3,789 research outputs found
A Grounded Theory Analysis of E-Collaboration Effects for Distributed Project Management
The emergence and widespread use of collaborative technologies for distributed project management has brought opened up a myriad of opportunities for business. While the opportunities for off-shore outsourcing and collaborative development are enticing, most tools and techniques for project management focus on on-site, long term relationships and sourcing strategies at a time when inter-organizational relationships are becoming dynamic and temporary. This paper uses grounded theory to analyze data on virtual teams. The analysis uncovers âeffectsâ in the way distributed projects are managed. These effects relate to coordination, communication and adaptation to distributed electronic work environments. Following an analysis of these eCollaboration âeffectsâ, a model for distributed project management is presented
Final state hadronic interactions and non-resonant decays
We evaluate the non-resonant decay amplitude of the process using an approach based on final state hadronic interactions
described in terms of meson exchanges. We conclude that this mechanism
generates inhomogeneities in the Dalitz plot of the B decay.Comment: 6 pages, 5 figures. Major changes. Version accepted for publication
in Phys. Lett.
Quasi-local Energy for Spherically Symmetric Spacetimes
We present two complementary approaches for determining the reference for the
covariant Hamiltonian boundary term quasi-local energy and test them on
spherically symmetric spacetimes. On the one hand, we isometrically match the
2-surface and extremize the energy. This can be done in two ways, which we call
programs I (without constraint) and II (with additional constraints). On the
other hand, we match the orthonormal 4-frames of the dynamic and the reference
spacetimes. Then, if we further specify the observer by requiring the reference
displacement to be the timelike Killing vector of the reference, the result is
the same as program I, and the energy can be positive, zero, or even negative.
If, instead, we require that the Lie derivatives of the two-area along the
displacement vector in both the dynamic and reference spacetimes to be the
same, the result is the same as program II, and it satisfies the usual
criteria: the energies are non-negative and vanish only for Minkowski (or
anti-de Sitter) spacetime.Comment: 16 pages, no figure
A spherical perfect lens
It has been recently proved that a slab of negative refractive index material
acts as a perfect lens in that it makes accessible the sub-wavelength image
information contained in the evanescent modes of a source. Here we elaborate on
perfect lens solutions to spherical shells of negative refractive material
where magnification of the near-field images becomes possible. The negative
refractive materials then need to be spatially dispersive with and . We concentrate on lens-like solutions for the
extreme near-field limit. Then the conditions for the TM and TE polarized modes
become independent of and respectively.Comment: Revtex4, 9 pages, 2 figures (eps
Three-Loop Radiative-Recoil Corrections to Hyperfine Splitting in Muonium
We calculate three-loop radiative-recoil corrections to hyperfine splitting
in muonium generated by the diagrams with the first order electron and muon
polarization loop insertions in graphs with two exchanged photons. These
corrections are enhanced by the large logarithm of the electron-muon mass
ratio. The leading logarithm squared contribution was obtained a long time ago.
Here we calculate the single-logarithmic and nonlogarithmic contributions. We
previously calculated the three-loop radiative-recoil corrections generated by
two-loop polarization insertions in the exchanged photons. The current paper
therefore concludes calculation of all three-loop radiative-recoil corrections
to hyperfine splitting in muonium generated by diagrams with closed fermion
loop insertions in the exchanged photons. The new results obtained here improve
the theory of hyperfine splitting, and affect the value of the electron-muon
mass ratio extracted from experimental data on the muonium hyperfine splitting.Comment: 27 pages, 6 figures, 7 table
A first principles study of sub-monolayer Ge on Si(001)
Experimental observations of heteroepitaxial growth of Ge on Si(001) show a
(2xn) reconstruction for sub-monolayer coverages, with dimer rows crossed by
missing-dimer trenches. We present first-principles density-functional
calculations designed to elucidate the energetics and relaxed geometries
associated with this reconstruction. We also address the problem of how the
formation energies of reconstructions having different stoichiometries should
be compared. The calculations reveal a strong dependence of the formation
energy of the missing-dimer trenches on spacing n, and demonstrate that this
dependence stems almost entirely from elastic relaxation. The results provide a
natural explanation for the experimentally observed spacings in the region of n
\~ 8.Comment: 13 pages, 4 figures, submitted to Surface Scienc
Covariant Vortex In Superconducting-Superfluid-Normal Fluid Mixtures with Stiff Equation of State
The integrals of motion for a cylindrically symmetric stationary vortex are
obtained in a covariant description of a mixture of interacting
superconductors, superfluids and normal fluids. The relevant integrated
stress-energy coefficients for the vortex with respect to a vortex-free
reference state are calculated in the approximation of a ``stiff'', i.e. least
compressible, relativistic equation of state for the fluid mixture. As an
illustration of the foregoing general results, we discuss their application to
some of the well known examples of ``real'' superfluid and superconducting
systems that are contained as special cases. These include Landau's two-fluid
model, uncharged binary superfluid mixtures, rotating conventional
superconductors and the superfluid neutron-proton-electron plasma in the outer
core of neutron stars.Comment: 14 pages, uses RevTeX and amssymb, submitte
Hydrodynamics of Spatially Ordered Superfluids
We derive the hydrodynamic equations for the supersolid and superhexatic
phases of a neutral two-dimensional Bose fluid. We find, assuming that the
normal part of the fluid is clamped to an underlying substrate, that both
phases can sustain third-sound modes and that in the supersolid phase there are
additional modes due to the superfluid motion of point defects (vacancies and
interstitials).Comment: 24 pages of ReVTeX and 7 uuencoded figures. Submitted for publication
in Phys. Rev.
Scalar Decay in Chaotic Mixing
I review the local theory of mixing, which focuses on infinitesimal blobs of
scalar being advected and stretched by a random velocity field. An advantage of
this theory is that it provides elegant analytical results. A disadvantage is
that it is highly idealised. Nevertheless, it provides insight into the
mechanism of chaotic mixing and the effect of random fluctuations on the rate
of decay of the concentration field of a passive scalar.Comment: 35 pages, 15 figures. Springer-Verlag conference style svmult.cls
(included). Published in "Transport in Geophysical Flows: Ten Years After,"
Proceedings of the Grand Combin Summer School, 14-24 June 2004, Valle
d'Aosta, Italy. Fixed some typo
Simultaneous Diagonal and Off Diagonal Order in the Bose--Hubbard Hamiltonian
The Bose-Hubbard model exhibits a rich phase diagram consisting both of
insulating regimes where diagonal long range (solid) order dominates as well as
conducting regimes where off diagonal long range order (superfluidity) is
present. In this paper we describe the results of Quantum Monte Carlo
calculations of the phase diagram, both for the hard and soft core cases, with
a particular focus on the possibility of simultaneous superfluid and solid
order. We also discuss the appearance of phase separation in the model. The
simulations are compared with analytic calculations of the phase diagram and
spin wave dispersion.Comment: 28 pages plus 24 figures, uuencoded Revtex+postscript file
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