Bulletin of the American Physical Society
2018 Joint Fall Meeting of the Texas Sections of APS, AAPT and Zone 13 of the SPS
Volume 63, Number 18
Friday–Saturday, October 19–20, 2018; University of Houston, Houston, Texas
Session C03: Astronomy and Astrophysics I |
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Chair: Liming Li, University of Houston Room: Science and Engineering Classroom (SEC) 203 |
Friday, October 19, 2018 2:25PM - 3:01PM |
C03.00001: Numerical Analysis of Magnetogenesis’ Primordial Mechanism Invited Speaker: David Garrison We present the results of Relativistic Magnetohydrodynamic simulations utilizing initial conditions from both the Electroweak and QCD phase transitions in order to see if seed magnetic fields may be generated via the Biermann Battery Mechanism of Magnetogensis. These simulations occur in a simulated early universe between 10^-11 s and 10^-3 s after the Big Bang. We find that magnetic fields greater than 10^-19 G are generated at small scales and magnetic fields of 10^-24 G are generated on the Mpc scale. Further work is needed to understand how these fields may have impacted the large-scale structures we observe today. |
(Author Not Attending)
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C03.00002: Using consistency tests between cosmological data sets to investigate gravity theory and cosmic acceleration Mustapha Ishak-Boushaki, Weikang Lin Testing general relativity at cosmological scales and probing the cause of cosmic acceleration are among the important objectives targeted by incoming and future astronomical surveys and experiments. I present our recent results on consistency tests that can provide insights about the underlying gravity theory and cosmic acceleration using cosmological data sets. We use new statistical measures that can detect discordances when present. We also use an algorithmic procedure that is able to identify in some cases whether an inconsistency is due to problems related to systematic effects in the data or to the underlying model. Some recent published tensions between data sets are also examined using our formalism, e.g. the Hubble constant, Planck and Large-Scale-Structure. |
Friday, October 19, 2018 3:13PM - 3:25PM |
C03.00003: Constraints on modified gravity parameters from Planck and other data sets. Cristhian Garcia Quintero, Logan K Fox, Mustapha Ishak-Boushaki, Weikang Lin A possible solution for the cosmic acceleration problem may be a modification of general relativity at large scales. We consider a parametrization for modified gravity using similar to that used in the Planck 2015 analysis. We use the Boltzmann code CAMB for calculating the Cosmic Microwave Background (CMB) theoretical power spectrum and the code COSMOMC for cosmological parameter estimation in order to analyze this parametrization. We reproduce Planck 2015 results but question how the tension with General Relativity is being reduced using CMB Lensing. Finally, we make some remarks on the non-gaussianity of the modified gravity parameters and examine closely the tension observed. |
Friday, October 19, 2018 3:25PM - 3:37PM |
C03.00004: Unveiling Exotic Celestial Activity in the Universe Kean Martinic, Blagoy Rangelov We have successfully carried out an observational program with the Chandra X-ray Observatory to determine the nature of 8 unidentified celestial gamma-ray sources. Based on intelligent parameter selection, we expect our observation data to be dominated by highly magnetized neutron stars, ~10^12 Guass, with a possible inclusion of X-ray binaries. For each source, we calculate X-ray fluxes in a range of energy bands (0.5-7keV), and search for counterparts at lower energies (e.g., Optical, IR). This multi-wavelength dataset is then prepped to be analyzed by a machine learning classification tool to determine the nature of these sources. For bright X-ray sources, we also extract X-ray spectra which allows for a more accurate source identification. Our preliminary results conclude that the unidentified Fermi sources 2FGL J1839.0-0102 and 2FGL J0340.5+5307 host the brightest X-ray sources of our eight observations. |
Friday, October 19, 2018 3:37PM - 3:49PM |
C03.00005: Creation and annihilation of a new dark matter candidate, as potentially observable by the CMS and ATLAS experiments at the LHC and the Fermi-LAT and AMS-02 experiments in space John Killough A new dark matter candidate [1,2] has couplings to Z and W gauge bosons that are in a sense weaker than those of other popular WIMPs (weakly interacting massive particles) -- principally the neutralino -- since they are either second-order or momentum-dependent. This may explain why dark matter particles have not yet been observed. On the other hand, this new particle should be observable in all the experiments that are currently searching for dark matter particles. For example, at the LHC, the CMS and ATLAS experiments should focus on events in which virtual Z bosons, or else W or Z boson pairs, produce particle- antiparticle pairs involving the new spin 1/2 neutral particle proposed here, which are then detected as missing transverse energy. The well-defined couplings and mass of this new WIMP provide a well-defined signature of its creation or annihilation, even though the cross-sections are smaller than for e.g. neutralinos. [1] Roland E. Allen and Aritra Saha, "Dark matter candidate with well-defined mass and couplings", |
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