47 research outputs found
Polarized fine structure in the excitation spectrum of a negatively charged quantum dot
We report polarized photoluminescence excitation spectroscopy of the negative
trion in single charge tunable InAs/GaAs quantum dots. The spectrum exhibits a
p-shell resonance with polarized fine structure arising from the direct
excitation of the electron spin triplet states. The energy splitting arises
from the axially symmetric electron-hole exchange interaction. The magnitude
and sign of the polarization are understood from the spin character of the
triplet states and a small amount of quantum dot asymmetry, which mixes the
wavefunctions through asymmetric e-e and e-h exchange interactions
Energetics and Vibrational States for Hydrogen on Pt(111)
We present a combination of theoretical calculations and experiments for the
low-lying vibrational excitations of H and D atoms adsorbed on the Pt(111)
surface. The vibrational band states are calculated based on the full
three-dimensional adiabatic potential energy surface obtained from first
principles calculations. For coverages less than three quarters of a monolayer,
the observed experimental high-resolution electron peaks at 31 and 68meV are in
excellent agreement with the theoretical transitions between selected bands.
Our results convincingly demonstrate the need to go beyond the local harmonic
oscillator picture to understand the dynamics of this system.Comment: In press at Phys. Rev. Lett - to appear in April 200
Analytic curves in algebraic varieties over number fields
We establish algebraicity criteria for formal germs of curves in algebraic
varieties over number fields and apply them to derive a rationality criterion
for formal germs of functions, which extends the classical rationality theorems
of Borel-Dwork and P\'olya-Bertrandias valid over the projective line to
arbitrary algebraic curves over a number field.
The formulation and the proof of these criteria involve some basic notions in
Arakelov geometry, combined with complex and rigid analytic geometry (notably,
potential theory over complex and -adic curves). We also discuss geometric
analogues, pertaining to the algebraic geometry of projective surfaces, of
these arithmetic criteria.Comment: 55 pages. To appear in "Algebra, Arithmetic, and Geometry: In Honor
of Y.i. Manin", Y. Tschinkel & Yu. Manin editors, Birkh\"auser, 200
Does inequality erode generalized trust? Evidence from Romanian youths
Generalized trust is a critical component of liberal democratic citizenship. We evaluate the extent to which exposure to socioeconomic inequality erodes trust among Romanian youths. Using national survey data of Romanian eighth-grade and high school students, we evaluate this effect as a product of socioeconomic diversity within the classroom, controlling for the social status of the students as well as socioeconomic inequality within the community where the school is located. Our analysis shows that generalized trust is higher for students in higher grades. However, despite this maturing effect, students exposed to greater levels of socioeconomic diversity have significantly lower levels of trust. The effect is particularly acute for students in the ninth grade. This finding holds when controlling for socioeconomic diversity and polarization in the community. The result reinforces the idea that generalized trust develops early in one’s life and is quite stable, although a major life transformation, such as entering high school, may alter trust depending on the social context
Evidence for a source of H chondrites in the outer main asteroid belt
Aims. In this paper we report near-infrared spectroscopic observations of one of the largest potentially hazardous asteroids, (214869) 2007 PA
Potenţialul biosorptiv al unor deşeuri de biomasă pentru îndepărtarea ionilor de Cu(II) din soluţii apoase
In this study, was analyzed the biosorptionpotential of somewaste biomasses in the removal process of Cu(II) ions from aqueous solution. Three types of biosorbents have been used in experiments, namely: marine algae waste,mustard waste and lignin. All these materials are resulted from different industrial activities, and their use for the metal ions removal from aqueous solution is in agreement with the principles of circular economy. The experimental results obtained for the influence of initial Cu(II) ions concentration and contact time on the removal efficiency from aqueous media were modelled using various isotherm and kinetics models. The parameters obtained from modelling have permitted the evaluation of biosorptive potential of these three types of waste biomasses in the removal processes of Cu(II) ions from aqueous solution