On the Hubble constant and the cosmological constant
نویسندگان
چکیده
منابع مشابه
The Hubble Constant and Dark Energy from Cosmological Distance Measures
We study how the determination of the Hubble constant from cosmological distance measures is affected by models of dark energy and vice versa. For this purpose, constraints on the Hubble constant and dark energy are investigated using the cosmological observations of cosmic microwave background, baryon acoustic oscillations and type Ia suprenovae. When one investigates dark energy, the Hubble c...
متن کاملThe Hubble Constant
Considerable progress has been made in determining the Hubble constant over the past two decades. We discuss the cosmological context and importance of an accurate measurement of the Hubble constant, and focus on six high-precision distance-determination methods: Cepheids, tip of the red giant branch, maser galaxies, surface-brightnes fluctuations, the TullyFisher relation and Type Ia supernova...
متن کاملThe Hubble Constant
I review the current state of determinations of the Hubble constant, which gives the length scale of the Universe by relating the expansion velocity of objects to their distance. There are two broad categories of measurements. The first uses individual astrophysical objects which have some property that allows their intrinsic luminosity or size to be determined, or allows the determination of t...
متن کاملIssues on the cosmological constant
Some issues of the cosmological constant or dark energy are briefly reviewed. There are an increasing number of observations that constrain the equation of state of dark energy more stringently and favor the time-independent cosmological constant. Then a plausible model of dark energy would be a theory with degenerate perturbative vacua in which its origin is explained by a nonperturbative effe...
متن کاملOn the Cosmological Constant Problem
We prove that Weyl invariant theories of gravity possess a remarkable property which, under very general assumptions, explains the stability of flat space-time. We show explicitly how conformal invariance is broken spontaneously by the vacuum expectation value of an unphysical scalar field; this process induces general relativity as an effective long distance limit. We show that all ghost degre...
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ژورنال
عنوان ژورنال: Monthly Notices of the Royal Astronomical Society
سال: 1997
ISSN: 0035-8711,1365-2966
DOI: 10.1093/mnras/286.1.173