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Full-Text Articles in Physical Sciences and Mathematics
Testing General Relativity With Current Cosmological Data, Scott F. Daniel, Eric V. Linder, Tristan L. Smith, Robert R. Caldwell
Testing General Relativity With Current Cosmological Data, Scott F. Daniel, Eric V. Linder, Tristan L. Smith, Robert R. Caldwell
Dartmouth Scholarship
Deviations from general relativity, such as could be responsible for the cosmic acceleration, would influence the growth of large-scale structure and the deflection of light by that structure. We clarify the relations between several different model-independent approaches to deviations from general relativity appearing in the literature, devising a translation table. We examine current constraints on such deviations, using weak gravitational lensing data of the CFHTLS and COSMOS surveys, cosmic microwave background radiation data of WMAP5, and supernova distance data of Union2. A Markov chain Monte Carlo likelihood analysis of the parameters over various redshift ranges yields consistency with general relativity …
Non-Gaussianity From Self-Ordering Scalar Fields, Daniel G. Figueroa, Robert R. Caldwell, Marc Kamionkowski
Non-Gaussianity From Self-Ordering Scalar Fields, Daniel G. Figueroa, Robert R. Caldwell, Marc Kamionkowski
Dartmouth Scholarship
The Universe may harbor relics of the post-inflationary epoch in the form of a network of self-ordered scalar fields. Such fossils, while consistent with current cosmological data at trace levels, may leave too weak an imprint on the cosmic microwave background and the large-scale distribution of matter to allow for direct detection. The non-Gaussian statistics of the density perturbations induced by these fields, however, permit a direct means to probe for these relics. Here we calculate the bispectrum that arises in models of self-ordered scalar fields. We find a compact analytic expression for the bispectrum, evaluate it numerically, and provide …
The Nature Of The Strong 24 Μmspitzersource J222557+601148: Not A Young Galactic Supernova Remnant, Robert A. Fesen, Dan Milisavljevic
The Nature Of The Strong 24 Μmspitzersource J222557+601148: Not A Young Galactic Supernova Remnant, Robert A. Fesen, Dan Milisavljevic
Dartmouth Scholarship
The nebula J222557+601148, tentatively identified by Morris et al. as a young Galactic supernova remnant (SNR) from Spitzer Galactic First Look Survey images and a follow-up mid-infrared spectrum, is unlikely to be an SNR remnant based on Hα, [O III], [S II] images, and low-dispersion optical spectra. The object is seen in Hα and [O III] λ5007 images as a faint, roughly circular ring nebula with dimensions matching that seen in 24 μm Spitzer images. Low-dispersion optical spectra show it to have narrow Hα and [N II] λλ6548,6583 line emissions with no evidence of broad or high-velocity (v ≥ …
Core Gas Sloshing In Abell 1644, Ryan E. Johnson, Maxim Markevitch, Gary A. Wegner, Christine Jones, William R. Forman
Core Gas Sloshing In Abell 1644, Ryan E. Johnson, Maxim Markevitch, Gary A. Wegner, Christine Jones, William R. Forman
Dartmouth Scholarship
We present an analysis of a 72 ks Chandra observation of the double cluster Abell 1644 (z = 0.047). The X-ray temperatures indicate that the masses are M 500 = (2.6 ± 0.4) × 1014 h –1 M ☉ for the northern sub-cluster and M 500 = (3.1 ± 0.4) × 1014 h –1 M ☉ for the southern, main cluster. We identify a sharp edge in the radial X-ray surface brightness of the main cluster, which we find to be a cold front, with a jump in temperature of a factor of ~3. This edge possesses …