Adiabatic charge pumping through a dot at the junction of N quantum wires

We study adiabatic charge pumping through a quantum dot placed at the junction of $N$ quantum wires. We explicitly map out the pattern of pumped charge as a function of the time-varying tunneling parameters coupling the wires to the dot and the phase between any two time varying parameters controlling the shape of the dot. We find that with $N-2$ time-independent well-coupled leads, the maximum pumped charge in the remaining two leads is strongly suppressed with increasing $N$, leading to the possibility of tuning of the pumped charge, by modulating the coupling of the $N-2$ leads.Comment: 5 pages, 6 figures, version to be published in PR

Cocrystal formation by Ionic liquid-assisted grinding: Case study with cocrystals of caffeine

iquid assisted grinding using imidazolium-based ionic liquids (IL-AG) was found to be effective in isolation of cocrystals and cocrystal polymorphs. Isolation of specific polymorphs of caffeine–citric acid (CAF–CA) and caffeine–glutaric acid (CAF–GLU) cocrystals highlights the tunability of ILs in polymorphic control

U(1) and SU(2) quantum dissipative systems: The Caldeira-Leggett vs. the Amegaokar-Eckern-Sch\"on approaches

There are two paradigmatic frameworks for treating quantum systems coupled to a dissipative environment: the Caldeira-Leggett and the Ambegaokar-Eckern-Sch\"on approaches. Here we recall the differences between them, and explain the consequences when each is applied to a zero dimensional spin (possessing an SU(2) symmetry) in a dissipative environment (a dissipative quantum dot near or beyond the Stoner instability point).Comment: Contribution for Leonid Keldysh 85 Festschrif

Magnetic scattering of Dirac fermions in topological insulators and graphene

We study quantum transport and scattering of massless Dirac fermions by spatially localized static magnetic fields. The employed model describes in a unified manner the effects of orbital magnetic fields, Zeeman and exchange fields in topological insulators, and the pseudo-magnetic fields caused by strain or defects in monolayer graphene. The general scattering theory is formulated, and for radially symmetric fields, the scattering amplitude and the total and transport cross sections are expressed in terms of phase shifts. As applications, we study ring-shaped magnetic fields (including the Aharanov-Bohm geometry) and scattering by magnetic dipoles.Comment: 11 pages, 4 figure

A Three Dimensional Lattice of Ion Traps

We propose an ion trap configuration such that individual traps can be stacked together in a three dimensional simple cubic arrangement. The isolated trap as well as the extended array of ion traps are characterized for different locations in the lattice, illustrating the robustness of the lattice of traps concept. Ease in the addressing of ions at each lattice site, individually or simultaneously, makes this system naturally suitable for a number of experiments. Application of this trap to precision spectroscopy, quantum information processing and the study of few particle interacting system are discussed.Comment: 4 pages, 4 Figures. Fig 1 appears as a composite of 1a, 1b, 1c and 1d. Fig 2 appears as a composite of 2a, 2b and 2

The impact of eliminating primary school tuition fees on child marriage in sub-Saharan Africa:A quasi-experimental evaluation of policy changes in 8 countries

BACKGROUND:Child marriage harms girls' health and hinders progress toward development goals. Randomized studies have shown that providing financial incentives for girls' education can effectively delay marriage, but larger-scale interventions are needed in light of slow progress toward curbing the practice. Many sub-Saharan African countries eliminated primary school tuition fees over the past two decades, resulting in massive increases in enrolment. We measured the effect of these policies on the probability of primary school completion and of marriage before 15 and 18 years of age. METHODS:We used Demographic and Health Surveys to assemble a dataset of women born between 1970 and 2000 in 16 countries. These data were merged with longitudinal information on the timing of tuition fee elimination in each country. We estimated the impact of fee removal using fixed effects regression to compare changes in the prevalence of child marriage over time between women who were exposed to tuition-free primary schooling and those who were not. RESULTS:The removal of tuition fees led to modest average declines in the prevalence of child marriage across all of the treated countries. However, there was substantial heterogeneity between countries. The prevalence of child marriage declined by 10-15 percentage points in Ethiopia and Rwanda following tuition elimination but we found no evidence that the removal of tuition fees had an impact on child marriage rates in Cameroon or Malawi. Reductions in child marriage were not consistently accompanied by increases in the probability of primary school completion. CONCLUSIONS:Eliminating tuition fees led to reductions in child marriage on a national scale in most countries despite challenges with implementation. Improving the quality of the education available may strengthen these effects and bolster progress toward numerous other public health goals