225,325 research outputs found
Periodic subvarieties of a projective variety under the action of a maximal rank abelian group of positive entropy
We determine positive-dimensional G-periodic proper subvarieties of an
n-dimensional normal projective variety X under the action of an abelian group
G of maximal rank n-1 and of positive entropy. The motivation of the paper is
to understand the obstruction for X to be G-equivariant birational to the
quotient variety of an abelian variety modulo the action of a finite group.Comment: Asian Journal of Mathematics (to appear), Special issue on the
occasion of Prof N. Mok's 60th birthda
Conditional transfer of quantum correlation in the intensity of twin beams
A conditional protocol of transferring quantum-correlation in continuous
variable regime was experimentally demonstrated. The quantum-correlation in two
pairs of twin beams, each characterized by intensity-difference squeezing of
7.0 dB, was transferred to two initially independent idler beams. The
quantum-correlation transfer resulted in intensity-difference squeezing of 4.0
dB between two idler beams. The dependence of preparation probability and
transfer fidellity on the selection bandwidth was also studied.Comment: 5 pages, submitte
Incompleteness of Representation Theory: Hidden symmetries and Quantum Non-Integrability
Representation theory is shown to be incomplete in terms of enumerating all
integrable limits of quantum systems. As a consequence, one can find exactly
solvable Hamiltonians which have apparently strongly broken symmetry. The
number of these hidden symmetries depends upon the realization of the
Hamiltonian.Comment: 4 pages, Revtex, Phys. Rev. Lett. , July 27 (1997), in pres
Exploring Quantum Phase Transitions with a Novel Sublattice Entanglement Scenario
We introduce a new measure called reduced entropy of sublattice to quantify
entanglement in spin, electron and boson systems. By analyzing this quantity,
we reveal an intriguing connection between quantum entanglement and quantum
phase transitions in various strongly correlated systems: the local extremes of
reduced entropy and its first derivative as functions of the coupling constant
coincide respectively with the first and second order transition points. Exact
numerical studies merely for small lattices reproduce several well-known
results, demonstrating that our scenario is quite promising for exploring
quantum phase transitions.Comment: 4 pages, 4 figure
Early Results on Radioactive Background Characterization for Sanford Laboratory and DUSEL Experiments
Measuring external sources of background for a deep underground laboratory at
the Homestake Mine is an important step for the planned low-background
experiments. The naturally occurring -ray fluxes at different levels in
the Homestake Mine are studied using NaI detectors and Monte Carlo simulations.
A simple algorithm is developed to convert the measured -ray rates into
-ray fluxes. A good agreement between the measured and simulated
-ray fluxes is achieved with the knowledge of the chemical composition
and radioactivity levels in the rock. The neutron fluxes and -ray
fluxes are predicted by Monte Carlo simulations for different levels including
inaccessible levels that are under construction for the planned low background
experiments.Comment: 16 pages, 2 figures, and 9 table
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