arXiv subjects

F. Rodríguez

Publications and source records attributed to F. Rodríguez.

4 recordsLinked to original sources

arXiv2023

Measuring the CMB primordial B-modes with Bolometric Interferometry

The Q&U Bolometric Interferometer for Cosmology (QUBIC) is the first bolometric interferometer designed to measure the primordial B-mode polarization of the Cosmic Microwave Background (CMB). Bolometric interferometry is a novel technique that combines the sensitivity of bolometric detectors with the control of systematic effects that is typical of interferometry, both key features in the quest for the faint signal of the primordial B-modes. A unique feature is the so-called "spectral imaging", i.e., the ability to recover the sky signal in several sub-bands within the physical band during data analysis. This feature provides an in-band spectral resolution of Δν/ν \sim 0.04 that is unattainable by a traditional imager. This is a key tool for controlling the Galactic foregrounds contamination. In this paper, we describe the principles of bolometric interferometry, the current status of the QUBIC experiment and future prospects.

astro-ph.CO↗

arXiv2022

Spectroscopy of the frustrated quantum antiferromagnet Cs$_2$CuCl$_4$

We investigate the electronic structure of Cs$_2$CuCl$_4$, a material discussed in the framework of a frustrated quantum antiferromagnet, by means of resonant inelastic x-ray scattering (RIXS) and Density Functional Theory (DFT). From the non-dispersive highly localized dd excitations, we resolve the crystal field splitting of the Cu$^{2+}$ ions in a strongly distorted tetrahedral coordination. This allows us to model the RIXS spectrum within the Crystal Field Theory (CFT), assign the dd orbital excitations and retrieve experimentally the values of the crystal field splitting parameters D$_q$, D$_s$ and D$_τ$. The electronic structure obtained ab-initio agrees with the RIXS spectrum and modelled by CFT, highlighting the potential of combined spectroscopic, cluster and DFT calculations to determine the electronic ground state of complex materials.

cond-mat.str-el↗

arXiv2022

Status of QUBIC, the Q&U Bolometer for Cosmology

The Q&U Bolometric Interferometer for Cosmology (QUBIC) is a novel kind of polarimeter optimized for the measurement of the B-mode polarization of the Cosmic Microwave Back-ground (CMB), which is one of the major challenges of observational cosmology. The signal is expected to be of the order of a few tens of nK, prone to instrumental systematic effects and polluted by various astrophysical foregrounds which can only be controlled through multichroic observations. QUBIC is designed to address these observational issues with a novel approach that combines the advantages of interferometry in terms of control of instrumental systematics with those of bolometric detectors in terms of wide-band, background-limited sensitivity.

astro-ph.IM↗

arXiv2022

Optimal Placement of Base Stations in Border Surveillance using Limited Capacity Drones

Imagine an island modeled as a simple polygon $¶$ with $n$ vertices whose coastline we wish to monitor. We consider the problem of building the minimum number of refueling stations along the boundary of $¶$ in such a way that a drone can follow a polygonal route enclosing the island without running out of fuel. A drone can fly a maximum distance $d$ between consecutive stations and is restricted to move either along the boundary of $¶$ or its exterior (i.e., over water). We present an algorithm that, given $\mathcal P$, finds the locations for a set of refueling stations whose cardinality is at most the optimal plus one. The time complexity of this algorithm is $O(n^2 + \frac{L}{d} n)$, where $L$ is the length of $\mathcal P$. We also present an algorithm that returns an additive $ε$-approximation for the problem of minimizing the fuel capacity required for the drones when we are allowed to place $k$ base stations around the boundary of the island; this algorithm also finds the locations of these refueling stations. Finally, we propose a practical discretization heuristic which, under certain conditions, can be used to certify optimality of the results.

cs.CG↗