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Galactic astronomy is the study of the Milky Way galaxy and all its contents. This is in contrast to extragalactic astronomy, which is the study of everything outside our galaxy, including all other galaxies.

1689 Results for the subject "Galactic Cosmology":

Weighting CMB and Galactic synchrotron polarisation

AbstractWe review the present knowledge of the diffuse Galactic synchrotron emission in polarisation. At microwave frequencies, we assess the expected contamination to the CMB polarisation angular power spectrum, for E and B modes, as expected after the WMAP first year measurements.

Carlo Baccigalupi Publication date: 2003/11/01
The structure and interpretation of cosmology: Part II. The concept of creation in inflation and quantum cosmology

AbstractThe purpose of the paper, of which this is part II, is to review, clarify, and critically analyse modern mathematical cosmology. The emphasis is upon mathematical objects and structures, rather than numerical computations. Part II provides a critical analysis of inflationary cosmology and quantum cosmology, with particular attention to the claims made that these theories can explain the creation of the universe.

Gordon McCabe Publication date: 2005/03/01
Near-field cosmology and the first stars: Insights from chemical evolution

AbstractI present a new Galactic chemical evolution model motivated by and grounded in the hierarchical theory of galaxy formation. This model accurately reproduces the “metallicity distribution function” (MDF) for Population II stars residing today in the Galactic halo, and implies that the IMF of the first stars was peaked in the range of massive stars that experience core-collapse supernovae (mean mass 〈M〉 = 8–42 M⊙), similar to the masses predicted by models of primordial star formation that account for formation feedback. The observed MDF and the apparent absence of true Population III stars from the Galactic halo strongly imply that there is some critical metallicity, Zcrit ≲ 10−4 Z⊙, below which low-mass star formation was inhibited. Metal-poor halo stars below [Fe/H] ≲ −3 had only 1–10 metal-free stars as their supernova precursors, such that the relative abundances in these halo stars exhibit IMF-weighted averages over the intrinsic yields of th Read more...

Jason Tumlinson Publication date: 2006/03/01
Perfect fluid solutions of Brans–Dicke and f(R) cosmology

AbstractBrans–Dicke cosmology with an (inverse) power-law potential is revisited in the light of modern quintessence and inflation models. A simple ansatz relating scale factor and scalar field recovers most of the known solutions and generates new ones. A phase space interpretation of the ansatz is provided and these universes are mapped into solutions of f(R) cosmology.

Dilek K. Çiftci Publication date: 2018/04/01
The quasi-steady-state cosmology

AbstractThis paper outlines an alternative cosmology called the quasi-steady-state cosmology (QSSC) which was proposed in 1993 as a rival to the standard big bang cosmology (SBBC). The motivation for an alternative cosmology is introduced by first discussing some of the weak points of the SBBC. The theoretical framework and observational tests of the QSSC are next described. Finally some tests which can distinguish between the SBBC and the QSSC are briefly mentioned.

Jayant V. Narlikar Publication date: 2003/05/01
Clusters of galaxies: new results from the CLEF hydrodynamics simulation

AbstractPreliminary results are presented from the CLEF hydrodynamics simulation, a large (N = 2 × 4283 particles within a 200 h−1 Mpc comoving box) simulation of the ΛCDM cosmology that includes both radiative cooling and a simple model for galactic feedback. Specifically, we focus on the X-ray properties of the simulated clusters at z = 0 and demonstrate a reasonable level of agreement between simulated and observed cluster scaling relations.

S.T. Kay Publication date: 2005/01/01
Gamma-ray constraints on the Galactic halo☆

AbstractSome findings from recent COS-B analyses of the diffuse Galactic γ-ray emission are briefly summarized, with emphasis on their impact for our understanding of the Galactic cosmic-ray halo.

J.B.G.M. Bloemen Publication date: 1990/01/01
On the galactic number of a hypercube

AbstractA galaxy is a union of vertex disjoint stars. The galactic number of a graph is the minimum number of galaxies which partition the edge set. The galactic number of complete graphs is determined. This result is used to give bounds on the galactic number of binary cube graphs. The problem of determining the galactic number of a graph is shown to be NP-complete.

Michael Fellows Publication date: 1988/01/01
Space elevator maturing into a Galactic Harbour

Highlights•3 modern Space Elevator Architectures merged into vision of Galactic Harbour.•Galactic Harbour is a new term for Space Elevator infrastructures.•Galactic Harbour Unifies Transportation and Business Enterprises.

Peter Swan Publication date: 2018/11/01
The cosmology of fluctuations

AbstractWe review a cosmology in which particles are fluctuationally created from a background zero point field. This cosmology is consistent with recent observations of an ever expanding and accelerating universe, as also the recently confirmed evolution of the fine structure constant. All hitherto mysterious and accidental, so called large number coincidences, in-fact follow from the theory.

