Topic
Cosmology
About: Cosmology is a research topic. Over the lifetime, 18004 publications have been published within this topic receiving 631028 citations. The topic is also known as: physical cosmology & cosmologies.
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TL;DR: In this article, a non-parametric method of smoothing supernova data over redshift using a Gaussian kernel was proposed to reconstruct important cosmological quantities including H(z) and w(z), in a model-independent manner.
Abstract: We propose a non-parametric method of smoothing supernova data over redshift using a Gaussian kernel in order to reconstruct important cosmological quantities including H(z) and w(z) in a model-independent manner. This method is shown to be successful in discriminating between different models of dark energy when the quality of data is commensurate with that expected from the future Supernova Acceleration Probe (SNAP). We find that the Hubble parameter is especially well determined and useful for this purpose. The look-back time of the Universe may also be determined to a very high degree of accuracy (≤0.2 per cent) using this method. By refining the method, it is also possible to obtain reasonable bounds on the equation of state of dark energy. We explore a new diagnostic of dark energy - the 'w-probe' - which can be calculated from the first derivative of the data. We find that this diagnostic is reconstructed extremely accurately for different reconstruction methods even if Ω 0m is marginalized over. The w-probe can be used to successfully distinguish between A cold dark matter and other models of dark energy to a high degree of accuracy.
193 citations
TL;DR: It is shown that the spectrum of Kaluza-Klein modes is radically altered, which allows the early Universe to evolve normally up to substantial temperatures, and completely negates the astrophysical constraints on M(*.
Abstract: We reconsider theories with low gravitational (or string) scale M where Newton’s constant is generated via new large-volume spatial dimensions, while Standard Model states are localized to a 3brane. Utilizing compact hyperbolic manifolds (CHM’s) we show that the spectrum of Kaluza-Klein (KK) modes is radically altered. This allows an early universe cosmology with normal evolution up to substantial temperatures , and completely negates the constraints on M arising from astrophysics. Furthermore, an exponential hierarchy between the usual Planck scale and the true fundamental scale of physics can emerge with only O(1) coecients. The linear size of the internal space remains small. The proposal has striking testable signatures.
193 citations
TL;DR: Current observations suggest that the “strong energy condition” was violated sometime between the epoch of galaxy formation and the present, which implies that no possible combination of “normal” matter is capable of fitting the observational data.
Abstract: The energy conditions of Einsteinian gravity (classical general relativity) do not require one to fix a specific equation of state. In a Friedmann-Robertson-Walker universe where the equation of state for the cosmological fluid is uncertain, the energy conditions provide simple, model-independent, and robust bounds on the behavior of the density and look-back time as a function of red shift. Current observations suggest that the “strong energy condition” was violated sometime between the epoch of galaxy formation and the present. This implies that no possible combination of “normal” matter is capable of fitting the observational data.
193 citations
Book•
01 Aug 1998
TL;DR: In 5D cosmology and astrophysics in 5D 5D electromagnetism the canonical metric and fifth force canonical solutions and physical quantities retrospect and prospect are described in this paper.
Abstract: Concepts and theories of physics, induced-matter theory the classical and other tests in 5D cosmology and astrophysics in 5D 5D electromagnetism the canonical metric and fifth force canonical solutions and physical quantities retrospect and prospect.
192 citations
Book•
01 Jan 1987
TL;DR: In this article, the authors present the original observations and fundamental data on quasars and galaxies, and explain why they have concluded that far from being the most distant objects in the universe, Quasars are associated in space with relatively nearby galaxies.
Abstract: For twenty years, the author has contested the 'establishment' view of quasars as the most distant objects in the universe. In this book, Arp presents the original observations and fundamental data on quasars and galaxies, and explains why he has concluded that: far from being the most distant objects in the universe, quasars are associated in space with relatively nearby galaxies; quasars' enormous redshifts do not arise from the expansion of the universe, but rather are intrinsic properties of the quasars themselves; many galaxies show redshift anomalies related to quasars' redshifts; quasars and galaxies have an origin far different from that assumed in the 'standard' big-bang model of the universe; many astronomers, despite the accumulation of compelling evidence, defend what Arp believes is a fundamentally incorrect assumption about cosmic objects.
192 citations