13,099 research outputs found
Higher covariant derivative regulators and non-multiplicative renormalization
The renormalization algorithm based on regularization methods with two
regulators is analyzed by means of explicit computations. We show in particular
that regularization by higher covariant derivative terms can be complemented
with dimensional regularization to obtain a consistent renormalized
4-dimensional Yang-Mills theory at the one-loop level. This shows that hybrid
regularization methods can be applied not only to finite theories, like \eg\
Chern-Simons, but also to divergent theories.Comment: 12 pages, phyzzx, no figure
Higher covariant derivative Pauli-Villars regularization does not lead to a consistent QCD
We compute the beta function at one loop for Yang-Mills theory using as
regulator the combination of higher covariant derivatives and Pauli-Villars
determinants proposed by Faddeev and Slavnov. This regularization prescription
has the appealing feature that it is manifestly gauge invariant and essentially
four-dimensional. It happens however that the one-loop coefficient in the beta
function that it yields is not as it should be, but The
difference is due to unphysical logarithmic radiative corrections generated by
the Pauli-Villars determinants on which the regularization method is based.
This no-go result discards the prescription as a viable gauge invariant
regularization, thus solving a long-standing open question in the literature.
We also observe that the prescription can be modified so as to not generate
unphysical logarithmic corrections, but at the expense of losing manifest gauge
invariance.Comment: 43 pages, Latex file (uses the macro axodraw.sty, instructions of how
to get it and use it included), FTUAM 94/9, NIKHEF-H 94/2
Regularization and Renormalization of Chern-Simons Theory
We analyze some features of the perturbative quantization of Chern-Simons
theory (CST) in the Landau gauge. In this gauge the theory is known to be
perturbatively finite. We consider the renormalization scheme in which the
renormalized parameter equals the bare or classical one and show that it
constitutes a natural parametrization for the quantum theory. The reason is
that, although in this renormalization scheme the value of the Green functions
depends on the regularization used, comparison among different regularization
methods shows that the observables (Wilson loops) are the same function of the
shifted monodromy parameter for all BRS invariant regulators used so
far for CST. We also discuss a particular BRS invariant regularization
prescription in which CST is perturbatively defined as the large mass limit of
dimensionally regularized topologically massive Yang-Mills theory. With this
regularization prescription the radiative corrections induced by two-loop
contributions do not entail observable consequences since they can be
reabsorbed by a finite rescaling of the fields only. This very mechanism is
conjectured to take place at higher perturbative orders. Talk presented by G.G.
at the NATO AWR on ``Low dimensional Topology and Quantum Field Theory'', 6-13
September 1992, Cambridge (UK).Comment: 10 pages, Phyzzx, LPTHE 92-4
Measuring farmers' attitude towards breeding tools: the Livestock Breeding Attitude Scale
Under-use of genetic improvement tools and low participation in breeding programmes are key drivers of breeding programmes under-performance. Both aspects are heavily influenced by farmers attitudes which, to date, have not been analysed in an objective and systematic manner. A key factor constraining the implementation of attitudinal studies towards livestock breeding tools is the lack of a reference scale for measuring attitudes. In this research, we provide the livestock breeding sector with such a reference measure. We developed the scale following the standardized psychometric methodologies and statistical tools. Then, as a case study, we used the scale to explore the attitudes of beef and dairy sheep farmers in Australia, New Zealand and Spain and analysed farmer and farming system factors related to those attitudes. Fourteen sheep and beef breed associations facilitated the implementation of a survey of 547 farmers, generating data that was used for the scale evaluation. The relationship between attitudinal factors and farmer and farming system factors was analysed using generalized linear models across and within breeds. The results suggest that the 8-item definitive scale we have developed is appropriate to measure farmer attitudes. We found that attitudes towards genetic improvement tools have two components; i) traditional selection and ii) genetic and genomic selection combined. This means that positive attitudes towards traditional phenotypic selection do not necessarily imply a negative attitude towards genetic and genomic selection tools. Farmer attitudes varied greatly not only across the studied breeds, species and countries, but also within them. High-educated farmers of business-oriented farms tend to have the most negative attitude towards traditional selection. However, attitudes towards genetic and genomic selection tools could not be linked to these factors. Finally, we found that the breed raised had a large effect on farmer attitude. These findings may help in the evolution of breeding programmes by identifying both the farmers most inclined to uptake breeding innovations in the early stages of its establishment and the farmers who would be more reluctant to participate in such programmes, thus informing where to focus extension efforts
Physically meaningful and not so meaningful symmetries in Chern-Simons theory
We explicitly show that the Landau gauge supersymmetry of Chern-Simons theory
does not have any physical significance. In fact, the difference between an
effective action both BRS invariant and Landau supersymmetric and an effective
action only BRS invariant is a finite field redefinition. Having established
this, we use a BRS invariant regulator that defines CS theory as the large mass
limit of topologically massive Yang-Mills theory to discuss the shift k \to
k+\cv of the bare Chern-Simons parameter in conncection with the Landau
supersymmetry. Finally, to convince ourselves that the shift above is not an
accident of our regularization method, we comment on the fact that all BRS
invariant regulators used as yet yield the same value for the shift.Comment: phyzzx, 21 pages, 2 figures in one PS fil
An Effective Temperature Scale for Late M and L Dwarfs, from Resonance Absorption Lines of CsI and RbI
We present Keck HIRES spectra of 6 late-M dwarfs and 11 L dwarfs. Our goal is
to assign effective temperatures to the objects using detailed atmospheric
models and fine analysis of the alkali resonance absorption lines of CsI and
RbI. These yield mutually consistent results (+-150 K) when we use
``cleared-dust'' models, which account for the removal of refractory species
from the molecular states but do not include dust opacities. We find a tendency
for the RbI line to imply a slightly higher temperature, which we ascribe to an
incomplete treatment of the overlying molecular opacities. The final effective
temperatures we adopt are based on the CsI fits alone, though the RbI fits
support the CsI temperature sequence. This work, in combination with results
from the infrared, hints that dust in these atmospheres has settled out of the
high atmosphere but is present in the deep photosphere. We also derive radial
and rotational velocities for all the objects, finding that the previously
discovered trend of rapid rotation for very low mass objects is quite
pervasive. To improve on our analysis, there is a clear need for better
molecular line lists and a more detailed understanding of dust formation and
dynamics.Comment: 53 pages, including 20 figures and 2 Tables; accepted in Ap
Reducción de los tiempos de observación en la evaluación del observación en la evaluación del comportamiento de conejas en producción. Análisis metodológico.
El objetivo de este trabajo fue evaluar diferentes técnicas de muestreo que redujeran el tiempo total de observación necesario para estimar el comportamiento de conejas alojadas en dos tipos de jaulas (convencionales vs. enriquecidas) y en dos estados fisiológicos distintos (gestantes vs. lactantes). Para ello, se compararon grabaciones completas de 24 h (método control de referencia) con estimaciones obtenidas a partir de grabaciones de diferente duración y frecuencia (métodos regular corto y regular largo y métodos irregulares de 6h y de 8h). A partir de los resultados obtenidos se observa que los métodos regulares se ajustaron mejor al método de referencia de 24h que los irregulares. Desde un punto de vista práctico el método regular corto sería el ideal, al reducir considerablemente el número total de horas de observación y análisi
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