Bulletin of the American Physical Society
APS April Meeting 2020
Volume 65, Number 2
Saturday–Tuesday, April 18–21, 2020; Washington D.C.
Session G10: New Techniques and Theories for Dark Matter and CosmologyLive
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Sponsoring Units: DAP Chair: Yacine Ali-Haimoud, New York University Room: Roosevelt 5 |
Sunday, April 19, 2020 8:30AM - 8:42AM Live |
G10.00001: Testing the Galactic Center Gamma-Ray Excess with the Known Catalogue of Gamma-Ray Point Sources Ilias Cholis The Fermi-LAT collaboration has recently released a new point source catalog, referred to as 4FGL. For the first time, we perform a template fit using information from this new catalog and find that the Galactic center excess is still present. On the other hand, we find that a wavelet-based search for point sources is highly sensitive to the use of the 4FGL catalog: no excess of small-angular-scale pixels is apparent when we mask out 4FGL point sources. We postulate that the 4FGL catalog contains the large majority of bright point sources that have previously been suggested to account for the excess in gamma rays detected at the Galactic center in Fermi-LAT data. Furthermore, after identifying which bright sources have no known counterpart, we place constraints on the luminosity function necessary for point sources to explain the smooth emission seen in the template fit. [Preview Abstract] |
Sunday, April 19, 2020 8:42AM - 8:54AM Live |
G10.00002: Testing Dark Energy with Multi-Messenger Observations Macarena Lagos We still have a considerable lack of understanding about the constituents of our Universe and, in addition, tensions are starting to arise between datasets as we reach subpercent precision constraints. In this talk, I will mention how we can use standard sirens to probe possible physics beyond the concordance LCDM model. In particular, I will show how the presence of a dynamical dark energy component can induce a time-evolving gravitational coupling, which modifies the propagation of gravitational waves, and can thus be tested with observations of compact binary mergers. I will also discuss how dynamical dark energy can bias independent constraints on the current Hubble rate set with future LIGO detections. Finally, I will clarify the role that other constraints on time-evolving gravitational couplings ---such as from Lunar Laser Ranging and Binary Pulsars--- play on the outlook of using standard sirens for testing dark energy. [Preview Abstract] |
Sunday, April 19, 2020 8:54AM - 9:06AM Live |
G10.00003: Primordial Black Holes as a common origin for baryons and dark matter. Sebastien Clesse The origin of the baryon asymmetry of the Universe (BAU) and the nature of dark matter are two of the most challenging problems in cosmology. I will present a scenario in which the gravitational collapse of large inhomogeneities at the quark-hadron epoch generates both the baryon asymmetry and dark matter in the form of primordial black holes(PBHs). The collapse of density fluctuations into PBHs is accompanied by the violent expulsion of surrounding material, which might be regarded as a sort of "primordial supernova". The acceleration of protons to relativistic speeds provides the ingredients for efficient baryogenesis around the collapsing regions and its subsequent propagation to the rest of the Universe. This scenario naturally explains the observed BAU and why the baryons and dark matter have comparable densities. No parameter fine-tuning is required if the PBH originate from the fluctuations of a light stochastic spectator field during inflation. The predicted wide mass distribution of PBH ranges from sub-solar to several hundred solar masses. It evades the current limits on the PBH abundance and could explain a series of observations, including the mass, rate and low effective spins of the black hole mergers detected by LIGO-Virgo. [Preview Abstract] |
Sunday, April 19, 2020 9:06AM - 9:18AM Live |
G10.00004: Canonical cosmological perturbation theory with geometrical clocks and Dirac observables Parampreet Singh, Kristina Giesel Working with an extended phase space, where lapse and shift are not treated as Lagrange multipliers, we explore connections between geometrical clocks, Dirac observables and gauge-invariant quantities in linearized canonical cosmological perturbation theory. Our approach allows understanding various gauge-invariant variables such as Bardeen potential in canonical setting which was not possible in the existing approach to canonical perturbation theory. In this sense, our analysis bridges gap between canonical perturbation theory and the conventional approach. An efficient method is introduced to derive evolution equations for gauge-invariant quantities which is illustrated for Bardeen potential and Mukhanov-Sasaki variable. [Preview Abstract] |
