Search results for "model theory"
showing 10 items of 681 documents
Dynamical equivalence of impulsive quasilinear equations
2015
Abstract Using Green type map we can find sufficient conditions under which an impulsive quasilinear equation is dynamically equivalent to its corresponding linear equation. This result extends Grobman Hartman theorem for equations without ordinary dichotomy.
Polaroid type operators under perturbations
2013
Explicit closed form solutions of boundary value problems for systems of difference equations
1990
In this paper boundary value problems for systems of difference equations of the type , where A j ∈ C p×p and bn y j+n ∈ C p , for 0≤j≤k − 1, are studied from an algebraic point of view. Existence conditions and closed form solutions are given in terms of co-solutions of the algebraic matrix equation .
Introducing the Time Series Change Visualization and Interpretation (TSCVI) method for the interpretation of global NDVI changes
2021
Abstract This paper presents a novel method for the visualization of changes in vegetation related variables. This method, termed Time Series Change Visualization and Interpretation (TSCVI), allows to summarize changes associated to both vegetation productivity and phenology in a single map. To that end, three metrics are retrieved on an annual basis from plotting NDVI (Normalized Difference Vegetation Index) values on a polar plot. Changes in these metrics are then analyzed and mapped in an IHS (Intensity Hue Saturation) image, where colors indicate changes regarding the growing-season (earlier or later occurrence, stronger or weaker seasonality), while changes associated to productivity a…
On the classification of observations structured into groups
1988
The paper is concerned with the problem of classifying a specific group into two populations (insect eggs of the same clutch belonging therefore to the same species). Two approaches, one parametric and the other non-parametric, are described. The classical likelihood ratio procedure is derived. An interpretation and a decomposition of the test criteria is given. A misclassification estimate using the Chernoff–Kullback–Kailath region is provided.
The Obstacle Problem in a Non-Linear Potential Theory
1988
M. Brelot gave rise to the concept harmonic space when he extended classical potential theory on ℝn to an axiomatic system on a locally compact space. I have recently constructed1 a non-linear harmonic space by dropping the assumption that the sum of two harmonic functions is harmonic and considering some other axioms instead. This approach has its origin in the work of O. Martio, P. Lindqvist and S. Granlund2,3,4, who have developed a non-linear potential theory on ℝn connected with variational integrals of the type ∫ F(x,∇u(x)) dm(x), where F(x, h) ≈ |h|p.
Exact mechanical models of fractional hereditary materials
2012
Fractional Viscoelasticity is referred to materials, whose constitutive law involves fractional derivatives of order β R such that 0 β 1. In this paper, two mechanical models with stress-strain relation exactly restituting fractional operators, respectively, in ranges 0 β 1 / 2 and 1 / 2 β 1 are presented. It is shown that, in the former case, the mechanical model is described by an ideal indefinite massless viscous fluid resting on a bed of independent springs (Winkler model), while, in the latter case it is a shear-type indefinite cantilever resting on a bed of independent viscous dashpots. The law of variation of all mechanical characteristics is of power-law type, strictly related to th…
Serrin-Type Overdetermined Problems: an Alternative Proof
2008
We prove the symmetry of solutions to overdetermined problems for a class of fully nonlinear equations, namely the Hessian equations. In the case of the Poisson equation, our proof is alternative to the proofs proposed by Serrin (moving planes) and by Weinberger. Moreover, our proof makes no direct use of the maximum principle while it sheds light on a relation between the Serrin problem and the isoperimetric inequality.
The chemical signature of jet-driven hypernovae
2020
Hypernovae powered by magnetic jets launched from the surface of rapidly rotating millisecond magnetars are one of the leading models to explain broad-lined Type Ic supernovae (SNe Ic-BL), and have been implicated as an important source of metal enrichment in the early Universe. We investigate the nucleosynthesis in such jet-driven hypernovae using a parameterised, but physically motivated, approach that analytically relates an artificially injected jet energy flux to the power available from the energy in differential rotation in the proto-neutron star. We find ejected $^{56}\mathrm{Ni}$ masses of $0.05\,\mathrm{M}_\odot - 0.45\,\mathrm{M}_\odot$ in our most energetic models with explosion…
Heavy sterile neutrinos in stellar core-collapse
2018
We perform spherically symmetric simulations of the core collapse of a single progenitor star of zero age main sequence mass $M_{\rm ZAMS} = 15 \, M_{\odot}$ with two models of heavy sterile neutrinos in the mass range of hundred MeV$/c^2$. According to both models, these hypothetical particles are copiously produced in the center, stream outwards a subsequently decay releasing energy into final states (including neutrinos) of the Standard Model. We find that they can lead to a successful explosion in otherwise non-exploding progenitors. Depending on their unknown parameters (e.g., mass and coupling constants with matter), we obtain either no explosion or an explosion of one of two types, i…