arXiv subjects

Claudia Moreno

Publications and source records attributed to Claudia Moreno.

At least 37 records · Page 2Linked to original sources

arXiv2023

Characterizing the gravitational wave temporal evolution of the gmode fundamental resonant frequency for a core collapse supernova: A neural network approach

We present a methodology based on the implementation of a fully connected neural network to estimate the gravitational wave (GW) temporal evolution of the gmode fundamental resonant frequency for a Core Collapse Supernova (CCSN). To perform the estimation, we construct a training data set, using synthetic waveforms, that serves to train the ML algorithm, and then use several CCSN waveforms to test the model. According to the results obtained from the implementation of our model, we provide numerical evidence to support the classification of progenitors according to their degree of rotation. The relative error associated with the estimate of the slope of the resonant frequency versus time for the GW from CCSN signals is within $13\%$ for the tested candidates included in this study. This method of classification does not require priors or templates, it is based on physical modelling, and can be combined with studies that classify the progenitor with other physical features.

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arXiv2023

Determination of the angular momentum of the Kerr black hole from equatorial geodesic motion

We present a method to determine the angular momentum of a black hole, based on observations of the trajectories of the bodies in the Kerr space-time. We use the Hamilton equations to describe the dynamics of a particle and present results for equatorial trajectories, obtaining an algebraic equation for the magnitude of the black hole's angular momentum. We tailor a numerical code to solve the dynamical equations and use it to generate synthetic data. We apply the method in some representative examples, obtaining the parameters of the trajectories as well as the black hole's angular momentum in good agreement with the input data.

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arXiv2023

A search for distinctive footprints of compact binary coalescence within alternatives theories of gravity

In this review we examine the amplitude intensity associated to tensorial and non-tensorial polarization modes generated by binary systems at their inspiral stage, within the alternative theories of gravity of Brans Dicke, Rosen, and Lightman Lee. This study is performed without making an explicit use of the Transverse Traceless gauge of the General Relativity approach, and at the Newtonian limit. Consequently such additional polarization modes appear (non-tensorial) due to additional degrees of freedom in modified theories of gravitation. We model and compare the different polarization modes and strain signals for each scheme varying the sky location. Our analysis allows us to identify the locations where these modes are more intense, and, therefore susceptible to being identified for the future interferometer detector network. This gives rise to a framework in which the amplitude and the intensity of all polarization modes of general relativity and alternative hypotheses can be compared.

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arXiv2023

Emission of spacetime waves from the partial collapse of a compact object

In this work we describe the partial collapse of a compact object and the emission of spacetime waves as a result of back-reaction effects. As a source mass term we propose a non-smooth continuous function that describes a mass-loss, and we then obtain the solution of such setting. We present three distinct examples of the evolution of the norm $|R_{nl}(t,r_{*})|$ in terms of $t$, and four different results are shown for the parameter $l=1,2,5,10$; here $r_{*}$ is the fixed radius of an observer outside the compact object. In all cases, the decay behaviour is actually present at $t\gg 1$ and becomes more evident for larger $l$. In addition, for the results that have smaller $l$'s their amplitudes are larger when the asymptotic character of $|R_{nl}(t,r_{*})|$ clearly appears. Finally, the farther away an observer is set, the fewer oscillations are perceived; however, from our particular fixed set of parameters, the best spot to observe the wiggles of the emitted spacetime waves is close to $r_{*}\simeq α$.

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arXiv2022

Cosmological Boundary Flux Parameter

The {\it{Cosmological Boundary Flux Parameter}} is a novel proposal that attempts to explain the origin of the cosmological parameter $Λ$ purely by geometric nature. Then we implement this new approach to a flat FLRW universe along with a barotropic fluid. We present an ansatz in which $Λ$ is straightforwardly coupled to the matter sector; therefore, only one additional parameter was introduced: $λ$. Also, through a statistical analysis, using late-time data of observational Hubble and type Ia Supernovae, we computed the joint best-fit value of the free parameters by means of the affine-invariant MCMC. We want to emphasise that the joint analysis produces a smaller $H_{0}^{\rm CBFP}=69.80\rm\,\, Km \,s^{-1}\,Mpc^{-1}$ in contrast to the flat $Λ$CDM result $H_{0}^{Λ\rm CDM}=70.53\rm\,\, Km \,s^{-1}\,Mpc^{-1}$. The work presented here seeks to contribute to the discussion of the possible explanation for the cosmos' acceleration, together with tackling other important questions in modern cosmology.

