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Black Holes, Gravitational Waves and Fundamental Physics: a Roadmap

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Black Holes, Gravitational Waves and Fundamental Physics: a Roadmap 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, Chris Belczynski9, Gianfranco Bertone5, Edi Bon11;12, Diego Blas13, Richard Brito14, Tomasz Bulik15, Clare Burrage8, Christian T. Byrnes16, Chiara Caprini17, Masha Chernyakova18;19, Piotr Chru´sciel20;21, Monica Colpi22;23, Valeria Ferrari24, Daniele Gaggero5, Jonathan Gair25, Juan Garc´ıa-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 Nardini37, 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 Nicola Tamanini14, Thomas M. Tauris33;47, L. Arturo Urena-L´opez48, Frederic Vincent49, Marta Volonteri50, Barry Wardell51, Norbert Wex33, Kent Yagi52 (Section coordinators) Tiziano Abdelsalhin24, Miguel Angel´ Aloy53, Pau 54;55;56 2 57 arXiv:1806.05195v1 [gr-qc] 13 Jun 2018 Amaro-Seoane , Lorenzo Annulli , Manuel Arca-Sedda , Ibrahima Bah58, Enrico Barausse50, Elvis Barakovic59, Robert Benkel7, Charles L. Bennett58, Laura Bernard2, Sebastiano Bernuzzi60, Christopher P. L. Berry42, Emanuele Berti58, Miguel Bezares38, Jose Juan Blanco-Pillado61, Jose Luis Bl´azquez-Salcedo62, Matteo Bonetti63;23, Mateja Boˇskovi´c2;64, Zeljka Bosnjak65, Katja Bricman66, Bernd Br¨uegmann60, Pedro R. Capelo67, Sante Carloni2, Pablo Cerd´a-Dur´an53, Christos Charmousis68, Sylvain Chaty69, Aurora Clerici66, Andrew Coates70, Marta Colleoni38, Lucas G. Collodel62, Geoffrey Comp`ere71, William Cook44, Isabel Cordero-Carri´on72, Miguel Correia2, Alvaro´ de la Cruz-Dombriz73, Viktor G. Czinner2;74, Kyriakos Destounis2, Kostas Dialektopoulos75;76, Daniela Black holes, gravitational waves and fundamental physics: a roadmap 2 Doneva70;77 Massimo Dotti22;23, Amelia Drew44, Christopher Eckner66, James Edholm78, Roberto Emparan79;80, Recai Erdem81, Miguel Ferreira2, Pedro G. Ferreira82, Andrew Finch83, Jose A. Font53;84, Nicola Franchini7, Kwinten Fransen85, Dmitry Gal'tsov86;87, Apratim Ganguly88, Davide Gerosa43, Kostas Glampedakis89, Andreja Gomboc66, Ariel Goobar27, Leonardo Gualtieri24, Eduardo Guendelman90, Francesco Haardt91, Troels Harmark92, Filip Hejda2, Thomas Hertog85, Seth Hopper93, Sascha Husa38, Nada Ihanec66, Taishi Ikeda2, Amruta Jaodand94;95, Philippe Jetzer96, Xisco Jimenez-Forteza24;76, Marc Kamionkowski58, David E. Kaplan58, Stelios Kazantzidis97, Masashi Kimura2, Shio Kobayashi98, Kostas Kokkotas70, Julian Krolik58, Jutta Kunz62, Claus L¨ammerzahl62;99, Paul Lasky100;101, Jos´eP. S. Lemos2, Jackson Levi Said83, Stefano Liberati102;103, Jorge Lopes2, Raimon Luna80, Yin-Zhe Ma104;105;106, Elisa Maggio107, Marina Martinez Montero85, Andrea Maselli2, Lucio Mayer67, Anupam Mazumdar108, Christopher Messenger29, Brice M´enard58, Masato Minamitsuji2, Christopher J. Moore2, David Mota109, Sourabh Nampalliwar70 Andrea Nerozzi2, David Nichols4, Emil Nissimov110, Martin Obergaulinger53, Roberto Oliveri111, George Pappas24, Vedad Pasic112, Hiranya Peiris27, Tanja Petrushevska66, Denis Pollney88, Geraint Pratten38, Nemanja Rakic113;114, Istvan Racz115;116, Fethi M. Ramazano˘glu117, Antoni Ramos-Buades38, Guilherme Raposo24, Marek Rogatko118, Dorota Rosinska119, Stephan Rosswog27, Ester Ruiz Morales120, Mairi Sakellariadou13, Nicol´asSanchis-Gual53, Om Sharan Salafia121, Alicia Sintes38, Majda Smole122, Carlos Sopuerta123;124, Rafael Souza-Lima67, Marko Stalevski11, Leo C. Stein43, Nikolaos Stergioulas125, Chris Stevens88, Tomas Tamfal67, Alejandro Torres-Forn´e53, Sergey Tsygankov126, Kıvan¸c I._ Unl¨ut¨urk¨ 117, Rosa Valiante127 Jos´eVelhinho128, Yosef Verbin129, Bert Vercnocke85, Daniele Vernieri2, Rodrigo Vicente2, Vincenzo Vitagliano130, Amanda Weltman73, Bernard Whiting131, Andrew Williamson4, Helvi Witek13, Aneta Wojnar118, Kadri Yakut132, Stoycho Yazadjiev133, Gabrijela Zaharijas66, Miguel Zilh~ao2 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 COST Action GWverse 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 . 23 4.2 BNS mergers . 28 4.3 Mixed BH-NS mergers . 30 5 Dynamical Formation of Stellar-mass Binary Black Holes 30 5.1 Introduction . 31 5.2 Merger rate estimates in dynamical channels . 31 5.3 Advances in numerical methods in dynamical modeling . 33 5.3.1 Direct N-body integration . 33 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 . 35 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 . 48 9 Numerical Simulations of Stellar-mass Compact Object Mergers 49 9.1 Motivations . 49 9.2 Recent results for binary neutron star mergers . 50 9.2.1 Gravitational waves and remnant properties . 50 9.2.2 Matter ejection and electromagnetic counterparts . 51 9.2.3 GW170817 and its counterparts . 52 9.3 Recent results for black hole-neutron star mergers . 53 9.4 Perspectives and future developments . 54 10 Electromagnetic Follow-up of Graviatational Wave Mergers 55 10.1 The High-energy Counterpart . 56 10.2 The Optical and Infrared Counterpart . 56 10.3 The Radio Counterpart . 58 10.4 Many Open Questions . 59 11 X-ray and gamma-ray binaries 59 12 Supermassive black hole binaries in the cores of AGN 61 12.1 Modeling electromagnetic signatures of merging SMBBHs . 64 13 Cosmology and cosmography with gravitational waves 65 13.1 Standard sirens as a probe of the late universe . 65 13.1.1 Redshift information . 67 13.1.2 Standard sirens with current GW data: GW170817 . 68 13.1.3 Cosmological forecasts with standard sirens . 69 13.1.4 Future prospects . 70 13.2 Interplay between GWs from binaries and from early-universe
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