8,317 research outputs found
Nonsmooth and level-resolved dynamics illustrated with the tight binding model
We point out that in the first order time-dependent perturbation theory, the
transition probability may behave nonsmoothly in time and have kinks
periodically. Moreover, the detailed temporal evolution can be sensitive to the
exact locations of the eigenvalues in the continuum spectrum, in contrast to
coarse-graining ideas. Underlying this nonsmooth and level-resolved dynamics is
a simple equality about the sinc function \sinc x \equiv \sin x / x. These
physical effects appear in many systems with approximately equally spaced
spectra, and is also robust for larger-amplitude coupling beyond the domain of
perturbation theory. We use a one-dimensional periodically driven tight-binding
model to illustrate these effects, both within and outside the perturbative
regime.Comment: Link with the Paley-Wiener theorem and another reference is added;
any comment is welcome and will be greatly appreciated
Growth, debt, and sovereign risk in a small, open economy
The continuing debt crisis that many developing countries have faced in the current decade has underscored the need to understand the relationships between debt accumulation and growth, as well as the need to develop policy approaches that foster adjustment in the external account while maintaining the growth of output. The purpose of this paper is to develop a macroeconomic model for a small open developing economy that borrows abroad. This model will assist in studying the dynamic interaction between debt and growth, as well as the impact of various policies and exogenous shocks on the rate of capital accumulation, the current account and debt. From this analysis, the authors make the following conclusions. An upward shift in the supply of debt leads to a long run decline in external debt, a higher domestic interest rate, less capital stock, and a reduced trade surplus. An increase in the marginal cost of debt may or may not lower long run external debt as well. An increase in productivity raises the long run stock of capital but leaves the level of external debt and the interest rate unchanged in the long run. Finally, fiscal expansion has almost no effect in either the short run or the long run.Economic Theory&Research,Environmental Economics&Policies,Strategic Debt Management,Banks&Banking Reform,Financial Intermediation
Entanglement entropy in fermionic Laughlin states
We present analytic and numerical calculations on the bipartite entanglement
entropy in fractional quantum Hall states of the fermionic Laughlin sequence.
The partitioning of the system is done both by dividing Landau level orbitals
and by grouping the fermions themselves. For the case of orbital partitioning,
our results can be related to spatial partitioning, enabling us to extract a
topological quantity (the `total quantum dimension') characterizing the
Laughlin states. For particle partitioning we prove a very close upper bound
for the entanglement entropy of a subset of the particles with the rest, and
provide an interpretation in terms of exclusion statistics.Comment: 4+ pages, 3 figures. Minor changes in v
High Quality Analytics with Poor Quality Data
Poor data quality has often been cited as the single most common problem hindering the deployment of Business Intelligence (BI) solutions. This problem is compounded when analytics is performed in non-conventional BI areas such as forestry and silviculture. In this paper, we describe a methodology to perform BI analytics on data that was never collected to be used for this purpose. We show that data of such low and poor quality can be transformed and loaded into the data warehouse which is then used for high quality reporting
Edge-localized states in quantum one-dimensional lattices
In one-dimensional quantum lattice models with open boundaries, we find and
study localization at the lattice edge. We show that edge-localized eigenstates
can be found in both bosonic and fermionic systems, specifically, in the
Bose-Hubbard model with on-site interactions and in the spinless fermion model
with nearest-neighbor interactions. We characterize the localization through
spectral studies via numerical diagonalization and perturbation theory, through
considerations of the eigenfunctions, and through the study of explicit time
evolution. We concentrate on few-particle systems, showing how more complicated
edge states appear as the number of particles is increased.Comment: 9 pages, 12 figure
The prevalence of occult hepatitis B virus (hbv) infection in a large multi-ethnic haemodialysis cohort.
Haemodialysis patients are at increased risk of exposure to blood borne viruses. To reduce transmission in the UK, all haemodialysis patients are regularly screened, and if susceptible to Hepatitis B virus (HBV) infection, vaccinated
Entropy and Exact Matrix Product Representation of the Laughlin Wave Function
An analytical expression for the von Neumann entropy of the Laughlin wave
function is obtained for any possible bipartition between the particles
described by this wave function, for filling fraction nu=1. Also, for filling
fraction nu=1/m, where m is an odd integer, an upper bound on this entropy is
exhibited. These results yield a bound on the smallest possible size of the
matrices for an exact representation of the Laughlin ansatz in terms of a
matrix product state. An analytical matrix product state representation of this
state is proposed in terms of representations of the Clifford algebra. For
nu=1, this representation is shown to be asymptotically optimal in the limit of
a large number of particles
A survey of the machine interference problem
This paper surveys the research published on the machine interference problem since the 1985 review by Stecke & Aronson. After introducing the basic model, we discuss the literature along several dimensions. We then note how research has evolved since the 1985 review, including a trend towards the modelling of stochastic (rather than deterministic) systems and the corresponding use of more advanced queuing methods for analysis. We conclude with some suggestions for areas holding particular promise for future studies.Natural Sciences and Engineering Research Council (NSERC) Discovery Grant 238294-200
Lubrication of DLC Coatings with Two Tris(pentafluoroethyl)trifluorophosphate Anion-Based Ionic Liquids
The lubrication of a Cr-DLC coating with ethyl-dimethyl-2-methoxyethylammonium tris(pentafluoroethyl)trifluoropho-sphate [(NEMM)MOE][FAP] and 1-butyl-1-methylpyrro-lidinium tris(pentafluoroethyl)trifluorophosphate [BMP] [FAP] ionic liquids (ILs) as 1 wt% additives to a polyalphaolefin (PAO 6) was studied. Zinc dialkyldithiophosphate (ZDDP) was also used as reference in order to evaluate the effectiveness of the ILs. Reciprocating ball-on-plate tribological tests at loads of 20 and 40 N were performed. The results showed that both ILs exhibited a friction reduction, especially at the lowest load tested. Antiwear properties were also improved; the PAO 6 + 1% [BMP][FAP] mixture was slightly better, close to the values for PAO 6 + 1% ZDDP. Scanning electron microscopy (SEM) images and X-ray photoelectron spectroscopy (XPS) analysis indicated that the additive–surface interaction was responsible for the tribological improvement
- …