NADA-FLD: A General Relativistic, Multi-dimensional Neutrino-hydrodynamics Code Employing Flux-limited Diffusion

We present the new code NADA-FLD to solve multi-dimensional neutrino-hydrodynamics in full general relativity (GR) in spherical polar coordinates. The energy-dependent neutrino transport assumes the flux-limited diffusion (FLD) approximation and evolves the neutrino energy densities measured in the frame comoving with the fluid. Operator splitting is used to avoid multi-dimensional coupling of grid cells in implicit integration steps involving matrix inversions. Terms describing lateral diffusion and advection are integrated explicitly using the Allen-Cheng or the Runge-Kutta-Legendre method, which remain stable even in the optically thin regime. We discuss several toy-model problems in one and two dimensions to test the basic functionality and individual components of the transport scheme. We also perform fully dynamic core-collapse supernova (CCSN) simulations in spherical symmetry. For a Newtonian model we find good agreement with the M1 code ALCAR, and for a GR model we reproduce the main effects of GR in CCSNe already found by previous works.Comment: 28 pages, 11 figures; accepted by MNRAS; supplemented by RKL method, resolution tests, and appendix with detailed derivations of FLD flux in response to referee comment

Impact of pions on binary neutron star mergers

We study the impact of pions in simulations of neutron star mergers and explore the impact on gravitational-wave observables. We model charged and neutral pions as a non-interacting Boson gas with a chosen, constant effective mass. We add the contributions of pions, which can occur as a condensate or as a thermal population, to existing temperature and composition dependent equations of state. Compared to the models without pions, the presence of a pion condensate decreases the characteristic properties of cold, non-rotating neutron stars such as the maximum mass, the radius and the tidal deformability. We conduct relativistic hydrodynamical simulations of neutron star mergers for these modified equations of state models and compare to the original models, which ignore pions. Generally, the inclusion of pions leads to a softening of the equation of state, which is more pronounced for smaller effective pion masses. We find a shift of the dominant postmerger gravitational-wave frequency by up to 150~Hz to higher frequencies and a reduction of the threshold binary mass for prompt black-hole formation by up to 0.07~$M_\odot$. We evaluate empirical relations between the threshold mass or the dominant postmerger gravitational-wave frequency and stellar parameters of nonrotating neutron stars. These relations are constructed to extract these stellar properties from merger observations and are built based on large sets of equation of state models which do not include pions. Comparing to our calculations with pions, we find that these empirical relations remain valid to good accuracy, which justifies their use although they neglect a possible impact of pions. We also address the mass ejection by neutron star mergers and observe a moderate enhancement of the ejecta mass by a few ten per cent. (abridged)Comment: 27 pages, 24 figures, accepted for publication in Phys. Rev.

STUDI EFISIENSI SALURAN SEKUNDER JARINGAN IRIGASI WUNDULAKO, KOLAKA

Secondary Channel Efficiency Study Wundulako Irrigation Network, Kolaka. One of the government's efforts to prosper the community during the current COVID-19 pandemic is to ensure that the food security of the community can be met. To achieve this, the rice field area as a food barn for rice plants requires sufficient availability. In addition, the availability of water must be supported by good irrigation facilities and infrastructure. The efficiency of irrigation canals can be used as an indicator of the performance of an irrigation service area. The most common problem faced by many network operating systems is the low efficiency of air distribution. D. I. Wundulako is one of the irrigation areas that has the widest potential for rice fields in Kolaka Regency. However, until now, it can only flow 1,695 Ha out of a total area of ​​3,113 Ha. Along with the development conditions in the district, D. I. Wundulako has greatly affected air conditions, irrigation networks, building conditions and rice fields, and there has been a lot of water loss/leakage before reaching its final destination. This loss causes unfulfilled water needs in rice fields and plants in Wundulako irrigation, so it is necessary to conduct a study related to canals in the operation of Wundulako irrigation networks