arXiv subjects

L. A. Núñez

Publications and source records attributed to L. A. Núñez.

At least 19 recordsLinked to original sources

arXiv2024

A Methodological Framework for Solving Einsteins Equations in Axially Symmetric Spacetimes

This work presents a novel methodology for deriving stationary and axially symmetric solutions to Einstein field equations using the 1+3 tetrad formalism. This approach reformulates the Einstein equations into first order scalar equations, enabling systematic resolution in vacuum scenarios. We derive two distinct solutions in polar and hyperbolic geometries by assuming the separability of a key metric function. Our method reproduces well known solutions such as Schwarzschild and Kerr metrics and extends the case of rotating spacetimes to hyperbolic configurations. Additionally, we explore the role of Killing tensors in enabling separable metric components, simplifying analyses of geodesic motion and physical phenomena. This framework demonstrates robustness and adaptability for addressing the complexities of axially symmetric spacetimes, paving the way for further applications to Kerr like solutions in General Relativity.

gr-qc↗

arXiv2023

MUYSC: An end-to-end muography simulation toolbox

Muography is an imaging technique based on attenuation of the directional muon flux traversing geological or anthropic structures. Several simulation frameworks help to perform muography studies by combining specialised codes from the muon generation (CORSIKA and CRY) and the muon transport (GEANT4, PUMAS, and MUSIC) to the detector performance (GEANT4). This methodology is very precise but consumes significant computational resources and time. In this work, we present the end-to-end python-based MUographY Simulation Code. MUYSC implements a muography simulation framework capable of rapidly estimating rough muograms of any geological structure worldwide. MUYSC generates the muon flux at the observation place, transports the muons along the geological target, and determines the integrated muon flux detected by the telescope. Additionally, MUYSC computes the muon detector parameters (acceptance, solid angle, and angular resolution) and reconstructs the 3-dimensional density distribution of the target. We evaluated its performance by comparing it with previous results of several simulation frameworks.

physics.geo-ph↗

arXiv2022

A lightning monitoring system for studying transient phenomena in cosmic ray observatories

During thunderstorms, the atmospheric electric field can increase above hundreds of kV/m, causing an acceleration in the charged particles of secondary cosmic rays. Such an acceleration causes avalanche processes in the atmosphere, enhancing/reducing the particle flux at ground level depending on the strength/polarity of the electric field. We present the design and implementation of a self-triggered and fast-recording lightning monitoring system used to study the transient electric field atmospheric effect on the secondary particle flux above cosmic ray observatories. The acquisition device records lightning electric field at 10 $μ$s resolution (during 1.2 s per event), covering a detection range up to 200 km ($I_{peak} >$ 100 kA)

physics.ao-ph↗

arXiv2022

RACIMO@Bucaramanga: A Citizen Science Project on Data Science and Climate Awareness

This paper describes a collaborative experience to empower organized communities to produce, curate and disseminate environmental data. A particular emphasis is done on the description of open hardware & software architecture and the processes of commissioning of the low cost Arduino-Raspberry-Pi weather station which measures: atmospheric pressure, temperature, humidity, precipitation, cloudiness, and illuminance/irradiance. The idea is to encourage more people to replicate this open-science initiative. We have started this experience training students & teachers from seven mid secondary schools through a syllabus of 12 two-hours lectures with a web-based support which exposes them to basic concepts and practices of Citizen Science and Open Data Science.

astro-ph.IM↗

arXiv2022

Muography in Colombia: simulation framework, instrumentation and data analysis

We present the Colombo-Argentinian Muography Program for studying inland Latin-American volcanoes. It describes the implementation of a simulation framework covering various factors with different spatial and time scales: the geomagnetic effects at a particular geographic point, the development of extensive air showers in the atmosphere, the propagation through the scanned structure and the detector response. Next, we sketch the criteria adopted for designing, building, and commissioning MuTe: a hybrid Muon Telescope based on a composite detection technique. It combines a hodoscope for particle tracking and a water Cherenkov detector to enhance the muon-to-background-signal separation due to extensive air showers' soft and multiple-particle components. MuTe also discriminates inverse-trajectory and low-momentum muons by using a picosecond Time-of-Flight system. We also characterise the instrument's structural (mechanical and thermal) behaviour, discussing preliminary results from the background composition and the telescope-health monitoring variables. Finally, we discuss the implementations of an optimisation algorithm to improve the volcano internal density distribution estimation and machine learning techniques for background rejection.

astro-ph.IM↗

arXiv2021

Simulated Annealing for Volcano Muography

Muography or muon radiography is a non-invasive emerging image technology relying on high energy atmospheric muons, which complements other standard geophysical tools to understand the Earth's subsurface. This work discusses a geophysical inversion methodology for volcanic muography, based on the Simulated Annealing algorithm, using a semi-empirical model of the muon flux to reach the volcano topography and a framework for the energy loss of muons in rock. The Metropolis-Simulated-Annealing algorithm starts from an 'observed' muon flux and obtains the best associated inner density distribution function inside a synthetic model of the Cerro Machin Volcano (Tolima-Colombia). The estimated initial density model was obtained with GEOMODELER, adapted to the volcano topography. We improved this model by including rock densities from samples taken from the crater, the dome and the areas associated with fumaroles. In this paper, we determined the minimum muon energy (a function of the arrival direction) needed to cross the volcanic building, the emerging integrated flux of muons, and the density profile inside a model of Cerro Machin. The present inversion correctly reconstructed the density differences inside the Machin, within a 1 percent error concerning our initial simulation model, giving a remarkable density contrast between the volcanic duct, the encasing rock and the fumaroles area.

