Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session G16: Cosmology with Gravitational Waves 
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Sponsoring Units: DAP DGRAV Chair: Ken herner, Fermilab Room: Sheraton Grand Ballroom I 
Sunday, April 14, 2019 8:30AM  8:42AM 
G16.00001: Update on Standard Siren Science Daniel Holz, HsinYu Chen, Maya Fishbach We review the present and future of gravitationalwave standard siren measurements. We discuss existing measurements with GW170817 and GW170814, focusing on both counterpart and statistical standard sirens. We also forecast measurements from upcoming gravitationalwave detector networks, showing that future networks may constrain the Hubble constant to ~2% within 5 years. 
Sunday, April 14, 2019 8:42AM  8:54AM 
G16.00002: Measuring the HubbleLemaître constant with neutron star black hole mergers Salvatore Vitale, HsinYu Chen The binary neutron star merger GW170817 allowed for the first standardsiren measurement of the HubbleLemaître constant. The amplitude of the gravitationalwave signal provided a measurement of the luminosity distance, while the identification of the host galaxy yielded the redshift. As more binary neutron star mergers are detected in the next few years, one can expect to achieve a measurement of the HubbleLemaître with an uncertainty of a few percent. The limiting factor in the measurement is expected to be the precision with which one can measure the luminosity distance of individual sources from the gravitationalwave data. In this talk we discuss a different class of gravitationalwave sources that are also expected to produce light, and could thus be used as standard sirens: neutron star black hole mergers. 
Sunday, April 14, 2019 8:54AM  9:06AM 
G16.00003: A standard siren measurement of the Hubble constant from GW170817 without the electromagnetic counterpart Maya Fishbach, Daniel Holz We perform a statistical standard siren analysis of GW170817. Our analysis does not utilize knowledge of NGC 4993 as the unique host galaxy to GW170817. Instead, we consider each galaxy within the GW170817 localization region as a potential host; combining the redshift from each galaxy with the distance estimate from GW170817 provides an estimate of the Hubble constant, H_{0}. We explore the dependence of our results on the thresholds by which galaxies are included in our sample, as well as the impact of weighting the galaxies by stellar mass and starformation rate. Considering all galaxies brighter than 0.01 L^{*}_{B} as equally likely to host a BNS merger, we find H_{0}=76^{+48}_{−23} km/s/Mpc. We show that weighting the host galaxies by stellar mass or starformation rate provides entirely consistent results with potentially tighter constraints. While these estimates are inferior to the value from the counterpart standard siren measurement utilizing NGC 4993 as the unique host, H0=76^{+19}_{−13} km/s/Mpc (determined from the same publicly available data), our analysis is a proofofprinciple demonstration of the statistical approach first proposed by Bernard Schutz over 30 years ago. 
Sunday, April 14, 2019 9:06AM  9:18AM 
G16.00004: Calibrating the cosmic distance ladder using gravitationalwave observations Anuradha Gupta, Sathyaprakash Bangalore, Bernard Schutz, Rahul Srinivasan Type Ia supernovae (SNe Ia) are one of the preeminent distance ladders and precision cosmology probes due to their intrinsic brightness which allows them to be observable even in the distant Universe. However, a correct understanding of their progenitors and physics relies on the accuracy with which one measures the distances to their host galaxies or galaxy clusters. This knowledge of the distance to SNe Ia host galaxies requires calibration with Cepheids whose role as standard candles is still under debate. Gravitational waves (GWs) from compact binary coalescences, on the other hand, are selfcalibrating standard candles, i.e., measuring GWs from coalescing binaries allow one to directly measure their distances without using the cosmic distance ladder. Therefore, GWs could be used to validate the distance to the galaxy or the cluster in which a supernova has already occurred. We investigate when in future it could be possible for GWs to calibrate distances to already known SNe Ia. We compute error in the distance measurement using various networks of second and third generation GW detectors and show that a good enough accuracy can be achieved in future such that GWs will be able to calibrate distances to the local SNe Ia. 
Sunday, April 14, 2019 9:18AM  9:30AM 
G16.00005: Does Dark Siren Cosmology Depend on the Host Galaxies of the Merger Event? James Annis, Antonella Palmese, Amber Lenon, Marcelle SoaresSantos, Kenneth Herner Dark siren cosmology is made possible by LIGO measured distances and spatial localizations and astronomer measured galaxy catalogs with redshifts or photometric redshifts. A central question is what if the binary black hole (BBH) mergers occur in galaxies not in the galaxy catalog? For example what if BBH mergers occur in low metallicity dwarf galaxies and we are using a highly complete massive red galaxy catalog? In cosmology this question is stated as: what if the galaxy tracer population has a bias relative to the dark matter different than the BBH mergers do? Does the H0 measurement made by a using a statistical redshift from galaxy photometric redshift catalogs and LIGO luminosity distances and spatial localizations depend on the bias of the source population and the bias of the tracer population? As different galaxy catalogs have different bias relative to dark matter. we use fast lognormal galaxy distributions generated by FLASK from mattermatter power spectra to simulate galaxy catalogs with different bias. We use these catalogs to measure the H_{0} measurement bias as a function of the source and tracer population bias. 
