1,060 research outputs found
Discrete analogues of maximally modulated singular integrals of Stein-Wainger type: bounds for
It is proved that certain discrete analogues of maximally modulated singular
integrals of Stein-Wainger type are bounded on for all
. This extends earlier work of the authors concerning the case
. Some open problems for further investigation are briefly discussed.Comment: 15 pages; changed title, final version to appear in JF
Discrete analogues of maximally modulated singular integrals of Stein-Wainger type: â2(Zn) bounds
Discrete analogues of maximally modulated singular integrals of Stein-Wainger type
Consider the maximal operator where is a
positive integer, a Calder\'on-Zygmund kernel and . This is a
discrete analogue of a real-variable operator studied by Stein and Wainger. The
nonlinearity of the phase introduces a variety of new difficulties that are not
present in the real-variable setting. We prove -bounds
for , answering a question posed by Lillian Pierce.Comment: 24 pages. Additional details inserted; final version to appear in
JEM
THE COMPLETE STORY: A POPULATIONâ BASED PERSPECTIVE ON SCHOOL PERFORMANCE AND EDUCATIONAL TESTING
All children born in Manitoba in 1984 were tracked for 18 years to assess their gradeâ 12 performance on a provincial examination according to a studentâs socioâeconomic status. The proportion of youths in families receiving social assistance judged to have passed their language arts exam dropped from 80 per cent to 12 per cent, depending on whether one counts only those in the cohort who took the test on time in 2002 or all youths born in 1984 who should have taken the test in 2002. Getting better data on performance and doing something about the discrepancies should become a Canadian priority. Key words: educational opportunity, exam performance, socioâeconomic status, testing, longitudinal studies Tous les enfants nĂ©s au Manitoba en 1984 ont Ă©tĂ© suivis sur une pĂ©riode de 18 ans en vue dâĂ©valuer leur rendement en 12e annĂ©e lors dâun examen provincial, tenant compte de leur statut socioĂ©conomique. La proportion de jeunes issus des familles recevant de lâaide sociale et considĂ©rĂ©s comme ayant rĂ©ussi leur examen au plan des compĂ©tences linguistiques passe de 80 % Ă 12 %, selon que lâon compte seulement ceux qui, dans la cohorte, ont subi lâexamen Ă temps en 2002 ou tous les jeunes nĂ©s en 1984 qui auraient dĂ» subir lâexamen. En matiĂšre dâĂ©galitĂ© des chances, la performance du systĂšme scolaire actuel au Canada laisse Ă dĂ©sirer. Mots clĂ©s: possibilitĂ©s Ă©ducatives, rĂ©sultats dâexamen, statut socioĂ©conomique, analyse longitudinale.
Environment-assisted quantum transport in a 10-qubit network
The way in which energy is transported through an interacting system governs
fundamental properties in many areas of physics, chemistry, and biology.
Remarkably, environmental noise can enhance the transport, an effect known as
environment-assisted quantum transport (ENAQT). In this paper, we study ENAQT
in a network of coupled spins subject to engineered static disorder and
temporally varying dephasing noise. The interacting spin network is realized in
a chain of trapped atomic ions and energy transport is represented by the
transfer of electronic excitation between ions. With increasing noise strength,
we observe a crossover from coherent dynamics and Anderson localization to
ENAQT and finally a suppression of transport due to the quantum Zeno effect. We
found that in the regime where ENAQT is most effective the transport is mainly
diffusive, displaying coherences only at very short times. Further, we show
that dephasing characterized by non-Markovian noise can maintain coherences
longer than white noise dephasing, with a strong influence of the spectral
structure on the transport effciency. Our approach represents a controlled and
scalable way to investigate quantum transport in many-body networks under
static disorder and dynamic noise.Comment: Mai
Clinical and genetic characterization of a Danish family with North Carolina macular dystrophy
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