276,496 research outputs found
Theory of the vortex matter transformations in high Tc superconductor YBCO
Flux line lattice in type II superconductors undergoes a transition into a
"disordered" phase like vortex liquid or vortex glass, due to thermal
fluctuations and random quenched disorder. We quantitatively describe the
competition between the thermal fluctuations and the disorder using the
Ginzburg -- Landau approach. The following T-H phase diagram of YBCO emerges.
There are just two distinct thermodynamical phases, the homogeneous and the
crystalline one, separated by a single first order transitions line. The line
however makes a wiggle near the experimentally claimed critical point at 12T.
The "critical point" is reinterpreted as a (noncritical) Kauzmann point in
which the latent heat vanishes and the line is parallel to the T axis. The
magnetization, the entropy and the specific heat discontinuities at melting
compare well with experiments.Comment: 4 pages 3 figure
The IT performance evaluation in the construction industry
To date there has been limited published work in
the construction management and engineering
literature that has provided empirical evidence to
demonstrate that IT can improve organizational
performance. Without an explicit understanding
about how IT can be effectively used to improve
organizational performance, its justification will
remain to be weak for managers. To ensure the
continuous increase in IT based applications in the
construction industry, sufficient evidence has to be
provided for management in various professions of
the construction industry to evaluate, allocate and
utilize appropriate IT systems. In an attempt to
explore the relationship between IT and
productivity, an empirical investigation of 60
Professional Consulting Firms (PCF) from the
Hong Kong construction industry was undertaken.
A model for determining the organizational
productivity of IT is proposed, and the
methodology used to test the model is described.
The findings are analyzed and a cross-profession
comparison of the results indicated the differences
in the use of IT. The research findings are discussed
with similarities being drawn. The limitations of the
research are then presented and discussed. The
implications of the findings and conclusions then
fully presented
Taming computational complexity: efficient and parallel SimRank optimizations on undirected graphs
SimRank has been considered as one of the promising link-based ranking algorithms to evaluate similarities of web documents in many modern search engines. In this paper, we investigate the optimization problem of SimRank similarity computation on undirected web graphs. We first present a novel algorithm to estimate the SimRank between vertices in O(n3+ Kn2) time, where n is the number of vertices, and K is the number of iterations. In comparison, the most efficient implementation of SimRank algorithm in [1] takes O(K n3 ) time in the worst case. To efficiently handle large-scale computations, we also propose a parallel implementation of the SimRank algorithm on multiple processors. The experimental evaluations on both synthetic and real-life data sets demonstrate the better computational time and parallel efficiency of our proposed techniques
The Precise Formula in a Sine Function Form of the norm of the Amplitude and the Necessary and Sufficient Phase Condition for Any Quantum Algorithm with Arbitrary Phase Rotations
In this paper we derived the precise formula in a sine function form of the
norm of the amplitude in the desired state, and by means of he precise formula
we presented the necessary and sufficient phase condition for any quantum
algorithm with arbitrary phase rotations. We also showed that the phase
condition: identical rotation angles, is a sufficient but not a necessary phase
condition.Comment: 16 pages. Modified some English sentences and some proofs. Removed a
table. Corrected the formula for kol on page 10. No figure
Nuclear quantum shape-phase transitions in odd-mass systems
Microscopic signatures of nuclear ground-state shape phase transitions in
odd-mass Eu isotopes are explored starting from excitation spectra and
collective wave functions obtained by diagonalization of a core-quasiparticle
coupling Hamiltonian based on energy density functionals. As functions of the
physical control parameter -- the number of nucleons -- theoretical low-energy
spectra, two-neutron separation energies, charge isotope shifts, spectroscopic
quadrupole moments, and reduced transition matrix elements accurately
reproduce available data, and exhibit more pronounced discontinuities at
neutron number , compared to the adjacent even-even Sm and Gd isotopes.
The enhancement of the first-order quantum phase transition in odd-mass systems
can be attributed to a shape polarization effect of the unpaired proton which,
at the critical neutron number, starts predominantly coupling to Gd core nuclei
that are characterized by larger quadrupole deformation and weaker proton
pairing correlations compared to the corresponding Sm isotopes.Comment: 6 pages, 4 figure
First-order coherence versus entanglement in a nano-mechanical cavity
The coherence and correlation properties of effective bosonic modes of a
nano-mechanical cavity composed of an oscillating mirror and containing an
optical lattice of regularly trapped atoms are studied. The system is modeled
as a three-mode system, two orthogonal polariton modes representing the coupled
optical lattice and the cavity mode, and one mechanical mode representing the
oscillating mirror. We examine separately the cases of two-mode and three-mode
interactions which are distinguished by a suitable tuning of the mechanical
mode to the polariton mode frequencies. In the two-mode case, we find that the
occurrence of entanglement between one of the polariton modes and the
mechanical mode is highly sensitive to the presence of the first-order
coherence between the modes. In particular, the creation of the first-order
coherence among the modes is achieved at the expense of entanglement between
the modes. In the three-mode case, we show that no entanglement is created
between the independent polariton modes if both modes are coupled to the
mechanical mode by the parametric interaction. There is no entanglement between
the polaritons even if the oscillating mirror is damped by a squeezed vacuum
field. The interaction creates the first-order coherence between the polaritons
and the degree of coherence can, in principle, be as large as unity. This
demonstrates that the oscillating mirror can establish the first-order
coherence between two independent thermal modes. A further analysis shows that
two independent thermal modes can be made entangled in the system only when one
of the modes is coupled to the intermediate mode by a parametric interaction
and the other is coupled by a linear-mixing interaction.Comment: Published versio
Could 2S 0114+650 be a magnetar?
We investigate the spin evolution of the binary X-ray pulsar 2S 0114+650,
which possesses the slowest known spin period of hours. We argue
that, to interpret such long spin period, the magnetic field strength of this
pulsar must be initially \gsim 10^{14} G, that is, it was born as a magnetar.
Since the pulsar currently has a normal magnetic field G, our
results present support for magnetic field decay predicted by the magnetar
model.Comment: 7 pages, 1 figure, accepted for publication in ApJ
Microscopic Analysis of Order Parameters in Nuclear Quantum Phase Transitions
Microscopic signatures of nuclear ground-state shape phase transitions in Nd
isotopes are studied using excitation spectra and collective wave functions
obtained by diagonalization of a five-dimensional Hamiltonian for quadrupole
vibrational and rotational degrees of freedom, with parameters determined by
constrained self-consistent relativistic mean-field calculations for triaxial
shapes. As a function of the physical control parameter -- the number of
nucleons, energy gaps between the ground state and the excited vibrational
states with zero angular momentum, isomer shifts, and monopole transition
strengths, exhibit sharp discontinuities at neutron number N=90, characteristic
of a first-order quantum phase transition.Comment: 5 pages, 4 figures, accepted for publication as a Rapid Communication
in Physical Review
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