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Bulletin ICRANet
Décembre 2021 - Janvier 2022
Décembre 2021 - Janvier 2022
RÉSUMÉ
1. Deep Learning in Searching the Spectroscopic Redshift of Quasars
2. 4ème Symposium International LeCosPA, meeting virtuel, 29 Novembre - 3 Décembre 2021
3. Éclipse antarctique et transits méridien, meeting virtuel, 4 Décembre 2021
4. Meeting Amati Fest, 6-7 Décembre 2021
5. Visites scientifiques auprès du centre ICRANet
6. Publications récentes
1. Deep Learning in Searching the Spectroscopic Redshift of Quasars
2. 4ème Symposium International LeCosPA, meeting virtuel, 29 Novembre - 3 Décembre 2021
3. Éclipse antarctique et transits méridien, meeting virtuel, 4 Décembre 2021
4. Meeting Amati Fest, 6-7 Décembre 2021
5. Visites scientifiques auprès du centre ICRANet
6. Publications récentes
1. Deep Learning in Searching the Spectroscopic Redshift of Quasars
The new work co-authored by ICRANet scientists is published by MNRAS on January 19, 2022
Fig. 1. The chosen architecture of 1-dimensional of FNet to learn higher-order features hidden in the input flux. It slides the flux via convolutional layers of kernel size = 500, 200 and 15, respectively to search for the "global" and "local" patterns in the flux of quasars. The fully connected layers output the redshift. Left: The structure of a residual block, the input x goes through two convolutional layers as H(x) then add itself as H(x)+x, batch normalization is applied after each convolutional layer, and the activation function ReLU acts on the first batch normalization layer. Right: The entire structure: The flux goes through 24 residual blocks, the first 21 blocks have channel size 32, followed by three blocks of channel size 64, 32 and 16 respectively. The output of blocks then is flattened and passes three fully convolutional layers and eventually outputs the redshift. The rectified linear unit (ReLU) is applied after each fully connected layer.
Quasi-stellar radio sources (Quasars) are high-luminosity active galactic nuclei (AGN). There is a broad consensus that quasars are powered by a gaseous accretion disk around a supermassive black hole (SMBH) of ~106 - 109 solar mass. Because of their high luminosity, quasars have been observed up to redshifts z~8 when the universe formed its first structures, i.e., in the reionization epoch. It makes quasars a powerful tool to study the cosmic history and structure formation in the early universe and, specifically, probe the physics governing the SMBHs and their surrounding accretion disk, as the rapid growth of SMBHs occurs at redshifts z = 5-10. Regarding their existence in a wide range of redshifts, quasars, as the cosmology’s standard candle, can also be utilized to put more constraints on the cosmological parameters.
On the one hand, the massive volume of data of astrophysical surveys makes the procedure for visual inspection of each spectrum to classify and determine the redshift highly time-consuming. For example, the Sloan Digital Sky Survey IV (SDSS-IV) quasar catalog from Data Release 16 (DR16) of the extended Baryon Oscillation Spectroscopic Survey (eBOSS), includes a "superset" of objects labelled as quasars containing 1440615 spectra.
On the other hand, the adapted automatic methods, that operate based on comparing each spectrum with a dataset of spectra, usually perform worse than visual inspection methods in classification tasks. Thus, implementing automated strategies with human–expert precision is of great importance.
Fig. 2. The accuracy of prediction vs. Δð. The red solid line and black dashed line represent the accuracy of the FNet and QuasarNE, respectively, for DR16Q sample. The blue solid line and grey dashed line represent the accuracy of the FNet and QuasarNET, respectively, for DR16Q sample when DR12Q is excluded. The green dashed lines shows the accuracy of FNet for 5,190 visually inspected sources in DR16Q when QuasarNET fails to estimate.
Over the last few years, machine learning (ML) and deep learning (DL) algorithms have become increasingly popular in astronomy and astrophysics. They are using various recognition patterns and are able to identify the spectral features of astrophysical objects such as emission/absorption lines, spectral breaks, and flux correlations, and perform the classification and redshift determination as accurate as the visual inspection.
With the goal to estimate the redshift of quasars in Sloan Digital Sky Survey IV (SDSS-IV) catalog from DR16 quasar-only (DR16Q) of eBOSS on a broad range of signal-to-noise ratios, the group of researchers which includes ICRANet scientists has developed a new tool, the FNet. FNet is a 1–dimensional convolutional neural network (CNN) with a residual neural network (ResNet) structure. This network has 24 convolutional layers and the ResNet structure with different kernel sizes of 500, 200, and 15, which makes it to discover the "local" and "global" patterns, as well as correlations of fluxes in a different wavelength, in the whole sample of spectra by a self-learning procedure; see Fig. 1. It reaches the accuracy of 97.0 % for the velocity difference for redshift, | Δð |< 6000 km/s and 98.0% for | Δð | <12000 km/s. Here Δð = c (Z-Z_VI)/(1+ZVI) is the velocity difference from redshift, c is the speed of light, Z_VI is the redshift from the visually inspected quasar sample, and Z is the predicted redshift.
While QuasarNET, which is a standard CNN adopted in the SDSS routine and is constructed by 4 convolutional layers (no ResNet structure), with kernel sizes of 10, to measure the redshift via identifying seven emission lines (local patterns), fails in estimating redshift of ∼ 1.3% of visually inspected quasars in DR16Q catalog, and it gives 97.8% for | Δð |< 6000 km/s and 97.9 % for | Δð |< 12000 km/s; see Fig 2. FNet is applicable for a wider range of SDSS spectra, especially for those missing the clear emission lines, which is necessary for other standard methods to work. These properties of FNet, together with the fast predictive power of machine learning, allow it to be a more accurate alternative for the pipeline redshift estimator and can make it practical in the upcoming catalogs to reduce the number of spectra to inspect visually.
