798 research outputs found
Double Higgs Production at the Linear Colliders and the Probing of the Higgs Self-Coupling
We study double Higgs production in the and modes
of the linear collider. It is also shown how one can probe the scalar potential
in these reactions. We discuss the effective longitudinal approximation in
processes and the luminosities in the two modes of a
high-energy linear collider. A generalised non-linear gauge-fixing condition,
which is particularly useful for tree-level calculations of electroweak
processes for the laser induced collider, is presented. Its connection with the
background-field approach to gauge fixing is given.Comment: 60 pages, LateX, uses epsf, needs FEYNMAN.tex, 26 figs. (eqs. 4.1 and
4.10 changed), full paper (including figs) is also available via www at
http://lapphp0.in2p3.fr/preplapp/psth/doublehiggs.ps.gz or via anonymous ftp
at ftp://lapphp0.in2p3.fr/pub/preprints-theorie/doublehiggsf.u
Motion of a scalar field coupled to a Yang Mills field reformulated locally with some gauge invariant variables
We show how to reformulate gauge theories coupled to scalar fields in terms of explicitly gauge-invariant variables. We show in the case of scalar QED that the classical theory can be reformulated in this way. We discuss the form of some realistic asymptotic solutions of these equations. The equations of motion are then also reformulated in the non-abelian case
New Physics with three-photon events at LEP
The effect of the most general \z3gt vertex in the reaction e^+e^- \ra
3\gamma is studied with a particular attention to LEP searches. We give exact
analytical expressions including realistic cuts for the signal and present a
detailed analysis based on a Monte Carlo that includes the effect of the
irreducible QED cross section. As special applications we discuss the
effect of heavy scalars, fermions and gauge bosons and comment on the
``monopole" connection.Comment: No changes made from previous version, 34 pages, LateX, uses epsf, 11
.eps figs., full paper (including figs) is also available via WWW at
http://lapphp0.in2p3.fr/preplapp/psth/lastee3g.ps.gz or via anonymous ftp at
ftp:///lapphp0.in2p3.fr/pub/preprints-theorie/ftpee3g.u
Reclaiming human machine nature
Extending and modifying his domain of life by artifact production is one of
the main characteristics of humankind. From the first hominid, who used a wood
stick or a stone for extending his upper limbs and augmenting his gesture
strength, to current systems engineers who used technologies for augmenting
human cognition, perception and action, extending human body capabilities
remains a big issue. From more than fifty years cybernetics, computer and
cognitive sciences have imposed only one reductionist model of human machine
systems: cognitive systems. Inspired by philosophy, behaviorist psychology and
the information treatment metaphor, the cognitive system paradigm requires a
function view and a functional analysis in human systems design process.
According that design approach, human have been reduced to his metaphysical and
functional properties in a new dualism. Human body requirements have been left
to physical ergonomics or "physiology". With multidisciplinary convergence, the
issues of "human-machine" systems and "human artifacts" evolve. The loss of
biological and social boundaries between human organisms and interactive and
informational physical artifact questions the current engineering methods and
ergonomic design of cognitive systems. New developpment of human machine
systems for intensive care, human space activities or bio-engineering sytems
requires grounding human systems design on a renewed epistemological framework
for future human systems model and evidence based "bio-engineering". In that
context, reclaiming human factors, augmented human and human machine nature is
a necessityComment: Published in HCI International 2014, Heraklion : Greece (2014
SMC^2: an efficient algorithm for sequential analysis of state-space models
We consider the generic problem of performing sequential Bayesian inference
in a state-space model with observation process y, state process x and fixed
parameter theta. An idealized approach would be to apply the iterated batch
importance sampling (IBIS) algorithm of Chopin (2002). This is a sequential
Monte Carlo algorithm in the theta-dimension, that samples values of theta,
reweights iteratively these values using the likelihood increments
p(y_t|y_1:t-1, theta), and rejuvenates the theta-particles through a resampling
step and a MCMC update step. In state-space models these likelihood increments
are intractable in most cases, but they may be unbiasedly estimated by a
particle filter in the x-dimension, for any fixed theta. This motivates the
SMC^2 algorithm proposed in this article: a sequential Monte Carlo algorithm,
defined in the theta-dimension, which propagates and resamples many particle
filters in the x-dimension. The filters in the x-dimension are an example of
the random weight particle filter as in Fearnhead et al. (2010). On the other
hand, the particle Markov chain Monte Carlo (PMCMC) framework developed in
Andrieu et al. (2010) allows us to design appropriate MCMC rejuvenation steps.
