state variable is a Riemannian structure and the control is a linear connection compatible to the Riemannian metric. We apply the obtained results in order to solve two flow-type optimal control problems on Riemannian setting: firstly, we maximize the total divergence of a fixed vector field; secondly, we optimize the total Laplacian (the gradient flux) of a fixed differentiable function. Each time, the result is a bang-bang-type optimal linear connection. Moreover, we emphasize the possibility of choosing at least two soliton-type optimal (semi-) Riemannian structures. Finally, these theoretical examples help us to conclude about the geometric optimal shape of pipes, induced by the direction of the flow passing through them.

math.OC↗

arXiv2011

Multitime controlled linear PDE systems

We derive new results regarding the controllability and the reachability of multitime controlled linear PDE systems of first order. These systems describe some important multitime evolution in engineering, economics and biology. Some of them come from evolution PDEs of superior order. The original results include a refinement and a supplement of multitime optimal control theory, developed in some recent papers by the second author. They refer to the complete integrability conditions, conditions for the existence of solutions, path independent curvilinear integrals, the multitime fundamental matrix, multitime adjoint Cauchy problems, control space, controllability and reachability of phases, controllability gramian, reachability gramian, controllability matrix, counter-examples and commentaries.

math.OC↗