The paper by F. Rastegar Nia, M. T. Mirtorabi, R. Moradi, A. Vafaei. Sadr, Y. Wang «Deep learning in searching the spectroscopic redshift of quasars» is published in Monthly Notices of the Royal Astronomical Society on 19 January 2022.
Link: https://doi.org/10.1093/mnras/stac076
Fig. 1. The chosen architecture of 1-dimensional of FNet to learn higher-order features hidden in the input flux. It slides the flux via convolutional layers of kernel size = 500, 200 and 15, respectively to search for the "global" and "local" patterns in the flux of quasars. The fully connected layers output the redshift. Left: The structure of a residual block, the input x goes through two convolutional layers as H(x) then add itself as H(x)+x, batch normalization is applied after each convolutional layer, and the activation function ReLU acts on the first batch normalization layer. Right: The entire structure: The flux goes through 24 residual blocks, the first 21 blocks have channel size 32, followed by three blocks of channel size 64, 32 and 16 respectively. The output of blocks then is flattened and passes three fully convolutional layers and eventually outputs the redshift. The rectified linear unit (ReLU) is applied after each fully connected layer.
Quasi-stellar radio sources (Quasars) are high-luminosity active galactic nuclei (AGN). There is a broad consensus that quasars are powered by a gaseous accretion disk around a supermassive black hole (SMBH) of ~106 - 109 solar mass. Because of their high luminosity, quasars have been observed up to redshifts z~8 when the universe formed its first structures, i.e., in the reionization epoch. It makes quasars a powerful tool to study the cosmic history and structure formation in the early universe and, specifically, probe the physics governing the SMBHs and their surrounding accretion disk, as the rapid growth of SMBHs occurs at redshifts z = 5-10. Regarding their existence in a wide range of redshifts, quasars, as the cosmology’s standard candle, can also be utilized to put more constraints on the cosmological parameters.
On the one hand, the massive volume of data of astrophysical surveys makes the procedure for visual inspection of each spectrum to classify and determine the redshift highly time-consuming. For example, the Sloan Digital Sky Survey IV (SDSS-IV) quasar catalog from Data Release 16 (DR16) of the extended Baryon Oscillation Spectroscopic Survey (eBOSS), includes a "superset" of objects labelled as quasars containing 1440615 spectra.
On the other hand, the adapted automatic methods, that operate based on comparing each spectrum with a dataset of spectra, usually perform worse than visual inspection methods in classification tasks. Thus, implementing automated strategies with human–expert precision is of great importance.
Fig. 2. The accuracy of prediction vs. Δð. The red solid line and black dashed line represent the accuracy of the FNet and QuasarNE, respectively, for DR16Q sample. The blue solid line and grey dashed line represent the accuracy of the FNet and QuasarNET, respectively, for DR16Q sample when DR12Q is excluded. The green dashed lines shows the accuracy of FNet for 5,190 visually inspected sources in DR16Q when QuasarNET fails to estimate.
Over the last few years, machine learning (ML) and deep learning (DL) algorithms have become increasingly popular in astronomy and astrophysics. They are using various recognition patterns and are able to identify the spectral features of astrophysical objects such as emission/absorption lines, spectral breaks, and flux correlations, and perform the classification and redshift determination as accurate as the visual inspection.
With the goal to estimate the redshift of quasars in Sloan Digital Sky Survey IV (SDSS-IV) catalog from DR16 quasar-only (DR16Q) of eBOSS on a broad range of signal-to-noise ratios, the group of researchers which includes ICRANet scientists has developed a new tool, the FNet. FNet is a 1–dimensional convolutional neural network (CNN) with a residual neural network (ResNet) structure. This network has 24 convolutional layers and the ResNet structure with different kernel sizes of 500, 200, and 15, which makes it to discover the "local" and "global" patterns, as well as correlations of fluxes in a different wavelength, in the whole sample of spectra by a self-learning procedure; see Fig. 1. It reaches the accuracy of 97.0 % for the velocity difference for redshift, | Δð |< 6000 km/s and 98.0% for | Δð | <12000 km/s. Here Δð = c (Z-Z_VI)/(1+ZVI) is the velocity difference from redshift, c is the speed of light, Z_VI is the redshift from the visually inspected quasar sample, and Z is the predicted redshift.
While QuasarNET, which is a standard CNN adopted in the SDSS routine and is constructed by 4 convolutional layers (no ResNet structure), with kernel sizes of 10, to measure the redshift via identifying seven emission lines (local patterns), fails in estimating redshift of ∼ 1.3% of visually inspected quasars in DR16Q catalog, and it gives 97.8% for | Δð |< 6000 km/s and 97.9 % for | Δð |< 12000 km/s; see Fig 2. FNet is applicable for a wider range of SDSS spectra, especially for those missing the clear emission lines, which is necessary for other standard methods to work. These properties of FNet, together with the fast predictive power of machine learning, allow it to be a more accurate alternative for the pipeline redshift estimator and can make it practical in the upcoming catalogs to reduce the number of spectra to inspect visually.
The paper by F. Rastegar Nia, M. T. Mirtorabi, R. Moradi, A. Vafaei. Sadr, Y. Wang «Deep learning in searching the spectroscopic redshift of quasars» is published in Monthly Notices of the Royal Astronomical Society on 19 January 2022.