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arXiv2022

Gravitational Waves from the Propagation of Long Gamma-Ray Burst jets

Gamma-ray bursts (GRBs) are produced during the propagation of ultra-relativistic jets. It is challenging to study the jet close to the central source, due to the high opacity of the medium. In this paper, we present numerical simulations of relativistic jets propagating through a massive, stripped envelope star associated to long GRBs, breaking out of the star and accelerating into the circumstellar medium. We compute the gravitational wave (GW) signal resulting from the propagation of the jet through the star and the circumstellar medium. We show that key parameters of the jet propagation can be directly determined by the GW signal. The signal presents a first peak corresponding to the jet duration and a second peak which corresponds to the break-out time for an observer located close to the jet axis (which in turn depends on the stellar size), or to much larger times (corresponding to the end of the acceleration phase) for off-axis observers. We also show that the slope of the GW signal before and around the first peak tracks the jet luminosity history and the structure of the progenitor star. The amplitude of the GW signal is $h_+D \sim$ hundreds to several thousands cm. Although this signal, for extragalactic sources, is outside the range of detectability of current GW detectors, it can be detected by future instruments as BBO, DECIGO and ALIA. Our results illustrate that future detections of GW associated to GRB jets may represent a revolution in our understanding of this phenomenon.

astro-ph.HE↗

arXiv2022

On the role of magnetic fields into the dynamics and gravitational wave emission of binary neutron stars

Modelling as a dipole the magnetic interaction of a binary system of neutron stars, we are able to include the magnetic effects in the Newtonian and in the inspiral dynamics of the system using an equivalent one-body description. Furthermore, in the inspiral stage we determine the role of the magnetic interaction in the waveforms generated by the system and obtain explicit formulas for the decrease in the separation of the stars, the time to reach a minimal radius, the gravitational luminosity and the change of gravitational wave frequency, all this within the quadrupole approximation. For the magnitude of the magnetic field that is consider to exist in these binaries $\sim 10^{16} {\rm G}$ we are able to show that its effect on the observable quantities is of the order of the 2PN correction, already close to the detection range of the gravitational waves observatories. %} We also discuss cases in which the magnetic field could have a more significant influence.

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arXiv2021

Using supervised learning algorithms as a follow-up method in the search of gravitational waves from core-collapse supernovae

We present a follow-up method based on supervised machine learning (ML) to improve the performance in the search of gravitational wave (GW) burts from core-collapse supernovae (CCSNe) using the coherent WaveBurst (cWB) pipeline. The ML model discriminates noise from signal events using as features a set of reconstruction parameters provided by cWB. Detected noise events are discarded yielding to a reduction of the false alarm rate (FAR) and of the false alarm probability (FAP) thus enhancing of the statistical significance. We tested the proposed method using strain data from the first half of the third observing run of advanced LIGO, and CCSNe GW signals extracted from 3D simulations. The ML model is learned using a dataset of noise and signal events, and then it is used to identify and discard noise events in cWB analyses. Noise and signal reduction levels were examined in single detector networks (L1 and H1) and two detector network (L1H1). The FAR was reduced by a factor of $\sim10$ to $\sim100$, there was an enhancement in the statistical significance of $\sim1$ to $\sim2σ$, while there was no impact in detection efficiencies.

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arXiv2021

Space-time waves from a collapsing universe with a gravitational attractor

We study a collapsing system attracted by a spherically symmetric gravitational source, with an increasing mass, that generates back-reaction effects that are the source of space-time waves. As an example, we consider an exponential collapse and the space-time waves emitted during this collapse due to the back-reaction effects, originated by geometrical deformation driven by the increment of the gravitational attracting mass during the collapse.

