38 research outputs found
Physics from Time Variability of the VHE Blazar PKS 2155-304
Blazars are the principal extragalactic sources of very high energy gamma-ray emission in the Universe. These objects constitute a sub-class of Active Galactic Nuclei whose
emission is dominated by Doppler boosted non-thermal radiation from plasma outflowing at relativistic speeds from the central engine. This plasma outflow happens in the
form of large-scale collimated structures called jets, which can extend for Mpc in length and transport energy from the central engine of the galaxy to the larger scale intergalac-
tic medium. Over thirty such sources have been discovered to date by ground-based gamma-ray telescopes such as H.E.S.S., and PKS 2155-304 is the prototypical southern-hemisphere representative of this population of objects.
In this thesis I have studied in detail some aspects of the temporal variability of the jet emission from PKS 2155-304, combining coordinated observations across the electromagnetic spectrum, from optical polarimetric measurements to X-ray and ground-based gamma-ray data. The temporal properties of the dataset allowed us to derive important physical information about the structure and emission mechanisms of the source and put constraints to the location of the sites of VHE emission and particle acceleration within the jet. We have also derived a sensitive statistical measure, called Kolmogorov distance,
which we applied to the large outburst observed from PKS 2155-304 in July 2006, to derive the most stringent constraints to date on limits for the violation of Lorentz invariance induced by quantum-gravity effects from AGN measurements
Astrophysical and Cosmological Searches for Lorentz Invariance Violation
Lorentz invariance is one of the fundamental tenets of Special Relativity,
and has been extensively tested with laboratory and astrophysical observations.
However, many quantum gravity models and theories beyond the Standard Model of
Particle Physics predict a violation of Lorentz invariance at energies close to
Planck scale. This article reviews observational and experimental tests of
Lorentz invariance violation (LIV) with photons, neutrinos and gravitational
waves. Most astrophysical tests of LIV using photons are based on searching for
a correlation of the spectral lag data with redshift and energy. These have
been primarily carried out using compact objects such as pulsars, Active
Galactic Nuclei (AGN), and Gamma-ray bursts (GRB). There have also been some
claims for LIV from some of these spectral lag observations with GRBs, which
however are in conflict with the most stringent limits obtained from other LIV
searches. Searches have also been carried out using polarization measurements
from GRBs and AGNs. For neutrinos, tests have been made using both
astrophysical observations at MeV energies (from SN 1987A) as well as in the
TeV-PeV energy range based on IceCube observations, atmospheric neutrinos, and
long-baseline neutrino oscillation experiments. Cosmological tests of LIV
entail looking for a constancy of the speed of light as a function of redshift
using multiple observational probes, as well as looking for birefringence in
Cosmic Microwave background observations. This article will review all of these
aforementioned observational tests of LIV, including results which are in
conflict with each other.Comment: 32 pages. Added some references related to GWs. Invited chapter for
the edited book {\it Recent Progress on Gravity Tests: Challenges and Future
Perspectives} (Eds. C. Bambi and A. C\'ardenas-Avenda\~no, Springer
Singapore, expected in 2023
Leptonic and Hadronic Radiative Processes in Supermassive-Black-Hole Jets
Supermassive black holes lying in the center of galaxies can launch
relativistic jets of plasma along their polar axis. The physics of black-hole
jets is a very active research topic in astrophysics, owing to the fact that
many questions remain open on the physical mechanisms of jet launching, of
particle acceleration in the jet, and on the radiative processes. In this work
I focus on the last item, and present a review of the current understanding of
radiative emission processes in supermassive-black-hole jets.Comment: Invited review in Galaxies special issue "Jet Physics of Accreting
Super Massive Black Holes
High-Energy Gamma-Ray Astronomy
