Hubble parameter

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Noun1.Hubble parameter - (cosmology) the ratio of the speed of recession of a galaxy (due to the expansion of the universe) to its distance from the observer; the Hubble constant is not actually a constant, but is regarded as measuring the expansion rate today
cosmogeny, cosmogony, cosmology - the branch of astrophysics that studies the origin and evolution and structure of the universe
constant - a number representing a quantity assumed to have a fixed value in a specified mathematical context; "the velocity of light is a constant"
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References in periodicals archive ?
Due to several further specifications, first by Baade (1952) and thereafter by Sandage (1954, 1958), based on an essentially more detailed and larger set of observational data, the rescaled value of the Hubble parameter at the present era, named the Hubble constant, gave for the age of the universe about 13.6 Gyr.
where the metric in the flat universe of FLRW is defined as d[s.sup.2] = d[t.sup.2] - [a.sup.2](t)[[summation].sub.i=1,2,3][(d[x.sup.i]).sup.2], a is the scale factor, and H = [??]/a is the Hubble parameter. Moreover, the vector of the space tangent and metric are defined with the relations [e.sup.A.sub.[mu]] = diag(1, a, a, a) and [g.sub.[mu]v] = diag(1, -[a.sup.2], -[a.sup.2], -[a.sup.2]), respectively.
where G is Newton's constant, and H the Hubble parameter. Note, with respect to [1], that we compute [[rho].sub.T] from (1) instead of the total dark fields density.
The universe's expansion rate, called the Hubble parameter or Hubble constant, not only sets the time scale for cosmic expansion but also the scale for the universe's size and age.
You can also calculate the mass of the galaxy cluster and you can calculate what is called the Hubble parameter, which tells us about the expansion of the universe.
The scale factor and Hubble parameter therefore depend on the average energy density and not the local field dynamics.
If all parameters [[alpha].sub.2n] for n > 1 equal zero then the Hubble parameter is described by the following formula:
and [H.sub.0] is the so called Hubble constant, the value of the Hubble parameter H(t) at t = [T.sub.0], the current age of the Universe.
Before the space telescope, astronomers only knew that the Hubble parameter -- a measure of the current expansion rate--was somewhere between 50 and 100 km/s per megaparsec (a parsec is about 3.26 light-years).
As a testimony to this, Hubble parameter has been widely used to obtain explicit accelerating cosmological models in the framework of spatially homogeneous space-time [10].
To find the Hubble parameter for the massive hadrons phase H(t > [a.sub.0]), we suggest the geometry transformation (5.3) in which the time [tau] : 0 [right arrow] [a.sub.0] for the quarks corresponds to the time t : 0 [right arrow] [infinity] for the massive hadrons phase.