2,298 research outputs found
Perturbative quantum gauge fields on the noncommutative torus
Using standard field theoretical techniques, we survey pure Yang-Mills theory
on the noncommutative torus, including Feynman rules and BRS symmetry. Although
in general free of any infrared singularity, the theory is ultraviolet
divergent. Because of an invariant regularization scheme, this theory turns out
to be renormalizable and the detailed computation of the one loop counterterms
is given, leading to an asymptoticaly free theory. Besides, it turns out that
non planar diagrams are overall convergent when is irrational.Comment: Latex 2e, 19 pages 5 eps figures, typos corrected and 1 reference
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Exact solitons on noncommutative tori
We construct exact solitons on noncommutative tori for the type of actions
arising from open string field theory. Given any projector that describes an
extremum of the tachyon potential, we interpret the remaining gauge degrees of
freedom as a gauge theory on the projective module determined by the tachyon.
Whenever this module admits a constant curvature connection, it solves exactly
the equations of motion of the effective string field theory. We describe in
detail such a construction on the noncommutative tori. Whereas our exact
solution relies on the coupling to a gauge theory, we comment on the
construction of approximate solutions in the absence of gauge fields.Comment: 22 pages, JHEP style, typos corrected and references improve
Parametric Representation of Rank d Tensorial Group Field Theory: Abelian Models with Kinetic Term
We consider the parametric representation of the amplitudes of Abelian models
in the so-called framework of rank Tensorial Group Field Theory. These
models are called Abelian because their fields live on . We concentrate
on the case when these models are endowed with particular kinetic terms
involving a linear power in momenta. New dimensional regularization and
renormalization schemes are introduced for particular models in this class: a
rank 3 tensor model, an infinite tower of matrix models over
, and a matrix model over . For all divergent amplitudes, we
identify a domain of meromorphicity in a strip determined by the real part of
the group dimension . From this point, the ordinary subtraction program is
applied and leads to convergent and analytic renormalized integrals.
Furthermore, we identify and study in depth the Symanzik polynomials provided
by the parametric amplitudes of generic rank Abelian models. We find that
these polynomials do not satisfy the ordinary Tutte's rules
(contraction/deletion). By scrutinizing the "face"-structure of these
polynomials, we find a generalized polynomial which turns out to be stable only
under contraction.Comment: 69 pages, 35 figure
The form factors existing in the b->s g^* decay and the possible CP violating effects in the noncommutative standard model
We study the form factors appearing in the inclusive decay b -> s g^*, in the
framework of the noncommutative standard model. Here g^* denotes the virtual
gluon. We get additional structures and the corresponding form factors in the
noncommutative geometry. We analyse the dependencies of the form factors to the
parameter p\Theta k where p (k) are the four momenta of incoming (outgoing) b
quark (virtual gluon g^*, \Theta is a parameter which measures the
noncommutativity of the geometry. We see that the form factors are weaklyComment: 8 pages, 7 figure
Revitalization of selected brownfields in urban space of Skierniewice with particular emphasis on environmentally friendly elements.
Transformation of urban space is a result of constant changes, which can also lead to a deterioration of the state of such space. City revitalization programs allow for the release of brownfields from crisis situations and adapting them to the needs of local communities, with particular emphasis on environmentally friendly elements. The aim of the article was to present the concept of revitalization activities, proposed for introduction in the brownfield site, in the city of Skierniewice, currently used by Stal-Car. These activities include treatments that can result in the creation of urban public spaces with environmentally friendly elements.Przekształcenie przestrzeni miejskiej to efekt ciągłych przemian, które mogą prowadzić również do pogorszenia jej stanu. Programy rewitalizacji miast pozwalają na wyprowadzenie ze stanu kryzysowego m.in. terenów poprzemysłowych i dostosowanie ich do wymogów lokalnych społeczności, ze szczególnym uwzględnieniem elementów przyjaznych środowisku. W artykule za cel przyjęto stworzenie koncepcji działań rewitalizacyjnych proponowanych do wprowadzenia na terenie poprzemysłowym w Skierniewicach, obecnie użytkowanym przez firmę Stal-Car. Działania te obejmują zabiegi, których następstwem może być powstanie miejskiej przestrzeni publicznej z elementami przyjaznymi środowisku
Driver Drowsiness Immediately before Crashes – A Comparative Investigation of EEG Pattern Recognition
Periodogram and other spectral power estimation methods are established in quantitative EEG analysis. Their outcome in case of drowsy subjects fulfilling a sustained attention task is difficult to interpret. Two novel kind of EEG analysis based on pattern recognition were proposed recently, namely the microsleep (MS) and the alpha burst (AB) pattern recognition. We compare both methods by applying them to the same experimental data and relating their output variables to two independent variables of driver drowsiness. The latter was an objective lane tracking performance variable and the first was a subjective variable of self-experienced sleepiness. Results offer remarkable differences between both EEG analysis methodologies. The expected increase with time since sleep as well as with time on task, which also exhibited in both independent variables, was not identified after applying AB recognition. The EEG immediately before fatigue related crashes contained both patterns. MS patterns were remarkably more frequent before crashes; almost every crash (98.5 %) was preceded by MS patterns, whereas less than 64 % of all crashes had AB patterns within a 10 sec pre-crash interval
Loewner integer-order approximation of MIMO fractional-order systems
A state–space integer–order approximation of commensurate–order systems is obtained using a data–driven interpolation approach based on Loewner matrices. Precisely, given the values of the original fractional–order transfer function at a number of generalised frequencies, a descriptor–form state–space model matching these frequency response values is constructed from a suitable Loewner matrix pencil, as already suggested for the reduction of high–dimensional integer–order systems. Even if the stability of the resulting integer–order system cannot be guaranteed, such an approach is particularly suitable for approximating (infinite–dimensional) fractional–order systems because: (i) the order of the approximation is bounded by half the number of interpolation points, (ii) the procedure is more robust and simple than alternative approximation methods, and (iii) the procedure is fairly flexible and often leads to satisfactory results, as shown by some examples discussed at the end of the article. Clearly, the approximation depends on the location, spacing and number of the generalised interpolation frequencies but there is no particular reason to choose the interpolation frequencies on the imaginary axis, which is a natural choice in integer–order model reduction, since this axis does not correspond to the stability boundary of the original fractional–order system
Quantum creep and quantum creep transitions in 1D sine-Gordan chains
Discrete sine-Gordon (SG) chains are studied with path-integral molecular
dynamics. Chains commensurate with the substrate show the transition from
collective quantum creep to pinning at bead masses slightly larger than those
predicted from the continuous SG model. Within the creep regime, a field-driven
transition from creep to complete depinning is identified. The effects of
disorder in the external potential on the chain's dynamics depend on the
potential's roughness exponent , i.e., quantum and classical fluctuations
affect the current self-correlation functions differently for .Comment: 4 pages, 3 figure
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