arXiv subjects

André Neves

Publications and source records attributed to André Neves.

At least 19 recordsLinked to original sources

arXiv2026

Counting Minimal Lagrangians Via Mirzakhani Functions

We show that for $k>1$ the number of genus $k$ minimal Lagrangians with area at most $A$ in a product of hyperbolic surfaces grows on the order of $A^{6(k-1)}$, with an explicit leading constant given in terms of the Mirzakhani function, and we obtain a similar result for products of nonpositively curved surfaces. We also prove rigidity of the Lagrangian area spectrum, and obtain analogous counting results for products of a higher genus surface with a circle.

math.DG↗

arXiv2026

Rigidity and non-rigidity of the stable norm on $T^n$

We show that the stable norm of flat metrics on $H_{d}(T^n,\mathbb{R})$ is locally rigid if $1\leq d<n-1$ and locally rigid among metrics of the same volume if $d=n-1$. We also show that the stable norm on $H_{2}(T^3,\mathbb{R})$ is not locally rigid. As applications, we answer negatively a question raised by Bangert in his ICM address, prove local rigidity of the marked $k$-area spectrum of flat metrics for $1\leq k\leq n-2$, and prove a local rigidity result for the volume spectrum of flat metrics on $T^n$.

math.DG↗

arXiv2026

Closed minimal surfaces of index one in Riemannian manifolds

In this paper we prove that an $(n+1)$-manifold, compactly $n$-enlargeable, where $3\leq (n+1)\leq 7$, has connected, immersed Morse index one, closed minimal hypersurfaces with unbounded volumes for bumpy metrics. We prove that in the three-dimensional case the hypersurfaces are geometrically distinct using cyclic coverings of manifolds with boundary. The proof extends to $(n+1)$-fiberings. We prove a scalar curvature rigidity theorem for area-nonincreasing maps of three-dimensional manifolds. The case of stable surfaces is also discussed by using cohomology classes and incompressible surfaces.

math.DG↗

arXiv2024

Rigidity theorems for the area widths of Riemannian manifolds

The volume spectrum of a compact Riemannian manifold is a sequence of critical values for the area functional, defined in analogy with the Laplace spectrum by Gromov. In this paper we prove that the canonical metric on the two-dimensional projective plane is determined modulo isometries by its volume spectrum. We also prove that the surface Zoll metrics on the three-dimensional sphere are characterized by the equality of the spherical area widths. These widths generalize to the surface case the Lusternik-Schnirelmann lengths of closed geodesics. We prove a new sharp area systolic inequality for metrics on the three-dimensional projective space.

math.DG↗

arXiv2024

Conformal currents and the entropy of negatively curved three-manifolds

In this paper, we describe the intersection between geodesic and conformal currents on closed hyperbolic three-manifolds. We use this to prove some sharp bounds which involve the Liouville entropy of a negatively curved metric, the minimal surface entropy, and the area ratio. Using these ideas we also give a new proof of the Mostow Rigidity Theorem in the three-dimensional case.

math.DG↗

arXiv2023

LASIGE and UNICAGE solution to the NASA LitCoin NLP Competition

Biomedical Natural Language Processing (NLP) tends to become cumbersome for most researchers, frequently due to the amount and heterogeneity of text to be processed. To address this challenge, the industry is continuously developing highly efficient tools and creating more flexible engineering solutions. This work presents the integration between industry data engineering solutions for efficient data processing and academic systems developed for Named Entity Recognition (LasigeUnicage\_NER) and Relation Extraction (BiOnt). Our design reflects an integration of those components with external knowledge in the form of additional training data from other datasets and biomedical ontologies. We used this pipeline in the 2022 LitCoin NLP Challenge, where our team LasigeUnicage was awarded the 7th Prize out of approximately 200 participating teams, reflecting a successful collaboration between the academia (LASIGE) and the industry (Unicage). The software supporting this work is available at \url{https://github.com/lasigeBioTM/Litcoin-Lasige_Unicage}.

cs.CL↗

arXiv2022

Smart meter data processing: a showcase for simple and efficient textual processing

The increase in the production and collection of data from devices is an ongoing trend due to the roll-out of more cyber-physical applications. Smart meters, because of their importance in power grids, are a class of such devices whose produced data requires meticulous processing. In this paper, we use Unicage, a data processing system based on classic Unix shell scripting, that delivers excellent performance in a simple package. We use this methodology to process smart meter data in XML format, subjected to the constraints posed by a real use case. We develop a solution that parses, validates and performs a simple aggregation of 27 million XML files in less than 10 minutes. We present a study of the solution as well as the benefits of its adoption.

cs.DC↗

arXiv2022

The Developers' Design Thinking Toolbox in Hackathons: A Study on the Recurring Design Methods in Software Development Marathons

Hackathons are time-bounded collaborative events of intense teamwork to build prototypes usually in the form of software, aiming to specific challenges proposed by the organizers. These events became a widespread practice in the IT industry, universities and many other scenarios, as a result of a growing open-innovation trend in the last decade. Since the main deliverable of these events is a demonstrable version of an idea, such as early hardware or software prototypes, the short time frame requires participants to quickly understand the proposed challenge or even identify issues related to a given domain. To create solutions, teams follow an ad-hoc but effective design approach, that many times seems informal since the background of the participants is rather centered on technical aspects (e.g., web and mobile programming) and does not involve any training in Design Thinking. To understand this creative process, we conducted 37 interviews (32 hackathons winners and 5 hackathon organizers) with people from 16 countries. We aimed to identify the design processes and recurring design methods applied by winners in these events. Also, we conducted a focus group with 8 people experienced in hackathons (participants and organizers) to discuss our findings. Our analysis revealed that although hackathon winners with IT background have no formal training on Design Thinking, they are aware of many design methods, typically following a sequence of phases that involve divergent and convergent thinking to explore the problem space and propose alternatives in a solution space, which is the rationale behind Design Thinking. We derived a set of recommendations based on design strategies that seem to lead to successful hackathon participation. These recommendations can also be useful to organizers who intend to enhance the experience of newcomers in hackathons.