Link: https://doi.org/10.1093/mnras/stac076
2. 4ème Symposium International LeCosPA, meeting vistuel, 29 Novembre - 3 Décembre 2021
Le 4ème Symposium International "LeCosPA 4th International Symposium, Unity of Physics - From Plasma Wakefields to Black Holes" s'est tenu auprès de l'Université Nationale de Taiwan et en ligne du 29 Novembre au 3 Décembre 2021. Pendant cette rencontre, beaucoup de sujets intéressants ont été discutés, tells que la lumière extrême, la science des hautes énergies et le plasma Wakefields, l'univers primitif et celui final, l'astrophysique des particules, les trous noirs, les ondes gravitationnelles et les tests sur la gravité modifié, le Paradoxe de l'information et le trou noir analogique.
Le 2 Décembre 2021, le Prof. Ruffini, Directeur d'ICRANet, a présenté sa conférence intitulé "What is the role of the rotational energy extraction from Black Holes", voici l'abstract:
We have demonstrated that the inner engine of GRBs and AGN produces high-energy emission by synchrotron radiation of electrons/protons that are accelerated in the rotating BH vicinity. The angular momentum of the Kerr BH and the surrounding magnetic field determine the energetics and characteristic radiation frequency, and their relative direction determines whether the motion of the electrons around the magnetic field lines follows a right-handed or a left-handed helix, and likewise the angular momentum inherited by the radiation.
Pour la vidéo YouTube de la présentation du Prof. Ruffini veuillez visiter:
https://www.youtube.com/watch?v=NaUJ7NqW3LQ
Fig. 3: Le Prof. Ruffini en train de présenter sa conférence à l'occasion du 4ème Symposium International LeCosPA, le 2 Décembre 2021.
Le 2 Décembre 2021, le Prof. Ruffini, Directeur d'ICRANet, a présenté sa conférence intitulé "What is the role of the rotational energy extraction from Black Holes", voici l'abstract:
We have demonstrated that the inner engine of GRBs and AGN produces high-energy emission by synchrotron radiation of electrons/protons that are accelerated in the rotating BH vicinity. The angular momentum of the Kerr BH and the surrounding magnetic field determine the energetics and characteristic radiation frequency, and their relative direction determines whether the motion of the electrons around the magnetic field lines follows a right-handed or a left-handed helix, and likewise the angular momentum inherited by the radiation.
Pour la vidéo YouTube de la présentation du Prof. Ruffini veuillez visiter:
https://www.youtube.com/watch?v=NaUJ7NqW3LQ
Fig. 3: Le Prof. Ruffini en train de présenter sa conférence à l'occasion du 4ème Symposium International LeCosPA, le 2 Décembre 2021.
3. Éclipse antarctique et transits au méridien, meeting virtuel, 4 Décembre 2021
Le meeting "Éclipse antarctique et transits méridien. Expérimentes de la mécanique céleste et d'astrophysique" s'est tenue en ligne le 4 Décembre 2021. Le Prof. Costantino Sigismondi, collaborateur d'ICRANet qui a présidé le meeting, a organisé cette rencontre virtuelle ainsi qu'un podcast afin de créer une occasion de débat avec les étudiants et les chercheures, grâce aussi à l'aide d'ICRANet et des autres scientifiques du monde entière.
L'éclipse total du Soleil a donné l'occasion de reconsidérer le diamètre solaire et ses mesures par la comparaison avec les éphémérides avec un diamètre standard. Le meeting est commencé le Samedi 4 Décembre à 10 heures du matin avec le discours d'ouverture par le Prof. Sigismondi. Après, on a eu des presentation par des éminents scientifiques qui portaient sur "The consultation of ephemerides", "Eclipse and timing: the measurement uncertainty and its role for the eclipse", "Meridian transits and timing", "The first results from the obelisk - meridian of Saint Peter on the transit and the solar diameter", "The entry of the Sun in Scorpio and in Sagittarius 2021 at Saint Peter, with the Sun and the stars (preliminary results and calibration of the instrument)" et "The eclipse in Antarctica and the double eclipse of the year 810 in the letter by Dungal to Charlemagne".
Cette partie théorique a été aussi intégrée avec le podcast préparé par le Prof. Sigismondi. Pour le programme de l'événement et les matériaux du podcast veuillez consulter:
http://www.icranet.org/index.php?option=com_content&task=view&id=1399
L'enregistrement du meeting est aussi disponible sur le canal YouTube d'ICRANet: https://www.youtube.com/watch?v=fLfBehXC-H4&t=696s
L'éclipse total du Soleil a donné l'occasion de reconsidérer le diamètre solaire et ses mesures par la comparaison avec les éphémérides avec un diamètre standard. Le meeting est commencé le Samedi 4 Décembre à 10 heures du matin avec le discours d'ouverture par le Prof. Sigismondi. Après, on a eu des presentation par des éminents scientifiques qui portaient sur "The consultation of ephemerides", "Eclipse and timing: the measurement uncertainty and its role for the eclipse", "Meridian transits and timing", "The first results from the obelisk - meridian of Saint Peter on the transit and the solar diameter", "The entry of the Sun in Scorpio and in Sagittarius 2021 at Saint Peter, with the Sun and the stars (preliminary results and calibration of the instrument)" et "The eclipse in Antarctica and the double eclipse of the year 810 in the letter by Dungal to Charlemagne".