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arXiv2021

Gravitational and electromagnetic perturbations of a charged black hole in a general gauge condition

We derive a set of coupled equations for the gravitational and electromagnetic perturbation in the Reissner-Nordström geometry using the Newman Penrose formalism. We show that the information of the physical gravitational signal is contained in the Weyl scalar function $Ψ_4$, as is well known, but for the electromagnetic signal the information is encoded in the function $χ$ which relates the perturbations of the radiative Maxwell scalars $φ_2$ and the Weyl scalar $Ψ_3$. In deriving the perturbation equations we do not impose any gauge condition and our analysis contains as a limiting case the results obtained previously for instance in Chandrashekhar's book. In our analysis, we also include the sources for the perturbations and focus on a dust-like charged fluid distribution falling radially into the black hole. Finally, by writing the functions on a basis of spin weighted spherical harmonics and the Reissner-Nordström spacetime in Kerr-Schild type coordinates a hyperbolic system of coupled partial differential equations is presented and numerically solved. In this way, we solve completely a system which generates a gravitational signal as well as an electromagnetic/gravitational one, which sets the basis to find correlations between them and thus facilitating the gravitational wave detection via the electromagnetic signal.

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arXiv2021

Detecting and reconstructing gravitational waves from the next Galactic core-collapse supernova in the Advanced Detector Era

We performed a detailed analysis of the detectability of a wide range of gravitational waves derived from core-collapse supernova simulations using gravitational-wave detector noise scaled to the sensitivity of the upcoming fourth and fifth observing runs of the Advanced LIGO, Advanced Virgo, and KAGRA. We use the coherent WaveBurst algorithm, which was used in the previous observing runs to search for gravitational waves from core-collapse supernovae. As coherent WaveBurst makes minimal assumptions on the morphology of a gravitational-wave signal, it can play an important role in the first detection of gravitational waves from an event in the Milky Way. We predict that signals from neutrino-driven explosions could be detected up to an average distance of 10 kpc, and distances of over 100 kpc can be reached for explosions of rapidly rotating progenitor stars. An estimated minimum signal-to-noise ratio of 10-25 is needed for the signals to be detected. We quantify the accuracy of the waveforms reconstructed with coherent WaveBurst and we determine that the most challenging signals to reconstruct are those produced in long-duration neutrino-driven explosions and models that form black holes a few seconds after the core bounce.

astro-ph.HE↗

arXiv2020

Deep learning for gravitational-wave data analysis: A resampling white-box approach

In this work, we apply Convolutional Neural Networks (CNNs) to detect gravitational wave (GW) signals of compact binary coalescences, using single-interferometer data from LIGO detectors. As novel contribution, we adopted a resampling white-box approach to advance towards a statistical understanding of uncertainties intrinsic to CNNs in GW data analysis. Resampling is performed by repeated $k$-fold cross-validation experiments, and for a white-box approach, behavior of CNNs is mathematically described in detail. Through a Morlet wavelet transform, strain time series are converted to time-frequency images, which in turn are reduced before generating input datasets. Moreover, to reproduce more realistic experimental conditions, we worked only with data of non-Gaussian noise and hardware injections, removing freedom to set signal-to-noise ratio (SNR) values in GW templates by hand. After hyperparameter adjustments, we found that resampling smooths stochasticity of mini-batch stochastic gradient descend by reducing mean accuracy perturbations in a factor of $3.6$. CNNs were quite precise to detect noise but not sensitive enough to recall GW signals, meaning that CNNs are better for noise reduction than generation of GW triggers. However, applying a post-analysis, we found that for GW signals of SNR $\geq 21.80$ with H1 data and SNR $\geq 26.80$ with L1 data, CNNs could remain as tentative alternatives for detecting GW signals. Besides, with receiving operating characteristic curves we found that CNNs show much better performances than those of Naive Bayes and Support Vector Machines models and, with a significance level of $5\%$, we estimated that predictions of CNNs are significant different from those of a random classifier. Finally, we elucidated that performance of CNNs is highly class dependent because of the distribution of probabilistic scores outputted by the softmax layer.

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arXiv2019

Space-time waves from a collapse with a time dependent cosmological parameter

We study the emission of space-time waves produced by back-reaction effects during a collapse of a spherically symmetric universe with a time dependent cosmological parameter, which is driven by a scalar field. As in a previous work the final state avoids the final singularity due to the fact the co-moving relativistic observer never reaches the center, because the physical time evolution $dτ=U_{0}\,dx^0$, decelerates for a co-moving observer which falls with the collapse. The equation of state of the system depends on the rate of the collapse, but always is positive: $0 < ω(p) < 0.25$.

