139,017 research outputs found
Online partial evaluation of sheet-defined functions
We present a spreadsheet implementation, extended with sheet-defined
functions, that allows users to define functions using only standard
spreadsheet concepts such as cells, formulas and references, requiring no new
syntax. This implements an idea proposed by Peyton-Jones and others.
As the main contribution of this paper, we then show how to add an online
partial evaluator for such sheet-defined functions. The result is a
higher-order functional language that is dynamically typed, in keeping with
spreadsheet traditions, and an interactive platform for function definition and
function specialization.
We describe an implementation of these ideas, present some performance data
from microbenchmarks, and outline desirable improvements and extensions.Comment: In Proceedings Festschrift for Dave Schmidt, arXiv:1309.455
Wiener-Hopf solution for impenetrable wedges at skew incidence
A new Wiener-Hopf approach for the solution of impenetrable wedges at skew incidence is presented. Mathematical aspects are described in a unified and consistent theory for angular region problems. Solutions are obtained using analytical and numerical-analytical approaches. Several numerical tests from the scientific literature validate the new technique, and new solutions for anisotropic surface impedance wedges are solved at skew incidence. The solutions are presented considering the geometrical and uniform theory of diffraction coefficients, total fields, and possible surface wave contribution
Fermi surface of MoO2 studied by angle-resolved photoemission spectroscopy, de Haas-van Alphen measurements, and electronic structure calculations
A comprehensive study of the electronic properties of monoclinic MoO2 from
both an experimental and a theoretical point of view is presented. We focus on
the investigation of the Fermi body and the band structure using angle resolved
photoemission spectroscopy, de Haas-van Alphen measurements, and electronic
structure calculations. For the latter, the new full-potential augmented
spherical wave (ASW) method has been applied. Very good agreement between the
experimental and theoretical results is found. In particular, all Fermi surface
sheets are correctly identified by all three approaches. Previous controversies
concerning additional hole-like surfaces centered around the Z- and B-point
could be resolved; these surfaces were an artefact of the atomic-sphere
approximation used in the old calculations. Our results underline the
importance of electronic structure calculations for the understanding of MoO2
and the neighbouring rutile-type early transition-metal dioxides. This includes
the low-temperature insulating phases of VO2 and NbO2, which have crystal
structures very similar to that of molybdenum dioxide and display the
well-known prominent metal-insulator transitions.Comment: 17 pages, 21 figures, more information at
http://www.physik.uni-augsburg.de/~eyert
Conjugate two-dimensional electric potential maps
Two dimensional electric potential maps based on voltage detection in
conducting paper are common practice in many physics courses in college. Most
frequently, students work on `capacitor-like' geometries with current flowing
between two opposite electrodes. A `topographical' investigation across the
embedding medium (map of equipotential curves) allows to reassure a number of
physical properties.
This paper focuses on some less common configurations that bear pedagogical
interest. We analyze `open-geometries' with electrodes in the form of long
strips with slits. They provide a natural groundwork to bring the student to
complex variable methods. Aided by this, we show that shaping the conducting
paper board one may analyze finite size effects, as well as some meaningful
discontinuities in the measured potential.
The concept of conjugate electric potentials is exploited. Equipotentials and
electric field lines acquire interchangeable roles and may be obtained in
complementary `dual' experiments. A feasible theoretical analysis based on
introductory complex variables and standardized numerics gives a remarkable
quantification of the experimental results.Comment: 15 pages, 8 figure
Density of states as a probe of electrostatic confinement in graphene
We theoretically analyze the possibility to confine electrons in single-layer
graphene with the help of metallic gates, via the evaluation of the density of
states of such a gate-defined quantum dot in the presence of a ring-shaped
metallic contact. The possibility to electrostatically confine electrons in a
gate-defined ``quantum dot'' with finite-carrier density, surrounded by an
undoped graphene sheet, strongly depends on the integrability of the electron
dynamics in the quantum dot. With the present calculations we can
quantitatively compare confinement in dots with integrable and chaotic
dynamics, and verify the prediction that the Berry phase associated with the
pseudospin leads to partial confinement in situations where no confinement is
expected according to the arguments relying on the classical dynamics only.Comment: 9 pages, 7 figure
The ECB's monetary analysis revisited
Monetary aggregates continue to play an important role in the ECB's policy strategy. This paper revisits the case for money, surveying the ongoing theoretical and empirical debate. The key conclusion is that an exclusive focus on non-monetary factors alone may leave the ECB with an incomplete picture of the economy. However, treating monetary factors as a separate matter is a second-best solution. Instead, a general-equilibrium inspired analytical framework that merges the economic and monetary pillars of the ECB's policy strategy appears the most promising way forward. The role played by monetary aggregates in such unified framework may be rather limited. However, an integrated framework would facilitate the presentation of policy decisions by providing a clearer narrative of the relative role of money in the interaction with other economic and financial sector variables, including asset prices, and their impact on consumer prices. --ECB,monetary analysis,monetary pillar,New Keynesian model,DSGE model,P* model,Twopillar Phillips curve,VAR model,generalized dynamic factor model
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