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| Fig. 4: Le soleil projeté sur le méridien de Saint Pierre, 24 Novembre 2021. | Fig. 5: L'estampe de Césarienne (1521) de Vitruvius, De Architectura, Livre IX - chapitre VII, avec la phrase sur la légende de Gerbert et le trésor d' Auguste. | Fig. 6: Le Soleil au méridien de Saint Pierre, jusqu'avant l'éclipse du méridien, 26 Novembre 2021. |
Cette partie théorique a été aussi intégrée avec le podcast préparé par le Prof. Sigismondi. Pour le programme de l'événement et les matériaux du podcast veuillez consulter:
http://www.icranet.org/index.php?option=com_content&task=view&id=1399
L'enregistrement du meeting est aussi disponible sur le canal YouTube d'ICRANet: https://www.youtube.com/watch?v=fLfBehXC-H4&t=696s
4. Meeting Amati Fest, 6-7 Décembre 2021
À l'occasion des célébrations du 50ème anniversaire du livre "Introducing the Black Hole", écrit par le Prof. Remo Ruffini et par le Prof. John A. Wheeler, l'ICRANet a organisé une rencontre virtuelle pour discuter des dernières découvertes sur le Rayon Gamma et leurs "moteur intérieur". Dans ce cadre, une attention majeure a été donné à la compréhension de la relation de Amati.
Fig. 7: L'afterglow du GRB 140114C observé par la bande Radio et VHE.
Ce meeting a eu lieu auprès de l'ICRANet à Pescara (Italie) et en ligne du 6 au 7 Décembre 2021 et a été aussi diffusée dans tout le monde sur le canal YouTube de l'ICRANet. La rencontre a commencé avec les discours d'ouverture du Prof. Remo Ruffini, Directeur d'ICRANet, et du Prof. Lorenzo Amati. Pendant cette rencontre, plusieurs scientifiques et chercheurs ont participé, afin de présenter leurs résultats les plus récents: le Prof. Marco Tavani (Président de l'INAF), le Prof. Narek Sahakyan (Directeur du siège ICRANet en Arménie), le Prof. Michael Kramer (Directeur - Max-Planck-Institut für Radioastronomie), le Prof. Jorge Armando Rueda Hernandez (ICRANet, Université de Ferrara), le Prof. Carlo Luciano Bianco (ICRA, ICRANet), le Prof. Gregory Vereshchagin (ICRANet), le Prof. She Sheng Xue (ICRANet), le Prof. Carlos Raul Arguelles (ICRANet, CONICET, Universidad Nacional de La Plata), le Prof. Soroush Shakeri (ICRANet, Isfahan University of Technology), le Prof. Piero Rosati (Université de Ferrara), le Prof. Razmik Mirzoyan (Max-Planck-Institute for Physics), le Prof. Cristiano Guidorzi (Université de Ferrara), le Prof. Massimo Della Valle (ICRANet, INAF Osservatorio Astronomico di Capodimonte), le Dr Luca Izzo (Osservatorio Astronomico di Capodimonte), le Prof. Yifu Cai (University of Sciences and Technology of China), le Prof. Yefei Yuan (University of Sciences and Technology of China), le Prof. Mimoza Hafizi (University of Tirana), le Prof. Claus Lämmerzahl (ZARM University of Bremen), le Prof. Stefano Scopel (CQUeST, Sogang University), la Prof. Simonetta Filippi (ICRA, University Campus Bio-medico of Rome), le Prof. Christian Cherubini (ICRA, University Campus Bio-medico of Rome), le Prof. Stefano Ansoldi (University of Udine), le Prof. Aldo Treves (University of Insubria), le Prof. Francesco Haardt (University of Insubria), le Dr Ana Penacchioni (CONICET, Universidad Nacional de La Plata), la Dr Laura Marcela Becerra Bayona (ICRANet, Universidad Católica de Chile), le Prof. Wang Yu (ICRANet), le Prof. Liang Li (ICRANet), le Prof. Rahim Moradi (ICRANet), le Dr Yerlan Aimuratov (ICRANet, Fesenkov Astrophysical Institute), le Dr Yunlong Zheng (ICRANet, University of Sciences and Technology of China), le Eduar Antonio Becerra Vergara (ICRANet), la Dr Fatemeh Rastegar Nia (ICRANet, Alzahra University) et la Dr Sareh Eslamzadeh Askestani (University of Mazandaran).
Après toutes les présentations, on a eu un longue débat sur les données et les résultats présentés par les scientifiques invités, qui ont eu l'opportunité d'avoir des intéressants échanges d'opinion avec les autres chercheurs. La rencontre s'est terminé le 7 Décembre avec les salutations du Prof. Remo Ruffini et du Prof. Lorenzo Amati.
Fig. 7: L'afterglow du GRB 140114C observé par la bande Radio et VHE.
