7,637 research outputs found
Generalized scalar field models with the same energy density and linear stability
We study how the properties of a Lagrangian density for a single real scalar
field in flat spacetime change with inclusion of an overall factor depending
only on the field. The focus of the paper is to obtain analytical results. So,
we show that even though it is possible to perform a field redefinition to get
an equivalent canonical model, it is not always feasible to write the canonical
model in terms of elementary functions. Also, we investigate the behavior of
the energy density and the linear stability of the solutions. Finally, we show
that one can find a class of models that present the same energy density and
the same stability potential.Comment: 6 pages, 4 figure
Managing performance in quality management: A two level study of employee-perceptions and workplace-performance
Purpose: This paper addresses potential effects of the control element in Quality Management. First, behavioural theories on how elements of performance management can affect organisational performance are examined. Secondly, theoretical models on how perceptions of work conditions may impact wellbeing and performance are considered. Direct and indirect pathways from performance management to productivity/quality are inferred.
Methodology: Matched employee-workplace data from an economy-wide survey in Britain and two-level structural equation models are used to test the hypothesised associations.
Findings: The use of practices in workplaces is inconsistent with a unified performance management approach. Distinct outcomes are expected from separate components in performance management and some may be contingent on workplace size. For example, within Quality-planning, strategy dissemination is positively associated with workplace-productivity; targets are negatively associated with perceptions of job demands and positively correlated with job satisfaction, which in turn can increase workplace-productivity. With respect to Information & Analysis: keeping and analysing records, or monitoring employee-performance via appraisals that assess training needs, are positively associated with workplace-productivity and quality.
Originality: This paper illustrates how control in Quality Management can be effective. Although the merits of performance management are subject to ongoing debate, arguments in the literature have tended to focus on performance appraisal. Analyses of economy-wide data linking performance management practices, within Quality Management, to employee perceptions of work conditions, wellbeing and aggregate performance are rare
Donors in Ge as Qubits: Establishing Physical Attributes
Quantum electronic devices at the single impurity level demand an
understanding of the physical attributes of dopants at an unprecedented
accuracy. Germanium-based technologies have been developed recently, creating a
necessity to adapt the latest theoretical tools to the unique electronic
structure of this material. We investigate basic properties of donors in Ge
which are not known experimentally, but are indispensable for qubit
implementations. Our approach provides a description of the wavefunction at
multiscale, associating microscopic information from Density Functional Theory
and envelope functions from state of the art multivalley effective mass
calculations, including a central cell correction designed to reproduce the
energetics of all group V donor species (P, As, Sb and Bi). With this
formalism, we predict the binding energies of negatively ionized donors (D-
state). Furthermore, we investigate the signatures of buried donors to be
expected from Scanning Tunneling Microscopy (STM). The naive assumption that
attributes of donor electrons in other semiconductors may be extrapolated to Ge
is shown to fail, similar to earlier attempts to recreate in Si qubits designed
for GaAs. Our results suggest that the mature techniques available for qubit
realizations may be adapted to germanium to some extent, but the peculiarities
of the Ge band structure will demand new ideas for fabrication and control
From Kinks to Compactons
This work deals with the presence of localized structures in relativistic
systems described by a single real scalar field in two-dimensional spacetime.
We concentrate on kinks and compactons in models with standard kinematics, and
we develop a procedure that help us to smoothly go from kinks to compactons in
the suggested scenario. We also show how the procedure works in the braneworld
scenario, for flat brane in the five-dimensional spacetime with a single extra
dimension of infinite extent. The brane unveils a hybrid profile when the kink
becomes a compacton, behaving as a thick or thin brane, depending on the extra
dimension being inside or outside a compact space.Comment: 7 pages, 7 figures; new version, to appear in PL
Analytic vortex solutions in generalized models of the Maxwell-Higgs type
This work deals with the presence of analytical vortex configurations in
generalized models of the Maxwell-Higgs type in the three-dimensional
spacetime. We implement a procedure that allows to decouple the first order
equations, which we use to solve the model analytically. The approach is
exemplified with three distinct models that show the robustness of the
construction. In the third model, one finds analytical solutions that exhibit
interesting compact vortex behavior.Comment: 9 pages, 10 figures. To appear in PL
Compact Structures in Standard Field Theory
We investigate the presence of static solutions in models described by real
scalar field in two-dimensional spacetime. After taking advantage of a
procedure introduced sometime ago, we solve intricate nonlinear ordinary
differential equations and illustrate how to find compact structures in models
engendering standard kinematics. In particular, we study linear stability and
show that all the static solutions we have found are linearly stable.Comment: 6 pages, 11 figures; version published in EP
Vortices in a generalized Maxwell-Higgs model with visible and hidden sectors
We investigate the presence of vortices in generalized Maxwell-Higgs models
with a hidden sector. The model engenders symmetry, in a
manner that the sectors are coupled via the visible magnetic permeability
depending only on the hidden scalar field. We develop a first order framework
in which the hidden sector decouples from the visible one. We illustrate the
results with two specific examples, that give rise to the presence of vortices
with internal structure.Comment: 9 two-column pages, 4 figures; version to appear in AHE
New Global Defect Structures
We investigate the presence of defects in systems described by real scalar
field in (D,1) spacetime dimensions. We show that when the potential assumes
specific form, there are models which support stable global defects for D
arbitrary. We also show how to find first-order differential equations that
solve the equations of motion, and how to solve models in D dimensions via
soluble problems in D=1. We illustrate the procedure examining specific models
and finding explicit solutions.Comment: RevTex4, 4 pages, 3 eps figures; to be published in Phys. Rev. Let
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