Bridging Methodologies: Angrist and Imbens' Contributions to Causal Identification

In the 1990s, Joshua Angrist and Guido Imbens studied the causal interpretation of Instrumental Variable estimates (a widespread methodology in economics) through the lens of potential outcomes (a classical framework to formalize causality in statistics). Bridging a gap between those two strands of literature, they stress the importance of treatment effect heterogeneity and show that, under defendable assumptions in various applications, this method recovers an average causal effect for a specific subpopulation of individuals whose treatment is affected by the instrument. They were awarded the Nobel Prize primarily for this Local Average Treatment Effect (LATE). The first part of this article presents that methodological contribution in-depth: the origination in earlier applied articles, the different identification results and extensions, and related debates on the relevance of LATEs for public policy decisions. The second part reviews the main contributions of the authors beyond the LATE. J. Angrist has pursued the search for informative and varied empirical research designs in several fields, particularly in education. G. Imbens has complemented the toolbox for treatment effect estimation in many ways, notably through propensity score reweighting, matching, and, more recently, adapting machine learning procedures.Comment: 44-page article, 9-page appendi

Damage-cluster distributions and size effect on strength in compressive failure

We investigate compressive failure of heterogeneous materials on the basis of a continuous progressive damage model. The model explicitely accounts for tensile and shear local damage and reproduces the main features of compressive failure of brittle materials like rocks or ice. We show that the size distribution of damage-clusters, as well as the evolution of an order parameter, the size of the largest damage-cluster, argue for a critical interpretation of fracture. The compressive failure strength follows a normal distribution with a very small size effect on the mean strength, in good agreement with experiments

Dual frequency emission in a compact semiconductor laser for coherent population trapping cesium atomic clocks

We present the dual-frequency emission of a diode-pumped vertical external-cavity semiconductor laser at 852 nm dedicated to coherent population trapping experiments. With a compact cavity more than 10mW is demonstrated in each polarization, with a frequency difference in the GHz range. One polarization has been stabilized on an atomic transitio

Towards an embedding of Graph Transformation in Intuitionistic Linear Logic

Linear logics have been shown to be able to embed both rewriting-based approaches and process calculi in a single, declarative framework. In this paper we are exploring the embedding of double-pushout graph transformations into quantified linear logic, leading to a Curry-Howard style isomorphism between graphs and transformations on one hand, formulas and proof terms on the other. With linear implication representing rules and reachability of graphs, and the tensor modelling parallel composition of graphs and transformations, we obtain a language able to encode graph transformation systems and their computations as well as reason about their properties

Tunable high-purity microwave signal generation from a dual-frequency VECSEL at 852 nm (orale)

International audienceWe demonstrate the dual-frequency emission of a diode-pumped vertical external-cavity semiconductor laser operating at 852 nm, dedicated to the coherent population trapping of cesium atoms for compact atomic frequency references. It is based on a single laser cavity sustaining the oscillation of two adjacent, cross-polarized, modes. The output power reaches 10 mW on each frequency. The frequency difference and the absolute laser frequencies are simultaneously precisely tuned and stabilized on external references, resulting in the generation of a high-purity optically-carried microwave signal. The laser design has focused on stability and compactness

Electron transport measurements in liquid xenon with Xenoscope, a large-scale DARWIN demonstrator

The DARWIN observatory is a proposed next-generation experiment with 40 tonnes of liquid xenon as an active target in a time projection chamber. To study challenges related to the construction and operation of a multi-tonne scale detector, we have designed and constructed a vertical, full-scale demonstrator for the DARWIN experiment at the University of Zurich. Here, we present the first results from a several-months run with $$343\,\hbox {kg}$$ of xenon and electron drift lifetime and transport measurements with a $$53\,\hbox {cm}$$ tall purity monitor immersed in the cryogenic liquid. After $$88\,\hbox {days}$$ of continuous purification, the electron lifetime reached a value of (664\,\pm \,23)\,\upmu \hbox {s}. We measured the drift velocity of electrons for electric fields in the range (25–75) V/cm, and found values consistent with previous measurements. We also calculated the longitudinal diffusion constant of the electron cloud in the same field range, and compared with previous data, as well as with predictions from an empirical model