6,990 research outputs found
Unitarity, ghosts and nonminimal terms in Lorentz violating QED
The unitarity of a Lorentz-invariance violating QED model with higher-order
Myers and Pospelov photons coupled to standard fermions is studied. As
expected, we find ghost states associated to the higher-order terms that may
lead to the loss of unitarity. An explicit calculation to check perturbative
unitarity in the process of electron-positron scattering is performed and it is
found to be possible to be preserved.Comment: Presented at the Sixth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 17-21, 201
Higher-order Lorentz-invariance violation, quantum gravity and fine-tuning
The issue of Lorentz fine-tuning in effective theories containing
higher-order operators is studied. To this end, we focus on the Myers-Pospelov
extension of QED with dimension-five operators in the photon sector and
standard fermions. We compute the fermion self-energy at one-loop order
considering its even and odd contributions. In the even sector we find
small radiative corrections to the usual parameters of QED which also turn to
be finite. In the odd sector the axial operator is shown to contain
unsuppressed effects of Lorentz violation leading to a possible fine-tuning. We
use dimensional regularization to deal with the divergencies and a generic
preferred four-vector. Taking the first steps in the renormalization procedure
for Lorentz violating theories we arrive to acceptable small corrections
allowing to set the bound .Comment: 11 pages, new version with the correct pole extractio
Predictive control of a solar air conditioning plant with simultaneous identification
This paper presents the application of a predictive
controller with simultaneous identification to a solar air conditioning plant. The time varying nature of the process makes
necessary an adjustment of the controller parameters to the
varying operational conditions. The main novelty with respect
to classic adaptive MPC scheme is to penalize the identification
error in the cost function used for control. The behaviour of the
controller is illustrated by simulations and experimental results.
The integration of identification and control avoids the tedious
identification procedure that is necessary before the start-up
of any predictive controller. This new adaptive MPC scheme
shows its effectiveness in controlling the outlet temperature in
the solar thermal plant.Ministerio de Ciencia y Tecnología DPI2004-07444-C04-0
Los Otros Hijos de Dios: Construcción de Identidades en Cristianos Evangélicos Gays y Lesbianas de Argentina
Los procesos de incorporación a un grupo o una serie de prácticas sociales particulares implican el desarrollo de vínculos comunitarios cimentados en sistemas donde se expresan las dimensiones de “uno” y “los otros” en niveles tanto individuales como colectivos. Estos sistemas, entendidos como referencias, vinculan dialécticamente lo subjetivo con la generalidad mediante valores, normas y representaciones sostenidas en códigos, valores, proyectos y experiencias.
El individuo en este contexto puede construir mediante diversos recursos, formas de “estar en el mundo” a partir de una “búsqueda de sentido” que permite resolver de manera funcional, los problemas de la vida cotidiana mediante la explicaciones materiales o simbólicas. Conflictos como la muerte, las desigualdades económicas o políticas así como la exclusión a distintos niveles son explicados mediante una serie de expresiones culturales que funcionan como alternativas donde puede escribirse de manera constante la historia personal
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