Ce meeting a eu lieu auprès de l'ICRANet à Pescara (Italie) et en ligne du 6 au 7 Décembre 2021 et a été aussi diffusée dans tout le monde sur le canal YouTube de l'ICRANet. La rencontre a commencé avec les discours d'ouverture du Prof. Remo Ruffini, Directeur d'ICRANet, et du Prof. Lorenzo Amati. Pendant cette rencontre, plusieurs scientifiques et chercheurs ont participé, afin de présenter leurs résultats les plus récents: le Prof. Marco Tavani (Président de l'INAF), le Prof. Narek Sahakyan (Directeur du siège ICRANet en Arménie), le Prof. Michael Kramer (Directeur - Max-Planck-Institut für Radioastronomie), le Prof. Jorge Armando Rueda Hernandez (ICRANet, Université de Ferrara), le Prof. Carlo Luciano Bianco (ICRA, ICRANet), le Prof. Gregory Vereshchagin (ICRANet), le Prof. She Sheng Xue (ICRANet), le Prof. Carlos Raul Arguelles (ICRANet, CONICET, Universidad Nacional de La Plata), le Prof. Soroush Shakeri (ICRANet, Isfahan University of Technology), le Prof. Piero Rosati (Université de Ferrara), le Prof. Razmik Mirzoyan (Max-Planck-Institute for Physics), le Prof. Cristiano Guidorzi (Université de Ferrara), le Prof. Massimo Della Valle (ICRANet, INAF Osservatorio Astronomico di Capodimonte), le Dr Luca Izzo (Osservatorio Astronomico di Capodimonte), le Prof. Yifu Cai (University of Sciences and Technology of China), le Prof. Yefei Yuan (University of Sciences and Technology of China), le Prof. Mimoza Hafizi (University of Tirana), le Prof. Claus Lämmerzahl (ZARM University of Bremen), le Prof. Stefano Scopel (CQUeST, Sogang University), la Prof. Simonetta Filippi (ICRA, University Campus Bio-medico of Rome), le Prof. Christian Cherubini (ICRA, University Campus Bio-medico of Rome), le Prof. Stefano Ansoldi (University of Udine), le Prof. Aldo Treves (University of Insubria), le Prof. Francesco Haardt (University of Insubria), le Dr Ana Penacchioni (CONICET, Universidad Nacional de La Plata), la Dr Laura Marcela Becerra Bayona (ICRANet, Universidad Católica de Chile), le Prof. Wang Yu (ICRANet), le Prof. Liang Li (ICRANet), le Prof. Rahim Moradi (ICRANet), le Dr Yerlan Aimuratov (ICRANet, Fesenkov Astrophysical Institute), le Dr Yunlong Zheng (ICRANet, University of Sciences and Technology of China), le Eduar Antonio Becerra Vergara (ICRANet), la Dr Fatemeh Rastegar Nia (ICRANet, Alzahra University) et la Dr Sareh Eslamzadeh Askestani (University of Mazandaran).
Après toutes les présentations, on a eu un longue débat sur les données et les résultats présentés par les scientifiques invités, qui ont eu l'opportunité d'avoir des intéressants échanges d'opinion avec les autres chercheurs. La rencontre s'est terminé le 7 Décembre avec les salutations du Prof. Remo Ruffini et du Prof. Lorenzo Amati.
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| Fig. 8: Le Prof. Lorenzo Amati et le Prof. Remo Ruffini à l'occasion du meeting Amati Fest. | Fig. 9: De gauche à droit: le Prof. Luca Izzo, le Prof. Jorge Rueda, le Prof. Lorenzo Amati, le Prof. Remo Ruffini, le Prof. Rahim Moradi, le Prof. Liang Lia et le Prof Wang Yu, en traine de discuter auprès de l'ICRANet à l'occasion du meeting Amati Fest. |
5. Visites scientifiques auprès du centre ICRANet
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Prof. Lorenzo Amati
INAF - Osservatorio di Astrofisica e Scienza dello Spazio
6-7 Décembre 2021 -
Prof. Jorge Armando Rueda Hernandez
ICRA, ICRANet et Université de Ferrara
6-7 Décembre 2021 -
Prof. Luca Izzo
Osservatorio di Capodimonte - Italie
6-7 Décembre 2021
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| Prof. Lorenzo Amati | Prof. Jorge Armando Rueda Hernandez | Prof. Luca Izzo |
Pendant leur visite, ils ont eu l'opportunité de discuter de leur travaux de recherché et d'avoir des intéressants échanges d'opinion avec les autres chercheurs ICRANet de toutes les parties du monde. Ils ont aussi participé au meeting Amati Fest, qui s'est tenue auprès du centre ICRANet à Pescara (Italie) et en ligne du 6 au 7 Décembre 2021.
6. Publications récents
J. A. Rueda and R. Ruffini, The quantum emission of an alive black hole, published in International Journal of Modern Physics D VOL. 30, NO. 14.
A long march of 50 years of successive theoretical progress and new physics discovered using observations of gamma-ray bursts has finally led to the formulation of an efficient mechanism able to extract the rotational energy of a Kerr black hole to power these most energetic astrophysical sources and active galactic nuclei. We here present the salient features of this long-sought mechanism, based on gravito-electrodynamics, and which represents an authentic shift of paradigm of black holes as forever "alive" astrophysical objects.
This essay is awarded third prize in the 2021 Essay Competition of the Gravity Research Foundation.
DOI: https://doi.org/10.1142/S0218271821410030
F. Rastegar Nia, M. T. Mirtorabi, R. Moradi, A. Vafaei Sadr, Y. Wang, Deep learning in searching the spectroscopic redshift of quasars, published in Monthly Notices of the Royal Astronomical Society on January 19, 2022.
Studying the cosmological sources at their cosmological rest-frames is crucial to track the cosmic history and properties of compact objects. In view of the increasing data volume of existing and upcoming telescopes/detectors, we here construct a 1–dimensional convolutional neural network (CNN) with a residual neural network (ResNet) structure to estimate the redshift of quasars in Sloan Digital Sky Survey IV (SDSS-IV) catalog from DR16 quasar-only (DR16Q) of eBOSS on a broad range of signal-to-noise ratios, named FNet. Owing to its 24 convolutional layers and the ResNet structure with different kernel sizes of 500, 200 and 15, FNet is able to discover the ‘local’ and ‘global’ patterns in the whole sample of spectra by a self-learning procedure. It reaches the accuracy of 97.0 per cent for the velocity difference for redshift, |Δν|<6000 km s−1 and 98.0 per cent for |Δν|<12000 km s−1. While QuasarNET, which is a standard CNN adopted in the SDSS routine and is constructed by 4 convolutional layers (no ResNet structure), with kernel sizes of 10, to measure the redshift via identifying seven emission lines (local patterns), fails in estimating redshift of ∼1.3 per cent of visually inspected quasars in DR16Q catalog, and it gives 97.8 per cent for |Δν|<6000 km s−1 and 97.9 per cent for |Δν|<12000 km s−1. Hence, FNet provides similar accuracy to QuasarNET, but it is applicable for a wider range of SDSS spectra, especially for those missing the clear emission lines exploited by QuasarNET. These properties of FNet, together with the fast predictive power of machine learning, allow FNet to be a more accurate alternative for the pipeline redshift estimator and can make it practical in the upcoming catalogs to reduce the number of spectra to visually inspect.
