143 research outputs found
Coulomb's law modification in nonlinear and in noncommutative electrodynamics
We study the lowest-order modifications of the static potential for
Born-Infeld electrodynamics and for the -expanded version of the
noncommutative U(1) gauge theory, within the framework of the gauge-invariant
but path-dependent variables formalism. The calculation shows a long-range
correction (-type) to the Coulomb potential in Born-Infeld
electrodynamics. However, the Coulomb nature of the potential (to order )
is preserved in noncommutative electrodynamics.Comment: 14 pages, 1 figur
Note on the dual BRST Symmetry in U(1) Gauge Theory
We analyze the relation between the Lagrangian and Hamiltonian BRST symmetry
generators for a recently proposed two-dimensional symmetry. In particular it
is shown that this symmetry may be obtained from a canonical transformation in
the ghost sector in a gauge independent way.Comment: 12 pages, late
Remarks on a Chern-Simons-like coupling
We consider the static quantum potential for a gauge theory which includes a
light massive vector field interacting with the familiar photon
via a Chern-Simons- like coupling, by using the gauge-invariant, but
path-dependent, variables formalism. An exactly screening phase is then
obtained, which displays a marked departure of a qualitative nature from
massive axionic electrodynamics. The above static potential profile is similar
to that encountered in axionic electrodynamics consisting of a massless
axion-like field, as well as to that encountered in the coupling between the
familiar photon and a second massive gauge field living in the
so-called hidden-sector, inside a superconducting box.Comment: 6 pages. To appear in Mod. Phys. Lett.
Coulomb's law corrections from a gauge-kinetic mixing
We study the static quantum potential for a gauge theory which includes the
mixing between the familiar photon and a second massive gauge
field living in the so-called hidden-sector . Our discussion is carried
out using the gauge-invariant but path-dependent variables formalism, which is
alternative to the Wilson loop approach. Our results show that the static
potential is a Yukawa correction to the usual static Coulomb potential.
Interestingly, when this calculation is done inside a superconducting box, the
Coulombic piece disappears leading to a screening phase.Comment: 4 page
Relevant developments and new insights on Sonoelectrochemistry
AbstractSonoelectrochemistry is undergoing a reemerging activity in the last years with an increasing number of papers appearing in a wide range of peer review journals. Applied studies cover environmental treatments, synthesis and characterization of nanostructures, polymeric materials synthesis, analytical procedures, films preparations, membrane preparations among other interesting applications. Fundamental analyses are also carried out focused on electrochemical processes using unconventional solvents, elucidation of mechanisms and combination with other techniques. The interrelation between Electrochemistry and Acoustics presents mutual benefits for both disciplines, providing interesting information about the bubble dynamics for acoustics physicists and a higher number of possible applications for electrochemists. However, the vast majority of this research has been carried out at laboratory scale with individually designed systems based on ultrasonic horns dipped into traditional glass electrochemistry vessels. It is remarkable that even with this rudimentary experimental set-up many interesting results have been generated. However sonoelectrochemistry has suffered a few drawbacks related to reproducibility, scale-up and design aspects which have slowed its development. Almost certainly the reason for this is the lack of reactors that have been purpose built for sonoelectrochemistry. There have been many attempts to build lab-scale systems e.g. for electroanalysis, nanomaterials synthesis and the electrooxidation of organic pollutants but the results are often contradictory. A few groups have attempted to characterize lab-scale sonochemical reactors adapted as sonoelectrochemical reactors but the true optimization of such reactors requires contributions from many disciplines including physics, fundamental and applied electrochemistry, chemical engineering and material science
Solutions for f(R) gravity coupled with electromagnetic field
In the presence of external, linear / nonlinear electromagnetic fields we
integrate f(R) \sim R+2{\alpha}\surd(R+const.) gravity equations. In contrast
to their Einsteinian cousins the obtained black holes are non-asymptotically
flat with a deficit angle. In proper limits we obtain from our general solution
the global monopole solution in f(R) gravity. The scale symmetry breaking term
adopted as the nonlinear electromagnetic source adjusts the sign of the mass of
the resulting black hole to be physical.Comment: 7 pages no figure, final version for publication in European Physical
Journal
Comments on the dual-BRST symmetry
In view of a raging controversy on the topic of
dual-Becchi-Rouet-Stora-Tyutin (dual-BRST/co-BRST) and anti-co-BRST symmetry
transformations in the context of four (3+1)-dimensional (4D) Abelian 2-form
and 2D (non-)Abelian 1-form gauge theories, we attempt, in our present short
note, to settle the dust by taking the help of mathematics of differential
geometry, connected with the Hodge theory, which was the original motivation
for the nomenclature of "dual-BRST symmetry" in our earlier set of works. It
has been claimed, in a recent set of papers, that the co-BRST symmetries are
not independent of the BRST symmetries. We show that the BRST and co-BRST
symmetries are independent symmetries in the same fashion as the exterior and
co-exterior derivatives are independent entities belonging to the set of de
Rham cohomological operators of differential geometry.Comment: LaTeX file, 6 pages, journal versio