cs.SE↗

arXiv2021

Riemannian metrics on the sphere with Zoll families of minimal hypersurfaces

In this paper we construct smooth Riemannian metrics on the sphere which admit smooth Zoll families of minimal hypersurfaces. This generalizes a theorem of Guillemin for the case of geodesics. The proof uses the Nash-Moser Inverse Function Theorem in the tame maps setting of Hamilton. This answers a question of Yau on perturbations of minimal hypersurfaces in positive Ricci curvature. We also consider the case of the projective space and characterize those metrics on the sphere with minimal equators.

math.DG↗

arXiv2020

Morse inequalities for the area functional

In this article we prove the strong Morse inequalities for the area functional in codimension one, assuming that the ambient dimension satisfies $3 \leq (n + 1) \leq 7$, in both the closed and the boundary cases.

math.DG↗

arXiv2020

Counting minimal surfaces in negatively curved 3-manifolds

We introduced an asymptotic quantity that counts area-minimizing surfaces in negatively curved closed 3-manifolds and show that quantity to only be minimized, among all metrics of sectional curvature less than or equal -1, by the hyperbolic metric.

math.DG↗

arXiv2019

Deteção de estruturas permanentes a partir de dados de séries temporais Sentinel 1 e 2

Mapping structures such as settlements, roads, individual houses and any other types of artificial structures is of great importance for the analysis of urban growth, masking, image alignment and, especially in the studied use case, the definition of Fuel Management Networks (FGC), which protect buildings from forest fires. Current cartography has a low generation frequency and their resolution may not be suitable for extracting small structures such as small settlements or roads, which may lack forest fire protection. In this paper, we use time series data, extracted from Sentinel-1 and 2 constellations, over Santarém, Mação, to explore the detection of permanent structures at a resolution of 10 by 10 meters. For this purpose, a XGBoost classification model is trained with 133 attributes extracted from the time series from all the bands, including normalized radiometric indices. The results show that the use of time series data increases the accuracy of the extraction of permanent structures when compared using only static data, using multitemporal data also increases the number of detected roads. In general, the final result has a permanent structure mapping with a higher resolution than state of the art settlement maps, small structures and roads are also more accurately represented. Regarding the use case, by using our final map for the creation of FGC it is possible to simplify and accelerate the process of delimitation of the official FGC.

cs.LG↗

arXiv2019

Morse index of multiplicity one min-max minimal hypersurfaces

In this paper, we prove that the Morse index of a multiplicity one, smooth, min-max minimal hypersurface is generically equal to the dimension of the homology class detected by the families used in the construction. This confirms part of the program (\cite{marques-icm}, \cite{marques-neves-cycles}, \cite{marques-neves-index}, \cite{neves-icm}) proposed by the authors with the goal of developing a Morse theory for the area functional.

math.DG↗

arXiv2018

Equidistribution of minimal hypersurfaces for generic metrics

For almost all Riemannian metrics (in the $C^\infty$ Baire sense) on a closed manifold $M^{n+1}$, $3\leq (n+1)\leq 7$, we prove that there is a sequence of closed, smooth, embedded, connected minimal hypersurfaces that is equidistributed in $M$. This gives a quantitative version of the main result of \cite{irie-marques-neves}, by Irie and the first two authors, that established denseness of minimal hypersurfaces for generic metrics. As in \cite{irie-marques-neves}, the main tool is the Weyl Law for the Volume Spectrum proven by Liokumovich and the first two authors in \cite{liokumovich-marques-neves}.

math.DG↗

arXiv2018

On short time existence for the planar network flow

We prove the existence of the flow by curvature of regular planar networks starting from an initial network which is non-regular. The proof relies on a monotonicity formula for expanding solutions and a local regularity result for the network flow in the spirit of B. White's local regularity theorem for mean curvature flow. We also show a pseudolocality theorem for mean curvature flow in any codimension, assuming only that the initial submanifold can be locally written as a graph with sufficiently small Lipschitz constant.

math.AP↗

arXiv2018

Weyl law for the volume spectrum

Given $M$ a Riemannian manifold with (possibly empty) boundary, we show that its volume spectrum $\{ω_p(M)\}_{p\in\mathbb{N}}$ satisfies a Weyl law that was conjectured by Gromov.

math.DG↗

arXiv2018

Density of minimal hypersurfaces for generic metrics

For almost all Riemannian metrics (in the $C^\infty$ Baire sense) on a closed manifold $M^{n+1}$, $3\leq (n+1)\leq 7$, we prove that the union of all closed, smooth, embedded minimal hypersurfaces is dense. This implies there are infinitely many minimal hypersurfaces thus proving a conjecture of Yau (1982) for generic metrics.

math.DG↗

arXiv2016

Morse index and multiplicity of min-max minimal hypersurfaces

The Min-max Theory for the area functional, started by Almgren in the early 1960s and greatly improved by Pitts in 1981, was left incomplete because it gave no Morse index estimate for the min-max minimal hypersurface. We advance the theory further and prove the first general Morse index bounds for minimal hypersurfaces produced by it. We also settle the multiplicity problem for the classical case of one-parameter sweepouts.

math.DG↗