31,309 research outputs found
Integrable theories and loop spaces: fundamentals, applications and new developments
We review our proposal to generalize the standard two-dimensional flatness
construction of Lax-Zakharov-Shabat to relativistic field theories in d+1
dimensions. The fundamentals from the theory of connections on loop spaces are
presented and clarified. These ideas are exposed using mathematical tools
familiar to physicists. We exhibit recent and new results that relate the
locality of the loop space curvature to the diffeomorphism invariance of the
loop space holonomy. These result are used to show that the holonomy is abelian
if the holonomy is diffeomorphism invariant.
These results justify in part and set the limitations of the local
implementations of the approach which has been worked out in the last decade.
We highlight very interesting applications like the construction and the
solution of an integrable four dimensional field theory with Hopf solitons, and
new integrability conditions which generalize BPS equations to systems such as
Skyrme theories. Applications of these ideas leading to new constructions are
implemented in theories that admit volume preserving diffeomorphisms of the
target space as symmetries. Applications to physically relevant systems like
Yang Mills theories are summarized. We also discuss other possibilities that
have not yet been explored.Comment: 64 pages, 8 figure
Automated transport and society. Identifying drawbacks, exploring possibilities
Automated Vehicles (AV) are those which are able to steer, break, accelerate, maintain speed, and perform a number of other operations without direct human interference. In the future, their level of automation is expected to move from simple driving to full automation. Recent research on AV tends to focus on how to make them a commercially viable technological reality and on their advantages. In this research, the merits of AV are presented in a very optimistic way while the drawbacks are either supressed or framed as âimplementation barriersâ. Furthermore the existing body of research look at AVs from a strictly legal and engineering perspective, therefore not taking into consideration the full range of potential outcomes of AV using a transdisciplinary approach.
The additional contribution of this paper would be to enrich the existing body of research providing appropriate attention to the societal impacts of AVs adoption, using a holistic and transdisciplinary approach, and focusing in particular on the AVs impacts on the equity of distribution of benefits and costs to the different social groups.
In more details this paper aims at providing (1) a contribution to fill this problematic research gap, through a critical multi-disciplinary analysis of the societal impacts of implementing AVs; (2) possible solutions to help solving these problems, when solutions can be envisioned.
A mixed methodology approach is used. First, a web-based survey has been conducted among different stakeholders and second, a number of semi-structured expert interviews has been directed with leading figures from different areas of expertise
Dilatonic, Current-Carrying Cosmic String
We study the implications of a scalar-tensorial gravity for the metric of an
isolated self-gravitating superconducting cosmic string. These modifications
are induced by an arbitrary coupling of a massless scalar field to the usual
tensorial field in the gravitational Lagrangian. We derive the metric in the
weak-field approximation and we analyse the behaviour of light in this
spacetime. We end with some discussions.Comment: 12 pp, Latex, no figures, based on a talk given by M. E. X. Guimaraes
at the COSMO 99, 27/9 to 02/10/99, ICTP, Trieste, I
Mean-field analysis of the majority-vote model broken-ergodicity steady state
We study analytically a variant of the one-dimensional majority-vote model in
which the individual retains its opinion in case there is a tie among the
neighbors' opinions. The individuals are fixed in the sites of a ring of size
and can interact with their nearest neighbors only. The interesting feature
of this model is that it exhibits an infinity of spatially heterogeneous
absorbing configurations for whose statistical properties we
probe analytically using a mean-field framework based on the decomposition of
the -site joint probability distribution into the -contiguous-site joint
distributions, the so-called -site approximation. To describe the
broken-ergodicity steady state of the model we solve analytically the
mean-field dynamic equations for arbitrary time in the cases n=3 and 4. The
asymptotic limit reveals the mapping between the statistical
properties of the random initial configurations and those of the final
absorbing configurations. For the pair approximation () we derive that
mapping using a trick that avoids solving the full dynamics. Most remarkably,
we find that the predictions of the 4-site approximation reduce to those of the
3-site in the case of expectations involving three contiguous sites. In
addition, those expectations fit the Monte Carlo data perfectly and so we
conjecture that they are in fact the exact expectations for the one-dimensional
majority-vote model
Eikonal profile functions and amplitudes for and scattering
The eikonal profile function obtained from the Model of the Stochastic
Vacuum is parametrized in a form suitable for comparison with experiment. The
amplitude and the extended profile function (including imaginary and real
parts) are determined directly from the complete pp and p elastic
scattering data at high energies. Full and accurate representation of the data
is presented, with smooth energy dependence of all parameters. The changes
needed in the original profile function required for description of scattering
beyond the forward direction are described.Comment: Latex, 28 pages and 16 figure
Exchange coupling between magnetic layers across non-magnetic superlattices
The oscillation periods of the interlayer exchange coupling are investigated
when two magnetic layers are separated by a metallic superlattice of two
distinct non-magnetic materials. In spite of the conventional behaviour of the
coupling as a function of the spacer thickness, new periods arise when the
coupling is looked upon as a function of the number of cells of the
superlattice. The new periodicity results from the deformation of the
corresponding Fermi surface, which is explicitly related to a few controllable
parameters, allowing the oscillation periods to be tuned.Comment: 13 pages; 5 figures; To appear in J. Phys.: Cond. Matte
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