Working Papers/Reports
Recent Submissions

Complementarity between labor and energy: A firmlevel analysis
(2021)Economics Working Paper SeriesThis paper adds a fresh angle to the ongoing debate on the potential negative employment effect of environmental policy by bringing to the fore a key factor that directly regulates its magnitude: the elasticity of substitution between labor and energy. Using firmlevel data from the French manufacturing sector, we provide rigorous micro estimates of this parameter that point to strong complementarity between labor and energy. We then ...Working Paper 
A Python tool and database of Amtrak departure and arrival times with weather information
(2021)engrXivThis article proposes a Pythonbased Amtrak and Weather Underground (PAWU) tool to collect data on Amtrak (the main passenger train operator in the United States) departure and arrival times with weather information. In addition, this article offers a database, developed with PAWU, of the operating characteristics of 16 Amtrak routes from 2008 to 2019. More specifically, PAWU enables users to retrieve Amtrak departure and arrival times ...Working Paper 
Asymptotic Floquet theory for first order ODEs with finite Fourier series perturbation and its applications to Floquet metamaterials
(2021)SAM Research ReportOur aim in this paper is twofold. Firstly, we develop a new asymptotic theory for Floquet exponents. We consider a linear system of differential equations with a timeperiodic coefficient matrix. Assuming that the coefficient matrix depends analytically on a small parameter, we derive a full asymptotic expansion of its Floquet exponents. Based on this, we prove that only the constant order Floquet exponents of multiplicity higher than one ...Report 
Understanding neural networks with reproducing kernel Banach spaces
(2021)SAM Research ReportCharacterizing the function spaces corresponding to neural networks can provide a way to understand their properties. In this paper we discuss how the theory of reproducing kernel Banach spaces can be used to tackle this challenge. In particular, we prove a representer theorem for a wide class of reproducing kernel Banach spaces that admit a suitable integral representation and include one hidden layer neural networks of possibly infinite ...Report 
Analytic regularity for the NavierStokes equations in polygons with mixed boundary conditions
(2021)SAM Research ReportWe prove weighted analytic regularity of LerayHopf variational solutions for the stationary, incompressible NavierStokes Equations (NSE) in plane polygonal domains, subject to analytic body forces. We admit mixed boundary conditions which may change type at each vertex, under the assumption that homogeneous Dirichlet (''noslip'') boundary conditions are prescribed on at least one side at each vertex of the domain. The weighted analytic ...Report 
On the vanishing viscosity limit of statistical solutions of the incompressible NavierStokes equations
(2021)SAM Research ReportWe study statistical solutions of the incompressible NavierStokes equation and their vanishing viscosity limit. We show that a formulation using correlation measures, which are probability measures accounting for spatial correlations, and moment equations is equivalent to statistical solutions in the Foiac{s}Prodi sense. Under the assumption of weak scaling, a weaker version of Kolmogorov's selfsimilarity at small scales hypothesis ...Report 
Finite volume methods for the computation of statistical solutions of the incompressible Euler equations
(2021)SAM Research ReportWe present an efficient numerical scheme based on Monte Carlo integration to approximate statistical solutions of the incompressible Euler equations. The scheme is based on finite volume methods, which provide a more flexible framework than previously existing spectral methods for the computation of statistical solutions for incompressible flows. This finite volume scheme is rigorously proven to, under experimentally verifiable assumptions, ...Report 
On the validity of the tightbinding method for describing systems of subwavelength resonators
(2021)SAM Research ReportThe goal of this paper is to relate the capacitance matrix formalism to the tightbinding approximation. By doing so, we open the way to the use of mathematical techniques and tools from condensed matter theory in the mathematical and numerical analysis of metamaterials, in particular for the understanding of their topological properties. We firstly study how the capacitance matrix formalism, both when the material parameters are static ...Report 
Modal decompositions and point scatterer approximations near the Minnaert resonance frequencies
(2021)SAM Research ReportAs a continuation of the previous works [13, 4, 15], this paper provides several contributions to the mathematical analysis of subwavelength resonances in a highcontrast medium containing N acoustic obstacles. Our approach is based on an exact decomposition formula which reduces the solution of the sound scattering problem to that of a N dimensional linear system, and characterizes resonant frequencies as the solutions to a Ndimensional ...Report 
Homogenization of soundabsorbing and highcontrast acoustic metamaterials in subcritical regimes
(2021)SAM Research ReportReport 
Nonreciprocal wave propagation in spacetime modulated media
