5,149 research outputs found
The collision of two-kinks defects
We have investigated the head-on collision of a two-kink and a two-antikink
pair that arises as a generalization of the model. We have evolved
numerically the Klein-Gordon equation with a new spectral algorithm whose
accuracy and convergence were attested by the numerical tests. As a general
result, the two-kink pair is annihilated radiating away most of the scalar
field. It is possible the production of oscillons-like configurations after the
collision that bounce and coalesce to form a small amplitude oscillon at the
origin. The new feature is the formation of a sequence of quasi-stationary
structures that we have identified as lump-like solutions of non-topological
nature. The amount of time these structures survives depends on the fine-tuning
of the impact velocity.Comment: 14 pages, 9 figure
Dual descriptions of spin two massive particles in via master actions
In the first part of this work we show the decoupling (up to contact terms)
of redundant degrees of freedom which appear in the covariant description of
spin two massive particles in . We make use of a master action which
interpolates, without solving any constraints, between a first, second and
third order (in derivatives) self-dual model. An explicit dual map between
those models is derived. In our approach the absence of ghosts in the third
order self-dual model, which corresponds to a quadratic truncation of
topologically massive gravity, is due to the triviality (no particle content)
of the Einstein-Hilbert action in . In the second part of the work, also
in , we prove the quantum equivalence of the gauge invariant sector of a
couple of self-dual models of opposite helicities (+2 and -2) and masses
and to a generalized self-dual model which contains a quadratic
Einstein-Hilbert action, a Chern-Simons term of first order and a Fierz-Pauli
mass term. The use of a first order Chern-Simons term instead of a third order
one avoids conflicts with the sign of the Einstein-Hilbert action.Comment: title and abstract slightly modified, 3 references added, comments on
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News out of the old: the evolving technological incoherence of the world's largest companies
Large established companies from a variety of industrial sectors typically show a highly diversified
knowledge base. A number of authors have found that this phenomenon can be measured using
several technological indicators such as educational data on engineering backgrounds and patent
applications (Granstrand and Sjölander, 1990; Patel and Pavitt 1994). The interesting feature of this
trend is that companies invest to acquire competence in areas that are unrelated to their production
specialisation in the market. However, this paradoxical empirical pattern is more easily observed
than explained. Recently, some explanations have been put forward, one of which is that large
innovative firms need to internalise many different branches of engineering knowledge in order to
cope with uneven rates of development in the components they rely on (Brusoni et al. 2001).
This work draws on the insights of the multi-technology corporation literature (e.g. Granstrand et al.
1997) and attempts to complement previous findings with a focus on the dynamic features of
technological diversification. The chapter has two main goals: to draw a map of the rate and direction
of technological diversification and, on this basis, to nourish a tentative discussion of the forces
behind the evolving profile of multi-technology firms. In order to do this we use patent counts and
classifications based on the SPRU database for nearly 500 of the world’s largest innovating
companies from 1980 to 1996, as ranked by sales revenues.
Large companies exhibit significant command of technologies unrelated to the actual making of their
principal product lines, i.e., they reveal a degree of technological diversity or ‘incoherence’ as it is
labelled throughout this chapter. Having underlined this contemporary stylised fact, we shall be
concerned with the existence of broad changes in the rate and direction of technological
diversification across and within industries. We find evidence of an emergent reorganization in
corporate technological portfolios. Although the extent to which companies patent outside their core
technical fields has remained stable, or even decreased slightly, the composition of the in-house
technological mix appears to have changed considerably over a period of less than two decades.
The technologies attracting the diversification movement in corporate capabilities, as revealed by
patents, have increasingly become information & communication technologies (ICT), new materials
and drugs & bioengineering. This is not entirely surprising since these technologies are commonly
regarded as ‘generic technologies’ or ‘general purpose-technologies’. However, this tendency
coincides with a remarkable regularity: for these three technology groups, the growth in patents was
consistently higher for non-specialist sectors than for specialist sectors.
