arXiv subjects

A. Navarro

Publications and source records attributed to A. Navarro.

12 recordsLinked to original sources

arXiv2024

On the impact of VR/AR applications on optical transport networks: First experiments with Meta Quest 3 gaming and conferencing application

With the advent of next-generation AR/VR headsets, many of them with affordable prices, telecom operators have forecasted an explosive growth of traffic in their networks. Penetration of AR/VR services and applications is estimated to grow exponentially in the next few years. This work attempts to shed light on the bandwidth capacity requirements and latency of popular AR/VR applications with four different real experimental settings on the Meta Quest 3 headsets, and their potential impact on the network.

cs.NI↗

arXiv2024

The OBDT-theta board: time digitization for the theta view of Drift Tubes chambers

We present the design and performance of the On-Board electronics for the Drift Tubes (OBDT) for the superlayer theta along the direction parallel to the beam-line, the new board built to substitute part of the CMS DT Muon on-detector electronics. The OBDT-theta is responsible for the time digitization of the DT chamber signals for the theta view, allowing further tracking and triggering of the barrel muons. It is also in charge of part of the slow-control of the DT chamber inner electronics in the theta view. Prototypes of the OBDT-theta board are under validation in different laboratories in CERN, as well as in demonstrator chambers installed in the CMS experiment. This allows evaluation of the full functionality of the boards in real conditions, showing very satisfactory results.

hep-ex↗

arXiv2023

Mancha3D code: Multi-purpose Advanced Non-ideal MHD Code for High resolution simulations in Astrophysics

The Mancha3D code is a versatile tool for numerical simulations of magnetohydrodynamic processes in solar/stellar atmospheres. The code includes non-ideal physics derived from plasma partial ionization, a realistic equation of state and radiative transfer, which allows performing high quality realistic simulations of magneto-convection, as well as idealized simulations of particular processes, such as wave propagation, instabilities or energetic events. The paper summarizes the equations and methods used in the Mancha3D code. It also describes its numerical stability and parallel performance and efficiency. The code is based on a finite difference discretization and memory-saving Runge-Kutta (RK) scheme. It handles non-ideal effects through super-time stepping and Hall diffusion schemes, and takes into account thermal conduction by solving an additional hyperbolic equation for the heat flux. The code is easily configurable to perform different kinds of simulations. Several examples of the code usage are given. It is demonstrated that splitting variables into equilibrium and perturbation parts is essential for simulations of wave propagation in a static background. A perfectly matched layer (PML) boundary condition built into the code greatly facilitates a non-reflective open boundary implementation. Spatial filtering is an important numerical remedy to eliminate grid-size perturbations enhancing the code stability. Parallel performance analysis reveals that the code is strongly memory bound, which is a natural consequence of the numerical techniques used, such as split variables and PML boundary conditions. Both strong and weak scalings show adequate performance up till several thousands of CPUs.

astro-ph.SR↗

arXiv2022

The Riemann-Roch theorem for the Adams operations

We prove the classical Riemann-Roch theorems for the Adams operations $\,ψ^j\,$ on $K$-theory: a statement with coefficients on $\mathbb{Z}[j^{-1}]$, that holds for arbitrary projective morphisms, as well as another one with integral coefficients, that is valid for closed immersions. In presence of rational coefficients, we also analyze the relation between the corresponding Riemann-Roch formula for one Adams operation and the analogous formula for the Chern character. To do so, we complete the elementary exposition of the work of Panin-Smirnov that was initiated by the first author in a previous work. Their notion of oriented cohomology theory of algebraic varieties allows to use classical arguments to prove general and neat statements, which imply all the aforementioned results as particular cases.

math.KT↗

arXiv2022

Dark Energy Survey Year 3 results: cosmology with moments of weak lensing mass maps

We present a cosmological analysis using the second and third moments of the weak lensing mass (convergence) maps from the first three years of data (Y3) data of the Dark Energy Survey (DES). The survey spans an effective area of 4139 square degrees and uses the images of over 100 million galaxies to reconstruct the convergence field. The second moment of the convergence as a function of smoothing scale contains information similar to standard shear 2-point statistics. The third moment, or the skewness, contains additional non-Gaussian information. The data is analysed in the context of the $Λ$CDM model, varying 5 cosmological parameters and 19 nuisance parameters modelling astrophysical and measurement systematics. Our modelling of the observables is completely analytical, and has been tested with simulations in our previous methodology study. We obtain a 1.7\% measurement of the amplitude of fluctuations parameter $S_8\equiv σ_8 (Ω_m/0.3)^{0.5} = 0.784\pm 0.013$. The measurements are shown to be internally consistent across redshift bins, angular scales, and between second and third moments. In particular, the measured third moment is consistent with the expectation of gravitational clustering under the $Λ$CDM model. The addition of the third moment improves the constraints on $S_8$ and $Ω_{\rm m}$ by $\sim$15\% and $\sim$25\% compared to an analysis that only uses second moments. We compare our results with {\it Planck} constraints from the Cosmic Microwave Background (CMB), finding a $2.2$ \textendash $2.8σ$ tension in the full parameter space, depending on the combination of moments considered. The third moment independently is in $2.8σ$ tension with {\it Planck}, and thus provides a cross-check on analyses of 2-point correlations.

astro-ph.CO↗

arXiv2020

The large Trans-Neptunian Object 2002 TC$_{302}$ from combined stellar occultation, photometry and astrometry data

