Dynamics and zeta functions on conformally compact manifolds

In this note, we study the dynamics and associated zeta functions of conformally compact manifolds with variable negative sectional curvatures. We begin with a discussion of a larger class of manifolds known as convex co-compact manifolds with variable negative curvature. Applying results from dynamics on these spaces, we obtain optimal meromorphic extensions of weighted dynamical zeta functions and asymptotic counting estimates for the number of weighted closed geodesics. A meromorphic extension of the standard dynamical zeta function and the prime orbit theorem follow as corollaries. Finally, we investigate interactions between the dynamics and spectral theory of these spaces

BoostNet: Bootstrapping detection of socialbots, and a case study from Guatemala

We present a method to reconstruct networks of socialbots given minimal input. Then we use Kernel Density Estimates of Botometer scores from 47,000 social networking accounts to find clusters of automated accounts, discovering over 5,000 socialbots. This statistical and data driven approach allows for inference of thresholds for socialbot detection, as illustrated in a case study we present from Guatemala.Comment: 7 pages, 4 figure

The Leonardo Code: Deciphering 50 Years of Artistic/Scientific Collaboration in the Texts and Images of Leonardo Journal, 1968-2018

International audienceLeonardo (1968-present), published by MIT Press, is the leading international peer-reviewed publication on the relationship between art, science and technology, making it an ideal dataset to analyze the emergence of such complex collaborations over time. To identify and analyze both the visible and latent interaction patterns, the research employs different granularities of data (article texts, images, publication dates, authors, their places of affiliation and disciplines) as part of a multimodal approach. Using a convolutional neural network, we examined the features of the images to analyze the modes of representing (and actually doing) art, science or engineering. We paired these features with information extracted using text mining to examine the relationships between the visual and the textual over time

Socialbots whitewashing contested elections; a case study from Honduras

We analyze socialbots active tweeting in relation to Juan Orlando Hern\'andez, the recently re-elected president of Honduras. We find a clear bimodal separation between humans and bots, using Botometer and its classifiers. Around one hundred separate communities of socialbots are identified and visualized, detected through the analysis of temporally coordinated retweets

The volume flux group and nonpositive curvature

We show that every closed nonpositively curved manifold with non-trivial volume flux group has zero minimal volume, and admits a finite covering with circle actions whose orbits are homologically essential. This proves a conjecture of Kedra-Kotschick-Morita for this class of manifolds.Comment: 6 pages, final version, to appear in Ann. Global Analysis and Geometr

Affine configurations and pure braids

We show that the fundamental group of the space of ordered affine-equivalent configurations of at least five points in the real plane is isomorphic to the pure braid group modulo its centre. In the case of four points this fundamental group is free with eleven generators.Comment: 5 pages, 1 figure, final version; to appear in Discrete & Computational Geometry, available from the publishers at http://www.springerlink.com/content/384516n7q24811ph

Minimal entropy and geometric decompositions in dimension four

We show vanishing results about the infimum of the topological entropy of the geodesic flow of homogeneous smooth four manifolds. We prove that any closed oriented geometric four manifold has zero minimal entropy if and only if it has zero simplicial volume. We also show that if a four manifold M admits a geometric decomposition, in the sense of Thurston, and does not have geometric pieces modelled on hyperbolic four-space, the complex hyperbolic plane or the product of two hyperbolic planes, then M admits an F-structure. It follows that M has zero minimal entropy and collapses with curvature bounded from below. We then analyse whether or not M admits a metric whose topological entropy coincides with the minimal entropy of M and provide new examples of manifolds for which the minimal entropy problem cannot be solved.Comment: 38 pages, corrected flat case; Theorem A is now in terms of F-structures, improved exposition; new final section collects all results needed for the proofs of the main theorem