LINK: https://doi.org/10.1093/mnras/stac076
Davood Rafiei Karkevandi, Soroush Shakeri, Violetta Sagun, and Oleksii Ivanytskyi, Bosonic dark matter in neutron stars and its effect on gravitational wave signal, published in Phys. Rev. D 105, 023001 on January 3, 2022.
We study an impact of self-interacting bosonic dark matter (DM) on various observable properties of neutron stars (NSs). The analysis is performed for asymmetric DM with masses from few MeV to GeV, the self-coupling constant of order
and various DM fractions. Allowing a mixture between DM and baryonic matter, the formation of a dense DM core or an extended dark halo has been explored. We find that both distribution regimes crucially depend on the mass and fraction of DM for sub-GeV boson masses in the strong coupling regime. From the combined analysis of the mass-radius relation and the tidal deformability of compact stars including bosonic DM, we set a stringent constraint on DM fraction. We conclude that observations of 2 Mâ NSs together with Λ 1.4 ≤ 580 constraint, set by LIGO/Virgo Collaboration, favor sub-GeV DM particles with low fractions below ∼5%.
LINK: https://doi.org/10.1103/PhysRevD.105.023001
Sareh Eslamzadeh, Javad T. Firouzjaee, Kourosh Nozari, Radiation from Einstein-Gauss-Bonnet de Sitter black hole via tunneling process, accepted for publication on EPJC on January 4, 2022.
In this paper, we probe in novel 4D Einstein-Gauss-Bonnet (EGB) black hole and its thermodynamics. We illustrate the three asymptotically 4D EGB spacetime as an asymptotically flat, de Sitter, and Anti-de Sitter. Also, we apply the tunneling of the massless particles from the event horizon of 4D EGB gravity and we investigate the correlation between the emission modes and temperature of the event horizon. In asymptotically flat spacetime, the existence of the coupling constant alone constructs the regular spacetime, the radiation deviates from the pure thermal, and the temperature of the black hole horizon would be finite in the final stage of the black hole evaporation. If we consider the 4D ds-EGB structure, then we will have three horizons in the specific mass range of the black hole. By carefully examining the temperature of the black hole and cosmological horizons with the tunneling of the massless particles from these horizons. As a result, the evolution of these temperatures is in direction of the remaining rest mass with the probably same temperature for black hole and cosmological horizon. In addition, the exciting result is that temperature behaviors exactly match with the temperature behaviors of a regular black hole in Lovelock gravity in a higher dimension. This confirms the bypassing of EGB in four dimensions of spacetime from the Lovelock gravity in higher dimensions.
LINK: https://doi.org/10.1140/epjc/s10052-022-09992-6
Yunis, Rafael; Argüelles, Carlos R.; Scóccola, Claudia G.; López Nacir, Diana; Giordano, Gastón, Self-Interacting Dark Matter in Cosmology: accurate numerical implementation and observational constraints, accepted for publication on JCAP (24 January 2022).
This paper presents a systematic and accurate treatment of the evolution of cosmological perturbations in self-interacting dark matter models, for particles which decoupled from the primordial plasma while relativistic. We provide a numerical implementation of the Boltzmann hierarchies developed in a previous paper [JCAP, 09 (2020) 041] in a publicly available Boltzmann code and show how it can be applied to realistic DM candidates such as sterile neutrinos either under resonant or non-resonant production mechanisms, and for different field mediators. At difference with traditional fluid approximations - also known as a c_eff − c_vis parametrizations- our approach follows the evolution of phase-space perturbations under elastic DM interactions for a wide range of interaction models, including the effects of late kinetic decoupling. Finally, we analyze the imprints left by different self interacting models on linear structure formation, which can be constrained using Lyman-α forest and satellite counts. We find new lower bounds on the particle mass that are less restrictive than previous constraints.
ArXiv: https://arxiv.org/abs/2108.02657
MAGIC collaboration, Search for Very High-energy Emission from the Millisecond Pulsar PSR J0218+4232, published in ApJ, Volume 922, Number 2 on December 3, 2021.
PSR J0218+4232 is one of the most energetic millisecond pulsars known and has long been considered as one of the best candidates for very high-energy (VHE; >100 GeV) γ-ray emission. Using 11.5 yr of Fermi Large Area Telescope (LAT) data between 100 MeV and 870 GeV, and ~90 hr of Major Atmospheric Gamma Imaging Cherenkov (MAGIC) observations in the 20 GeV to 20 TeV range, we searched for the highest energy γ-ray emission from PSR J0218+4232. Based on the analysis of the LAT data, we find evidence for pulsed emission above 25 GeV, but see no evidence for emission above 100 GeV (VHE) with MAGIC. We present the results of searches for γ-ray emission, along with theoretical modeling, to interpret the lack of VHE emission. We conclude that, based on the experimental observations and theoretical modeling, it will remain extremely challenging to detect VHE emission from PSR J0218+4232 with the current generation of Imaging Atmospheric Cherenkov Telescopes, and maybe even with future ones, such as the Cherenkov Telescope Array.
