8,822 research outputs found
Dressed coordinates: the path-integrals approach
The recent introduced \textit{dressed coordinates} are studied in the
path-integral approach. These coordinates are defined in the context of a
harmonic oscillator linearly coupled to massless scalar field and, it is shown
that in this model the dressed coordinates appear as a coordinate
transformation preserving the path-integral functional measure. The analysis
also generalizes the \textit{sum rules} established in a previous work.Comment: 9 pages, Latex2
On tree decomposability of Henneberg graphs
In this work we describe an algorithm that generates well constrained geometric constraint graphs which are solvable by the tree-decomposition constructive technique. The algorithm is based on Henneberg constructions and would be of help in transforming underconstrained problems into well constrained problems as well as in exploring alternative constructions over a given set of geometric elements.Postprint (published version
A supersymmetric exotic field theory in (1+1) dimensions. One loop soliton quantum mass corrections
We consider one loop quantum corrections to soliton mass for the
supersymmetric extension of the (1+1)-dimensional scalar field theory with the
potential . First, we compute
the one loop quantum soliton mass correction of the bosonic sector. To do that,
we regularize implicitly such quantity by subtracting and adding its
corresponding tadpole graph contribution, and use the renormalization
prescription that the added term vanishes with the corresponding counterterms.
As a result we get a finite unambiguous formula for the soliton quantum mass
corrections up to one loop order. Afterwards, the computation for the
supersymmetric case is extended straightforwardly and we obtain for the one
loop quantum correction of the SUSY kink mass the expected value previously
derived for the SUSY sine-Gordon and models. However, we also have
found that for a particular value of the parameters, contrary to what was
expected, the introduction of supersymmetry in this model worsens ultraviolet
divergences rather than improving them.Comment: 16 pages, 8 figures; Major modifications included to match version
published in JHE
A Henneberg-based algorithm for generating tree-decomposable minimally rigid graphs
In this work we describe an algorithm to generate tree-decomposable minimally rigid graphs on a given set of vertices V . The main idea is based on the well-known fact that all minimally rigid graphs, also known as Laman graphs, can be generated via Henneberg sequences. Given that not each minimally rigid graph is tree-decomposable, we identify a set of conditions on the way Henneberg steps are applied so that the resulting graph is tree-decomposable. We show that the worst case running time of the algorithm is O(|V|3).Postprint (author's final draft
Slip avalanches in a fiber bundle model
We study slip avalanches in disordered materials under an increasing external
load in the framework of a fiber bundle model. Over-stressed fibers of the
model do not break, instead they relax in a stick-slip event which may trigger
an entire slip avalanche. Slip avalanches are characterized by the number
slipping fibers, by the slip length, and by the load increment, which triggers
the avalanche. Our calculations revealed that all three quantities are
characterized by power law distributions with universal exponents. We show by
analytical calculations and computer simulations that varying the amount of
disorder of slip thresholds and the number of allowed slips of fibers, the
system exhibits a disorder induced phase transition from a phase where only
small avalanches are formed to another one where a macroscopic slip appears.Comment: 6 pages, 6 figure
Implications for New Physics from Fine-Tuning Arguments: II. Little Higgs Models
We examine the fine-tuning associated to electroweak breaking in Little Higgs
scenarios and find it to be always substantial and, generically, much higher
than suggested by the rough estimates usually made. This is due to implicit
tunings between parameters that can be overlooked at first glance but show up
in a more systematic analysis. Focusing on four popular and representative
Little Higgs scenarios, we find that the fine-tuning is essentially comparable
to that of the Little Hierarchy problem of the Standard Model (which these
scenarios attempt to solve) and higher than in supersymmetric models. This does
not demonstrate that all Little Higgs models are fine-tuned, but stresses the
need of a careful analysis of this issue in model-building before claiming that
a particular model is not fine-tuned. In this respect we identify the main
sources of potential fine-tuning that should be watched out for, in order to
construct a successful Little Higgs model, which seems to be a non-trivial
goal.Comment: 39 pages, 26 ps figures, JHEP forma
Landslide Risk: Economic Valuation in the North-Eastern Zone of Medellin City
Natural disasters of a geodynamic nature can cause enormous economic and human losses. The economic costs of a landslide disaster include relocation of communities and physical repair of urban infrastructure. However, when performing a quantitative risk analysis, generally, the indirect economic consequences of such an event are not taken into account. A probabilistic approach methodology that considers several scenarios of hazard and vulnerability to measure the magnitude of the landslide and to quantify the economic costs is proposed. With this approach, it is possible to carry out a quantitative evaluation of the risk by landslides, allowing the calculation of the economic losses before a potential disaster in an objective, standardized and reproducible way, taking into account the uncertainty of the building costs in the study zone. The possibility of comparing different scenarios facilitates the urban planning process, the optimization of interventions to reduce risk to acceptable levels and an assessment of economic losses according to the magnitude of the damage. For the development and explanation of the proposed methodology, a simple case study is presented, located in north-eastern zone of the city of MedellĂn. This area has particular geomorphological characteristics, and it is also characterized by the presence of several buildings in bad structural conditions. The proposed methodology permits to obtain an estimative of the probable economic losses by earthquake-induced landslides, taking into account the uncertainty of the building costs in the study zone. The obtained estimative shows that the structural intervention of the buildings produces a reduction the order of 21 % in the total landslide risk. © Published under licence by IOP Publishing Ltd
Sum rules in the oscillator radiation processes
We consider the problem of an harmonic oscillator coupled to a scalar field
in the framework of recently introduced dressed coordinates. We compute all the
probabilities associated with the decay process of an excited level of the
oscillator. Instead of doing direct quantum mechanical calculations we
establish some sum rules from which we infer the probabilities associated to
the different decay processes of the oscillator. Thus, the sum rules allows to
show that the transition probabilities between excited levels follow a binomial
distribution.Comment: comments and references added, LaTe
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