Publications
368 results found
Jaffe A, 1996, H<inf>0</inf> and odds on cosmology, Astrophysical Journal, Vol: 471, Pages: 24-29, ISSN: 0004-637X
Recent observations by the Hubble Space Telescope of Cepheids in the Virgo cluster imply a Hubble constant H0 = 80 ± 17 km s-1 Mpc-1; other recent observations find 70 ≲ H0 ≲ 90 km s-1 Mpc-1, with several large excursions in either direction. We attempt to clarify some issues of interpretation of these results for determining the global cosmological parameters Ω and A. In this paper, we use these results as a case study in the formalism of Bayesian model comparison, allowing a rigorous comparison of the different cosmological possibilities. We concentrate our analysis on three recent determinations of the Hubble constant, but the results are generic so long as they prefer H0t0 ≳ 1, which would seem to require ∧ gt; 0 within the context of Friedmann-Robertson-Walker cosmologies. With our more rigorous methods, the data do indeed suggest a universe with a nonzero cosmological constant but vanishing curvature: Ω + ∧ = 1. © 1996. The American Astronomical Society. All rights reserved.
Jaffe AH, Kaiser N, 1995, Likelihood analysis of large-scale flows, Astrophysical Journal, Vol: 455, Pages: 26-31, ISSN: 0004-637X
We apply a likelihood analysis to the data of Lauer and Postman, with P(k) parameterized by (σ8, Γ), the likelihood function peaks at σ8 ≃ 0.3, Γ ≲ 0.025, indicating at face value very strong large-scale power, although at a level incompatible with COBE. There is, however, a ridge of likelihood such that more conventional power spectra do not seem strongly disfavored. The likelihood calculated using as data only the components of the bulk flow solution peaks at higher σ8, in agreement with other analyses, but it is rather broad. The likelihood incorporating both bulk flow and shear gives a different picture. The components of the shear are all low, and this pulls the peak to lower amplitudes as a compromise. The Lauer and Postman velocity data alone are therefore consistent with models with very strong large- scale power which generates a large bulk flow, but the small shear (which also probes fairly large scales) requires that the power would have to be at very large scales, which is strongly disfavored by COBE. The velocity data also seem compatible with more conventional P(k) with 0.2 ≲ Γ ≲ 0.5, and the likelihood is peaked around σ8 ∼ 1, in which case the bulk flow is a moderate, but not extreme, statistical fluctuation. If we apply the same techniques to the data of Riess, Press, & Kirshner, the results are quite different. The flow is not inconsistent with the microwave dipole, and we derive only an upper limit to the amplitude of the power spectrum: σ8 ≲ 1.5 at ∼99%.
GAVRIN VN, FAIZOV EL, KALIKHOV AV, et al., 1994, RECENT RESULTS FROM SAGE, Publisher: ELSEVIER SCIENCE BV, Pages: 412-417, ISSN: 0550-3213
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Jaffe AH, Stebbins A, Frieman JA, 1994, Minimal microwave anisotropy from perturbations induced at late times, Astrophysical Journal, Vol: 420, Pages: 9-25, ISSN: 0004-637X
Aside from primordial gravitational instability of the cosmological fluid, various mechanisms have been proposed to generate large-scale structure at relatively late times, including, e.g., "late-time" cosmological phase transitions. In these scenarios, it is envisioned that the universe is nearly homogeneous at the time of last scattering and that perturbations grow rapidly sometimes after the primordial plasma recombines. On this basis, it was suggested that large inhomogeneities could be generated while leaving relatively little imprint on the cosmic microwave background (MBR) anisotropy. In this paper, we calculate the minimal anisotropies possible in any "late-time" scenario for structure formation, given the level of inhomogeneity observed at present. Since the growth of the inhomogeneity involves time-varying gravitational fields, these scenarios inevitably generate significant MBR anisotropy via the Sachs-Wolfe effect. Moreover, we show that the large-angle MBR anisotropy produced by the rapid post-recombination growth of inhomogeneity is generally greater than that produced by the same inhomogeneity grown via gravitational instability. In "realistic" scenarios one can decrease the anisotropy compared to models with primordial adiabatic fluctuations, but only on very small angular scales. The value of any particular measure of the anisotropy can be made small in late-time models, but only by making the time-dependence of the gravitational field sufficiently "pathological".