Aplicación de ondas sónicas y ultrasónicas como medio de control del ataque de termitas subterráneas Reticulitermes flavipes (Kollar) en madera de Pino Radiata
Se analizó el comportamiento de las termitas al aplicar campos sónicos y ultrasónicos con diferentes frecuencias, niveles de energía y formas de onda, de modo de establecer las condiciones para crear una barrera física frente a la acción de las termitas en probetas de madera de pino radiata.Los ensayos a nivel del rango ultrasónico se efectuaron con frecuencias de 100, 500 y 1000kHz en probetas de 1x4x10cm mediante una adaptación de la norma Europea EN118.La aplicación de irradiación a nivel sónico se realizó sobre probetas de diferentes escuadrías comerciales en dirección transversal considerando distintas orientaciones de los anillos de crecimiento (radial, tangencial y mixto) y tres niveles de densidad (baja, media y alta). Para este efecto se diseñó un sistema constituido de un mini-termitero conteniendo 500 termitas unido a la muestra y una fuente de alimentación de modo de establecer un flujo continuo de termitas a través de una perforación central practicada en la muestra.En el rango ultrasónico se obtuvo que con una frecuencia de 500kHz, fue posible inhibir la alimentación de las termitas mientras el campo acústico se mantiene activo.En el rango audible estudiado, (16Hz a 20kHz) se observó que a una frecuencia de 80Hz se inhibe el paso de las termitas a través de la muestra alterándose drásticamente su comportamiento; en tiempos superiores a una hora de irradiación continúa, la rapidez de recuperación es parcial, disminuyendo las tasas de alimentación y la sobrevivencia, lo que evidencia la generación de un efecto fisiológico irreversible. AbstractThe behavior of the termites was analyzed when applying sonic and ultrasonic waves with different frequencies, levels of energy, and waveform to establish the conditions to create a physical barrier to the action of the termites in wood specimens of radiata pine.The tests at ultrasonic level were conducted using frequencies of 100, 500 and 1000kHz in specimens of 1x4x10cm by means of an adaptation of European Standard EN118.The application of irradiation at sonic level was made on specimens with different cross section in transverse direction considering different orientation of growth rings (radial, tangential and mixed) and three levels of density (low, medium and high). For this effect was constituted a system of a scale termite nest containing 500 termites with the wood specimen and a feed supply to establish a continuous flow of termites through a practiced central perforation in the specimen.In the ultrasonic rank it was obtained that with a frequency of 500kHz it is possible to inhibit the feeding of the termites while the acoustic field stays assets.In the studied audible rank, (16Hz to 20kHz) it was observed that to a frequency of 80Hz the passage of the termites through the sample was inhibited and they altered their behavior; in times superior to one hour of continuous irradiation the rapidity of recovery is partial, diminishing the rates of feeding and survival with generation of irreversible a physiological effect
Optical-to-NIR magnitude measurements of the Starlink LEO Darksat satellite and effectiveness of the darkening treatment
Four observations of Starlink's LEO communication satellites, Darksat and
STARLINK-1113, were conducted on two nights with two telescopes. The Chakana
0.6\,m telescope at the Ckoirama observatory (Chile) observed both satellites
on 5\,Mar\,2020 (UTC) and 7\,Mar\,2020 (UTC) using a Sloan r' and Sloan i'
filter, respectively. The ESO VISTA 4.1\,m telescope with the VIRCAM instrument
observed both satellites on 5\,Mar\,2020 (UTC) and 7\,Mar\,2020 (UTC) in the
NIR J-band and Ks-band, respectively. The calibration, image processing, and
analysis of the Darksat images give r\,\,5.6\,mag,
i\,\,5.0\,mag, J\,\,4.2\,mag, and Ks\,\,4.0\,mag
when scaled to a range of 550\,km (airmass ) and corrected for the solar
incidence and observer phase angles. In comparison, the STARLINK-1113 images
give r\,\,4.9\,mag, i\,\,4.4\,mag, J\,\,3.8\,mag,
and Ks\,\,3.6\,mag when corrected for range, solar incidence, and
observer phase angles. The data and results presented in this work show that
the special darkening coating used by Starlink for Darksat has darkened the
Sloan r' magnitude by 50\,\%, Sloan i' magnitude by 42\,\%, NIR J magnitude by
32\,\%, and NIR Ks magnitude by 28\,\%. The results show that both satellites
increase in reflective brightness with increasing wavelength and that the
effectiveness of the darkening treatment is reduced at longer wavelengths. This
shows that the mitigation strategies being developed by Starlink and other LEO
satellite operators need to take into account other wavelengths, not just the
optical. This work highlights the continued importance of obtaining
multi-wavelength observations of many different LEO satellites in order to
characterise their reflective properties and to aid the community in developing
impact simulations and developing mitigation tools.Comment: Accepted for publication in A&A, 10 pages, 10 figures, 3 table
Energy States of Colored Particle in a Chromomagnetic Field
The unitary transformation, which diagonalizes squared Dirac equation in a
constant chromomagnetic field is found. Applying this transformation, we find
the eigenfunctions of diagonalized Hamiltonian, that describe the states with
definite value of energy and call them energy states. It is pointed out that,
the energy states are determined by the color interaction term of the particle
with the background chromofield and this term is responsible for the splitting
of the energy spectrum.
We construct supercharge operators for the diagonal Hamiltonian, that ensure
the superpartner property of the energy states.Comment: 25 pages, some calculation details have been removed, typos correcte
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