1,316 research outputs found
Pseudo-electromagnetic fields in topological semimetals
Dirac and Weyl semimetals, materials where electrons behave as relativistic
fermions, react to position- and time-dependent perturbations, such as strain,
as if emergent electromagnetic fields were applied. Since they differ from
external electromagnetic fields in their symmetries and phenomenology they are
called pseudo-electromagnetic fields, and enable a simple and unified
description of a variety of inhomogeneous systems involving topological
semimetals. We review the different physical ways to create effective
pseudo-fields, their observable consequences as well as their similarities and
differences compared to electromagnetic fields. Among these difference is their
effect on quantum anomalies, the absence of a classical symmetry in the quantum
theory, which we revisit from a quantum field theory and a semiclassical
viewpoint. We conclude with predicted observable signatures of the
pseudo-fields and the nascent experimental status.Comment: 18 pages, 6 (preliminary) figures. Original submitted version,
comments welcom
Interference, Coulomb blockade, and the identification of non-abelian quantum Hall states
We examine the relation between different electronic transport phenomena in a
Fabry-Perot interferometer in the fractional quantum Hall regime. In
particular, we study the way these phenomena reflect the statistics of quantum
Hall quasi-particles. For two series of states we examine, one abelian and one
non-abelian, we show that the information that may be obtained from
measurements of the lowest order interference pattern in an open Fabry-Perot
interferometer is identical to the one that may be obtained from the
temperature dependence of Coulomb blockade peaks in a closed interferometer. We
argue that despite the similarity between the experimental signatures of the
two series of states, interference and Coulomb blockade measurements are likely
to be able to distinguish between abelian and non-abelian states, due to the
sensitivity of the abelian states to local perturbations, to which the
non-abelian states are insensitive.Comment: 10 pages. Published versio
State-space based mass event-history model I: many decision-making agents with one target
A dynamic decision-making system that includes a mass of indistinguishable
agents could manifest impressive heterogeneity. This kind of nonhomogeneity is
postulated to result from macroscopic behavioral tactics employed by almost all
involved agents. A State-Space Based (SSB) mass event-history model is
developed here to explore the potential existence of such macroscopic
behaviors. By imposing an unobserved internal state-space variable into the
system, each individual's event-history is made into a composition of a common
state duration and an individual specific time to action. With the common state
modeling of the macroscopic behavior, parametric statistical inferences are
derived under the current-status data structure and conditional independence
assumptions. Identifiability and computation related problems are also
addressed. From the dynamic perspectives of system-wise heterogeneity, this SSB
mass event-history model is shown to be very distinct from a random effect
model via the Principle Component Analysis (PCA) in a numerical experiment.
Real data showing the mass invasion by two species of parasitic nematode into
two species of host larvae are also analyzed. The analysis results not only are
found coherent in the context of the biology of the nematode as a parasite, but
also include new quantitative interpretations.Comment: Published in at http://dx.doi.org/10.1214/08-AOAS189 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
East, west, would home really be best? On dissatisfaction with offshore-outsourcing and firms' inclination to backsource
With so many firms seemingly disenchanted with their experiences of offshore outsourcing one may well wonder why relatively few of these firms choose to ‘backsource’ – i.e., bring their offshored operations back in-house. Of all sourcing decisions that firms take, backsourcing is perhaps the least understood and least researched. In this article we draw on the behavioral theory of the firm (BTF) to propose a new model in which differences in firms' inclination to backsource are ascribed to the level of dissatisfaction at not having achieved offshoring aspirations. Building on BTF concepts of bounded rationality, problemistic search and satisficing decisions, the model suggests that how this dissatisfaction with offshoring affects a firm's inclination to backsource is dependent on managerial expectations regarding the technical challenges of reintegrating activities and the possible financial losses and decline in quality following backsourcing, as well as on internal political support and financial slack for backsourcing. SEM analysis of data from U.S. and U.K. firms shows support for the model. The study highlights the importance of recognizing the role of managerial perceptions and biases and subgroup political relations in shaping firms' backsourcing behaviors. We also discuss the study's contributions to research and practice
Telling donor-conceived children about their conception: Evaluation of the use of the Donor Conception Network children's books
If parents have used donated gametes, it is a personal choice whether they disclose to their children. For those that do, there is, however, little advice on how to tell their children. The Donor Conception Network (DCN) has made a series of books to help parents disclose. This study evaluated parents’ experience of using these books. An online survey with both quantitative and qualitative questions was used. The DCN membership and social media were used to publicize the survey, and 108 responses were analysed. At the time of conception, the parents’ family types were mainly mother and father (56.5%) and solo mothers (36.1%). The method of conception was mainly donor spermatozoa (55.6%) followed by donor egg (38.0%), double donation (8.3%) and one case of surrogacy. Most parents had read the book to their children before 2 years of age (76.9%). Before reading the books, some of the parents had some confidence in telling (43.5%) or were very confident in telling (30.6%). After reading the books, 60.2% reported having much more confidence in telling. Most parents felt their children had no understanding (76.8%) or only some understanding (22.3%) of donor conception before reading the books. After reading the books most parents felt their children's understanding had increased (71.3%). Most parents felt that reading the books had given them more confidence in using donor conception language (90.7%). The use of books to tell children about their conception may be a useful resource for parents wishing to be open with their children
Organizing The Innovation System For Reusability: The Case Of Made-To-Order Markets
This paper examines the transfer of designs between projects within firm in the context of made-to-order producing companies. This practice is also known as knowledge reuse. Past studies has provided a detailed account of the strategies and processes involved in the reuse of technologies. Nonetheless, a large portion of this research was based on evidence collected in mass-producing companies. This paper attempts to develop a complementary framework to identify the strategies involved in reusing technologies in the made-to-order context. Data were drawn from three aerospace companies based in Israel. Two strategies emerged from the empirical evidence: exploit product success and design for reuse
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