arXiv subjects

Donald M Davis

Publications and source records attributed to Donald M Davis.

10 recordsLinked to original sources

arXiv2025

The connective KO theory of the Eilenberg-MacLane space K(Z/2,2)

We compute ko_*(K(Z/2,2)) and ko^*(K(Z/2,2)), the connective KO-homology and -cohomology of the mod 2 Eilenberg-MacLane space K(Z/2,2), using the Adams spectral sequence. The work relies heavily on work done several years earlier for the (complex) ku groups by the author and W.S.Wilson. We illustrate an interesting duality relation between the ko-homology and -cohomology groups. We deduce a new result about Stiefel-Whitney classes in Spin manifolds.

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arXiv2024

The connective KO-theory of the Eilenberg-MacLane space K(Z_2,2), I: the E_2 page

We compute the $E_2$ page of the Adams spectral sequence converging to the connective KO-theory of the second mod 2 Eilenberg-MacLane space, $ko_*(K(Z/2,2))$. This required a careful analysis of the structure of $H^*(K(Z/2,2);Z_2)$ as a module over the subalgebra of the Steenrod algebra generated by $Sq^1$ and $Sq^2$. Complete analysis of the spectral sequence will be performed in a subsequent paper.

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arXiv2023

Isomorphism classes of cut loci for a cube

We prove that a face of a cube can be optimally partitioned into connected 193 sets on which the cut locus, or ridge tree, is constant up to isomorphism as a labeled graph. These are 60 connected open sets, curves bounding them, and intersection points of curves. Polynomial equations for the curves are provided. Sixteen pairs of sets support the same cut locus class. We present the 177 distinct cut locus classes.

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arXiv2020

Geodesics in the configuration spaces of two points in R^n

We determine explicit formulas for geodesics (in the Euclidean metric) in the configuration space of ordered pairs (x,x') of points in R^n which satisfy d(x,x')>=epsilon. We interpret this as two or three (depending on the parity of n) geodesic motion-planning rules for this configuration space. In the associated unordered configuration space, we need not prescribe that the points stay apart by epsilon. For this space, with a Euclidean metric, we show that geodesic motion-planning rules correspond to ordinary motion-planning rules on RP^{n-1}.

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arXiv2019

K-theory and immersions of spatial polygon spaces

For ell a generic n-tuple of positive numbers, N(ell) denotes the space of isometry classes of oriented n-gons in R^3 with side lengths specified by ell. We determine the algebra K(N(ell)) and use this to obtain nonimmersions of the 2(n-3)-manifold N(ell) in Euclidean space for several families of ell. We also use obstruction theory to tell exactly when N(ell) immerses in R^{4n-14} for two families of ell.

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arXiv2018

Bounds for higher topological complexity of real projective space implied by BP

We use Brown-Peterson cohomology to obtain lower bounds for the higher topological complexity, TC_k(RP^n), of real projective spaces, which are often much stronger than those implied by ordinary mod-2 cohomology.

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arXiv2017

A lower bound for higher topological complexity of real projective space

We obtain an explicit formula for the best lower bound for the higher topological complexity, TC_k(P^n), of real projective space implied by mod 2 cohomology.

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arXiv2017

The symmetrized topological complexity of the circle

We determine the symmetrized topological complexity of the circle, using primarily just general topology.

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arXiv2009

Odd-primary homotopy exponents of compact simple Lie groups

We note that a recent result of the second author yields upper bounds for odd-primary homotopy exponents of compact simple Lie groups which are often quite close to the lower bounds obtained from v_1-periodic homotopy theory.

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arXiv2008

Divisibility by 2 and 3 of certain Stirling numbers

The numbers e_p(k,n) defined as min(nu_p(S(k,j)j!): j >= n) appear frequently in algebraic topology. Here S(k,j) is the Stirling number of the second kind, and nu_p(-) the exponent of p. The author and Sun proved that if L is sufficiently large, then e_p((p-1)p^L + n -1, n) >= n-1+nu_p([n/p]!). In this paper, we determine the set of integers n for which equality holds in this inequality when p=2 and 3. The condition is roughly that, in the base-p expansion of n, the sum of two consecutive digits must always be less than p.

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