Jaffe AH, 1994, Quasilinear evolution of compensated cosmological perturbations: The nonlinear σ model, Physical Review D, Vol: 49, Pages: 3893-3909, ISSN: 0556-2821
We consider the evolution of perturbations to a flat FRW universe that arise from a ''stiff source,'' such as a self-ordering cosmic field that forms in a global symmetry-breaking phase transition and evolves via the Kibble mechanism. Although the linear respone of the normal matter to the source depends on the details of the source dynamics, we show that the higher-order nonlinear perturbative equations reduce to a form identical to those of source-free Newtonian gravity in the small wavelength limit. Consequently, the resulting n-point correlation functions and their spectral counterparts will have a hierarchical contribution arising from this gravitational evolution (as in the source-free case) in addition to that possibly coming from non-Gaussian initial conditions. We apply this formalism to the O(N) nonlinear σ model at large N and find that observable differences from the case of initially Gaussian perturbations and Newtonian gravity in the bispectrum and higher-order correlations are not expected on scales smaller than about 100h-1 Mpc. © 1994 The American Physical Society.
Frieman JA, Jaffe AH, 1992, Cosmological constraints on pseudo Nambu-Goldstone bosons, Physical Review D, Vol: 45, Pages: 2674-2684, ISSN: 0556-2821
Particle-physics models with pseudo Nambu-Goldstone bosons (PNGB's) are characterized by two mass scales: a global spontaneous-symmetry-breaking scale f and a soft (explicit) symmetry-breaking scale . We investigate general model-insensitive constraints on this two-dimensional parameter space arising from the cosmological and astrophysical effects of PNGB's. In particular, we study constraints arising from vacuum misalignment and thermal production of PNGB's, topological defects, and the cosmological effects of PNGB decay products, as well as astrophysical constraints from stellar PNGB emission. Bounds on the Peccei-Quinn axion scale, 1010GeVfPQ 1010-1012GeV, emerge as a special case, where the soft breaking scale is fixed at QCD 100 MeV. © 1992 The American Physical Society.
Prather M, Jaffe AH, 1990, Global impact of the Antarctic ozone hole: Chemical propagation, Journal of Geophysical Research: Atmospheres, Vol: 95, Pages: 3473-3492, ISSN: 0148-0227
<jats:p>A model is presented for the chemical mixing of stratospheric air over spatial scales from tens of kilometers to meters. Photochemistry, molecular diffusion, and strain (the stretching of air parcels due to wind shear) are combined into a single one‐dimensional model. The model is applied to the case in which chemically perturbed air parcels from the Antarctic stratosphere are transported to mid‐latitudes and strained into thin ribbon‐like filaments until they are diffusively mixed with the ambient stratosphere. We find that the parcels may be treated as evolving in chemical isolation until the final mixing. When parcels reach a transverse thickness of 50–100 m in the lower stratosphere, they are rapidly dispersed by the combination of molecular diffusion and strain. The rapidity of the final mixing implies a lower limit to the vertical scales of inhomogeneities observed in the lower stratosphere. For this sensitivity study we consider four types of Antarctic air: a control case representing unprocessed polar air; heterogeneous processing by polar stratospheric clouds (PSCs) that has repartitioned the Cl<jats:sub><jats:italic>x</jats:italic></jats:sub> and NO<jats:sub><jats:italic>y</jats:italic></jats:sub> families; processing that also includes denitrification and dehydration; and all processing plus 90% ozone depletion. Large abundances of ClO, resulting initially from heterogeneous processing of stratospheric air on PSCs, are sustained by extensive denitrification. (One exception is the case of Antarctic air with major ozone depletion in which ClO is converted rapidly to HCl upon release of small amounts of NO<jats:sub><jats:italic>x</jats:italic></jats:sub> as a result of the extremely nonlinear Cl<jats:sub><jats:italic>x</jats:italic></jats:sub>‐NO<jats:sub><jats:italic>y</jats:italic></jats:sub> chemical system.) ClO conc
Guenther DB, Jaffe A, Demarque P, 1989, The standard solar model - Composition, opacities, and seismology, The Astrophysical Journal, Vol: 345, Pages: 1022-1022, ISSN: 0004-637X
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