Sunday, April 14, 2019 9:30AM  9:42AM 
G16.00006: A Possible Solution to the Disagreement about the Hubble Constant F R Tangherlini Recently the author [1] has proposed that a solution to the disagreement between the Planck collaboration CMB lower H_{0 }value, together with the BOSS collaboration BAO equally lower value, and the significantly higher value found by the SHOES collaboration cosmic distance ladder (CDL) study, arises from the CMB and BAO values being for a decelerating universe, rather than an accelerating universe. In contrast, the CDL H_{0 } is for an accelerating universe. To check , it is shown that when the deceleration parameter q_{0} =  0.55 in the CDL expression for H_{0 } is replaced by q_{0} = 0.5 for the decelerating Einstein de Sitter (EdS) universe, CDL H_{0 } agrees with CMB and BAO values for z = 0.16, and z = 0.17, respectively. Earlier [2], it was shown that an EdS universe, with a dark energy that, instead of having a negative pressure, has a nondispersive index of refraction n ≈1.5, for 0 ≤ z ≤ 0.6, so that the speed of light through intergalactic, but not galactic, space is ~2c/3, yields an alternative explanation for the increased apparent magnitude of the SNe Ia, and increased distance to the BAO "standard ruler." An astronomical test based on discordant redshifts has been proposed [3]. ^{1} F. R. Tangherlini, J. Mod. Phys., 9, 1827 (2018); ^{2} 6, 78 (2015); ^{3} 8, 622 (2017). 
Sunday, April 14, 2019 9:42AM  9:54AM 
G16.00007: Nonadiabatic universe and the cosmological constant Rajendra P Gupta We have shown that the Hubble constant H_{0} embodies the information about the evolutionary nature of the cosmological constant Λ, gravitational constant G, and the speed of light c. By explicitly incorporating the nonadiabatic nature of the universe in the Friedmann equation through the evolution of the energy density, we have derived expressions for the time evolution of G/c^{2} (≡K) and dark energy density ε_{Λ }related to Λ. We found (dK/dt)/K = 1.8H_{0} and, for redshift z, ε_{Λ,z}/ε_{Λ,0} = [0.4+0.6(1+z)^{1.5}]^{2}. Since the two expressions are related, we believe that the time variation of K (and therefore that of G and c) is manifested as dark energy in cosmological models. When we adapt the standard ΛCDM model for the z dependency of ε_{Λ} rather than it being a constant, we obtain surprisingly good results fitting the SNe Ia redshift z vs distance modulus µ data. Even more significant finding is that the new ΛCDM model, when parameterized with z < 0.5 data set, yields significantly better fit to the z > 0.5 data sets than the standard ΛCDM model. Thus the new model may be considered robust and reliable enough for predicting distances of radiation emitting extragalactic redshift sources for which luminosity distance measurement may be difficult, unreliable, or no longer possible. 
Sunday, April 14, 2019 9:54AM  10:06AM 
G16.00008: Spacetime Structure, Massenergy Structure, and Explanation of Hubble's Redshift, Dark Matter, and Dark Energy Dayong Cao, Dayong Cao There are massenergy structure, spacetime structure, massenergy center, spacetime center, massenergy big bang, and spacetime big bang. A balance structure between massenergy and spacetime can explain among the homogeneous, isotropic, and flat structure of the universe. There is not only a expansion of scale factor of space but also a expansion of scale factor of time. And there is a expansion of scale factor of massenergy. Following the structure expansions, the light spectrums and speed of light will change. But the old theory of explanation both of the Hubble’s redshift and expansion of the universe did not consider them. Replacing history structure with current structure, according to Einstein Lorentz transformation, the new explanations both of Hubble’s red shift and dark energy is the expansions of light cause by structure field between massenergy and spacetime when the light (from a center structure) travel through the flat universe (to a other center structure). The negative gravity of spacetime structure can explain of the dark matter. In 2008, the author defined space is amplitude square; defined time is frequency. http://meetings.aps.org/Meeting/APR18/Session/Y13.2 http://meetings.aps.org/link/BAPS.2014.APR.Y9.1 http://meetings.aps.org/link/BAPS.2008.DNP.LG.6

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