LINK: https://doi.org/10.3847/1538-4357/ac20d7
MAGIC collaboration, Observation of the Gamma-Ray Binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS Telescopes, published in ApJ, Volume 923, Number 2 on December 24, 2021.
The results of gamma-ray observations of the binary system HESS J0632 + 057 collected during 450 hr over 15 yr, between 2004 and 2019, are presented. Data taken with the atmospheric Cherenkov telescopes H.E.S.S., MAGIC, and VERITAS at energies above 350 GeV were used together with observations at X-ray energies obtained with Swift-XRT, Chandra, XMM-Newton, NuSTAR, and Suzaku. Some of these observations were accompanied by measurements of the Hα emission line. A significant detection of the modulation of the very high-energy gamma-ray fluxes with a period of 316.7 ± 4.4 days is reported, consistent with the period of 317.3 ± 0.7 days obtained with a refined analysis of X-ray data. The analysis of data from four orbital cycles with dense observational coverage reveals short-timescale variability, with flux-decay timescales of less than 20 days at very high energies. Flux variations observed over a timescale of several years indicate orbit-to-orbit variability. The analysis confirms the previously reported correlation of X-ray and gamma-ray emission from the system at very high significance, but cannot find any correlation of optical Hα parameters with fluxes at X-ray or gamma-ray energies in simultaneous observations. The key finding is that the emission of HESS J0632 + 057 in the X-ray and gamma-ray energy bands is highly variable on different timescales. The ratio of gamma-ray to X-ray flux shows the equality or even dominance of the gamma-ray energy range. This wealth of new data is interpreted taking into account the insufficient knowledge of the ephemeris of the system, and discussed in the context of results reported on other gamma-ray binary systems.
LINK: https://doi.org/10.3847/1538-4357/ac29b7
A long march of 50 years of successive theoretical progress and new physics discovered using observations of gamma-ray bursts has finally led to the formulation of an efficient mechanism able to extract the rotational energy of a Kerr black hole to power these most energetic astrophysical sources and active galactic nuclei. We here present the salient features of this long-sought mechanism, based on gravito-electrodynamics, and which represents an authentic shift of paradigm of black holes as forever "alive" astrophysical objects.
This essay is awarded third prize in the 2021 Essay Competition of the Gravity Research Foundation.
DOI: https://doi.org/10.1142/S0218271821410030
F. Rastegar Nia, M. T. Mirtorabi, R. Moradi, A. Vafaei Sadr, Y. Wang, Deep learning in searching the spectroscopic redshift of quasars, published in Monthly Notices of the Royal Astronomical Society on January 19, 2022.
Studying the cosmological sources at their cosmological rest-frames is crucial to track the cosmic history and properties of compact objects. In view of the increasing data volume of existing and upcoming telescopes/detectors, we here construct a 1–dimensional convolutional neural network (CNN) with a residual neural network (ResNet) structure to estimate the redshift of quasars in Sloan Digital Sky Survey IV (SDSS-IV) catalog from DR16 quasar-only (DR16Q) of eBOSS on a broad range of signal-to-noise ratios, named FNet. Owing to its 24 convolutional layers and the ResNet structure with different kernel sizes of 500, 200 and 15, FNet is able to discover the ‘local’ and ‘global’ patterns in the whole sample of spectra by a self-learning procedure. It reaches the accuracy of 97.0 per cent for the velocity difference for redshift, |Δν|<6000 km s−1 and 98.0 per cent for |Δν|<12000 km s−1. While QuasarNET, which is a standard CNN adopted in the SDSS routine and is constructed by 4 convolutional layers (no ResNet structure), with kernel sizes of 10, to measure the redshift via identifying seven emission lines (local patterns), fails in estimating redshift of ∼1.3 per cent of visually inspected quasars in DR16Q catalog, and it gives 97.8 per cent for |Δν|<6000 km s−1 and 97.9 per cent for |Δν|<12000 km s−1. Hence, FNet provides similar accuracy to QuasarNET, but it is applicable for a wider range of SDSS spectra, especially for those missing the clear emission lines exploited by QuasarNET. These properties of FNet, together with the fast predictive power of machine learning, allow FNet to be a more accurate alternative for the pipeline redshift estimator and can make it practical in the upcoming catalogs to reduce the number of spectra to visually inspect.
LINK: https://doi.org/10.1093/mnras/stac076
Davood Rafiei Karkevandi, Soroush Shakeri, Violetta Sagun, and Oleksii Ivanytskyi, Bosonic dark matter in neutron stars and its effect on gravitational wave signal, published in Phys. Rev. D 105, 023001 on January 3, 2022.
We study an impact of self-interacting bosonic dark matter (DM) on various observable properties of neutron stars (NSs). The analysis is performed for asymmetric DM with masses from few MeV to GeV, the self-coupling constant of order
and various DM fractions. Allowing a mixture between DM and baryonic matter, the formation of a dense DM core or an extended dark halo has been explored. We find that both distribution regimes crucially depend on the mass and fraction of DM for sub-GeV boson masses in the strong coupling regime. From the combined analysis of the mass-radius relation and the tidal deformability of compact stars including bosonic DM, we set a stringent constraint on DM fraction. We conclude that observations of 2 Mâ NSs together with Λ 1.4 ≤ 580 constraint, set by LIGO/Virgo Collaboration, favor sub-GeV DM particles with low fractions below ∼5%.
