3,053 research outputs found
Non-linear Redshift-Space Power Spectra
Distances in cosmology are usually inferred from observed redshifts - an
estimate that is dependent on the local peculiar motion - giving a distorted
view of the three dimensional structure and affecting basic observables such as
the correlation function and power spectrum. We calculate the full non-linear
redshift-space power spectrum for Gaussian fields, giving results for both the
standard flat sky approximation and the directly-observable angular correlation
function and angular power spectrum. Coupling between large and small scale
modes boosts the power on small scales when the perturbations are small. On
larger scales power is slightly suppressed by the velocities perturbations on
smaller scales. The analysis is general, but we comment specifically on the
implications for future high-redshift observations, and show that the
non-linear spectrum has significantly more complicated angular structure than
in linear theory. We comment on the implications for using the angular
structure to separate cosmological and astrophysical components of 21 cm
observations.Comment: 22 pages, 6 figures, changed to version accepted in Physics Review
Engine technology challenges for a 21st Century High-Speed Civil Transport
Ongoing NASA-funded studies by Boeing, McDonnell-Douglas, General Electric, and Pratt & Whitney indicate that an opportunity exists for a 21st Century High-Speed Civil Transport (HSCT) to become a major part of the international air transportation system. However, before industry will consider an HSCT product launch and an investment estimated to be over $15 billion for design and certification, major technology advances must be made. An overview of the propulsion-specific technology advances that must be in hand before an HSCT product launch could be considered is presented
Massive neutrinos and magnetic fields in the early universe
Primordial magnetic fields and massive neutrinos can leave an interesting signal in the CMB temperature and polarization. We perform a systematic analysis of general perturbations in the radiation-dominated universe, accounting for any primordial magnetic field and including leading-order effects of the neutrino mass. We show that massive neutrinos qualitatively change the large-scale perturbations sourced by magnetic fields, but that the effect is much smaller than previously claimed. We calculate the CMB power spectra sourced by inhomogeneous primordial magnetic fields, from before and after neutrino decoupling, including scalar, vector and tensor modes, and consistently modeling the correlation between the density and anisotropic stress sources. In an appendix we present general series solutions for the possible regular primordial perturbations
A Cyto-Taxonomic Study of the Genus Geranium within the Wasatch Region
The western North American species of the genus Geranium have never been satisfactorily clarified. The perennial, indigenous species of this interesting group have been particularly confusing. One important reason for confusion in this group is the fact that the taxonomic problems of the perennial species have never been studied from the genetic point of view. A sound delimitation of specific and subspecific boundaries and phylogenetic relationships cannot be achieved without the application of cyto-genetic principles.
In respect to the cytological phase of this study, the author has placed emphasis on chromosome numbers in order to show evidences for and possible origin of polyploidy. Detailed chromosome morphology has not been attempted because of the very small size of the chromosomes.
This study has been limited to the Wasatch region. this area represents a natural geographical unit which is small enough to permit a detailed field study of the group and yet provide a wide range of habitats, both ecologic and geographic. This region forms the western front of the Rocky Mountain province and extends 200 miles south from the great bend in the Bear river at Soda springs, Idaho, to the pass south of Mt. Nebo and east of Nephi, Utah
Beam Halo Monitoring at CDF
Losses from the proton and antiproton beams of the Fermilab Tevatron have
been shown to produce a halo which contribute to backgrounds to physics signals
in the Collider Detector at Fermilab (CDF). To provide a measure of the beam
halo and losses, we have installed arrays of scintillation counters on both
sides of the CDF detector. We describe here the physical configuration of these
counters, their implementation and performance within the Fermilab Accelerator
Control Network (ACNET). We show correlations between these new devices and the
accelerator operating conditions. We point out that the use of these monitors
is leading to improvement in the accelerator operations and reduced backgrounds
in CDF.Comment: 27 pages, 17 figures, submitted to NIM
Constraining Primordial Magnetism
Primordial magnetic fields could provide an explanation for the galactic
magnetic fields observed today, in which case they may also leave interesting
signals in the CMB and the small-scale matter power spectrum. We discuss how to
approximately calculate the important non-linear magnetic effects within the
guise of linear perturbation theory, and calculate the matter and CMB power
spectra including the SZ contribution. We then use various cosmological
datasets to constrain the form of the magnetic field power spectrum. Using
solely large-scale CMB data (WMAP7, QUaD and ACBAR) we find a 95% CL on the
variance of the magnetic field at 1 Mpc of B_\lambda < 6.4 nG. When we include
SPT data to constrain the SZ effect, we find a revised limit of B_\lambda < 4.1
nG. The addition of SDSS Lyman-alpha data lowers this limit even further,
roughly constraining the magnetic field to B_\lambda < 1.3 nG.Comment: 12 pages, 9 figure
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