Bulletin of the American Physical Society
2021 Annual Meeting of the APS Four Corners Section
Volume 66, Number 11
Friday–Saturday, October 8–9, 2021; Virtual; Mountain Daylight Time
Session K02: Gravitational Physics |
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Chair: John Harton, Colorado State University |
Saturday, October 9, 2021 1:00PM - 1:24PM |
K02.00001: Wrangling the Beast – Precision Supermassive Black Hole Mass Measurement With ALMA Invited Speaker: Benjamin Boizelle While supermassive black holes (BHs) gravitationally dominate only the innermost regions of galaxies, their masses correlate with large-scale galaxy properties, hinting that BHs co-evolve with their host galaxies over the age of the universe. These correlations suggest a distinct evolutionary pathway for the most luminous galaxies; however, an incomplete census of >$10^9$ solar mass BHs (and large measurement uncertainties) prevent any definitive conclusions. While still useful in mapping out the circumnuclear region of these massive galaxies, I will demonstrate that warm molecular and ionized gas tracers tend to be turbulent probes. Emission-line observations with the Atacama Large Millimeter/submillimeter Array (ALMA) are opening a new avenue for studying BH demographics in nearby galaxies. I will present ongoing ALMA CO imaging that has resolved circularly-rotating molecular gas disks in the nuclei of a growing number of very luminous galaxies, providing ideal probes of their inner gravitational potentials. I will highlight results from recent gas-dynamical modeling efforts, which have enabled some of the most precise direct BH mass determinations to date and important cross-checks with other measurement techniques. I will also discuss the prospect of future telescopes like the next-generation Very Large Array (ngVLA) to expand on ALMA's revolutionary capabilities. [Preview Abstract] |
Saturday, October 9, 2021 1:24PM - 1:36PM |
K02.00002: Asymmetric Reheating by Primordial Black Holes Barmak Shams Es Haghi, Pearl Sandick, Kuver Sinha We investigate Hawking evaporation of a population of primordial black holes (PBHs) prior to Big Bang Nucleosynthesis (BBN) as a mechanism to achieve asymmetric reheating of two sectors coupled solely by gravity. While the visible sector is reheated by the inflaton or a modulus, the dark sector is reheated by PBHs. Compared to inflationary or modular reheating of both sectors, there are two advantages: $(i)$ inflaton or moduli mediated operators that can subsequently thermalize the dark sector with the visible sector are not relevant to the asymmetric reheating process; $(ii)$ the mass and abundance of the PBHs provide parametric control of the thermal history of the dark sector, and in particular the ratio of the temperatures of the two sectors. Asymmetric reheating with PBHs turns out to have a particularly rich dark sector phenomenology, which we explore using a single self-interacting real scalar field in the dark sector as a template. Four thermal histories, involving non-relativistic and relativistic dark matter (DM) at chemical equilibrium, followed by the presence or absence of cannibalism, are explored. These histories are then constrained by the observed relic abundance in the current Universe and the Bullet Cluster. [Preview Abstract] |
Saturday, October 9, 2021 1:36PM - 1:48PM |
K02.00003: Towards Binary Black Hole Mergers in Einstein-Maxwell-Dilaton-Axion Theory Sebastian Vander Ploeg Fallon, Eric Hirschmann, David Neilsen If detected, differences between the observed gravitational wave signatures of binary black hole mergers and the signatures predicted by general relativity could provide direct evidence of the improvements that a new theory of gravity might require. We describe numerical approaches to predict the gravitational wave signatures from the collision of two Kerr-Sen black holes in Einstein-Maxwell-dilaton-axion (EMDA) theory. Being able to do this will allow us to compare gravitational wave signatures from an alternative theory of gravity with the predictions of general relativity. We describe our efforts in this direction. In particular, we detail our code generation techniques, our approach to solving the resulting BSSN equations with Kerr-Sen initial data, some initial tests, and some preliminary results of the code. [Preview Abstract] |
Saturday, October 9, 2021 1:48PM - 2:00PM |
K02.00004: Simulating binary black hole systems with intermediate mass ratios Eric Hirschmann, Milinda Fernando, David Neilsen, Hari Sundar, Yosef Zlochower Binary black hole (BBH) systems with components that have very different masses are a subset of the BBH population that, from a computational perspective, are more challenging to simulate than near equal mass binaries. Their resource demands are significant and it is understood that successfully evolving these requires computational approaches that are tuned to this region of the parameter space. We combine two such approaches, namely a parallel octree-refined adaptive mesh and a wavelet adaptive multiresolution method to produce the mesh. This results in a highly scalable framework that allows for a more efficient and rapid simulation of such intermediate mass ratio BBHs. We present some results from these efforts. [Preview Abstract] |
Saturday, October 9, 2021 2:00PM - 2:12PM |
K02.00005: A new class of monopole solutions in five-dimensional general relativityand the role of negative scalar field energy in vacuum solutions Yaroslav Balytskyi, Detlef Hoyer, Anatoliy Pinchuk, Lance Williams Using numerical algebra tools, new classes of monopole solutions are obtained to the static, spherically-symmetric vacuum field equations of five-dimensional general relativity. First proposed by Kaluza, 5D general relativity unites gravity and classical electromagnetism with a scalar field. These monopoles correspond to bodies carrying mass, electric charge, and scalar charge. The Reissner-Nordstr \textasciidieresis om limit allows us to constrain the signature of the fifth component to be space-like, but valid solutions are obtained for either sign of the scalar field. We find that Kaluza vacuum solutions imply the scalar field energy density is the negative of the electric field energy density, so the total electric and scalar field energy of the monopole is zero. Yet the new solutions provide reasonable Reissner-Nordstr \textasciidieresis om and Coulomb limits in mathematical form, with varying possibilities for the scalar field. The vanishing of the total electric and scalar field energy density for vacuum solutions seems to imply the scalar field can be understood as a negative-energy foundation on which the electric field is built. [Preview Abstract] |
Saturday, October 9, 2021 2:12PM - 2:24PM |
K02.00006: Kibble mechanism for electroweak magnetic monopoles and magnetic fields Teerthal Patel, Tanmay Vachaspati Magnetic fields are known to exist throughout the Universe on scales ranging from stars to that of galaxies and galactic clusters. Indications of their presence on cosmological scales by blazar observations have motivated studies into a primordial origin. We studied one such promising candidate, the electroweak phase transition(EWPT) in the early Universe. Magnetic monopoles and strings that connect them arise in electroweak theory of the standard model and their subsequent annihilation can be thought to leave behind relic cosmological magnetic fields. The Kibble mechanism has been used to study topological defect formation during a phase transition, most notably in the context of cosmic strings. We have adopted a suitably modified Kibble mechanism to study EWPT and the resulting properties of the monopoles, strings and magnetic fields are discussed in this work. The initial conditions obtained through this analysis can be used for further evolution and thus presents an opportunity to probe EWPT using a cosmological observable. [Preview Abstract] |
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