Book of Abstracts Ii Contents
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Gravitational Wave Probes of Fundamental Physics Monday, 11 November 2019 - Wednesday, 13 November 2019 Volkshotel, Amsterdam, The Netherlands Book of Abstracts ii Contents Welcome ............................................. 1 Detecting Gauged Lµ − Lτ using Neutron Star Binaries .................. 1 Primordial Gravitational Waves from Modified Gravity and Cosmology .......... 1 Novel signatures of dark matter in laser-interferometric gravitational-wave detectors . 1 Audible Axions ......................................... 2 Gravitational waves and collider probes of extended Higgs sectors ............. 3 Simulating black hole dynamics and gravitational wave emission in galactic-scale simula- tions ............................................. 3 Dark Energy Instabilities induced by Gravitational Waves ................. 3 Probing the Early and Late Universe with the Gravitational-Wave Background . 4 Dark, Cold, and Noisy: Constraining Secluded Hidden Sectors with Gravitational Waves 4 Extreme Dark Matter Tests with Extreme Mass Ratio Inspirals ............... 5 Cosmological Tests of Gravity with Gravitational Waves .................. 5 Gravitational Collider Physics ................................. 5 Radiation from Global Topological Strings using Adaptive Mesh Refinement . 6 Massive black hole binaries in the cosmos .......................... 6 Constraining the speed of gravity using astrometric measurements ............ 7 Cross-correlation of the astrophysical gravitational-wave background with galaxy cluster- ing .............................................. 7 Fundamental and Gravitational Wave Science with Pulsar Timing ............. 7 test short talk .......................................... 8 Binary black holes beyond general relativity ......................... 8 Discussion session: particle physics around black holes ................... 8 Discussion session: numerics ................................. 9 iii Dense matter equation of state constraints from NICER ................... 9 New prospects in numerical relativity ............................. 9 A Unique Multi-Messenger Probe of QCD Axion Dark Matter ............... 9 Gravitational-wave echoes ................................... 10 Gravitational Wave Detection at low frequency with Atom Interferometry . 10 Black holes in string theory and observations ........................ 11 Clarifying the Hubble Constant Tension ........................... 11 Phase Transitions, Dark Sectors and Gravitational Waves . 11 Gravitational Waves signatures from collisions of exotic compact objects . 11 Gravitational probes of exotic compact objects ........................ 12 Discussion session: primordial black holes .......................... 12 Gravity waves from ALP dark matter fragmentation ..................... 12 Discussion session: cosmology ................................. 12 Wrap-up talk .......................................... 13 Hearing the sirens of the early Universe: Primordial Black Holes and Gravitational Waves 13 NANOGrav: progress toward detecting a SMBHB stochastic background . 13 iv Gravitational Wave Probes of Fundamental Physics / Book of Abstracts 1 Welcome Lightning talks / 44 Detecting Gauged Lµ − Lτ using Neutron Star Binaries Author: Ranjan Laha1 Co-authors: Toby Oliver Opferkuch 1; Jeff Dror 2 1 CERN 2 Lawrence Berkeley National Laboratory Corresponding Authors: [email protected], [email protected], [email protected] We show that gravitational wave emission from neutron star binaries can be used to discover ultra- light U(1)Lµ−Lτ vectors by making use of the large inevitable abundance of muons inside neutron stars. In pulsar binaries the U(1)Lµ−Lτ vectors induce an anomalously fast decay of the orbital period through the emission of dipole radiation. We study a range of different pulsar binaries, finding the most powerful constraints for vector masses below O(10−18 eV). For merging binaries the presence of muons in neutron stars can result in dipole radiation as well as a modification of the chirp mass during the inspiral phase. We make projections for a prospective search using the GW170817 event and find that current data can discover light vectors with masses below O(10−18 eV). In both cases, the limits attainable with neutron stars reach gauge coupling g0 <∼ 10−20, which are many orders of magnitude stronger than previous constraints. We also show projections for next generation experiments, such as Einstein Telescope. Lightning talks / 48 Primordial Gravitational Waves from Modified Gravity and Cos- mology Author: Anish Ghoshal1 1 L Corresponding Author: [email protected] We will review gravitational wave propagation in standard and non-standard cosmological