Effects of Vacuum Polarization in Strong Magnetic Fields with an Allowance Made for the Anomalous Magnetic Moments of Particles

Given the anomalous magnetic moments of electrons and positrons in the one-loop approximation, we calculate the exact Lagrangian of an intense constant magnetic field that replaces the Heisenberg-Euler Lagrangian in traditional quantum electrodynamics (QED). We have established that the derived generalization of the Lagrangian is real for arbitrary magnetic fields. In a weak field, the calculated Lagrangian matches the standard Heisenberg-Euler formula. In extremely strong fields, the field dependence of the Lagrangian completely disappears, and the Lagrangian tends to a constant determined by the anomalous magnetic moments of the particles.Comment: 19 pages, 3 figure

Impactos en las propiedades del suelo de los bosques de pinabete en terrenos agrícolas abandonados

Forest floor is considered a major feature distinguishing forest from agricultural soils. Forest floor develops as forest stands grow and is composed of more or less altered plant-tissue biomass accumulated on the soil surface. Our study’s aim was to find whether properties of both the organic layers and mineral soil differ according to the land-use history of the sites compared. Each site included an afforested area of immature 50-year-old spruce forest (AFF) on formerly agricultural land plus an adjacent area of old-growth 100-year-old spruce stand (FOR). The localities are situated at altitudes ranging between 600 and 850 metres above sea level. From the results of our study it can be concluded that both forest floor and mineral soil had higher pH and Ca concentration at formerly agricultural sites. C/N ratio is significantly lower in afforested soil. First-generation humus was significantly higher in phosphorus.El piso forestal es considerado una de las principales características distintivas de los suelos forestales frente a los agrícolas. El piso forestal se desarrolla según crecen las masas forestales y se compone de tejidos de vegetales de la biomasa más o menos alterados acumulados en la superficie del suelo. El objetivo de nuestro estudio fue determinar si las propiedades de las capas orgánicas y minerales del suelo difieren de acuerdo a la historia del uso del suelo de los sitios. Cada sitio incluye un área reforestada de bosque de pinabete inmaduro de 50 años de edad (AFF) en antiguo terreno agrícola, más un área adyacente madura de pinabete de 100 años de edad. Las localidades se encuentran en altitudes que oscilan entre 600 y 850 metros sobre el nivel del mar. De los resultados de nuestro estudio se puede concluir que tanto el suelo del bosque como el suelo mineral tenían un pH más alto y mayor concentración de Ca en los sitios agrícolas abandonados. La relación C/N es significativamente menor en los suelos reforestados. La primera generación de humus presentó un significativamente mayor contenido en fósforo

Determining the Hubble Constant with Black Hole Mergers in Active Galactic Nuclei

Gravitational waves from neutron star mergers have long been considered a promising way to measure the Hubble constant, $H_0$, which describes the local expansion rate of the Universe. While black hole mergers are more abundantly observed, their expected lack of electromagnetic emission and poor gravitational-wave localization makes them less suited for measuring $H_0$. Black hole mergers within the disks of Active Galactic Nuclei (AGN) could be an exception. Accretion from the AGN disk may produce an electromagnetic signal, pointing observers to the host galaxy. Alternatively, the low number density of AGNs could help identify the host galaxy of $1-5\%$ of mergers. Here we show that black hole mergers in AGN disks may be the most sensitive way to determine $H_0$ with gravitational waves. If 1% of LIGO/Virgo's observations occur in AGN disks with identified host galaxies, we could measure $H_0$ with 1% uncertainty within five years, likely beyond the sensitivity of neutrons star mergers.Comment: 4 pages, 2 figure

Kinematic Responses to Changes in Walking Orientation and Gravitational Load in Drosophila melanogaster

Walking behavior is context-dependent, resulting from the integration of internal and external influences by specialized motor and pre-motor centers. Neuronal programs must be sufficiently flexible to the locomotive challenges inherent in different environments. Although insect studies have contributed substantially to the identification of the components and rules that determine locomotion, we still lack an understanding of how multi-jointed walking insects respond to changes in walking orientation and direction and strength of the gravitational force. In order to answer these questions we measured with high temporal and spatial resolution the kinematic properties of untethered Drosophila during inverted and vertical walking. In addition, we also examined the kinematic responses to increases in gravitational load. We find that animals are capable of shifting their step, spatial and inter-leg parameters in order to cope with more challenging walking conditions. For example, flies walking in an inverted orientation decreased the duration of their swing phase leading to increased contact with the substrate and, as a result, greater stability. We also find that when flies carry additional weight, thereby increasing their gravitational load, some changes in step parameters vary over time, providing evidence for adaptation. However, above a threshold that is between 1 and 2 times their body weight flies display locomotion parameters that suggest they are no longer capable of walking in a coordinated manner. Finally, we find that functional chordotonal organs are required for flies to cope with additional weight, as animals deficient in these proprioceptors display increased sensitivity to load bearing as well as other locomotive defects

Bremsstrahlung photon polarization for ee±→(eγ)e±ee^\pm\to (e\gamma)e^\pm, and ep→(eγ)pep\to (e\gamma)p high energy collisions

The polarization of bremsstrahlung photon in the processes $ee^\pm\to (e\gamma)e^\pm$, and $ep\to (e\gamma)p$ is calculated for peripheral kinematics, in the high energy limit where the cross section does not decrease with the incident energy. When the initial electron is unpolarized(longitudinally polarized) the final photon can be linearly (circularly) polarized. The Stokes parameters of the photon polarization are calculated as a function of the kinematical variables of process: the energy of recoil particle, the energy fraction of scattered electron, and the polar and azimuthal angles of photon. Numerical results are given in form of tables, for typical values of the relevant kinematic variables.Comment: 9 pages, 3 figure