5,375 research outputs found
Classical and Quantum Complexity of the Sturm-Liouville Eigenvalue Problem
We study the approximation of the smallest eigenvalue of a Sturm-Liouville
problem in the classical and quantum settings. We consider a univariate
Sturm-Liouville eigenvalue problem with a nonnegative function from the
class and study the minimal number n(\e) of function evaluations
or queries that are necessary to compute an \e-approximation of the smallest
eigenvalue. We prove that n(\e)=\Theta(\e^{-1/2}) in the (deterministic)
worst case setting, and n(\e)=\Theta(\e^{-2/5}) in the randomized setting.
The quantum setting offers a polynomial speedup with {\it bit} queries and an
exponential speedup with {\it power} queries. Bit queries are similar to the
oracle calls used in Grover's algorithm appropriately extended to real valued
functions. Power queries are used for a number of problems including phase
estimation. They are obtained by considering the propagator of the discretized
system at a number of different time moments. They allow us to use powers of
the unitary matrix , where is an
matrix obtained from the standard discretization of the Sturm-Liouville
differential operator. The quantum implementation of power queries by a number
of elementary quantum gates that is polylog in is an open issue.Comment: 33 page
Initial Conditions, European Colonialism and Africa's Growth
We investigate the role of initial conditions at colonial independence on economic growth in Africa in the post-independence period using Bayesian Model Averaging (BMA). A key innovation in our estimation methodology is that we incorporate parameter heterogeneity in model averaging as well as try to mitigate the endogeneity problem present in growth regressions. In order to ensure that differences in the growth determinants between Africa and the world are not driven by experiences of an alternative group of countries, we also control for the presence of OECD countries and former European colonies in the global sample. We find that the impact of different initial conditions on growth in Africa is strikingly different from the world. We argue that these initial conditions reflect the state of development at the close of the colonial era and are therefore inherently related with the legacy of colonialism.
Average Case Tractability of Non-homogeneous Tensor Product Problems
We study d-variate approximation problems in the average case setting with
respect to a zero-mean Gaussian measure. Our interest is focused on measures
having a structure of non-homogeneous linear tensor product, where covariance
kernel is a product of univariate kernels. We consider the normalized average
error of algorithms that use finitely many evaluations of arbitrary linear
functionals. The information complexity is defined as the minimal number n(h,d)
of such evaluations for error in the d-variate case to be at most h. The growth
of n(h,d) as a function of h^{-1} and d depends on the eigenvalues of the
covariance operator and determines whether a problem is tractable or not. Four
types of tractability are studied and for each of them we find the necessary
and sufficient conditions in terms of the eigenvalues of univariate kernels. We
illustrate our results by considering approximation problems related to the
product of Korobov kernels characterized by a weights g_k and smoothnesses r_k.
We assume that weights are non-increasing and smoothness parameters are
non-decreasing. Furthermore they may be related, for instance g_k=g(r_k) for
some non-increasing function g. In particular, we show that approximation
problem is strongly polynomially tractable, i.e., n(h,d)\le C h^{-p} for all d
and 0<h<1, where C and p are independent of h and d, iff liminf |ln g_k|/ln k
>1. For other types of tractability we also show necessary and sufficient
conditions in terms of the sequences g_k and r_k
On the dc Magnetization, Spontaneous Vortex State and Specific Heat in the superconducting state of the weakly ferromagnetic superconductor RuSrGdCuO
Magnetic-field changes 0.2 Oe over the scan length in magnetometers that
necessitate sample movement are enough to create artifacts in the dc
magnetization measurements of the weakly ferromagnetic superconductor
RuSrGdCuO (Ru1212) below the superconducting transition
temperature 30 K. The observed features depend on the specific
magnetic-field profile in the sample chamber and this explains the variety of
reported behaviors for this compound below . An experimental procedure
that combines improvement of the magnetic-field homogeneity with very small
scan lengths and leads to artifact-free measurements similar to those on a
stationary sample has been developed. This procedure was used to measure the
mass magnetization of Ru1212 as a function of the applied magnetic field H (-20
Oe H 20 Oe) at and discuss, in conjunction with
resistance and ac susceptibility measurements, the possibility of a spontaneous
vortex state (SVS) for this compound. Although the existence of a SVS can not
be excluded, an alternative interpretation of the results based on the granular
nature of the investigated sample is also possible. Specific-heat measurements
of SrGdRuO (Sr2116), the precursor for the preparation of Ru1212
and thus a possible impurity phase, show that it is unlikely that Sr2116 is
responsible for the specific-heat features observed for Ru1212 at .Comment: 17 pages, 6 figure
Bilinear structure and Schlesinger transforms of the -P and -P equations
We show that the recently derived (-) discrete form of the Painlev\'e VI
equation can be related to the discrete P, in particular if one
uses the full freedom in the implementation of the singularity confinement
criterion. This observation is used here in order to derive the bilinear forms
and the Schlesinger transformations of both -P and -P.Comment: 10 pages, Plain Te
Individual differences in infant fixation duration relate to attention and behavioral control in childhood
Individual differences in fixation duration are considered a reliable measure of attentional control in adults. However, the degree to which individual differences in fixation duration in infancy (0â12 months) relate to temperament and behavior in childhood is largely unknown. In the present study, data were examined from 120 infants (mean age = 7.69 months, SD = 1.90) who previously participated in an eye-tracking study. At follow-up, parents completed age-appropriate questionnaires about their childâs temperament and behavior (mean age of children = 41.59 months, SD = 9.83). Mean fixation duration in infancy was positively associated with effortful control (β = 0.20, R2 = .02, p = .04) and negatively with surgency (β = â0.37, R2 = .07, p = .003) and hyperactivity-inattention (β = â0.35, R2 = .06, p = .005) in childhood. These findings suggest that individual differences in mean fixation duration in infancy are linked to attentional and behavioral control in childhood
Supporting material for co-researchers
This pack has been designed to be used alongside the Peer Research Training Resource (https://doi.org/10.25561/94819) and includes: ⢠Skills, experience, and training reviews for Advisory Group Members and Peer Researchers ⢠Zoom Interviews: Guide for Peer Researchers ⢠Useful COVID-19 resources for people living with HIV The pack is suitable for academics and public involvement practitioners who are involving people with lived experience as co-researchers in research. The material presented here was developed for a participatory research study on COVID-19 experiences among people living with HIV where interviews were conducted online
First-year Accounting studentsâ confidence levels during Covid-19: Evidence over a period of two years at a South African university
The Coronavirus Disease (Covid-19) outbreak has caused serious and continuous concerns globally within the higher education sector. One of these is the confidence levels of students to perform specific academic-related tasks. This study explored first-year accounting studentsâ confidence levels during Covid-19 over a two-year period at a South African university to determine if any associations exist between studentsâ gender, age, choice of study, language, and method of study funding, compared to confidence level, whilst applying a quantitative research design. Mixed results were obtained. Areas for further research identified include collaboration with other universities, and to expand the scope of the population, to determine the status of studentsâ confidence levels for different accountancy-related modules during and post-Covid-19. The study will inform and sensitise lecturers, students and academic institutions regarding the confidence levels of students to perform specific academic-related tasks within accounting education and training under Covid-19 conditions
- âŚ