Stochastic excitation of acoustic modes in stars

For more than ten years, solar-like oscillations have been detected and frequencies measured for a growing number of stars with various characteristics (e.g. different evolutionary stages, effective temperatures, gravities, metal abundances ...). Excitation of such oscillations is attributed to turbulent convection and takes place in the uppermost part of the convective envelope. Since the pioneering work of Goldreich & Keely (1977), more sophisticated theoretical models of stochastic excitation were developed, which differ from each other both by the way turbulent convection is modeled and by the assumed sources of excitation. We review here these different models and their underlying approximations and assumptions. We emphasize how the computed mode excitation rates crucially depend on the way turbulent convection is described but also on the stratification and the metal abundance of the upper layers of the star. In turn we will show how the seismic measurements collected so far allow us to infer properties of turbulent convection in stars.Comment: Notes associated with a lecture given during the fall school organized by the CNRS and held in St-Flour (France) 20-24 October 2008 ; 39 pages ; 11 figure

Instrumental Variable Estimation for Duration Data

In this article we develop an Instrumental Variable estimation procedure that corrects for possible endogeneity of a variable in a duration model. We assume a Generalized Accelerated Failure Time (GAFT) model. This model is based on transforming the durations and assuming a distribution for these transformed durations. The GAFT model encompasses two competing approaches to duration data; the (Mixed) Proportional Hazard (MPH) model and the Accelerated Failure Time (AFT) model. The basis of the Instrumental Variable Linear Rank estimator (IVLR) is that for the true GAFT model the instrument does not influence the hazard of the transformed duration. The inverse of an extended rank test provide the estimation equations the IVLR estimation procedure is based on. We discuss the large sample properties and the efficiency of this estimator. We discuss the practical issues of implementation of the estimator. We apply the IVLR estimation approach to the Illinois re-employment bonus experiment. In this experiment individuals who became unemployed were divided at random in three groups: two bonus groups and a control group. Those in the bonus groups could refuse to participate in the experiment. It is very likely that this decision is related to the unemployment duration. We use the IVLR estimator to obtain the effect of these endogenous claimant and employer bonuses on the re-employment hazard

Neutrino oscillation studies with IceCube-DeepCore

AbstractIceCube, a gigaton-scale neutrino detector located at the South Pole, was primarily designed to search for astrophysical neutrinos with energies of PeV and higher. This goal has been achieved with the detection of the highest energy neutrinos to date. At the other end of the energy spectrum, the DeepCore extension lowers the energy threshold of the detector to approximately 10 GeV and opens the door for oscillation studies using atmospheric neutrinos. An analysis of the disappearance of these neutrinos has been completed, with the results produced being complementary with dedicated oscillation experiments. Following a review of the detector principle and performance, the method used to make these calculations, as well as the results, is detailed. Finally, the future prospects of IceCube-DeepCore and the next generation of neutrino experiments at the South Pole (IceCube-Gen2, specifically the PINGU sub-detector) are briefly discussed

A muon-track reconstruction exploiting stochastic losses for large-scale Cherenkov detectors

IceCube is a cubic-kilometer Cherenkov telescope operating at the South Pole. The main goal of IceCube is the detection of astrophysical neutrinos and the identification of their sources. High-energy muon neutrinos are observed via the secondary muons produced in charge current interactions with nuclei in the ice. Currently, the best performing muon track directional reconstruction is based on a maximum likelihood method using the arrival time distribution of Cherenkov photons registered by the experiment\u27s photomultipliers. A known systematic shortcoming of the prevailing method is to assume a continuous energy loss along the muon track. However at energies >1 TeV the light yield from muons is dominated by stochastic showers. This paper discusses a generalized ansatz where the expected arrival time distribution is parametrized by a stochastic muon energy loss pattern. This more realistic parametrization of the loss profile leads to an improvement of the muon angular resolution of up to 20% for through-going tracks and up to a factor 2 for starting tracks over existing algorithms. Additionally, the procedure to estimate the directional reconstruction uncertainty has been improved to be more robust against numerical errors

Unresolved questions in nudging research: Putting the psychology back in nudging

Nudging interventions are broadly defined as a rearrangement of a choice context that gently suggests a specific choice. Their increasing popularity has attracted attention and discussion from researchers, policy makers, and practitioners alike. After some applications to domains such as health, environmental issues, and retirement savings, the next step in nudging is to understand the psychological boundary conditions when applied to varied domains of daily life. It is yet unclear for example to what extent nudging interventions can be transparent without losing effectiveness, or how permanent the effects are. These unresolved questions may have contributed to heated political and scientific discussions, on for example the ethics of using nudges in the public health domain, due to the missing scientific evidence. Indeed, this popularity may have led to forget how nudging harnesses insights from decades of research in psychology to change people’s behavior. The aim of this paper is to shift the focus back to the psychological premises nudges were built upon. It summarizes several outstanding questions that future research in the psychology of nudging should address. Advancing research in nudging will help to improve our understanding of applied nudging interventions and provide clarity to debates such as ethical appropriateness, effectiveness, and public approval

Unresolved questions in nudging research: Putting the psychology back in nudging

Nudging interventions are broadly defined as a rearrangement of a choice context that gently suggests a specific choice. Their increasing popularity has attracted attention and discussion from researchers, policy makers, and practitioners alike. After some applications to domains such as health, environmental issues, and retirement savings, the next step in nudging is to understand the psychological boundary conditions when applied to varied domains of daily life. It is yet unclear for example to what extent nudging interventions can be transparent without losing effectiveness, or how permanent the effects are. These unresolved questions may have contributed to heated political and scientific discussions, on for example the ethics of using nudges in the public health domain, due to the missing scientific evidence. Indeed, this popularity may have led to forget how nudging harnesses insights from decades of research in psychology to change people’s behavior. The aim of this paper is to shift the focus back to the psychological premises nudges were built upon. It summarizes several outstanding questions that future research in the psychology of nudging should address. Advancing research in nudging will help to improve our understanding of applied nudging interventions and provide clarity to debates such as ethical appropriateness, effectiveness, and public approval