physics.geo-ph↗

arXiv2021

Systematic effects on the diversity of dwarf galaxies rotation curves

Cosmological simulations of structure formation are invaluable to study the evolution of the Universe and the development of galaxies in it successfully reproducing many observations in the context of the cosmological paradigm $Λ$CDM. However, there are remarkable discrepancies with observations that are a matter of debate. One of the most recently reported is the diversity of shapes in the rotation curves of dwarf galaxies in the local Universe which is in contrast to the apparent homogeneity of rotation curves in cosmological hydrodynamic simulations. Previous studies on similar problems have shown that sometimes can be alleviated by accounting for the impact of observational effects in the comparison. For this reason, in this work we present a set of controlled experiments to measure the impact that some systematic effects, associated with modeling the observation process in a realistic way, have on the diversity of synthetic rotation curves. Our results demonstrate that factors such as spectral power, spatial resolution and inclination angle, can naturally induce noticeable fluctuations on the shape of the rotation curves, reproducing up to $47\%$ of the diversity reported in the observations. This is remarkable, especially considering that we limited the sample to highly-symmetric disks simulated in isolation. This shows that a more realistic modeling of synthetic rotation curves may alleviate the reported tension between simulations and observations, without posing a challenge to the standard cosmological model of cold dark matter.

astro-ph.GA↗

arXiv2021

Modeling and simulation of the R5912 photomultiplier for the LAGO project

We present the results of modeling and simulating the Hamamatsu R5912 photomultiplier tube that is used in most of the sites of the Latin American Giant Observatory (LAGO). The model was compared with data of in-operation water Cherenkov detectors (WCD) installed at Bucaramanga-Colombia and Bariloche-Argentina. The LAGO project is an international experiment that spans across Latin America at different altitudes joining more than 35 institutions of 11 countries. It is mainly oriented to basic research on gamma-ray bursts and space weather phenomena. The LAGO network consists of single or small arrays of WCDs composed mainly by a photomultiplier tube and a readout electronics that acquires single-particle or extensive air shower events triggered by the interaction of cosmic rays with the Earth atmosphere.

physics.ins-det↗

arXiv2021

Characterization and on-field performance of the MuTe Silicon Photomultipliers

The Muon Telescope is a muography experiment for imaging volcanoes in Colombia. It consists of a scintillator tracking system and a water Cherenkov detector used for particle deposited energy measurement. The MuTe operates autonomously in high altitude environments where the temperature gradient reaches up to $10$$^{\circ}$C. In this work, we characterize the breakdown voltage, gain, and noise of the telescope silicon photomultipliers for temperature variations spanning $0$ to $40$$^{\circ}$C. We demonstrated that the discrimination threshold for the MuTe hodoscope must be above 5 pe to avoid contamination due to the SiPM dark count, crosstalk, and afterpulsing. We also assess the MuTe counting rate depending on day-night temperature variations.

physics.ins-det↗

arXiv2021

Relativistic Anisotropic Polytropic Spheres: Physical Acceptability

In this work we evaluate the physical acceptability of relativistic anisotropic spheres modeled by two polytropic equations of state -- with the same newtonian limit -- commonly used to describe compact objects in General Relativity. We integrate numerically the corresponding Lane-Emden equation in order to get density, mass and pressure profiles. An ansatz is used for the anisotropic pressure allowing us to have material configurations slightly deviated from isotropic condition. Numerical models are classified in a parameter space according to the number of physical acceptability conditions that they fulfil. We found that the polytropes considering total energy density are more stable than the second type of polytropic EoS.

gr-qc↗

arXiv2021

Radiating jump conditions in General Relativity

We present a unified description of spherical discontinuity surfaces in General Relativity based on two parameters: mass function and surface permeability. The surfaces considered are: \textit{Impulsive fronts}, massive permeable layer; \textit{Surface layers}, massive impermeable layer; \textit{Shock fronts}, massless permeable surface; and \textit{Boundary surfaces}, massless impermeable surface. We derive the exact jump conditions for the physical variables across all these surfaces. Finally, we discuss the quasi-static approximation from studying slow hydrodynamic processes involving discontinuity surfaces.

gr-qc↗

arXiv2021

Physical acceptability conditions for realistic neutron star equations of state

We select 37 most common and realistic dense matter equation of states to integrate the general relativistic stellar structure equations for static spherically symmetric matter configurations. For all these models, we check the compliance of the acceptability conditions that every stellar model should satisfy. It was found that some of the non-relativistic equation of states violate the causality and/or the dominant energy condition and that adiabatic instabilities appear in the inner crust for all equation of state considered.

gr-qc↗

arXiv2020

Design and construction of MuTe: a hybrid Muon Telescope to study Colombian Volcanoes

