4,560 research outputs found
Wright: Comparative Conflict Resolution Procedures in Taxation
A Review of Comparative Conflict Resolution Procedures in Taxation edited by L. Hart Wrigh
Renormalization of Molecular Electronic Levels at Metal-Molecule Interfaces
The electronic structure of benzene on graphite (0001) is computed using the
GW approximation for the electron self-energy. The benzene quasiparticle energy
gap is predicted to be 7.2 eV on graphite, substantially reduced from its
calculated gas-phase value of 10.5 eV. This decrease is caused by a change in
electronic correlation energy, an effect completely absent from the
corresponding Kohn-Sham gap. For weakly-coupled molecules, this correlation
energy change is seen to be well described by a surface polarization effect. A
classical image potential model illustrates trends for other conjugated
molecules on graphite.Comment: 4 pages, 3 figures, 2 table
Unbiased contaminant removal for 3D galaxy power spectrum measurements
Citation: Kalus, B., Percival, W. J., Bacon, D. J., & Samushia, L. (2016). Unbiased contaminant removal for 3D galaxy power spectrum measurements. Monthly Notices of the Royal Astronomical Society, 463(1), 467-476. doi:10.1093/mnras/stw2008We assess and develop techniques to remove contaminants when calculating the 3D galaxy power spectrum. We separate the process into three separate stages: (i) removing the contaminant signal, (ii) estimating the uncontaminated cosmological power spectrum and (iii) debiasing the resulting estimates. For (i), we show that removing the best-fitting contaminant (mode subtraction) and setting the contaminated components of the covariance to be infinite (mode deprojection) are mathematically equivalent. For (ii), performing a quadratic maximum likelihood (QML) estimate after mode deprojection gives an optimal unbiased solution, although it requires the manipulation of large matrices (N-mode being the total number of modes), which is unfeasible for recent 3D galaxy surveys. Measuring a binned average of the modes for (ii) as proposed by Feldman, Kaiser & Peacock (FKP) is faster and simpler, but is sub-optimal and gives rise to a biased solution. We present a method to debias the resulting FKP measurements that does not require any large matrix calculations. We argue that the sub-optimality of the FKP estimator compared with the QML estimator, caused by contaminants, is less severe than that commonly ignored due to the survey window
Previous attentional set can induce an attentional blink with task-irrelevant initial targets
Identification of a second target is often impaired by the requirement to process a prior target in a rapid serial visual presentation (RSVP). This is termed the attentional blink. Even when the first target is task-irrelevant an attentional blink may occur providing this first target shares similar features with the second target (contingent capture). An RSVP experiment was undertaken to assess whether this first target can still cause an attentional blink when it did not require a response and did not share any features with the following target. The results revealed that such task-irrelevant targets can induce an attentional blink providing that they were task-relevant on a previous block of trials. This suggests that irrelevant focal stimuli can distract attention on the basis of a previous attentional set
Electronic states and Landau levels in graphene stacks
We analyze, within a minimal model that allows analytical calculations, the
electronic structure and Landau levels of graphene multi-layers with different
stacking orders. We find, among other results, that electrostatic effects can
induce a strongly divergent density of states in bi- and tri-layers,
reminiscent of one-dimensional systems. The density of states at the surface of
semi-infinite stacks, on the other hand, may vanish at low energies, or show a
band of surface states, depending on the stacking order
The Communication Cost of Simulating Bell Correlations
What classical resources are required to simulate quantum correlations? For
the simplest and most important case of local projective measurements on an
entangled Bell pair state, we show that exact simulation is possible using
local hidden variables augmented by just one bit of classical communication.
Certain quantum teleportation experiments, which teleport a single qubit,
therefore admit a local hidden variables model.Comment: 4 pages, 2 figures; reference adde
Stabilizing distinguishable qubits against spontaneous decay by detected-jump correcting quantum codes
A new class of error-correcting quantum codes is introduced capable of
stabilizing qubits against spontaneous decay arising from couplings to
statistically independent reservoirs. These quantum codes are based on the idea
of using an embedded quantum code and exploiting the classical information
available about which qubit has been affected by the environment. They are
immediately relevant for quantum computation and information processing using
arrays of trapped ions or nuclear spins. Interesting relations between these
quantum codes and basic notions of design theory are established
SAURON Observations of Disks in Spheroids
The panoramic integral-field spectrograph SAURON is currently being used to
map the stellar kinematics, gaseous kinematics, and stellar populations of a
large number of early-type galaxies and bulges. Here, we describe SAURON
observations of cold stellar disks embedded in spheroids (NGC3384, NGC4459,
NGC4526), we illustrate the kinematics and ionization state of large-scale
gaseous disks (NGC4278, NGC7742), and we show preliminary comparisons of SAURON
data with barred galaxy N-body simulations (NGC3623).Comment: 8 pages including 5 figures. To appear in Galaxies: The Third
Dimension, eds. M. Rosado, L. Binnette, & L. Arias (ASP: San Francisco
SAURON: An Innovative Look at Early-Type Galaxies
A summary of the SAURON project and its current status is presented. SAURON
is a panoramic integral-field spectrograph designed to study the stellar
kinematics, gaseous kinematics, and stellar populations of spheroids. Here, the
sample of galaxies and its properties are described. The instrument is detailed
and its capabilities illustrated through observational examples. These includes
results on the structure of central stellar disks, the kinematics and
ionization state of gaseous disks, and the stellar populations of galaxies with
decoupled cores.Comment: 10 pages, 6 figures. To appear in "The Dynamics, Structure & History
of Galaxies", eds. G. S. Da Costa & E. M. Sadler (San Francisco: ASP).
Version with full resolution images available at
http://www.strw.leidenuniv.nl/~dynamics/Instruments/Sauron/pub_list.htm
Decoherence-Free Subspaces for Multiple-Qubit Errors: (I) Characterization
Coherence in an open quantum system is degraded through its interaction with
a bath. This decoherence can be avoided by restricting the dynamics of the
system to special decoherence-free subspaces. These subspaces are usually
constructed under the assumption of spatially symmetric system-bath coupling.
Here we show that decoherence-free subspaces may appear without spatial
symmetry. Instead, we consider a model of system-bath interactions in which to
first order only multiple-qubit coupling to the bath is present, with
single-qubit system-bath coupling absent. We derive necessary and sufficient
conditions for the appearance of decoherence-free states in this model, and
give a number of examples. In a sequel paper we show how to perform universal
and fault tolerant quantum computation on the decoherence-free subspaces
considered in this paper.Comment: 18 pages, no figures. Major changes. Section on universal fault
tolerant computation removed. This section contained a crucial error. A new
paper [quant-ph/0007013] presents the correct analysi
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