history. Particularly, we will discuss the spectrum of primordial gravitational (PWG) waves spectrum in- duced due to inflation in such scenarios. Then we will show the predictions in scenarios aspre- dicted by various modified gravity theories, motivated by beyond ΛCDM model of cosmology and dark energy scenarios. As an example, we will discuss scalar-tensor theory as modified cosmology candidate. Next we will comment upon the sensitivity reaches of such predictions within the future and current GW detectors. Short talks / 49 Novel signatures of dark matter in laser-interferometric gravitational- wave detectors Page 1 Gravitational Wave Probes of Fundamental Physics / Book of Abstracts Authors: Yevgeny Stadnik1; Hartmut Grote2 1 Kavli IPMU, University of Tokyo 2 Cardiff University Corresponding Authors: [email protected], [email protected] Dark matter may induce apparent temporal variations in the physical “constants”, including the electromagnetic fine-structure constant and fermion masses. In particular, a coherently oscillating classical dark-matter field may induce apparent oscillations of physical constants in time, whilethe passage of macroscopic dark-matter objects (such as topological defects) may induce apparent tran- sient variations in the physical constants. We point out several new signatures of the aforementioned types of dark matter that can arise due to the geometric asymmetry created by the beam-splitter ina two-arm laser interferometer. These new signatures include dark-matter-induced time-varying size changes of a freely-suspended beam-splitter and associated time-varying shifts of the main reflect- ing surface of the beam-splitter that splits and recombines the laser beam, as well as time-varying refractive-index changes in the freely-suspended beam-splitter and time-varying size changes of freely-suspended arm mirrors. We demonstrate that existing ground-based experiments already have sufficient sensitivity to probe extensive regions of unconstrained parameter space inmodels involving oscillating scalar dark-matter fields and domain walls composed of scalar fields. Inthe case of oscillating dark-matter fields, Michelson interferometers — in particular, the GEO\,600 de- tector — are especially sensitive. The sensitivity of Fabry-Perot-Michelson interferometers, includ- ing LIGO, VIRGO and KAGRA, to oscillating dark-matter fields can be significantly increased by making the thicknesses of the freely-suspended Fabry-Perot arm mirrors different in the two arms. Not-too-distantly-separated laser interferometers can benefit from cross-correlation measurements in searches for effects of spatially coherent dark-matter fields. In addition to broadband searches for oscillating dark-matter fields, we also discuss how small-scale Michelson interferometers, such as the Fermilab holometer, could be used to perform resonant narrowband searches for oscillating dark-matter fields with enhanced sensitivity to dark matter. Finally, we discuss the possibility of using future space-based detectors, such as LISA, to search for dark matter via time-varying size changes of and time-varying forces exerted on freely-floating test masses. Reference: H. Grote and Y. V. Stadnik, arXiv:1906.06193 Lightning talks / 50 Audible Axions Authors: Wolfram Ratzinger1; Benjamin Stefanek2; Pedro Klaus Schwaller3; Camila S. Machado3 1 Johannes Gutenberg Universität Mainz 2 JGU Mainz 3 Mainz University Corresponding Authors: [email protected], [email protected], [email protected], [email protected] mainz.de Conventional approaches to probing axions and axion-like particles (ALPs) typically rely on a cou- pling to photons. However, if this coupling is extremely weak, ALPs become invisible and are ef- fectively decoupled from the Standard Model. We show that such invisible axions, which are viable candidates for dark matter, can produce a stochastic gravitational wave background in the early uni- verse. This signal is generated in models where the invisible axion couples to a dark gaugeboson that experiences a tachyonic instability when the axion begins to oscillate. Incidentally,the same mechanism also widens the viable parameter space for axion dark matter. Quantum fluctuations amplified by the exponentially growing gauge boson modes source chiral gravitational waves. We discuss the parameter space where this signal can possibly be detected by pulsar timing arrays or space/ground-based gravitational wave detectors, taking into account obstructions to the tachyonic growth like kinetic mixing of the gauge boson resulting in a thermal mass. Page 2 Gravitational Wave Probes of Fundamental Physics / Book of Abstracts Lightning talks / 51 Gravitational waves and collider probes of extended Higgs sec- tors Author: Maria Ramos1 1 LIP Corresponding Author: [email protected]