331 research outputs found
Singlet-triplet transitions in highly correlated nanowire quantum dots
We consider a quantum dot embedded in a three-dimensional nanowire with
tunable aspect ratio a. A configuration interaction theory is developed to
calculate the energy spectra of the finite 1D quantum dot systems charged with
two electrons in the presence of magnetic fields B along the wire axis.
Fruitful singlet-triplet transition behaviors are revealed and explained in
terms of the competing exchange interaction, correlation interaction, and spin
Zeeman energy. In the high aspect ratio regime, the singlet-triplet transitions
are shown designable by tuning the parameters a and B. The transitions also
manifest the highly correlated nature of long nanowire quantum dots.Comment: 4 pages, 4 figure
Statistical mechanics of RNA folding: importance of alphabet size
We construct a minimalist model of RNA secondary-structure formation and use
it to study the mapping from sequence to structure. There are strong,
qualitative differences between two-letter and four or six-letter alphabets.
With only two kinds of bases, there are many alternate folding configurations,
yielding thermodynamically stable ground-states only for a small set of
structures of high designability, i.e., total number of associated sequences.
In contrast, sequences made from four bases, as found in nature, or six bases
have far fewer competing folding configurations, resulting in a much greater
average stability of the ground state.Comment: 7 figures; uses revtex
Effect of Parametric Resonances on the Bunched-beam Dilution Mechanism
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
CE22: Nonlinear Beam Dynamics Experiments at the IUCF Cooler Ring
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Limit Cycle Instability of Proton Beams Generated by Nonlinear Electron-Cooling Force
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Nonlinear Beam Dynamics Experiments: CE-22
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Siberian Snake Overcomes "Overlapping" Depolarizing Resonances
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
The Beam Transfer Function Experiments: CE-37
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Transverse and Longitudinal Nonlinear Beam Dynamics
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Measurement of K^+K^- production in two-photon collisions in the resonant-mass region
K^+K^- production in two-photon collisions has been studied using a large
data sample of 67 fb^{-1} accumulated with the Belle detector at the KEKB
asymmetric e^+e^- collider. We have measured the cross section for the process
gamma gamma -> K^+ K^- for center-of-mass energies between 1.4 and 2.4 GeV, and
found three new resonant structures in the energy region between 1.6 and 2.4
GeV. The angular differential cross sections have also been measured.Comment: 24 pages, 8 figures, to appear in Euro. Phys. Jour.
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