			Home About us Contact

Cosmological Implications (cosmological + implication)

Distribution by Scientific Domains

Physics and Astronomy	100%

Distribution within Physics and Astronomy

Astronomy & Astrophysics	50%

Selected Abstracts

Cosmological implications of the PSCz PDF and its moments

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2001
Manolis Plionis
We compare the probability density function (PDF) and its low-order moments (variance and skewness) of the smoothed IRAS Point Source Catalogue Redshift Survey (PSCz) galaxy density field and of the corresponding simulated PSCz look-alikes, generated from N -body simulations of six different dark matter models: four structure-normalized with and , one COBE -normalized, and the old standard cold dark matter model. The galaxy distributions are smoothed with a Gaussian window at three different smoothing scales, , 10 and 15 h,1 Mpc. We find that the simulation PSCz look-alike PDFs are sensitive only to the normalization of the power spectrum, probably owing to the shape similarity of the simulated galaxy power spectrum on the relevant scales. We find that the only models that are consistent, at a high significance level, with the observed PSCz PDF are models with a relatively low power spectrum normalization . From the phenomenologically derived ,8,moments relation, fitted from the simulation data, we find that the PSCz moments suggest . [source]

Effective supergravity from the weakly coupled heterotic string

FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 2-3 2006
M.K. Gaillard
The motivation for Calabi-Yau-like compactifications of the weakly coupled E8 , E8 heterotic string theory, its particle spectrum and the issue of dilaton stabilization are briefly reviewed. Modular invariant models for hidden sector condensation and supersymmetry breaking are described at the quantum level of the effective field theory. Their phenomenological and cosmological implications, including a possible origin for R-parity, are discussed. [source]

The revival of cosmic strings

ANNALEN DER PHYSIK, Issue 4-5 2006
M. Sakellariadou
Abstract Cosmic strings are one-dimensional topological defects which could have been formed in the early stages of our Universe. They triggered a lot of interest, mainly for their cosmological implications: they could offer an alternative to inflation for the generation of density perturbations. It was shown however that cosmic strings lead to inconsistencies with the measurements of the cosmic microwave background temperature anisotropies. The picture has changed recently. It was shown that, on the one hand, cosmic strings can be generically formed in the framework of supersymmetric grand unified theories and that, on the other hand, cosmic superstrings could play the role of cosmic strings. There is also some possible observational support. All this led to a revival of cosmic strings research and this is the topic of my lecture. [source]

Unsolved problems in observational astronomy.

ASTRONOMISCHE NACHRICHTEN, Issue 6-8 2004

Abstract We present the highlights of current observational programs in stellar optical spectroscopy carried out with 8-10 m class telescopes as well as with smaller telescopes. Topics discussed include: 1. light elements abundances and their cosmological implications; 2. search for Population III stars and spectroscopy of extremely metal deficient stars; 3. abundances of different stellar populations in the Galaxy; 4. spectroscopy of resolved stars in Local Group galaxies; 5. Li and Be abundances and internal mixing in stars; 6. spectroscopy of very-low mass stars and brown dwarfs; 7. radial velocity search of extrasolar planets; 8. stellar oscillations and asteroseismology; 9. stellar magnetic activity and Doppler imaging of stellar surface features. We also highlight the role that dedicated 1-2 m automatic telescopes with spectroscopic capabilities can play in several fields of stellar optical spectroscopy. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]