7,275 research outputs found
Formation of InAs Self-Assembled Quantum Rings on InP
Shape transformations of partially capped self-assembled InAs quantum dots
grown on InP are studied. Atomic force microscopy images show large anisotropic
redistribution of the island material after coverage by a 1 nm thick InP layer.
The anisotropic material redistribution occurs within a few minutes and leads
to a change from lens-like to elongated ring-like islands. The shape
transformation is not accompanied by dot material compositional change. The
formation of InAs/InP quantum rings disagrees with a previous model of
InAs/GaAs ring formation that assumes that the driving force for the dot to
ring transformation is the difference in surface diffusion velocity of indium
and gallium atoms.Comment: 13 pages, including 2 figures and 1 table. Submitted to Appl. Phys.
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Towards More Data-Aware Application Integration (extended version)
Although most business application data is stored in relational databases,
programming languages and wire formats in integration middleware systems are
not table-centric. Due to costly format conversions, data-shipments and faster
computation, the trend is to "push-down" the integration operations closer to
the storage representation.
We address the alternative case of defining declarative, table-centric
integration semantics within standard integration systems. For that, we replace
the current operator implementations for the well-known Enterprise Integration
Patterns by equivalent "in-memory" table processing, and show a practical
realization in a conventional integration system for a non-reliable,
"data-intensive" messaging example. The results of the runtime analysis show
that table-centric processing is promising already in standard, "single-record"
message routing and transformations, and can potentially excel the message
throughput for "multi-record" table messages.Comment: 18 Pages, extended version of the contribution to British
International Conference on Databases (BICOD), 2015, Edinburgh, Scotlan
Evolution of spin correlations in SrDy2O4 in an applied magnetic field
The development of short- and long-range magnetic order induced in a
frustrated zig-zag ladder compound SrDy2O4 by an applied field is studied using
neutron diffraction techniques. In zero field, SrDy2O4 lacks long-range
magnetic order down to temperatures as low as 60 mK, and the observed powder
neutron diffraction (PND) patterns are dominated by very broad diffuse
scattering peaks. Single crystal neutron diffraction reveals that the
zero-field magnetic structure consists of a collection of antiferromagnetic
chains running along the c axis and that there is very little correlation
between the chains in the ab plane. In an applied magnetic field, the broad
diffuse scattering features in PND are gradually replaced by much sharper
peaks, however, the pattern remains rather complex, reflecting the highly
anisotropic nature of SrDy2O4. Single crystal neutron diffraction shows that a
moderate field applied along the b axis induces an up-up-down magnetic order
associated with a 1/3-magnetisation plateau, in which magnetic correlation
length in the ab plane is significantly increased, but it nevertheless remains
finite. The resolution limited k = 0 peaks associated with a ferromagnetic
arrangement appear in powder and single crystal neutron diffraction patterns in
fields of 2.5 T and above.Comment: 10 pages, 11 figure
On the number of representations providing noiseless subsystems
This paper studies the combinatoric structure of the set of all
representations, up to equivalence, of a finite-dimensional semisimple Lie
algebra. This has intrinsic interest as a previously unsolved problem in
representation theory, and also has applications to the understanding of
quantum decoherence. We prove that for Hilbert spaces of sufficiently high
dimension, decoherence-free subspaces exist for almost all representations of
the error algebra. For decoherence-free subsystems, we plot the function
which is the fraction of all -dimensional quantum systems which
preserve bits of information through DF subsystems, and note that this
function fits an inverse beta distribution. The mathematical tools which arise
include techniques from classical number theory.Comment: 17 pp, 4 figs, accepted for Physical Review
An Exact Conformal Symmetry Ansatz on Kaluza-Klein Reduced TMG
Using a Kaluza-Klein dimensional reduction, and further imposing a conformal
Killing symmetry on the reduced metric generated by the dilaton, we show an
Ansatz that yields many of the known stationary axisymmetric solutions to TMG.Comment: 20 pages, 1 figure, v3: postprint, added one re
Relativistic coupled-cluster single-double method applied to alkali-metal atoms
A relativistic version of the coupled-cluster single-double (CCSD) method is
developed for atoms with a single valence electron. In earlier work, a
linearized version of the CCSD method (with extensions to include a dominant
class of triple excitations) led to accurate predictions for energies,
transition amplitudes, hyperfine constants, and other properties of monovalent
atoms. Further progress in high-precision atomic structure calculations for
heavy atoms calls for improvement of the linearized coupled-cluster
methodology. In the present work, equations for the single and double
excitation coefficients of the Dirac-Fock wave function, including all
non-linear coupled-cluster terms that contribute at the single-double level are
worked out. Contributions of the non-linear terms to energies, electric-dipole
matrix elements, and hyperfine constants of low-lying states in alkali-metal
atoms from Li to Cs are evaluated and the results are compared with other
calculations and with precise experiments.Comment: 12 page
Hydrodynamical evolution near the QCD critical end point
Hydrodynamical calculations have been successful in describing global
observables in ultrarelativistic heavy ion collisions, which aim to observe the
production of the quark-gluon plasma. On the other hand, recently, a lot of
evidence that there exists a critical end point (CEP) in the QCD phase diagram
has been accumulating. Nevertheless, so far, no equation of state with the CEP
has been employed in hydrodynamical calculations. In this paper, we construct
the equation of state with the CEP on the basis of the universality hypothesis
and show that the CEP acts as an attractor of isentropic trajectories. We also
consider the time evolution in the case with the CEP and discuss how the CEP
affects the final state observables, such as the correlation length,
fluctuation, chemical freezeout, kinetic freezeout, and so on. Finally, we
argue that the anomalously low kinetic freezeout temperature at the BNL
Relativistic Heavy Ion Collider suggests the possibility of the existence of
the CEP.Comment: 13 pages, 12 figures, accepted for publication in Physical Review
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