(2021)SAM Research ReportWe prove the possibility of achieving nonreciprocal wave propagation in spacetime modulated media and give an asymptotic analysis of the nonreciprocity property in terms of the amplitude of the timemodulation. Such modulation causes a folding of the band structure of the material, which may induce degenerate points. By breaking timereversal symmetry, we show that these degeneracies may open into nonsymmetric, unidirectional band ...Report 
Spurious QuasiResonances in Boundary Integral Equationsfor the Helmholtz Transmission Problem
(2021)SAM Research ReportWe consider the Helmholtz transmission problem with piecewiseconstant material coefficients, and the standard associated direct boundary integral equations. For certain coefficients and geometries, the norms of the inverses of the boundary integral operators grow rapidly through an increasing sequence of frequencies, even though this is not the case for the solution operator of the transmission problem; we call this phenomenon that of ...Report 
Long Expressive Memory for Sequence Modeling
(2021)SAM Research ReportWe propose a novel method called Long Expressive Memory (LEM) for learning longterm sequential dependencies. LEM is gradientbased, it can efficiently process sequential tasks with very longterm dependencies, and it is sufficiently expressive to be able to learn complicated inputoutput maps. To derive LEM, we consider a system of multiscale ordinary differential equations, as well as a suitable timediscretization of this system. For ...Report 
The 19th of July: Divided or United in Cyberspace? From the EU and NATO to Five Eyes and Japan
(2021)The coordinated public attribution campaign by the EU, NATO, Five Eyes and Japan on 19 July 2021 has been portrayed as a largely coherent effort of likeminded countries confronting China’s malicious cyber activities. Based on the public information available as of the time of writing, this Elcano Royal Institute working paper by CSS' Stefan Soesanto shows, this was the case neither in substance nor in form and aims to disentangle and ...Working Paper 
A molecular framework for proximal secondary vein branching in the Arabidopsis thaliana embryo
(2021)bioRxivThe establishment of a closed vascular network in foliar organs is achieved through the coordinated specification of newly recruited procambial cells, their proliferation and elongation. An important, yet poorly understood component of this process, is secondary vein branching; a mechanism employed in Arabidopsis thaliana cotyledons to extend vascular tissues throughout the organ’s surface by secondary vein formation. To investigate ...Working Paper 
Controls on spatial and temporal patterns of slope deformation in a paraglacial environment
(2021)Earth and Space Science Open ArchiveA comprehensive surface displacement monitoring system installed in the recently deglaciated bedrock slopes of the Aletsch Valley shows systematic reversible motions at the annual scale. We explore potential drivers for this deformation signal and demonstrate that the main driver is pore pressure changes of phreatic groundwater in fractured granitic mountain slopes. The spatial pattern of these reversible annual deformations shows similar ...Working Paper 
Multidisciplinary characterizations of the Bedretto Lab – a unique underground geoscience research facility
(2021)Solid Earth DiscussionsThe increased interest in subsurface development (e.g., unconventional hydrocarbon, deep geothermal, waste disposal) and the associated (triggered or induced) seismicity calls for a better understanding of the hydroseismomechanical coupling in fractured rock masses. Being able to bridge the knowledge gap between laboratory and reservoir scales, controllable mesoscale in situ experiments are deemed indispensable. In an effort to access ...Working Paper 
Rock slope temperature evolution and micrometerscale deformation at a retreating glacier margin
(2021)Earth and Space Science Open ArchiveIn deglaciating environments, rock mass weakening and potential formation of rock slope instabilities is driven by longterm and seasonal changes in thermal and hydraulic boundary conditions, combined with unloading due to ice melting. However, insitu observations are rare. In this study, we present new monitoring data from three highly instrumented boreholes, and numerical simulations to investigate rock slope temperature evolution and ...Working Paper 
Expanding measures: Random walks and rigidity on homogeneous spaces
(2021)arXivLet G be a real Lie group, Λ<G a lattice and H<G a connected semisimple subgroup without compact factors and with finite center. We define the notion of Hexpanding measures μ on H and, applying recent work of EskinLindenstrauss, prove that μstationary probability measures on G/Λ are homogeneous. Transferring a construction by BenoistQuint and drawing on ideas of EskinMirzakhaniMohammadi, we construct Lyapunov/Margulis functions to ...Working Paper 
MOBISCOVID19/61
(2021)Arbeitsberichte Verkehrs und RaumplanungOn March 16, 2020, 3700 participants who completed the MOBIS study between September 2019 and January 2020 were invited to reinstall the GPS Logger and Travel Diary App ‘CatchMyDay’, developed by MotionTag, to record their mobility behaviour during the period of special measures implemented to control the spread of the Corona Virus. The first 4 weeks of mobility data from the original MOBIS Study is taken for each participant as a ...Report