50,272 research outputs found
Defect free global minima in Thomson's problem of charges on a sphere
Given unit points charges on the surface of a unit conducting sphere,
what configuration of charges minimizes the Coulombic energy ? Due to an exponential rise in good local minima, finding global
minima for this problem, or even approaches to do so has proven extremely
difficult. For \hbox{} recent theoretical work based on
elasticity theory, and subsequent numerical work has shown, that for --1000 adding dislocation defects to a symmetric icosadeltahedral lattice
lowers the energy. Here we show that in fact this approach holds for all ,
and we give a complete or near complete catalogue of defect free global minima.Comment: Revisions in Tables and Reference
The Exchange Gate in Solid State Spin Quantum Computation: The Applicability of the Heisenberg Model
Solid state quantum computing proposals rely on adiabatic operations of the
exchange gate among localized spins in nanostructures. We study corrections to
the Heisenberg interaction between lateral semiconductor quantum dots in an
external magnetic field. Using exact diagonalization we obtain the regime of
validity of the adiabatic approximation. We also find qualitative corrections
to the Heisenberg model at high magnetic fields and in looped arrays of spins.
Looped geometries of localized spins generate flux dependent, multi-spin terms
which go beyond the basic Heisenberg model.Comment: 13 pages, 8 figure
About the determination of critical exponents related to possible phase transitions in nuclear fragmentation
We introduce a method based on the finite size scaling assumption which
allows to determine numerically the critical point and critical exponents
related to observables in an infinite system starting from the knowledge of the
observables in finite systems. We apply the method to bond percolation in 2
dimensions and compare the results obtained when the bond probability p or the
fragment multiplicity m are chosen as the relevant parameter.Comment: 12 pages, TeX, 4 figure
Implications of sterile neutrinos for medium/long-baseline neutrino experiments and the determination of
We revisit some of the recent neutrino observations and anomalies in the
context of sterile neutrinos. Based on a general parametrization motivated in
the presence of sterile neutrinos, the consistency of the MINOS disappearance
data with additional sterile neutrinos is discussed. We also explore the
implications of sterile neutrinos for the measurement of in this
case. Regarding the determination of , we observe that the existence
of sterile neutrinos may induce a significant modification of the
angle in neutrino appearance experiments like T2K and MINOS, over and above the
ambiguities and degeneracies that are already present in 3-neutrino parameter
extractions. The modification is less significant in reactor neutrino
experiments like Double-CHOOZ, Daya Bay and RENO and therefore the extracted
value when sterile neutrinos are present is close to the one that
would be obtained in the 3-neutrino case. We also conclude that the results
from T2K imply a 90% C.L. lower-bound on , in the "" neutrino
case, which is still within the sensitivity of future reactor neutrino
experiments like Daya Bay, and consistent with the one- range of
recently reported by the Double-CHOOZ experiment. Finally,
we argue that for the recently determined best-fit parameters, the results in
the "" scenario would be very close to the medium/long baseline results
obtained in the "" case analyzed in this work.Comment: 25 pages, 9 figures, revtex4-1. Typos corrected, published versio
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