arXiv subjects

J. Hernández-Aguilar

Publications and source records attributed to J. Hernández-Aguilar.

3 recordsLinked to original sources

arXiv2026

Data reduction pipeline for the SuMAC millimeter-wave spectrometer at the LMT

We present the data reduction and analysis pipeline for the SuperSpec-MUSCAT Collaboration (SuMAC) along with several key science data products. In Summer 2025, SuperSpec on-chip spectrometers operating from $190-300$ GHz at $R\sim200$ were deployed in the MUSCAT cryostat at the Large Millimeter Telescope, obtaining several days of on-sky data. Analysis of these data has been used to characterize noise performance and study spectra of various astrophysical sources, establishing the viability of deploying SuperSpec detectors in future instruments. These proceedings discuss the modular data reduction pipeline which uses timestreams of the kinetic inductance detectors (KIDs) and auxiliary instrument data to generate a variety of data products. We present an on-sky calibration method for converting the KID fractional frequency shift to on-sky brightness temperature. The mapmaking module generates 3D data cubes of extended sources, while the spectrum module produces a millimeter-wave spectrum of an object. The observations all incorporate measurements of the atmosphere to model and correct for absorption. We also discuss data processing choices including detector weighting, despiking, and notch filtering. Finally, we present preliminary data products including detection of carbon monoxide in NGC 253 and spectral maps of the central region of the Orion KL nebula.

astro-ph.IM↗

arXiv2026

Lorentzian Vacuum Transitions in $f(R)$ gravity

We study Lorentzian vacuum transition probabilities between two minima of a scalar field potential within the framework of $f(R)$ gravity. The analysis extends the previously considered WKB expansion of the Wheeler-DeWitt equation to modified gravity theories, up to second order. We apply the general method for homogeneous and isotropic FLRW universes, with zero and positive spatial curvature, for any $f(R)$ model. For the flat case we obtain analytic expressions for the transition probabilities for any model if we assume a constant Ricci scalar; this assumption has been considered in previous studies, in the Euclidean approach, from symmetry arguments. On the other hand, we also obtain explicit solutions without this assumption for power-law $f(R)=R^{1+n}$ models. Moreover, in the positive curvature scenario, we obtain that the assumption of a constant Ricci scalar is not consistent, but we are able to find analytical solutions in approximated regimes. In all cases we have found that the general behavior of the probabilities already found for Einstein Gravity is preserved, including the prediction of a non-singular initial state due to quantum corrections, even though the probabilities increase or decrease in a model dependent way.

gr-qc↗

arXiv2024

Effects of quantum corrections to Lorentzian vacuum transitions in the presence of gravity

We present a study of the vacuum transition probabilities taking into account quantum corrections. We first introduce a general method that expands previous works employing the Lorentzian formalism of the Wheeler-De Witt equation by considering higher order terms in the semiclassical expansion. The method presented is applicable in principle to any model in the minisuperspace and up to any desired order in the quantum correction terms. Then, we apply this method to obtain analytical solutions for the probabilities up to second quantum corrections for homogeneous isotropic and anisotropic universes. We use the Friedmann-Lemaitre-Robertson-Walker metric with positive and zero curvature for the isotropic case and the Bianchi III and Kantowski-Sachs metrics for the anisotropic case. Interpreting the results as distribution probabilities of creating universes by vacuum decay with a given size, we found that the general behaviour is that considering up to the second quantum correction leads to an avoidance of the initial singularity. However, we show that this result can only be achieved for the isotropic universe. Furthermore, we also study the effect of anisotropy on the transition probabilities.

gr-qc↗