Mothers’ Attributions in Reminiscing Conversations About Children’s Successes and Failures: Connections With Children’s Self-Evaluations

Effects of feedback on children’s self-evaluations are well established, yet little is known about how parents talk with children about everyday successes and failures, despite the importance of parent–child reminiscing in children’s psychological understanding. We examine mothers’ attributions and performance evaluations in conversations about their 5-year-olds’ (N = 80) success and failure experiences, and connections between conversations and children’s self-evaluations. Conversations differed for success and failure: Mothers were equally likely to make internal-person, internal-process, or external attributions for successes, but were most likely to make an evaluation. For failures, mothers were equally likely to make internal-process or external attributions, or evaluations. Internal-person attributions for success and external attributions were associated with negative self-evaluations. However, children expressed fewer negative self-evaluations when mothers made internal-process attributions for failure, or positively evaluated the success. Results support the experimental literature and extend it to external attributions, which were common in mothers’ framing and linked to negative self-evaluations

The end points in the dispersion of Holstein polarons

We investigate the existence of end points in the dispersion of Holstein polarons in various dimensions, using the Momentum Average approximation which has proved to be very accurate for this model. An end point separates momenta for which the lowest-energy state is a discrete level, i.e., an infinitely-lived polaron, from those where the lowest-energy feature is a continuum in which the "polaron'" is signalled by a resonance with a finite lifetime. While such end points are known to not appear in 1D, we show here that they are generic in 3D if the particle-boson coupling is not too strong. The 2D case is "critical": a pure 2D Holstein model has no end points, like the 1D case. However, any amount of interlayer hopping leads to 3D-like behavior. As a result, such end points are expected to appear in the spectra of layered, quasi-2D systems described by Holstein models. Generalizations to other models are also briefly discussed.Comment: 6 pages, 6 figure

Elusive electron-phonon coupling in quantitative analyses of the spectral function

We examine multiple techniques for extracting information from angle-resolved photoemission spectroscopy (ARPES) data, and test them against simulated spectral functions for electron-phonon coupling. We find that, in the low-coupling regime, it is possible to extract self-energy and bare-band parameters through a self-consistent Kramers-Kronig bare-band fitting routine. We also show that the effective coupling parameters deduced from the renormalization of quasiparticle mass, velocity, and spectral weight are momentum dependent and, in general, distinct from the true microscopic coupling; the latter is thus not readily accessible in the quasiparticle dispersion revealed by ARPES.Comment: A high-resolution version can be found at http://www.physics.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Articles/KKBF.pd

An Inheritance

A collection of seven short stories

Momentum average approximation for models with electron-phonon coupling dependent on the phonon momentum

We generalize the momentum average (MA) approximation to study the properties of models with momentum-dependent electron-phonon coupling. As in the case of the application of the original MA to the Holstein model, the results are analytical, numerically trivial to evaluate, exact for both zero bandwidth and for zero electron-phonon coupling, and are accurate everywhere in parameter space. Comparison with available numerical data confirms this accuracy. We then show that further improvements can be obtained based on variational considerations, using the one-dimensional breathing-mode Hamiltonian as a specific example. For example, by using this variational MA, we obtain ground state energies within at most 0.3% error of the numerical data.Comment: 15 pages, 10 figure

Development and Confirmatory Factor Analysis of the Community Norms of Child Neglect Scale

This article describes the development of the Community Norms of Child Neglect Scale (CNCNS), a new measure of perceptions of child neglect, for use in community samples. The CNCNS differentiates among four subtypes of neglect (failure to provide for basic needs, lack of supervision, emotional neglect, and educational neglect). Scenarios ranging in seriousness for each subtype were presented to a large community sample (N = 3,809). Confirmatory factor analyses indicated that a four-factor model provided a better fit to the data than did a model specifying only one overall neglect factor, suggesting this sample distinguished among the four subtypes of neglect. The authors tested measurement equivalence across individuals who work with children and lay community respondents and across rural and urban respondents, with results indicating a very similar structure across these groups. These initial reliability and validity data suggest that the CNCNS may be of use in comparing perceptions of child neglect among individuals and across communities

A spectral function tour of electron-phonon coupling outside the Migdal limit

We simulate spectral functions for electron-phonon coupling in a filled band system - far from the asymptotic limit often assumed where the phonon energy is very small compared to the Fermi energy in a parabolic band and the Migdal theorem predicting 1+lambda quasiparticle renormalizations is valid. These spectral functions are examined over a wide range of parameter space through techniques often used in angle-resolved photoemission spectroscopy (ARPES). Analyzing over 1200 simulations we consider variations of the microscopic coupling strength, phonon energy and dimensionality for two models: a momentum-independent Holstein model, and momentum-dependent coupling to a breathing mode phonon. In this limit we find that any `effective coupling', lambda_eff, inferred from the quasiparticle renormalizations differs from the microscopic dimensionless coupling characterizing these Hamiltonians, lambda, and could drastically either over- or under-estimate it depending on the particular parameters and model. In contrast, we show that perturbation theory retains good predictive power for low coupling and small momenta, and that the momentum-dependence of the self-energy can be revealed via the relationship between velocity renormalization and quasiparticle strength. Additionally we find that (although not strictly valid) it is often possible to infer the self-energy and bare electronic structure through a self-consistent Kramers-Kronig bare-band fitting; and also that through lineshape alone, when Lorentzian, it is possible to reliably extract the shape of the imaginary part of a momentum-dependent self-energy without reference to the bare-band.Comment: 15 pages, 11 figures. High resolution available here: http://www.physics.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Articles/sf_tour.pd