Taken together, these findings can be interpreted as evidence that ‘new economy’ technology fields
have gained weight against ‘older’ technologies, like the chemicals and mechanical fields, within the
large established companies of the ‘old economy’. The observed patent regularities raise other
issues. In particular, they could provide a useful perspective to an ongoing debate on whether the
rise of new technologies has been associated with the substitution of or, on the contrary, complementarity with, older technologies. While there is considerable inter-industry diversity, the
pattern of growth in ICT, materials and drugs & bioengineering patent groups seems to suggest that
there is room for both stories.
What is the meaning of this set of changes? On a macroscopic perspective we suggest these
developments can be understood as an expression of an ongoing technological revolution in the neo-
Schumpeterian sense of Freeman and Louçã (2001). As this paper has a more detailed perspective,
we concentrate on the discussion of the strategic rationale behind the dynamics of diversification in
the corporate knowledge base. At this stage we offer two intertwined hypotheses that fit with the
observations.
The chapter begins by addressing the empirical and conceptual contributions of the literature on
technological diversification. Section 3 describes the data set and considers the methodological
conditions necessary for a prudent use of patents as indicators of technological capabilities. Section
4 then reports on the analysis of our sample, which constitutes the core of the chapter. Section 5
critically assesses the empirical results, discusses implications for technology management and
suggests some unsettled questions for innovation studies. The last section, Section 6, forms the
conclusion
Futures research at DaimlerChrysler: socio-technology at the core of the corporate knowledge system
In today’s globalising and turbulent economy the way to achieve long-term leading position
has become an increasingly tough dynamic process. Because a company’s market position is
not safe for long if it systematically fails to keep up with the pace of change, sustaining
competitive advantage is a continuous and restless task at the heart of which technological
and organisational innovations prove fundamental. As in any other large business
organisation, strategic planning at DaimlerChrysler (DC) is an activity of vital importance.
The creation and renovation of a company’s competencies, i.e., its ability to master
knowledge about production and distribution and its understanding of demand and users’
needs, has become itself institutionalised as a business of a particular trade. Most of the
world’s leading corporations have a Research & Development (R&D) department where
new science-based ideas and designs are tested and applied to the resolution of specific
technological problems. Only more recently some large companies are carrying the internal
division of labour a step further by establishing a new department or division exclusively
devoted to socio-economic and strategic research. These units have the job of assessing the
possible future directions of the organization in contrast with where the accumulation of
competencies is leading.
In this contribution we supply a description of the ways in which Society and Technology
Research Group (STRG), the research and consulting institution within the DaimlerChrysler
business group, helps strategic policy-making through the scenario methodology. We also
aim at producing more general comments about the implications of the scenario-building
process for managerial competence. Specifically, we elaborate on the analogy between R&D
and futures research and argue that complex methodologies of interactive learning such as
scenarios can be regarded as socio-technology. We also point out the significant role social
sciences can be play in the process of generating useful knowledge for corporate
management.
The empirical base of this research is mainly composed by documentation provided by
STRG and by an interview carried out with Frank Ruff, one of its senior managers. This
evidence is compounded by reference to complementary data, namely from the case of Royal
Dutch/Shell and its group-planning unit
Static potential in scalar QED with non-minimal coupling
Here we compute the static potential in scalar at leading order in
. We show that the addition of a non-minimal coupling of Pauli-type
(\eps j^{\mu}\partial^{\nu}A^{\alpha}), although it breaks parity, it does
not change the analytic structure of the photon propagator and consequently the
static potential remains logarithmic (confining) at large distances. The
non-minimal coupling modifies the potential, however, at small charge
separations giving rise to a repulsive force of short range between opposite
sign charges, which is relevant for the existence of bound states. This effect
is in agreement with a previous calculation based on Mller
scattering, but differently from such calculation we show here that the
repulsion appears independently of the presence of a tree level Chern-Simons
term which rather affects the large distance behavior of the potential turning
it into constant.Comment: 13 pages, 3 figure
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