LINK: https://doi.org/10.1103/PhysRevD.105.023001
Sareh Eslamzadeh, Javad T. Firouzjaee, Kourosh Nozari, Radiation from Einstein-Gauss-Bonnet de Sitter black hole via tunneling process, accepted for publication on EPJC on January 4, 2022.
In this paper, we probe in novel 4D Einstein-Gauss-Bonnet (EGB) black hole and its thermodynamics. We illustrate the three asymptotically 4D EGB spacetime as an asymptotically flat, de Sitter, and Anti-de Sitter. Also, we apply the tunneling of the massless particles from the event horizon of 4D EGB gravity and we investigate the correlation between the emission modes and temperature of the event horizon. In asymptotically flat spacetime, the existence of the coupling constant alone constructs the regular spacetime, the radiation deviates from the pure thermal, and the temperature of the black hole horizon would be finite in the final stage of the black hole evaporation. If we consider the 4D ds-EGB structure, then we will have three horizons in the specific mass range of the black hole. By carefully examining the temperature of the black hole and cosmological horizons with the tunneling of the massless particles from these horizons. As a result, the evolution of these temperatures is in direction of the remaining rest mass with the probably same temperature for black hole and cosmological horizon. In addition, the exciting result is that temperature behaviors exactly match with the temperature behaviors of a regular black hole in Lovelock gravity in a higher dimension. This confirms the bypassing of EGB in four dimensions of spacetime from the Lovelock gravity in higher dimensions.
LINK: https://doi.org/10.1140/epjc/s10052-022-09992-6
Yunis, Rafael; Argüelles, Carlos R.; Scóccola, Claudia G.; López Nacir, Diana; Giordano, Gastón, Self-Interacting Dark Matter in Cosmology: accurate numerical implementation and observational constraints, accepted for publication on JCAP (24 January 2022).
This paper presents a systematic and accurate treatment of the evolution of cosmological perturbations in self-interacting dark matter models, for particles which decoupled from the primordial plasma while relativistic. We provide a numerical implementation of the Boltzmann hierarchies developed in a previous paper [JCAP, 09 (2020) 041] in a publicly available Boltzmann code and show how it can be applied to realistic DM candidates such as sterile neutrinos either under resonant or non-resonant production mechanisms, and for different field mediators. At difference with traditional fluid approximations - also known as a c_eff − c_vis parametrizations- our approach follows the evolution of phase-space perturbations under elastic DM interactions for a wide range of interaction models, including the effects of late kinetic decoupling. Finally, we analyze the imprints left by different self interacting models on linear structure formation, which can be constrained using Lyman-α forest and satellite counts. We find new lower bounds on the particle mass that are less restrictive than previous constraints.
ArXiv: https://arxiv.org/abs/2108.02657
MAGIC collaboration, Search for Very High-energy Emission from the Millisecond Pulsar PSR J0218+4232, published in ApJ, Volume 922, Number 2 on December 3, 2021.
PSR J0218+4232 is one of the most energetic millisecond pulsars known and has long been considered as one of the best candidates for very high-energy (VHE; >100 GeV) γ-ray emission. Using 11.5 yr of Fermi Large Area Telescope (LAT) data between 100 MeV and 870 GeV, and ~90 hr of Major Atmospheric Gamma Imaging Cherenkov (MAGIC) observations in the 20 GeV to 20 TeV range, we searched for the highest energy γ-ray emission from PSR J0218+4232. Based on the analysis of the LAT data, we find evidence for pulsed emission above 25 GeV, but see no evidence for emission above 100 GeV (VHE) with MAGIC. We present the results of searches for γ-ray emission, along with theoretical modeling, to interpret the lack of VHE emission. We conclude that, based on the experimental observations and theoretical modeling, it will remain extremely challenging to detect VHE emission from PSR J0218+4232 with the current generation of Imaging Atmospheric Cherenkov Telescopes, and maybe even with future ones, such as the Cherenkov Telescope Array.
LINK: https://doi.org/10.3847/1538-4357/ac20d7
MAGIC collaboration, Observation of the Gamma-Ray Binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS Telescopes, published in ApJ, Volume 923, Number 2 on December 24, 2021.
The results of gamma-ray observations of the binary system HESS J0632 + 057 collected during 450 hr over 15 yr, between 2004 and 2019, are presented. Data taken with the atmospheric Cherenkov telescopes H.E.S.S., MAGIC, and VERITAS at energies above 350 GeV were used together with observations at X-ray energies obtained with Swift-XRT, Chandra, XMM-Newton, NuSTAR, and Suzaku. Some of these observations were accompanied by measurements of the Hα emission line. A significant detection of the modulation of the very high-energy gamma-ray fluxes with a period of 316.7 ± 4.4 days is reported, consistent with the period of 317.3 ± 0.7 days obtained with a refined analysis of X-ray data. The analysis of data from four orbital cycles with dense observational coverage reveals short-timescale variability, with flux-decay timescales of less than 20 days at very high energies. Flux variations observed over a timescale of several years indicate orbit-to-orbit variability. The analysis confirms the previously reported correlation of X-ray and gamma-ray emission from the system at very high significance, but cannot find any correlation of optical Hα parameters with fluxes at X-ray or gamma-ray energies in simultaneous observations. The key finding is that the emission of HESS J0632 + 057 in the X-ray and gamma-ray energy bands is highly variable on different timescales. The ratio of gamma-ray to X-ray flux shows the equality or even dominance of the gamma-ray energy range. This wealth of new data is interpreted taking into account the insufficient knowledge of the ephemeris of the system, and discussed in the context of results reported on other gamma-ray binary systems.
LINK: https://doi.org/10.3847/1538-4357/ac29b7