arXiv subjects

Henry P. Wynn

Publications and source records attributed to Henry P. Wynn.

25 records · Page 2Linked to original sources

arXiv2013

Subgroup Majorization

The extension of majorization (also called the rearrangement ordering), to more general groups than the symmetric (permutation) group, is referred to as $G$-majorization. There are strong results in the case that $G$ is a reflection group and this paper builds on this theory in the direction of subgroups, normal subgroups, quotient groups and extensions. The implications for fundamental cones and order-preserving functions are studied. The main example considered is the hyperoctahedral group, which, acting on a vector in $\mathbb R^n$, permutes and changes the signs of components.

math.ST↗

arXiv2012

The algebraic method in experimental design

The algebraic method provides useful techniques to identify models in designs and to understand aliasing of polynomial models. The present note surveys the topic of Gröbner bases in experimental design and then describes the notion of confounding and the algebraic fan of a design. The ideas are illustrated with a variety of design examples ranging from Latin squares to screening designs.

stat.ME↗

arXiv2011

(U,V)-Ordering and a Duality Theorem for Risk Aversion and Lorenz-type Orderings

There is a duality theory connecting certain stochastic orderings between cumulative distribution functions F_1,F_2 and stochastic orderings between their inverses F_1^(-1),F_2^(-1). This underlies some theories of utility in the case of the cdf and deprivation indices in the case of the inverse. Under certain conditions there is an equivalence between the two theories. An example is the equivalence between second order stochastic dominance and the Lorenz ordering. This duality is generalised to include the case where there is "distortion" of the cdf of the form v(F) and also of the inverse. A comprehensive duality theorem is presented in a form which includes the distortions and links the duality to the parallel theories of risk and deprivation indices. It is shown that some well-known examples are special cases of the results, including some from the Yaari social welfare theory and the theory of majorization.

math.ST↗

arXiv2011

Differential cumulants, hierachical models and monomial ideals

For a joint probability density function f(x) of a random vector X the mixed partial derivatives of log f(x) can be interpreted as limiting cumulants in an infinitesimally small open neighborhood around x. Moreover, setting them to zero everywhere gives independence and conditional independence conditions. The latter conditions can be mapped, using an algebraic differential duality, into monomial ideal conditions. This provides an isomorphism between hierarchical models and monomial ideals. It is thus shown that certain monomial ideals are associated with particular classes of hierarchical models.

math.ST↗

arXiv2008

Smooth supersaturated models

In areas such as kernel smoothing and non-parametric regression there is emphasis on smooth interpolation and smooth statistical models. Splines are known to have optimal smoothness properties in one and higher dimensions. It is shown, with special attention to polynomial models, that smooth interpolators can be constructed by first extending the monomial basis and then minimising a measure of smoothness with respect to the free parameters in the extended basis. Algebraic methods are a help in choosing the extended basis which can also be found as a saturated basis for an extended experimental design with dummy design points. One can get arbitrarily close to optimal smoothing for any dimension and over any region, giving a simple alternative models of spline type. The relationship to splines is shown in one and two dimensions. A case study is given which includes benchmarking against kriging methods.

stat.CO↗

arXiv2008

Asymptotic behaviour of a family of gradient algorithms in R^d and Hilbert spaces

The asymptotic behaviour of a family of gradient algorithms (including the methods of steepest descent and minimum residues) for the optimisation of bounded quadratic operators in R^d and Hilbert spaces is analyzed. The results obtained generalize those of Akaike (1959) in several directions. First, all algorithms in the family are shown to have the same asymptotic behaviour (convergence to a two-point attractor), which implies in particular that they have similar asymptotic convergence rates. Second, the analysis also covers the Hilbert space case. A detailed analysis of the stability property of the attractor is provided.

math.OC↗

arXiv2004

Monomial ideals and the Scarf complex for coherent systems in reliability theory

A certain type of integer grid, called here an echelon grid, is an object found both in coherent systems whose components have a finite or countable number of levels and in algebraic geometry. If α=(α_1,...,α_d) is an integer vector representing the state of a system, then the corresponding algebraic object is a monomial x_1^{α_1}... x_d^{α_d} in the indeterminates x_1,..., x_d. The idea is to relate a coherent system to monomial ideals, so that the so-called Scarf complex of the monomial ideal yields an inclusion-exclusion identity for the probability of failure, which uses many fewer terms than the classical identity. Moreover in the ``general position'' case we obtain via the Scarf complex the tube bounds given by Naiman and Wynn [J. Inequal. Pure Appl. Math. (2001) 2 1-16]. Examples are given for the binary case but the full utility is for general multistate coherent systems and a comprehensive example is given.

math.ST↗