This volume celebrates the 30th anniversary of the first very-high energy (VHE) gamma-ray Source detection: the Crab Nebula, observed by the pioneering ground-based Cherenkov telescope Whipple, at teraelectronvolts (TeV) energies, in 1989. As we entered a new era in TeV astronomy, with the imminent start of operations of the Cherenkov Telescope Array (CTA) and new facilities such as LHAASO and the proposed Southern Wide-Field Gamma-ray Observatory (SWGO), we conceived of this volume as a broad reflection on how far we have evolved in the astrophysics topics that dominated the field of TeV astronomy for much of recent history.In the past two decades, H.E.S.S., MAGIC and VERITAS pushed the field of TeV astronomy, consolidating the field of TeV astrophysics, from few to hundreds of TeV emitters. Today, this is a mature field, covering almost every topic of modern astrophysics. TeV astrophysics is also at the center of the multi-messenger astrophysics revolution, as the extreme photon energies involved provide an effective probe in cosmic-ray acceleration, propagation and interaction, in dark matter and exotic physics searches. The improvement that CTA will carry forward and the fact that CTA will operate as the first open observatory in the field, mean that gamma-ray astronomy is about to enter a new precision and productive era.This book aims to serve as an introduction to the field and its state of the art, presenting a series of authoritative reviews on a broad range of topics in which TeV astronomy provided essential contributions, and where some of the most relevant questions for future research lie
Quantum gravity phenomenology at the dawn of the multi-messenger era : a review
The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review, prepared within the COST Action CA18108 "Quantum gravity phenomenology in the multi-messenger approach", is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers
Quantum gravity phenomenology at the dawn of the multi-messenger era—A review
The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review, prepared within the COST Action CA18108 “Quantum gravity phenomenology in the multi-messenger approach”, is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers
Quantum gravity phenomenology at the dawn of the multi-messenger era-A review
The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review, prepared within the COST Action CA18108 "Quantum gravity phenomenology in the multi-messenger approach", is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers. (C) 2022 The Authors. Published by Elsevier B.V.Peer reviewe
Quantum gravity phenomenology at the dawn of the multi-messenger era—A review
The exploration of the universe has recently entered a new era thanks to the multimessenger
paradigm, characterized by a continuous increase in the quantity and quality
of experimental data that is obtained by the detection of the various cosmic messengers
(photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They
give us information about their sources in the universe and the properties of the
intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to
search for phenomenological signatures of quantum gravity. On the one hand, the most
energetic events allow us to test our physical theories at energy regimes which are not
directly accessible in accelerators; on the other hand, tiny effects in the propagation of
very high energy particles could be amplified by cosmological distances. After decades
of merely theoretical investigations, the possibility of obtaining phenomenological indications
of Planck-scale effects is a revolutionary step in the quest for a quantum theory
of gravity, but it requires cooperation between different communities of physicists
(both theoretical and experimental). This review, prepared within the COST Action
CA18108 ‘‘Quantum gravity phenomenology in the multi-messenger approach", is aimed
at promoting this cooperation by giving a state-of-the art account of the interdisciplinary
expertise that is needed in the effective search of quantum gravity footprints in the
production, propagation and detection of cosmic messengers.Talent Scientific Research Program of College of Physics, Sichuan University 1082204112427Fostering Program in Disciplines Possessing Novel Features for Natural Science of Sichuan University 2020SCUNL2091000 Talent program of Sichuan province 2021Xunta de GaliciaEuropean Commission
European Union ERDF, "Maria de Maeztu'' Units of Excellence program MDM-2016-0692Red Tematica Nacional de Astroparticulas RED2018-102661-TLa Caixa Foundation 100010434European Commission 847648
LCF/BQ/PI21/11830030
754510Ministry of Education, Science & Technological Development, Serbia 451-03-9/2021-14/200124FSR Incoming Postdoctoral Fellowship Ministry of Education, Science and Technological Development, Serbia 451-03-9/2021-14/200124University of Rijeka grant uniri-prirod-18-48Croatian Science Foundation (HRZZ) IP-2016-06-9782Villum Fonden 29405
