Search results for "space-time"
showing 8 items of 58 documents
Nonparametric intensity estimation in space-time point processes and application to seismological problems
2008
Missing Data in Space-time: Long Gaps Imputation Based On Functional Data Analysis
2017
High dimensional data with spatio-temporal structures are of great interest in many elds of research, but their exhibited complexity leads to practical issues when formulating statistical models. Functional data analysis through smoothing methods is a proper framework for incorporating space-time structures: extending the basic methodology to the multivariate spatio-temporal setting, we refer to Generalized Additive Models for estimating functional data taking the spatial and temporal dependences into account, and to Functional Principal Component Analysis as a classical dimension reduction technique to cope with the high dimensionality and with the number of estimated eects. Since spatial …
Exploring mobilities in time and space
2013
La modélisation de l'information spatio-temporelle
2012
Understanding Urban Fabric with the OH_FET model based on Social Use, Space and Time
2008
The proposed principle for understanding the urban fabric is based on considering the town as a set of complex objects, taking a systemic approach. The town system used to study the urban fabric over large time spans is composed of three sub-systems relating to historical objects from the level of the excavation to that of the former urban space: function (social use), space (location, surface area and morphology) and time (dating, duration and chronology). The historical object is the analytical unit of the space studied. It is the Cartesian product of the three sets, Social use, Space and Time, from which it stems. On the basis of this process, the Historical Object (OH) is broken down in…
Pseudospectrum of Reissner-Nordström black holes: Quasinormal mode instability and universality
2021
Black hole spectroscopy is a powerful tool to probe the Kerr nature of astrophysical compact objects and their environment. The observation of multiple ringdown modes in gravitational waveforms could soon lead to high-precision gravitational spectroscopy, so it is critical to understand if the quasinormal mode spectrum is stable against perturbations. It was recently shown that the pseudospectrum can shed light on the spectral stability of black hole quasinormal modes. We study the pseudospectrum of Reissner-Nordstr\"om spacetimes and we find a spectral instability of scalar and gravitoelectric quasinormal modes in subextremal and extremal black holes, extending similar findings for the Sch…
Scattering of Co-Current Surface Waves on an Analogue Black Hole
2018
We report on what is to our knowledge the first scattering experiment of surface waves on an accelerating transcritical flow, which in the analogue gravity context is described by an effective spacetime with a black-hole horizon. This spacetime has been probed by an incident co-current wave, which partially scatters into an outgoing countercurrent wave on each side of the horizon. The measured scattering amplitudes are compatible with the predictions of the hydrodynamical theory, where the kinematical description in terms of the effective metric is exact.
Proposition méthodologique pour la visualisation et l'exploration des mobilités géographiques
2016
Daily mobility data are multidimensional and desaggregated, what make them hard to manipulate and to analyze. Although methods of representation and analyze have been proposed, none of them seem to be able to efficiently bring out knowledge from data. We propose to combinate this solutions and a methodology of innovative reaggregation to visualize and explore mobility data.