B.G. Sidharth Publication date: 2003/05/01
Elements of string cosmology

AbstractAspects of string cosmology for critical and non-critical strings are discussed emphasizing the necessity to account for the dilaton dynamics for a proper incorporation of “large-small” duality. This drastically modifies the intuition one has with Einstein's gravity. For example winding modes, even though contributing to the energy density, oppose expansion and if not annihilated will stop the expansion. Moreover we find that the radiation dominated era of the standard cosmology emerges quite naturally in string cosmology. Our analysis of non-critical string cosmology provides a reinterpretation of the (universal cover of the) recently studied two-dimensional black hole solution as a conformal realization of cosmological solutions found previously by Mueller.

A.A. Tseytlin Publication date: 1992/03/16
The first soft gamma-ray image of the Galactic Centre with arc-min accuracy

AbstractPreliminary results from the SIGMA telescope observations of the Galactic Centre in the energy range of 35 keV - 1.3 MeV are presented and discussed. The telescope makes use of the coded aperture imaging technique. Our images from 35 to 300 keV reveal a strong source identified without any doubt with 1E 1740.7–2942, i. e. more than 45 arcmin away from the Galactic Nucleus. If this source is at the distance of the Galactic Centre, it is one of the most luminous objects in the galaxy at these energies.

B. Cordier Publication date: 1991/01/01
Axions in inflationary cosmology

AbstractThe problem of the cosmological constraints on the axion mass is re-examined. It is argued that in the context of inflationary cosmology the constraint ma≳10−5 eV can be avoided even when the axion perturbations produced during inflation are taken into account. It is shown also that in most axion models the effective parameter ƒa rapidly changes during inflation. This modifies some earlier statements concerning isothermal perturbations in the axion cosmology. A hybrid inflation scenario is proposed which combines some advantages of chaotic inflation with specific features of new and/or extended inflation. Its implications for theaxion cosmology are discussed.

Andrei Linde Publication date: 1991/04/18
Quark matter and cosmology

AbstractThe possible implications of the quark-hadron transition for cosmology are explored. Possible signatures are discussed such as dark matter candidates like strange nuggets or planetary mass black holes. Much discussion is devoted to the possible role of the transition for cosmological nucleosynthesis. It is emphasized that even an optimized first order phase transition will not significantly alter the nucleosynthesis constraints on the cosmological baryon density nor on neutrino counting. However, it is noted that Be and B observations in old stars may eventually be able to be a signature of a cosmologically significant quark-hadron transition. It is pointed out that spallation cannot produce a BBe ratio below 7.6. A supporting signature for cosmological would be Be and B ratios to oxygen that greatly exceed galactic values. At present, all data is consistent with a spallagenic origin.

David N. Schramm Publication date: 1992/07/20
Role of the brane curvature scalar in the brane world cosmology

AbstractWe include the brane curvature scalar to study its cosmological implication in the brane world cosmology. This term is usually introduced to obtain the well-defined stress-energy tensor on the boundary of anti-de-Sitter–Schwarzschild space. Here we treat this as the perturbed term for cosmological purpose. We find corrections to the well-known equation of the brane cosmology. It contains new interesting terms which may play the important role in the brane cosmology.

N.J. Kim Publication date: 2001/04/19
Baryonic dark matter

AbstractThis paper discusses the existence of baryonic dark matter in the universe confronted with the fundamental parameters and observations in cosmology. The various possible baryonic candidates are discussed with special emphasis on the MACHOs, which would be dim compact halo objects clustered at galactic scales.

M. Spiro Publication date: 1999/05/01
A quick and dirty early universe/ cosmology course

This series of lectures is intended to provide an introductory, non-rigorous overview of those aspects of the standard, hot big bang cosmology useful for understanding and appreciating the astroparticle physics-cosmology connection. Following a minimal introduction to the cosmography and dynamics of the Universe, the basic physics underlying the early evolution of the Universe is outlined. The intent of these lectures is pedagogical and no claim of originality is made. If these lectures are succssful, the previously unitiated might be prepared to proceed from here to an understanding of current literature on the particle physics-cosmology connection.

Gary Steigman Publication date: 1995/01/01
Massive neutrinos ?

AbstractVarious aspects of the subject of neutrino masses and their implications are outlined: Dirac and Majorana masses, suggestions from unified gauge theories, limits and hints from cosmology, galactic neutrinos and their detectability, experiments involving weak decays. The main voluntary lacunae are oscillations and double beta decay.

A. De Rújula Publication date: 1982/01/25
Induced star formation and non-linear multipopulation models for galactic evolution

AbstractI discuss the physical ingredients necessary for a coherent treatment of the star formation processes on galactic scales.

Federico Ferrini Publication date: 2000/07/01
The angular power spectra of polarized Galactic synchrotron

AbstractWe derive the angular power spectra of intensity and polarization of Galactic synchrotron emission in the range 36≤ℓ≲103 from the Parkes survey mapping the southern Galactic plane at 2.4 GHz. The polarization spectra of both electric and magnetic parity up to ℓ≃103 are approximated very well by power laws with slope coefficients ≃1.4, quite different from the CMB spectra. We show that no problem should arise from Galactic synchrotron for measurements of CMB polarization in the cosmological window.

M. Tucci Publication date: 2000/07/01
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