DGA-FSE 2020-E2117REuropean Regional Development Fund through the Center of Excellence (TK133) "The Dark Side of the Universe''
European Regional Development Fund (ESIF/ERDF)Ministry of Education, Youth & Sports - Czech Republic CoGraDS-CZ.02.1.01/0.0/0.0/15 003/0000437Blavatnik grantBasque Government IT-97916
Basque Foundation for Science (IKERBASQUE)European Space Agency C4000120711
4000132310FNRS (Belgian Fund for Research)Programa de Apoyo a Proyectos de Investigacion e Innovacion Tecnologica (PAPIIT)Universidad Nacional Autonoma de Mexico TA100122National University of La Plata X909
DICYT 042131GRNational Research, Development & Innovation Office (NRDIO) - Hungary 123996FQXiSwiss National Science Foundation (SNSF)European Commission 181461
199307Netherlands Organization for Scientific Research (NWO) 680-91-119
15MV71Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)
Japan Society for the Promotion of ScienceGrants-in-Aid for Scientific Research (KAKENHI) 20H01899
20H05853
JP21F21789Estonian Research Council PRG356Julian Schwinger FoundationGeneralitat Valenciana Excellence PROMETEO-II/2017/033
PROMETEO/2018/165Istituto Nazionale di Fisica Nucleare (INFN)European ITN project HIDDeN H2020-MSCA-ITN-2019//860881-HIDDeNSwedish Research CouncilEuropean Commission 2016-05996
European Research Council (ERC)
European Commission 668679Advanced ERC grant TReXMinistry of Education, Universities and Research (MIUR) 2017X7X85KFonds de la Recherche Scientifique - FNRS 4.4501.18Ministry of Research, Innovation and Digitization - Romania PN19-030102-INCDFM
PN-III-P4ID-PCE-2020-2374United States Department of Energy (DOE) DE-SC0020262Ministry of Science, ICT & Future Planning, Republic of Korea 075-15-2020-778German Academic Scholarship Foundation
German Research Foundation (DFG) 408049454
420243324
425333893
445990517
Germany's Excellence Strategy (EXC 2121 "Quantum Universe'') 390833306
390837967
Federal Ministry of Education & Research (BMBF) 05 A20GU2
05 A20PX1Centro de Excelencia "Severo Ochoa'' SEV-2016-0588CERCA program of the Generalitat de CatalunyaAgencia de Gestio D'Ajuts Universitaris de Recerca Agaur (AGAUR)
Generalitat de Catalunya 2017-SGR-1469
2017-SGR-929
ICCUB CEX2019-000918-MNational Science Centre, Poland 2019/33/B/ST2/00050
2017/27/B/ST2/01902Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ) 306414/2020-1Dicyt-USACH 041931MFNational Science Fund of Bulgaria KP-06-N 38/11
RCN ROMFORSK 302640Comunidad de Madrid 2018-T1/TIC-10431
2019-T1/TIC-13177
S2018/NMT-4291UK Research & Innovation (UKRI)Science & Technology Facilities Council (STFC) ST/T000759/1
ST/P000258/1
ST/T000732/1
ST/V005596/1Portuguese Foundation for Science and Technology UIDB/00618/2020
UIDB/00777/2020
UIDP/00777/2020
CERN/FIS-PAR/0004/2019
PTDC/FIS-PAR/29436/2017
PTDC/FISPAR/31938/2017
PTDC/FIS-OUT/29048/2017
SFRH/BD/137127/2018Centre National de la Recherche Scientifique (CNRS), LabEx UnivEarthS ANR-10-LABX-0023
ANR18-IDEX-0001Junta de Andalucia
European Commission A-FQM-053-UGR18Natural Sciences and Engineering Research Council of Canada (NSERC) RGPIN-2021-03644National Science Centre Poland Sonata Bis 2019/33/B/ST2/00050
DEC-2017/26/E/ST2/00763Natural Sciences and Engineering Research Council of Canada (NSERC)
DGIID-DGA 2015-E24/2Spanish Research State Agency and Ministerio de Ciencia e Innovacion MCIN/AEI PID2019-104114RB-C32
PID2019-105544GB-I00
PID2019-105614GB-C21
PID2019106515GB-I00
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PID2019-107394GB-I00
PID2019-107844GB-C21
PID2019-107847RB-C41
MCIN/AEI PGC2018-095328-B-I00
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FPA2017-84543-P
FPA2016-76005-C2-1-PSpanish 'Ministerio de Universidades' BG20/00228
Spanish Government PID2020-115845GBI00
Generalitat de Catalunya
Comunidad de Madrid S2018/NMT-4291
Spanish Government PID2019-105544GB-I00Perimeter Institute for Theoretical PhysicsGovernment of Canada through the Department of Innovation, Science and Economic DevelopmentProvince of Ontario through the Ministry of Colleges and UniversitiesIstituto Nazionale di Fisica Nucleare (INFN)Centre National de la Recherche Scientifique (CNRS)Netherlands Organization for Scientific Research (NWO)Fundamental Questions Institute (FQXi)European Cooperation in Science and Technology (COST) CA18108Research Council of University of GuilanIniziativa Specifica TEONGRAV
Iniziativa Specifica QGSKY
Iniziativa Specifica QUAGRAP
Iniziativa Specifica GeoSymQFTthe Spanish Research State Agency and Ministerio de Ciencia e Innovacion MCIN/AEI PID2020-115845GBI00
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FPU18/0457