16,829 research outputs found
Renormalization in a Lorentz-violating model and higher-order operators
The renormalization in a Lorentz-breaking scalar-spinor higher-derivative
model involving self-interaction and the Yukawa-like coupling is
studied. We explicitly de- monstrate that the convergence is improved in
comparison with the usual scalar-spinor model, so, the theory is
super-renormalizable, with no divergences beyond four loops. We compute the
one-loop corrections to the propagators for the scalar and fermionic fields and
show that in the presence of higher-order Lorentz invariance violation, the
poles that dominate the physical theory, are driven away from the standard
on-shell pole mass due to radiatively induced lower dimensional operators. The
new operators change the standard gamma-matrix structure of the two-point
functions, introduce large Lorentz-breaking corrections and lead to
modifications in the renormalization conditions of the theory. We found the
physical pole mass in each sector of our model.Comment: 20 pages, 5 figures. New version with modifications in the
renormalized Lagrangian. To be published in EPJ
A Gaussian Weave for Kinematical Loop Quantum Gravity
Remarkable efforts in the study of the semi-classical regime of kinematical
loop quantum gravity are currently underway. In this note, we construct a
``quasi-coherent'' weave state using Gaussian factors. In a similar fashion to
some other proposals, this state is peaked in both the connection and the spin
network basis. However, the state constructed here has the novel feature that,
in the spin network basis, the main contribution for this state is given by the
fundamental representation, independently of the value of the parameter that
regulates the Gaussian width.Comment: 15 pages, 3 figures, Revtex file. Comments added and references
updated. Final version to appear in IJMP-
Is This a Joke? Detecting Humor in Spanish Tweets
While humor has been historically studied from a psychological, cognitive and
linguistic standpoint, its study from a computational perspective is an area
yet to be explored in Computational Linguistics. There exist some previous
works, but a characterization of humor that allows its automatic recognition
and generation is far from being specified. In this work we build a
crowdsourced corpus of labeled tweets, annotated according to its humor value,
letting the annotators subjectively decide which are humorous. A humor
classifier for Spanish tweets is assembled based on supervised learning,
reaching a precision of 84% and a recall of 69%.Comment: Preprint version, without referra
Digital compensation of the side-band-rejection ratio in a fully analog 2SB sub-millimeter receiver
In observational radio astronomy, sideband-separating receivers are
preferred, particularly under high atmospheric noise, which is usually the case
in the sub-millimeter range. However, obtaining a good rejection ratio between
the two sidebands is difficult since, unavoidably, imbalances in the different
analog components appear. We describe a method to correct these imbalances
without making any change in the analog part of the sideband-separating
receiver, specifically, keeping the intermediate-frequency hybrid in place.
This opens the possibility of implementing the method in any existing receiver.
We have built hardware to demonstrate the validity of the method and tested it
on a fully analog receiver operating between 600 and 720GHz. We have tested the
stability of calibration and performance vs time and after full resets of the
receiver. We have performed an error analysis to compare the digital
compensation in two configurations of analog receivers, with and without
intermediate frequency (IF) hybrid. An average compensated sideband rejection
ratio of 46dB is obtained. Degradation of the compensated sideband rejection
ratio on time and after several resets of the receiver is minimal. A receiver
with an IF hybrid is more robust to systematic errors. Moreover, we have shown
that the intrinsic random errors in calibration have the same impact for
configuration without IF hybrid and for a configuration with IF hybrid with
analog rejection ratio better than 10dB. Compensated rejection ratios above
40dB are obtained even in the presence of high analog rejection. The method is
robust allowing its use under normal operational conditions at any telescope.
We also demonstrate that a full analog receiver is more robust against
systematic errors. Finally, the error bars associated to the compensated
rejection ratio are almost independent of whether IF hybrid is present or not
Spatial dispersion in Casimir forces: A brief review
We present the basic principles of non-local optics in connection with the
calculation of the Casimir force between half-spaces and thin films.
At currently accessible distances , non-local corrections amount to about
half a percent, but they increase roughly as 1/L at smaller separations. Self
consistent models lead to corrections with the opposite sign as models with
abrupt surfaces.Comment: Proceedings of QFEXT05, Barcelona, Sept. 5-9, 200
Riccati-parameter solutions of nonlinear second-order ODEs
It has been proven by Rosu and Cornejo-Perez in 2005 that for some nonlinear
second-order ODEs it is a very simple task to find one particular solution once
the nonlinear equation is factorized with the use of two first-order
differential operators. Here, it is shown that an interesting class of
parametric solutions is easy to obtain if the proposed factorization has a
particular form, which happily turns out to be the case in many problems of
physical interest. The method that we exemplify with a few explicitly solved
cases consists in using the general solution of the Riccati equation, which
contributes with one parameter to this class of parametric solutions. For these
nonlinear cases, the Riccati parameter serves as a `growth' parameter from the
trivial null solution up to the particular solution found through the
factorization procedureComment: 5 pages, 3 figures, change of title and more tex
A one-sided Prime Ideal Principle for noncommutative rings
Completely prime right ideals are introduced as a one-sided generalization of
the concept of a prime ideal in a commutative ring. Some of their basic
properties are investigated, pointing out both similarities and differences
between these right ideals and their commutative counterparts. We prove the
Completely Prime Ideal Principle, a theorem stating that right ideals that are
maximal in a specific sense must be completely prime. We offer a number of
applications of the Completely Prime Ideal Principle arising from many diverse
concepts in rings and modules. These applications show how completely prime
right ideals control the one-sided structure of a ring, and they recover
earlier theorems stating that certain noncommutative rings are domains (namely,
proper right PCI rings and rings with the right restricted minimum condition
that are not right artinian). In order to provide a deeper understanding of the
set of completely prime right ideals in a general ring, we study the special
subset of comonoform right ideals.Comment: 38 page
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