Black Holes, Gravitational Waves and Fundamental Physics: a Roadmap
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Black holes, gravitational waves and fundamental physics: a roadmap Leor Barack1, Vitor Cardoso2,3, Samaya Nissanke4,5,6, Thomas P. Sotiriou7,8 (editors) Abbas Askar9,10, Krzysztof Belczynski9, Gianfranco Bertone5, Edi Bon11,12, Diego Blas13, Richard Brito14, Tomasz Bulik15, Clare Burrage8, Christian T. Byrnes16, Chiara Caprini17, Masha Chernyakova18,19, Piotr Chruściel20,21, Monica Colpi22,23, Valeria Ferrari24, Daniele Gaggero5, Jonathan Gair25, Juan García-Bellido26, S. F. Hassan27, Lavinia Heisenberg28, Martin Hendry29, Ik Siong Heng29, Carlos Herdeiro30, Tanja Hinderer4,14, Assaf Horesh31, Bradley J. Kavanagh5, Bence Kocsis32, Michael Kramer33,34, Alexandre Le Tiec35, Chiara Mingarelli36, Germano Nardini37a,37b, Gijs Nelemans4,6 Carlos Palenzuela38, Paolo Pani24, Albino Perego39,40, Edward K. Porter17, Elena M. Rossi41, Patricia Schmidt4, Alberto Sesana42, Ulrich Sperhake43,44, Antonio Stamerra45,46, Leo C. Stein43, Nicola Tamanini14, Thomas M. Tauris33,47, L. Arturo Urena-López48, Frederic Vincent49, Marta Volonteri50, Barry Wardell51, Norbert Wex33, Kent Yagi52 (Section coordinators) Tiziano Abdelsalhin24, Miguel Ángel Aloy53, Pau arXiv:1806.05195v4 [gr-qc] 1 Feb 2019 Amaro-Seoane54,55,56, Lorenzo Annulli2, Manuel Arca-Sedda57, Ibrahima Bah58, Enrico Barausse50, Elvis Barakovic59, Robert Benkel7, Charles L. Bennett58, Laura Bernard2, Sebastiano Bernuzzi60, Christopher P. L. Berry42, Emanuele Berti58,61, Miguel Bezares38, Jose Juan Blanco-Pillado62, Jose Luis Blázquez-Salcedo63, Matteo Bonetti64,23, Mateja Bošković2,65, Zeljka Bosnjak66, Katja Bricman67, Bernd Brügmann60, Pedro R. Capelo68, Sante Carloni2, Pablo Cerdá-Durán53, Christos Charmousis69, Sylvain Chaty70, Aurora Clerici67, Andrew Coates71, Marta Colleoni38, Lucas G. Collodel63, Geoffrey Compère72, William Cook44, Isabel Cordero-Carrión73, Miguel Correia2, Álvaro de la Cruz-Dombriz74, Viktor G. Czinner2,75, Kyriakos Destounis2, Kostas Dialektopoulos76,77, Daniela Black holes, gravitational waves and fundamental physics: a roadmap 2 Doneva71,78 Massimo Dotti22,23, Amelia Drew44, Christopher Eckner67, James Edholm79, Roberto Emparan80,81, Recai Erdem82, Miguel Ferreira2, Pedro G. Ferreira83, Andrew Finch84, Jose A. Font53,85, Nicola Franchini7, Kwinten Fransen86, Dmitry Gal’tsov87,88, Apratim Ganguly89, Davide Gerosa43, Kostas Glampedakis90, Andreja Gomboc67, Ariel Goobar27, Leonardo Gualtieri24, Eduardo Guendelman91, Francesco Haardt92, Troels Harmark93, Filip Hejda2, Thomas Hertog86, Seth Hopper94, Sascha Husa38, Nada Ihanec67, Taishi Ikeda2, Amruta Jaodand95,96, Philippe Jetzer97, Xisco Jimenez-Forteza24,77, Marc Kamionkowski58, David E. Kaplan58, Stelios Kazantzidis98, Masashi Kimura2, Shiho Kobayashi99, Kostas Kokkotas71, Julian Krolik58, Jutta Kunz63, Claus Lämmerzahl63,100, Paul Lasky101,102, José P. S. Lemos2, Jackson Levi Said84, Stefano Liberati103,104, Jorge Lopes2, Raimon Luna81, Yin-Zhe Ma105,106,107, Elisa Maggio108, Alberto Mangiagli22,23, Marina Martinez Montero86, Andrea Maselli2, Lucio Mayer68, Anupam Mazumdar109, Christopher Messenger29, Brice Ménard58, Masato Minamitsuji2, Christopher J. Moore2, David Mota110, Sourabh Nampalliwar71 Andrea Nerozzi2, David Nichols4, Emil Nissimov111, Martin Obergaulinger53, Niels A. Obers93, Roberto Oliveri112, George Pappas24, Vedad Pasic113, Hiranya Peiris27, Tanja Petrushevska67, Denis Pollney89, Geraint Pratten38, Nemanja Rakic114,115, Istvan Racz116,117, Miren Radia44, Fethi M. Ramazanoğlu118, Antoni Ramos-Buades38, Guilherme Raposo24, Marek Rogatko119, Roxana Rosca-Mead44, Dorota Rosinska120, Stephan Rosswog27, Ester Ruiz-Morales121, Mairi Sakellariadou13, Nicolás Sanchis-Gual53, Om Sharan Salafia122, Anuradha Samajdar6, Alicia Sintes38, Majda Smole123, Carlos Sopuerta124,125, Rafael Souza-Lima68, Marko Stalevski11, Nikolaos Stergioulas126, Chris Stevens89, Tomas Tamfal68, Alejandro Torres-Forné53, Sergey Tsygankov127, Kıvanç İ. Ünlütürk118, Rosa Valiante128 Maarten van de Meent14 José Velhinho129, Yosef Verbin130, Bert Vercnocke86, Daniele Vernieri2, Rodrigo Vicente2, Vincenzo Vitagliano131, Amanda Weltman74, Bernard