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Lucile Vandembroucq

Publications and source records attributed to Lucile Vandembroucq.

16 recordsLinked to original sources
arXiv2025

Parametrized topological complexity of bundles of real projective spaces, I

Analysis of motion algorithms for autonomous systems operating under variable external conditions leads to the concept of parametrized topological complexity \cite{CFW}. In \cite{CFW}, \cite{CFW2} the parametrized topological complexity was computed in the case of the Fadell - Neuwirth bundle which is pertinent to algorithms of collision free motion of many autonomous systems in ${\Bbb R}^d$ avoiding collisions with multiple obstacles. The parametrized topological complexity of sphere bundles was studied in detail in \cite{FW}, \cite{FW2}, \cite{FP}. In this paper we make the next step by studying parametrized topological complexity of bundles of real projective spaces which arise as projectivisations of vector bundles. This leads us to new problems of algebraic topology involving theory of characteristic classes and geometric topology. We establish sharp upper bounds for parametrized topological complexity ${\sf TC}[p:E\to B]$ improving the general upper bounds. We develop algebraic machinery for computing lower bounds for ${\sf TC}[p:E\to B]$ based on the Stiefel - Whitney characteristic classes. Combining the lower and the upper bounds we compute explicitly many specific examples.

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arXiv2025

Maps from Grassmannians of 2-planes to projective spaces

Using quaternions and octonions, we construct some maps from the Grassmannian of 2-dimensional planes of $\mathbb{R}^n$, $\mathrm{Gr}_2(\mathbb{R}^n)$, to the projective space $\mathbb{R}\mathrm{P}^k$, for certain values of $n$ and $k$. All of our maps induce an isomorphism at the level of fundamental groups, and two of them are shown to be submersions. As an application, we obtain new estimates of the Lusternik-Schnirelmann category of $\mathrm{Gr}_2(\mathbb{R}^n)$ for specific values of $n$.

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arXiv2024

Explicit Quillen models for Cartesian products of $2$-cones

We give an explicit minimal Quillen model for the Cartesian product $X\times Y$ of rational $2$-cones in terms of derivations and a binary operation $\star \colon \mathbb{M}(V)\otimes \mathbb{L}(W)\to \mathbb{L}(V\oplus W\oplus s(V\otimes W))$, where $(\mathbb{L}(V), \partial)$ and $(\mathbb{L}(W), \partial)$ are Quillen minimal models for $X$ and $Y$ respectively and $\mathbb{M}$ denotes the free magma on $W$. The model presented also allows us to explicitly describe a model for the diagonal map $Δ\colon X\to X\times X$.

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arXiv2023

An upper bound for the rational topological complexity of a family of elliptic spaces

In this work, we show that, for any simply-connected elliptic space $S$ admitting a pure minimal Sullivan model with a differential of constant length, we have ${\rm TC}_0(S)\leq 2{\rm cat}_0(S)+χ_π(S)$ where $χ_π(S)$ is the homotopy characteristic. This is a consequence of a structure theorem for this type of models, which is actually our main result.

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arXiv2022

On the rational topological complexity of coformal elliptic spaces

We establish some upper and lower bounds of the rational topological complexity for certain classes of elliptic spaces. Our techniques permit us in particular to show that the rational topological complexity coincides with the dimension of the rational homotopy for some special families of coformal elliptic spaces.

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arXiv2021

On the topological complexity of manifolds with abelian fundamental group

We find conditions which ensure that the topological complexity of a closed manifold $M$ with abelian fundamental group is nonmaximal, and see through examples that our conditions are sharp. This generalizes results of Costa and Farber on the topological complexity of spaces with small fundamental group. Relaxing the commutativity condition on the fundamental group, we also generalize results of Dranishnikov on the Lusternik-Schnirelmann category of the cofibre of the diagonal map $Δ: M \to M \times M$ for nonorientable surfaces by establishing the nonmaximality of this invariant for a large class of manifolds.

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arXiv2018

Motion planning in connected sums of real projective spaces

The topological complexity ${\sf TC}(X)$ is a homotopy invariant of a topological space $X$, motivated by robotics, and providing a measure of the navigational complexity of $X$. The topological complexity of a connected sum of real projective planes, that is, a high genus nonorientable surface, is known to be maximal. We use algebraic tools to show that the analogous result holds for connected sums of higher dimensional real projective spaces.

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arXiv2017

Hopf Invariants for sectional category with applications to topological robotics

We develop a theory of generalized Hopf invariants in the setting of sectional category. In particular we show how Hopf invariants for a product of fibrations can be identified as shuffle joins of Hopf invariants for the factors. Our results are applied in the study of Farber's topological complexity for 2-cell complexes, as well as in the construction of a counter-example to the analogue for topological complexity of Ganea's conjecture on Lusternik-Schnirelmann category.

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arXiv2017

Topological Complexity of the Klein bottle

We show that the (normalized) topological complexity of the Klein bottle is $4$. We also show that, for any $g\geq 2$, $TC(N_g)=4$. This completes the recent work by Dranishnikov on the topological complexity of non-orientable surfaces.

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arXiv2017

Q-Topological Complexity

By analogy with the invariant Q-category defined by Scheerer, Stanley and Tanré, we introduce the notions of Q-sectional category and Q-topological complexity. We establish several properties of these invariants. We also obtain a formula for the behaviour of the sectional category with respect to a fibration which generalizes the classical formulas for Lusternik-Schnirelmann category and topological complexity.

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arXiv2016

Hopf invariants, topological complexity, and LS-category of the cofiber of the diagonal map for two-cell complexes

Let $X$ be a two-cell complex with attaching map $α\colon S^q\to S^p$, and let $C_X$ be the cofiber of the diagonal inclusion $X\to X\times X$. It is shown that the topological complexity (${\rm TC}$) of $X$ agrees with the Lusternik-Schnirelmann category (${\rm cat}$) of $C_X$ in the (almost stable) range $q\leq2p-1$. In addition, the equality ${\rm TC}(X)={\rm cat}(C_X)$ is proved in the (strict) metastable range $2p-1<q\leq3(p-1)$ under fairly mild conditions by making use of the Hopf invariant techniques recently developed by the authors in their study of the sectional category of arbitrary maps.

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arXiv2009

Joins of DGA modules and sectional category

We construct an explicit semifree model for the fiber join of two fibrations p: E --> B and p': E' --> B from semifree models of p and p'. Using this model, we introduce a lower bound of the sectional category of a fibration p which can be calculated from any Sullivan model of p and which is closer to the sectional category of p than the classical cohomological lower bound given by the nilpotency of the kernel of p^*: H^*(B;Q) --> H^*(E;Q). In the special case of the evaluation fibration X^I --> X x X we obtain a computable lower bound of Farber's topological complexity TC(X). We show that the difference between this lower bound and the classical cohomological lower bound can be arbitrarily large.

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arXiv2007

Simplicial resolutions and Ganea fibrations

In this work, we compare the two approximations of a path-connected space $X$, by the Ganea spaces $G_n(X)$ and by the realizations $\|Λ_\bullet X\|_{n}$ of the truncated simplicial resolutions emerging from the loop-suspension cotriple $ΣΩ$. For a simply connected space $X$, we construct maps $\|Λ_\bullet X\|_{n-1}\to G_n(X)\to \|Λ_\bullet X\|_{n}$ over $X$, up to homotopy. In the case $n=2$, we prove the existence of a map $G_2(X)\to\|Λ_\bullet X\|_{1}$ over $X$ (up to homotopy) and conjecture that this map exists for any $n$.

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