Computational General Relativistic Force-Free Electrodynamics: II. Characterization of Numerical Diffusivity

Scientific codes are an indispensable link between theory and experiment; in (astro-)plasma physics, such numerical tools are one window into the universe's most extreme flows of energy. The discretization of Maxwell's equations - needed to make highly magnetized (astro)physical plasma amenable to its numerical modeling - introduces numerical diffusion. It acts as a source of dissipation independent of the system's physical constituents. Understanding the numerical diffusion of scientific codes is the key to classify their reliability. It gives specific limits in which the results of numerical experiments are physical. We aim at quantifying and characterizing the numerical diffusion properties of our recently developed numerical tool for the simulation of general relativistic force-free electrodynamics, by calibrating and comparing it with other strategies found in the literature. Our code correctly models smooth waves of highly magnetized plasma. We evaluate the limits of general relativistic force-free electrodynamics in the context of current sheets and tearing mode instabilities. We identify that the current parallel to the magnetic field ($\mathbf{j}_\parallel$), in combination with the break-down of general relativistic force-free electrodynamics across current sheets, impairs the physical modeling of resistive instabilities. We find that at least eight numerical cells per characteristic size of interest (e.g. the wavelength in plasma waves or the transverse width of a current sheet) are needed to find consistency between resistivity of numerical and of physical origins. High-order discretization of the force-free current allows us to provide almost ideal orders of convergence for (smooth) plasma wave dynamics. The physical modeling of resistive layers requires suitable current prescriptions or a sub-grid modeling for the evolution of $\mathbf{j}_\parallel$.Comment: 14 pages, 9 figures, submitted to A&

Computational General Relativistic Force-Free Electrodynamics: I. Multi-Coordinate Implementation and Testing

General relativistic force-free electrodynamics is one possible plasma-limit employed to analyze energetic outflows in which strong magnetic fields are dominant over all inertial phenomena. The amazing images of black hole shadows from the galactic center and the M87 galaxy provide a first direct glimpse into the physics of accretion flows in the most extreme environments of the universe. The efficient extraction of energy in the form of collimated outflows or jets from a rotating BH is directly linked to the topology of the surrounding magnetic field. We aim at providing a tool to numerically model the dynamics of such fields in magnetospheres around compact objects, such as black holes and neutron stars. By this, we probe their role in the formation of high energy phenomena such as magnetar flares and the highly variable teraelectronvolt emission of some active galactic nuclei. In this work, we present numerical strategies capable of modeling fully dynamical force-free magnetospheres of compact astrophysical objects. We provide implementation details and extensive testing of our implementation of general relativistic force-free electrodynamics in Cartesian and spherical coordinates using the infrastructure of the Einstein Toolkit. The employed hyperbolic/parabolic cleaning of numerical errors with full general relativistic compatibility allows for fast advection of numerical errors in dynamical spacetimes. Such fast advection of divergence errors significantly improves the stability of the general relativistic force-free electrodynamics modeling of black hole magnetospheres.Comment: 19 pages, 15 figures, submitted to A&

The aT distribution of the Z boson at hadron colliders

We provide the first theoretical study of a novel variable, $a_T$, proposed in Ref.[1] as a more accurate probe of the region of low transverse momentum $p_T$, for the $Z$ boson $p_T$ distribution at hadron colliders. The $a_T$ is the component of $p_T$ transverse to a suitably defined axis. Our study involves resummation of large logarithms in $a_T$ up to the next-to--leading logarithmic accuracy and we compare the results to those for the well-known $p_T$ distribution, identifying important physical differences between the two cases. We also test our resummed result at the two-loop level by comparing its expansion to order $\alpha_s^2$ with the corresponding fixed-order results and find agreement with our expectations.Comment: 30 pages, 3 figures, JHEP class included. Final version published in JHE

Primera secuencia antracológica de la localidad arqueológica Laguna del Diamante (San Carlos, Mendoza)

En el presente trabajo se exponen los resultados del análisis antracológico del sitio Laguna del Diamante 4 (LD-S4), emplazado a 3290 msnm, en ambiente Altoandino. Cronológicamente comprende desde 1100 años AP a c.a.200 años AP. Este sitio y otros ubicados en la Localidad Laguna del Diamante, consisten en recintos pircados, donde se ha recuperado cerámica con características estilísticas y tecnológicas propias de complejos culturales de Chile Central (i.e. Llolleo, Aconcagua e Inca). El principal objetivo es caracterizar cualicuantitativamente el registro antracológico del sitio y comparar los resultados con otros de sitios con características similares previamente estudiados (i.e. El Indígeno).Trabajo publicado en Gómez Otero, Julieta (comp.). X Jornadas de Arqueología de la Patagonia. Libro de resúmenes. Puerto Madryn: Instituto de Diversidad y Evolución Austral, 2017.Facultad de Ciencias Naturales y Muse

Primera secuencia antracológica de la localidad arqueológica Laguna del Diamante (San Carlos, Mendoza)

En el presente trabajo se exponen los resultados del análisis antracológico del sitio Laguna del Diamante 4 (LD-S4), emplazado a 3290 msnm, en ambiente Altoandino. Cronológicamente comprende desde 1100 años AP a c.a.200 años AP. Este sitio y otros ubicados en la Localidad Laguna del Diamante, consisten en recintos pircados, donde se ha recuperado cerámica con características estilísticas y tecnológicas propias de complejos culturales de Chile Central (i.e. Llolleo, Aconcagua e Inca). El principal objetivo es caracterizar cualicuantitativamente el registro antracológico del sitio y comparar los resultados con otros de sitios con características similares previamente estudiados (i.e. El Indígeno).Trabajo publicado en Gómez Otero, Julieta (comp.). X Jornadas de Arqueología de la Patagonia. Libro de resúmenes. Puerto Madryn: Instituto de Diversidad y Evolución Austral, 2017.Facultad de Ciencias Naturales y Muse

Primera secuencia antracológica de la localidad arqueológica Laguna del Diamante (San Carlos, Mendoza)

En el presente trabajo se exponen los resultados del análisis antracológico del sitio Laguna del Diamante 4 (LD-S4), emplazado a 3290 msnm, en ambiente Altoandino. Cronológicamente comprende desde 1100 años AP a c.a.200 años AP. Este sitio y otros ubicados en la Localidad Laguna del Diamante, consisten en recintos pircados, donde se ha recuperado cerámica con características estilísticas y tecnológicas propias de complejos culturales de Chile Central (i.e. Llolleo, Aconcagua e Inca). El principal objetivo es caracterizar cualicuantitativamente el registro antracológico del sitio y comparar los resultados con otros de sitios con características similares previamente estudiados (i.e. El Indígeno).Trabajo publicado en Gómez Otero, Julieta (comp.). X Jornadas de Arqueología de la Patagonia. Libro de resúmenes. Puerto Madryn: Instituto de Diversidad y Evolución Austral, 2017.Facultad de Ciencias Naturales y Muse

Vortex Plastic Motion in Twinned Superconductors

We present simulations, without electrodynamical assumptions, of $B(x,y,H(t)), M(H(t))$, and $J_c(H(t))$, in hard superconductors, for a variety of twin-boundary pinning potential parameters, and for a range of values of the density and strength of the pinning sites. We numerically solve the overdamped equations of motion of up to 10^4 flux-gradient-driven vortices which can be temporarily trapped at $\sim 10^6$ pinning centers. These simulations relate macroscopic measurements (e.g., M(H), ``flame'' shaped $B(x,y)$ profiles) with the underlying microscopic pinning landscape and the plastic dynamics of individual vortices