Whiting132, Andrew Williamson4, Helvi Witek13, Aneta Wojnar119, Kadri Yakut133, Haopeng Yan93, Stoycho Yazadjiev134, Gabrijela Zaharijas67, Miguel Zilhão2 Black holes, gravitational waves and fundamental physics: a roadmap 3 Abstract. The grand challenges of contemporary fundamental physics—dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem—all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on “Black holes, Gravitational waves and Fundamental Physics”. Black holes, gravitational waves and fundamental physics: a roadmap 4 Glossary Here we provide an overview of the acronyms used throughout this paper and also in common use in the literature. BBH Binary black hole BH Black hole BNS Binary neutron star BSSN Baumgarte-Shapiro-Shibata-Nakamura CBM Compact binary mergers CMB Cosmic microwave background DM Dark matter ECO Exotic Compact Object EFT Effective Field theory EMRI Extreme-mass-ratio inspiral EOB Effective One Body model EOS Equation of state eV electron Volt GR General Relativity GSF Gravitational self-force GRB Gamma-ray burst GW Gravitational Wave HMNS Hypermassive neutron star IMBH Intermediate-mass black hole IVP Initial Value Problem LVC LIGO Scientific and Virgo Collaborations MBH Massive black hole NK Numerical kludge model NSB Neutron star binary NS Neutron star NR Numerical Relativity PBH Primordial black hole PN Post-Newtonian PM Post-Minkowskian QNM Quasinormal modes sBH Black hole of stellar origin SGWB Stochastic GW background SM Standard Model SMBBH Supermassive binary black hole SOBBH Stellar-origin binary black hole SNR Signal-to-noise ratio ST Scalar-tensor CONTENTS 5 Contents Chapter I: The astrophysics of compact object mergers: prospects and challenges 11 1 Introduction 11 2 LIGO and Virgo Observations of Binary Black Hole Mergers and a Binary Neutron Star 12 3 Black hole genesis and archaeology 14 3.1 Black Hole Genesis . 14 3.2 Black Hole Binaries: the difficulty of pairing . 19 4 The formation of compact object mergers through classical binary stellar evolution 20 4.1 Stellar-origin black holes . 20 4.1.1 Single star evolution . 20 4.1.2 Binary star evolution . 23 4.1.3 Reconciling observations and theory . 24 4.2 BNS mergers . 29 4.3 Mixed BH-NS mergers . 30 5 Dynamical Formation of Stellar-mass Binary Black Holes 31 5.1 Introduction . 31 5.2 Merger rate estimates in dynamical channels . 31 5.3 Advances in numerical methods in dynamical modeling . 34 5.3.1 Direct N-body integration . 34 5.3.2 Monte-Carlo methods . 34 5.3.3 Secular Symplectic N-body integration . 35 5.3.4 Semianalytical methods . 35 5.4 Astrophysical interpretation of dynamical sources . 36 5.4.1 Mass distribution . 36 5.4.2 Spin distribution . 36 5.4.3 Eccentricity distribution . 37 5.4.4 Sky location distribution . 37 5.4.5 Smoking gun signatures . 37 6 Primordial Black Holes and Dark Matter 38 6.1 Motivation and Formation Scenarios. 38 6.2 Astrophysical probes . 40 6.3 Discriminating PBHs from astrophysical BHs . 42 CONTENTS 6 7 Formation of supermassive black hole binaries in galaxy mergers 42 8 Probing supermassive black hole binaries with pulsar timing arrays 46 8.1 The Gravitational-Wave Background . 47 8.2 Continuous Gravitational Waves . 49 9 Numerical Simulations of Stellar-mass Compact Object Mergers 49 9.1 Motivations . 49 9.2 Recent results for binary neutron star mergers . 51 9.2.1 Gravitational waves and remnant properties . 51 9.2.2 Matter ejection and electromagnetic counterparts . 52 9.2.3 GW170817 and its counterparts . 53 9.3 Recent results for black hole-neutron star mergers . 54 9.4 Perspectives and future developments . 54 10 Electromagnetic Follow-up of Gravitational Wave Mergers 56 10.1 The High-energy Counterpart . 57 10.2 The Optical and Infrared Counterpart . 57 10.3 The Radio Counterpart . 59 10.4 Many Open Questions . 60 11 X-ray and gamma-ray binaries 60 12 Supermassive black hole binaries in the cores of AGN 62 12.1 Modeling electromagnetic signatures of merging SMBBHs . 65 13 Cosmology and cosmography with gravitational waves 66 13.1 Standard sirens as a probe of the late universe . 66 13.1.1 Redshift information . 67 13.1.2 Standard sirens with current GW data: GW170817 . 69 13.1.3 Cosmological forecasts with standard