arXiv subjects

Alexandre Rocha

Publications and source records attributed to Alexandre Rocha.

4 recordsLinked to original sources

arXiv2019

Generic properties of Ma\~n\'e's set of exact magnetic Lagrangians

Let $M$ be a closed manifold and $L$ an exact magnetic Lagrangian. In this paper we proved that there exists a residual $\mathcal{G}$ of $H^{1}\left( M;\mathbb{R}\right)$ such that the property: \begin{equation*} {\widetilde{\mathcal{M}}}\left( c\right) ={\widetilde{\mathcal{A}}}\left( c\right) ={\widetilde{\mathcal{N}}}\left( c\right), \forall c\in \mathcal{G} \end{equation*} with ${\widetilde{\mathcal{M}}}\left( c\right)$ supports on a uniquely ergodic measure, is generic in the family of exact magnetic Lagrangians. We also prove that, fixed the cohomology class $c$, there exists a residual set of exact magnetic Lagrangians such that when this unique measure is supported on a periodic orbit, this orbit is hyperbolic and its stable and unstable manifolds intersect transversally. This result is a version of Theorem D of \cite{gon5} for the exact magnetic Lagrangian case.

math.DS↗

arXiv2014

Optical spectrum of bottom-up graphene nanoribbons: towards efficient atom-thick excitonic solar cells

Recently, atomically well-defined cove-shaped graphene nanoribbons have been obtained using bottom-up synthesis. These nanoribbons have an optical gap in the visible range of the spectrum which make them candidates for donor materials in photovoltaic devices. From the atomistic point of view, their electronic and optical properties are not clearly understood. Therefore, in this work we carry out ab-initio density functional theory calculations combine with many-body perturbation formalism to study their electronic and optical properties. Through the comparison with experimental measurements, we show that an accurate description of the nanoribbon's optical properties requires the inclusion of electron-hole correlation effects. The energy, binding energy and the corresponding excitonic transitions involved are analyzed. We found that in contrast to zigzag graphene nanoribbons, the excitonic peaks in the absorption spectrum are a consequence of a group of transitions involving the first and second conduction and valence bands. Finally, we estimate some relevant optical properties that strengthen the potential of these nanoribbons for acting as a donor materials in photovoltaic.

cond-mat.mes-hall↗

arXiv2012

A dynamical condition for differentiability of Mather's average action

We prove the differentiability of $β$ of Mather function on all homology classes corresponding to rotation vectors of measures whose supports are contained in a Lipschitz Lagrangian absorbing graph, invariant by Tonelli Hamiltonians. We also show the relationship between local differentiability of $β$ and local integrability of the Hamiltonian flow.

math.DS↗

arXiv2012

A Generic Property of Exact Magnetic Lagrangians

We prove that for the set of Exact Magnetic Lagrangians the property "There exist finitely many static classes for every cohomology class" is generic. We also prove some dynamical consequences of this property.

math.DS↗