Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session G16: Beyond Einstein Gravity: Numerical SimulationsRecordings Available
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Sponsoring Units: DGRAV Chair: Helvi Witek, University of Illinois at Urbana-Champai Room: Sky Lobby |
Sunday, April 10, 2022 8:30AM - 8:42AM |
G16.00001: Stability of rotating relativistic boson stars Nikolay Sukhov, Frans Pretorius We present on progress investigating stability of various rotating relativistic boson stars with non-linear self-interaction potential. It has been shown that there exist relativistic boson stars so compact that they possess bound circular null geodesics, which can have an impact on their stability. Depending on the self-interaction potential, rotating relativistic boson stars exibit a variety of different forms starting from usual donut-like shapes and ending with nearly shell-like structures. Such stars could be interesting alternative candidates for binary star mergers and produce gravitational waveforms that are very different from the waveforms produced in black hole and neutron star mergers. |
Sunday, April 10, 2022 8:42AM - 8:54AM |
G16.00002: Malaise and remedy of binary boson-star initial data Thomas Helfer, Ulrich Sperhake, Robin Croft, Bo-Xuan Ge, Eugene Lim, Miren Radia Through numerical simulations of boson-star head-on collisions, we explore the quality of binary initial data obtained from the superposition of single-star spacetimes. Our results demonstrate that evolutions starting from a plain superposition of individual boosted boson-star spacetimes are vulnerable to significant unphysical artefacts. These difficulties can be overcome with a simple modification of the initial data suggested in for collisions of oscillatons. |
Sunday, April 10, 2022 8:54AM - 9:06AM |
G16.00003: Non-linear dynamics of binary boson stars Nils Siemonsen, William E East Particle physics models of dark matter, and extensions to the Standard Model, predict the existence of a large abundance of light scalar degrees of freedom in the universe. From a diffuse cloud, these can form into rotating clumps of energy - boson stars. Additionally, due to their high compactness, close to that of black holes, and numerically favorable properties, these solutions serve as excellent test beds to study the non-linear dynamics of a large class of ultra-compact objects. We discuss the non-linear dynamics of binary boson star systems particularly during merger and ringdown, as well as their possible observational signatures. |
Sunday, April 10, 2022 9:06AM - 9:18AM |
G16.00004: Numerical relativity simulation of inspiraling binary black holes with massive scalar condensate clouds Cheng-Hsin Cheng, Giuseppe Ficarra, Helvi Witek Massive scalar fields in the vicinity of a rotating black hole may form condensates, e.g., due to the superradiant instability or due to accretion. These scalar fields may represent wave-like dark matter candidates or axion-like particles proposed in the string axiverse. In a binary black hole system the presence of such scalar condensates may lead to an enriched dynamical evolution, additional scalar (dipole) radiation and imprints in the gravitational wave emission. We will report on new numerical relativity simulations for which we construct constraint satisfying initial data and self-consistently solve the Einstein-Klein-Gordon equations. We then discuss implications of our results for gravitational-wave observations. |
Sunday, April 10, 2022 9:18AM - 9:30AM |
G16.00005: Numerical simulations of Effective Field Theory motivated extensions to General Relativity in the non-linear regime. Ramiro Cayuso With the goal of exploring and understanding departures from General Relativity a wide range of alternative theories have been proposed, some of whose predictions have been put under tests in different relevant regimes. However, most of these predictions have been obtained in the linearized regime, whilst only recently some effort has been put into obtaining predictions in the very important highly dynamic and non-linear regime, e.g. compact binary coalescence. In this talk I will first present the formal and practical challenges that appear when performing numerical simulations in a particular Effective Field Theory motivated (higher derivatives) extension to General Relativity. Finally I will present the results from numerical simulations where the implementation of novel methods can help us get accurate predictions in the non-linear regime for this type of higher derivative theories of gravity. |
Sunday, April 10, 2022 9:30AM - 9:42AM |
G16.00006: Nonlinear Dynamics in Quadratic Gravity Hyun Lim, Aaron Held We present the first numerically stable nonlinear evolution for quadratic gravity. We first demonstrate our results in spherical symmetry. We explore well-posedness of the respective initial-value problem by simulating randomly perturbed flat-space and black-hole initial data. Our study serves as a proof-of-principle for the possibility of stable numerical evolution in the presence of higher derivatives. We will also demonstrate current effort to simulate in full 3+1 dimensions using Dendro framework, wavelet adaptive multiresolution code for relativistic astrophysics. |
Sunday, April 10, 2022 9:42AM - 9:54AM |
G16.00007: Binary Black Hole simulations in scalar-Gauss-Bonnet gravity Alexandru Dima A thorough modeling of the strong-field regime in alternative theories of gravity is fundamental for exploiting the full potential of gravitational-wave observations and constraining deviations from General Relativity. This is a challenging task that often requires non-trivial extensions to the well-established Numerical Relativity framework. We present preliminary results on a regularization scheme inspired by the Israel-Stewart technique, developed with the aim of obtaining a well-posed initial value problem in scalar-Gauss-Bonnet effective field theory of gravity. |
Sunday, April 10, 2022 9:54AM - 10:06AM |
G16.00008: Dynamical scalarization in dynamical Chern-Simons gravity Chloe Richards Despite its success story to describe astrophysical phenomena, Einstein's General Relativity is not a viable candidate for quantum gravity. Among the most popular extensions of general relativity are quadratic gravity theories. In this talk, we will present first results on dynamical scalarization or descalarization of black holes in dynamical Chern-Simons gravity, in which a dynamical pseudo-scalar field is coupled to the Pontryagin density. We have performed numerical relativity simulations of binary black holes in this theory with a nonlinear coupling of the scalar field. |
Sunday, April 10, 2022 10:06AM - 10:18AM |
G16.00009: Evolving black holes in a nonsingular bouncing universe maxence corman One of the main unanswered questions of theoretical cosmology is whether the universe emerged from a big bang followed by a period of inflation or whether it had no beginning at all and bounced from a period of slow contraction to the current expanding phase.
It has been shown recently that it is possible for the universe to undergo a nonsingular bounce at energies well below the Planck scale such that the entire evolution can be treated classically. It is however still unclear how to treat the passage of any pre-existing black holes through the bounce to the expanding phase. In this talk, we use numerical techniques to consider the classical evolution of a black hole in a non-singular universe driven by a ``ghost'' scalar field. We show that at least for small enough black holes, the black hole passes through the bounce freely and discuss cosmological implications. |
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