Sunday, April 19, 2020 9:18AM - 9:30AM |
G10.00005: Magnetic Helicity and Dynamos in Galaxies Ethan Vishniac, Amir Jafari Magnetic helicity is a robustly conserved topological invariant, even in the presence of turbulence. It produces a back reaction which suppresses kinematic dynamos. In shearing and rotating objects, like galaxies, turbulence produces a magnetic helicity flux, aligned with the axis of the system. The resulting accumulation of magnetic helicity dominates over the kinetic helicity in one eddy turnover time and drives a dynamo which can grow much more rapidly than a conventional kinematic dynamo. We will discuss the implications for the early history of galactic magnetic fields and their saturation strengths. [Preview Abstract] |
Sunday, April 19, 2020 9:30AM - 9:42AM |
G10.00006: Exotic Compact Objects in a Dissipative Dark Sector Jae Hyeok Chang, Daniel Egana-Ugrinovic, Rouven Essig, Chris Kouvaris We study the complete history of structure formation of a simple dark sector and show how to form exotic compact objects that vary in size from a few to millions of solar masses. These exotic compact objects may be detected and their properties measured at new high- precision astronomical observatories, giving insight into the particle nature of the dark sector without the requirement of non-gravitational interactions with the visible sector. [Preview Abstract] |
Sunday, April 19, 2020 9:42AM - 9:54AM On Demand |
G10.00007: A new approach to subhalo mass modeling in cosmology simulations Imran Sultan, Nick Frontiere, Katrin Heitmann, Salman Habib, Eve Kovacs, Patricia Larsen, Adrian Pope, Steve Rangel, Tom Uram The Last Journey simulation, an extreme-scale gravity-only cosmology simulation, ran on the Mira supercomputer at the Argonne Leadership Computing Facility and evolved over 1.24 trillion particles in a (5025 Mpc)$^3$ volume. We plan to add galaxies to Last Journey using a semi-analytic model; the result of this project will enable us to create detailed synthetic sky maps for cosmological surveys. To include subhalo information in galaxy modeling, we have developed a core tracking approach which is much less computationally expensive than subhalo finding. We accumulate and track cores, the central particles of halos, for all output steps. Using a downscaled simulation, we have applied a subhalo mass loss model found in literature to cores of halos that have merged into a host. We show that the mass function of the modeled cores agrees well with the mass function of subhalos identified by a subhalo finding algorithm after adjusting the model parameters, providing a powerful tool to use within semi-analytic galaxy modeling. [Preview Abstract] |
Sunday, April 19, 2020 9:54AM - 10:06AM On Demand |
G10.00008: High-resolution cosmological simulations of fuzzy dark matter Gabriel Lynch, Salman Habib Fuzzy dark matter (FDM) is a theoretically well-motivated model which posits that dark matter consists of a condensate of ultra-light bosons with a macroscopic de Broglie wavelength on the order of 10 kpc. Cosmological simulations of FDM are computationally demanding because the de Broglie scale must always be resolved in order to obtain accurate dynamics, and as such it has been difficult to systematically study large-scale structure and halo properties in FDM models. Here, we use a spectral Schr\"odinger-Poisson solver in order to directly simulate the macroscopic wave-function of the FDM condensate in a cosmological volume. This solver uses a distributed 3D Fast Fourier Transform that can efficiently handle simulation grids of up to 10$^6$ points, allowing for the necessary small scales to be resolved. As an application, we calculate density profiles for FDM halos taken from a large simulation volume. [Preview Abstract] |
Sunday, April 19, 2020 10:06AM - 10:18AM |
G10.00009: MADHAT: a tool for constraining dark matter annihilation in dwarf galaxies Pearl Sandick We present a brief overview of the Model-Agnostic Dark Halo Analysis Tool (\texttt{MADHAT}), a numerical tool that implements a Fermi-LAT data-driven, model-independent analysis of gamma-ray emission from dwarf satellite galaxies and dwarf galaxy candidates due to dark matter annihilation, dark matter decay, or other nonstandard or unknown astrophysics. This tool efficiently provides statistical upper bounds on the number of observed photons in excess of the number expected, based on empirical determinations of foregrounds and backgrounds, using a stacked analysis of any selected set of dwarf targets. It also calculates the resulting bounds on the properties of dark matter under any assumptions the user makes regarding dark sector particle physics or astrophysics. The methodology and implementation of MADHAT will be discussed, as well as an example of its utility. [Preview Abstract] |
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