We present a hybrid Muon Telescope, MuTe, designed and built for imaging active Colombian volcanoes. The MuTe has a resolution of tens of meters, low power consumption, robustness and transportability making it suitable for use in difficult access zones where active volcanoes usually are. The main feature of MuTe is the implementation of a hybrid detection technique combining two scintillation panels for particle tracking and a Water Cherenkov Detector for filtering background sources due to the electromagnetic component of extended air showers and multiple particle events. MuTe incorporates particle-identification techniques for reducing the background noise sources and discrimination of fake events by a picosecond Time-of-Flight system. We also describe the mechanical behavior of the MuTe during typical tremors and wind conditions at the observation place, as well as the frontend electronics design and power consumption.

physics.ins-det↗

arXiv2020

Simulated Response of MuTe, a Hybrid Muon Telescope

In this paper we present a complete and detailed computational model of the response of the hybrid Muon Telescope (MuTe), designed to perform muography volcanic studies. This instrument combines two particle detection techniques: first, a muon hodoscope based on two panels of plastic scintillator bars; and a Water Cherenkov detector located behind the rear scintillator panel acting both as a coincidence and a discriminating detector. The simulation model includes: materials, geometries, dimensions, and the photo-sensitiveness of the detectors. The simulation results, in agreement with the measured data, were used to set up the muon detector trigger for the expected energy dependent signal.

physics.ins-det↗

arXiv2020

sPad of Super Accuracy and Geometry in Old Babylon. -- sPad de Súper Exactitud y Geometría en la Antigua Babilonia

Recently it has been discovered that on a stone tablet over 3800 years old, the Plimpton-322 table, are carved the geometric relations that exist between the sides of 15 right triangles chosen in a very special way. Due to its property as a super accuracy calculation tool, in this work we have called it sPad by stone pad, and we have calculated its machine accuracy $ε_m$. Additionally, we present the physical and astrophysical constants most used in science and engineering in sexagesimal base. ----- Reciéntemente se ha descubierto que en una tableta de piedra de más de 3800 años de antigüedad, la Tabla Plimpton 322, están ta\-lla\-das las relaciones geométricas que existen entre los lados de 15 triángulos rectángulos escogidos de manera muy especial. Debido a su propiedad como herramienta de cálculo súper preciso, en este trabajo la hemos llamado sPad por \emph{stone pad}, y hemos calculado su exactitud de máquina $ε_{m}$. Adicionalmente presentamos las constantes físicas y astrofísicas más usadas en ciencia e ingeniería en base sexagesimal.

math.HO↗

arXiv2019

Radiation Dose Charts for Long Geodetic and Polar Flights with CARI-7A

We have calculated by using CARI-7A the effective and ambient radiation doses absorbed by a reference human phantom inside aircrafts with cruise speed, and averaged ascent/descent rates as presented by real airplanes such as: Airbus 380, Boeing 777, 787, Hercules C-130 and Twin Otter DHC-6, in a sample of flight aerial routes in a range of flight levels. In the sample, fifteen routes are between the longest non-stop flight around the world, where four flights pass over the Arctic and we have considered one air route involving the Antarctica with two additional special cases. The Earth curvature based on model WGS84 was taken into account for every point in each route by using the INVERSE3D software. Then we constructed radiation dose charts according to the ICRP-103 conditions by using the radiometric results coming from the CARI-7A simulations. These charts present the effective absorbed radiation dose as a function of flight level and flight time in a year of normal operations of the crew as recommended by the FAA. We have also characterized geographically and kinematically the cosmic effective radiation absorption rates at Earth's atmosphere in terms of the structure and order of polynomials in the altitude. From the flight with the leading rate of irradiation we found a thumb rule to estimate the effective absorbed radiation dose and the ambient equivalent dose that gives a superior threshold for any flight of the sample and perhaps on Earth, valid in altitude interval [20000, 50000] ft.

physics.med-ph↗

arXiv2019

Contributions of the LAGO Collaboration to the 36th ICRC

The LAGO (Latin American Giant Observatory) observatory is an experiment that spans over Latin America in a wide range of latitudes that gives different rigidity cut offs for the enter of cosmic rays in the atmosphere. The motivation of the Observatory is to study atmospheric radiation and space weather through the measurement of the secondary emission of low energy cosmic rays at ground level using Water Cherenkov Detectors (WCD). This work presents the contributions of the LAGO collaboration to the 2019 36th ICRC.

hep-ex↗

arXiv2018

Are there any models with homogeneous energy density?

By applying a recent method --based on a tetrad formalism in General Relativity and the orthogonal splitting of the Riemann tensor-- to the simple spherical static case, we found that the only static solution with homogeneous energy density is the Schwarzschild solution and that there are no spherically symmetric dynamic solutions consistent with the homogeneous energy density assumption. Finally, a circular equivalence is shown among the most frequent conditions considered in the spherical symmetric case: homogeneous density, isotropy in pressures, conformally flatness and shear-free conditions. We demonstrate that, due to the regularity conditions at the center of the matter distribution, the imposition of two conditions necessarily leads to the static case.

gr-qc↗