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arXiv2019

Enabling real-time multi-messenger astrophysics discoveries with deep learning

Multi-messenger astrophysics is a fast-growing, interdisciplinary field that combines data, which vary in volume and speed of data processing, from many different instruments that probe the Universe using different cosmic messengers: electromagnetic waves, cosmic rays, gravitational waves and neutrinos. In this Expert Recommendation, we review the key challenges of real-time observations of gravitational wave sources and their electromagnetic and astroparticle counterparts, and make a number of recommendations to maximize their potential for scientific discovery. These recommendations refer to the design of scalable and computationally efficient machine learning algorithms; the cyber-infrastructure to numerically simulate astrophysical sources, and to process and interpret multi-messenger astrophysics data; the management of gravitational wave detections to trigger real-time alerts for electromagnetic and astroparticle follow-ups; a vision to harness future developments of machine learning and cyber-infrastructure resources to cope with the big-data requirements; and the need to build a community of experts to realize the goals of multi-messenger astrophysics.

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arXiv2019

Exponential collapse with variable time scale driven by a scalar field

We study the dynamic collapse driven by a scalar field, when a relativistic observer falls co-moving with the collapse and cross the horizon of a Schwarzschild black-hole (BH), at $t=t_0$. During the collapse the scale of time is considered as variable. Back-reaction effects and gravitational waves produced during the exponential collapse are studied. We demonstrate that back-reaction effects act as the source of gravitational waves emitted during the collapse, and wavelengths of gravitational waves (GW) are in the range: $λ\ll r_s\equiv {e^{-2h_0t_0}\over 2 h_0}$, that is, smaller than the Schwarzschild radius. We demonstrate that during all the collapse the global topology of the space-time remains hyperbolic when the observer cross the horizon.

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arXiv2018

Collapse driven by a scalar field without final singularity

We explore a collapsing cosmology driven by a scalar field which is minimally coupled to gravity in a spatially at and spherically symmetric, isotropic and homogeneous space-time, with a variable timescale that avoids the final singularity. The equation of state that describes the collapse is $ω=1$. We calculate the back-reaction of the space-time during the collapse and the energy density fluctuations related to this back-reaction has a spectral index $n_s = 0$, favouring short-wavelengths modes to be detected. The interesting is that the amplitude of these fluctuations increase with time when the collapse is sufficiently strong.

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arXiv2018

An independent search of gravitational waves in the first observation run of advanced LIGO using cross-correlation

This work describes a template-free method to search gravitational waves (GW) using data from the LIGO observatories simultaneously. The basic idea of this method is that a GW signal is present in a short-duration data segment if the maximum correlation-coefficient between the strain signals is higher than a significant threshold and its time difference is lower than the 10 ms of inter-observatory light propagation time. Hence, this method can be used to carry out blind searches of any types of GW irrespective of the waveform and of the source type and sky location. An independent search of injected and real GW signals from compact binary coalescences (CBC) contained in the first observation run (O1) of advanced LIGO was carried out to asses its performance. On the basis of the results, the proposed method was able to detect GW produced by binary systems without making any assumption about them.

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arXiv2017

Obtaining Gravitational Waves from Inspiral Binary Systems using LIGO data

The discovery of the astrophysical events GW150926 and GW151226 has experimentally confirmed the existence of gravitational waves (GW) and has demonstrated the existence of binary stellar-mass black hole systems. This finding marks the beginning of a new era that will reveal unexpected features of our universe. This work presents a basic insight to the fundamental theory of GW emitted by inspiral binary systems and describes the scientific and technological efforts developed to measure these waves using the interferometer-based detector called LIGO. Subsequently, the work presents a comprehensive data analysis methodology based on the matched filter algorithm, which aims to recovery GW signals emitted by inspiral binary systems of astrophysical sources. This algorithm was evaluated with freely available LIGO data containing injected GW waveforms. Results of the experiments performed to assess detection accuracy showed the recovery of 85% of the injected GW.

astro-ph.IM↗