Thus, the theta-particles target the correct posterior distribution at each
iteration t, despite the intractability of the likelihood increments. We
explore the applicability of our algorithm in both sequential and
non-sequential applications and consider various degrees of freedom, as for
example increasing dynamically the number of x-particles. We contrast our
approach to various competing methods, both conceptually and empirically
through a detailed simulation study, included here and in a supplement, and
based on particularly challenging examples.Comment: 27 pages, 4 figures; supplementary material available on the second
author's web pag
Sequential quasi-Monte Carlo: Introduction for Non-Experts, Dimension Reduction, Application to Partly Observed Diffusion Processes
SMC (Sequential Monte Carlo) is a class of Monte Carlo algorithms for
filtering and related sequential problems. Gerber and Chopin (2015) introduced
SQMC (Sequential quasi-Monte Carlo), a QMC version of SMC. This paper has two
objectives: (a) to introduce Sequential Monte Carlo to the QMC community, whose
members are usually less familiar with state-space models and particle
filtering; (b) to extend SQMC to the filtering of continuous-time state-space
models, where the latent process is a diffusion. A recurring point in the paper
will be the notion of dimension reduction, that is how to implement SQMC in
such a way that it provides good performance despite the high dimension of the
problem.Comment: To be published in the proceedings of MCMQMC 201
Brst Cohomology and Invariants of 4D Gravity in Ashtekar Variables
We discuss the BRST cohomologies of the invariants associated with the
description of classical and quantum gravity in four dimensions, using the
Ashtekar variables. These invariants are constructed from several BRST
cohomology sequences. They provide a systematic and clear characterization of
non-local observables in general relativity with unbroken diffeomorphism
invariance, and could yield further differential invariants for four-manifolds.
The theory includes fluctuations of the vierbein fields, but there exits a
non-trivial phase which can be expressed in terms of Witten's topological
quantum field theory. In this phase, the descent sequences are degenerate, and
the corresponding classical solutions can be identified with the conformally
self-dual sector of Einstein manifolds. The full theory includes fluctuations
which bring the system out of this sector while preserving diffeomorphism
invariance.Comment: 15 page
Crustal influx, indentation, ductile thinning and gravity redistribution in a continental wedge: Building a Moldanubian mantled gneiss dome with underthrust Saxothuringian material (European Variscan belt)
27 p.International audience[1] The contribution of lateral forces, vertical load, gravity redistribution and erosion to the origin of mantled gneiss domes in internal zones of orogens remains debated. In the Orlica-Snieznik dome (Moldanubian zone, European Variscan belt), the polyphase tectono-metamorphic history is initially characterized by the development of subhorizontal fabrics associated with medium- to high-grade metamorphic conditions in different levels of the crust. It reflects the eastward influx of a Saxothuringian-type passive margin sequence below a Teplá-Barrandian upper plate. The ongoing influx of continental crust creates a thick felsic orogenic root with HP rocks and migmatitic orthogneiss. The orogenic wedge is subsequently indented by the eastern Brunia microcontinent producing a multiscale folding of the orogenic infrastructure. The resulting kilometre-scale folding is associated with the variable burial of the middle crust in synforms and the exhumation of the lower crust in antiforms. These localized vertical exchanges of material and heat are coeval with a larger crustal-scale folding of the whole infrastructure generating a general uplift of the dome. It is exemplified by increasing metamorphic conditions and younging of 40Ar/39Ar cooling ages toward the extruded migmatitic subdomes cored by HP rocks. The vertical growth of the dome induces exhumation by pure shear-dominated ductile thinning laterally evolving to non-coaxial detachment faulting, while erosion feeds the surrounding sedimentary basins. Modeling of the Bouguer anomaly grid is compatible with crustal-scale mass transfers between a dense superstructure and a lighter infrastructure. The model implies that the Moldanubian Orlica-Snieznik mantled gneiss dome derives from polyphase recycling of Saxothuringian material
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