On 28th January 2018, the large Trans-Neptunian Object (TNO) 2002TC302 occulted a m$_v= $15.3 star with ID 130957813463146112 in the Gaia DR2 stellar catalog. 12 positive occultation chords were obtained from Italy, France, Slovenia and Switzerland. Also, 4 negative detections were obtained near the north and south limbs. This represents the best observed stellar occultation by a TNO other than Pluto, in terms of the number of chords published thus far. From the 12 chords, an accurate elliptical fit to the instantaneous projection of the body, compatible with the near misses, can be obtained. The resulting ellipse has major and minor axes of 543 $\pm$ 18 km and 460 $\pm$ 11 km, respectively, with a position angle of 3 $\pm$ 1 degrees for the minor axis. This information, combined with rotational light curves obtained with the 1.5m telescope at Sierra Nevada Observatory and the 1.23m telescope at Calar Alto observatory, allows us to derive possible 3D shapes and density estimations for the body, based on hydrostatic equilibrium assumptions. The effective area equivalent diameter is $\sim$ 84 km smaller than the radiometrically derived diameter using thermal data from Herschel and Spitzer Space Telescopes. This might indicate the existence of an unresolved satellite of up to $\sim$ 300 km in diameter, to account for all the thermal flux, although the occultation and thermal diameters are compatible within their error bars given the considerable uncertainty of the thermal results. The existence of a potential satellite also appears to be consistent with other ground-based data presented here. From the effective occultation diameter combined with H$_V$ measurements we derive a geometric albedo of 0.147 $\pm$ 0.005, which would be somewhat smaller if 2002TC302 has a satellite. The best occultation light curves do not show any signs of ring features or any signatures of a global atmosphere.

astro-ph.EP↗

arXiv2017

On the Riemann-Roch formula without projective hypothesis

Let $S$ be a finite dimensional noetherian scheme. For any proper morphism between smooth $S$-schemes, we prove a Riemann-Roch formula relating higher algebraic $K$-theory and motivic cohomology, thus with no projective hypothesis neither on the schemes nor on the morphism. We also prove, without projective assumptions, an arithmetic Riemann-Roch theorem involving Arakelov's higher $K$-theory and motivic cohomology as well as an analogue result for the relative cohomology of a morphism. These results are obtained as corollaries of a motivic statement that is valid for morphisms between oriented absolute spectra in the stable homotopy category of $S$.

math.AT↗

arXiv2015

On the uniqueness of the Gauss-Bonnet-Chern formula (after Gilkey-Park-Sekigawa)

On an oriented Riemannian manifold, the Gauss-Bonnet-Chern formula asserts that the Pfaffian of the metric represents, in de Rham cohomology, the Euler class of the tangent bundle. Hence, if the underlying manifold is compact, the integral of the Pfaffian is a topological invariant; namely, the Euler characteristic of the manifold. In this paper we refine a result originally due to Gilkey that characterizes this formula as the only (non-trivial) integral of a differential invariant that is independent of the underlying metric.

math.DG↗

arXiv2002

Effective Hamiltonians in quantum optics: a systematic approach

We discuss a general and systematic method for obtaining effective Hamiltonians that describe different nonlinear optical processes. The method exploits the existence of a nonlinear deformation of the usual su(2) algebra that arises as the dynamical symmetry of the original model. When some physical parameter, dictated by the process under consideration, becomes small, we immediately get a diagonal effective Hamiltonian that correctly represents the dynamics for arbitrary states and long times. We extend the technique to su(3) and su(N), finding the corresponding effective Hamiltonians when some resonance conditions are fulfilled.

quant-ph↗

arXiv2002

Convergence of Scalar-Tensor theories toward General Relativity and Primordial Nucleosynthesis

In this paper, we analyze the conditions for convergence toward General Relativity of scalar-tensor gravity theories defined by an arbitrary coupling function $α$ (in the Einstein frame). We show that, in general, the evolution of the scalar field $(ϕ)$ is governed by two opposite mechanisms: an attraction mechanism which tends to drive scalar-tensor models toward Einstein's theory, and a repulsion mechanism which has the contrary effect. The attraction mechanism dominates the recent epochs of the universe evolution if, and only if, the scalar field and its derivative satisfy certain boundary conditions. Since these conditions for convergence toward general relativity depend on the particular scalar-tensor theory used to describe the universe evolution, the nucleosynthesis bounds on the present value of the coupling function, $α_0$, strongly differ from some theories to others. For example, in theories defined by $α\propto \midϕ\mid$ analytical estimates lead to very stringent nucleosynthesis bounds on $α_0$ ($\lesssim 10^{-19}$). By contrast, in scalar-tensor theories defined by $α\propto ϕ$ much larger limits on $α_0$ ($\lesssim 10^{-7}$) are found.

gr-qc↗

arXiv2001

Lie-type transformations and effective Hamiltonians in nonlinear quantum optics: applications to multilevel systems

We reelaborate on a general method for diagonalizing a wide class of nonlinear Hamiltonians describing different quantum optical models. This method makes use of a nonlinear deformation of the usual su(2) algebra and when some physical parameter, dictated by the particular model under consideration, becomes small, it gives a diagonal effective Hamiltonian that describes correctly the dynamics for arbitrary states and long times. We extend the technique to $N$-level atomic systems interacting with quantum fields, finding the corresponding effective Hamiltonians when the condition of $k$-photon resonance is fulfilled.

quant-ph↗

arXiv1999

Asymptotic and Exact Solutions of Perfect-Fluid Scalar-Tensor Cosmologies

We present a method which enables exact solutions to be found for at homogeneous and isotropic scalar-tensor cosmologies with an arbitrary $ω(Φ)$ function and satisfying the general perfect fluid state equation $P=(γ-1)ρc^2$. This method has been used to analyze a wide range of asymptotic analytical solutions at early and late times for different epochs in the cosmic history: false vacuum inflationary models, vacuum and radiation-dominated models, and matter-dominated models. We also describe the qualitative behavior of models at intermediary times and give exact solutions at any time for some particular scalar-tensor theories.

astro-ph↗