Speed of sound in cosmological models
WebFeb 11, 2014 · A cosmological model based on a canonical scalar field is not successful from the point of view of structure formation because its speed of sound is always equal … WebGalactic dynamo models take as input certain parameters of the interstellar turbulence, most essentially the correlation time τ, root-mean-square turbulent speed u, and correlation scale l. However, these quantities are difficult, or, in the case of τ, impossible, to directly observe, and theorists have mostly relied on order of magnitude estimates. …
Speed of sound in cosmological models
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WebHDE models while allowing the investigation of cosmological perturbations. Here we will adopt a phenomenological approach and assume the existence of a DE uid having an evolv-ing equation of state w de(a) derived from the UV/IR relation (1.2). As for the description of DE perturbations, we opt for a constant sound speed in the uid rest-frame ^c2 WebThe stability condition implies 12 ≤ α and the positive energy requirement gives b + 1 ≥ 2a. The subluminal speed of sound condition produces the inequality 1 ≤ α. The positive …
http://sro.sussex.ac.uk/id/eprint/57284/1/Accuracy%20of%20cosmological%20parameters-JCAP-1501-2015-Accepted.pdf WebOct 18, 2006 · In the cosmological models which postulate a phantom energy (a fluid with ) leading to a big-rip, the dominant energy condition in general relativity is violated. As far as I know this implies FTL effects. I don't know if it IMPLIES FTL effects, I believe it is true that FTL effects break the weak energy condition.
WebThese squared speeds of sound models depend on equation-of-state (EoS) parameter. We discuss the accelerated expansion of the universe through some cosmological … WebAug 30, 2024 · We compare our result to lower-order approximations to the sound speed and the energy budget and investigate the impact on the gravitational wave signal. We find …
WebFurthermore, we show that for such action the sound speed of gravitational waves is unity. Thus, this model serves as dark energy as well as an inflaton even though the presence of the dependence of the kinetic term of a scalar field in the non-minimal coupling, different from the case in metric formalism.
WebJul 4, 2024 · 1. The equation for the sound horizon is simply the equation for the particle horizon, with the speed of light replaced by the speed of sound, there's nothing more to it. Nevertheless, you have to keep in mind that the speed of sound also changes with time, since the matter density dilutes with a growing scale factor, so you have to treat the ... how to spell swervingWebMay 14, 2024 · That is the standard definition of the speed of sound as long as you are dealing with adiabatic perturbations. You might want to check this. On the other hand, for … rdv fort smithWebdevelopment of scientific models. If a model clashes with Scripture, then it needs to be amended or discarded. Contemporary Young-Earth Creationist Models . that Tacitly Affirm an Old Universe The first creationist cosmological model to appeal to time dilation as a solution to the light travel time problem was that of D. Russell Humphreys in 1994. rdv goodfellowinc.comhttp://www.sound-physics.com/Sound/Speed-Of-Sound/ how to spell swimming in frenchWebMay 25, 2016 · Using the bag model, the numerical value of the minimum sound speed can be calculated as where the uncertainty comes from the selection of the number of relativistic quark species. Thus we can say that the quark-hadron phase transition has no drastic effect on the development of cosmological density perturbations. rdv fictifWebRelativistic cosmologies Einstein’s model. To derive his 1917 cosmological model, Einstein made three assumptions that lay outside the scope of his equations. The first was to suppose that the universe is homogeneous and isotropic in the large (i.e., the same everywhere on average at any instant in time), an assumption that the English … rdv genthial yves maiaWebFeb 21, 2024 · With the "standard model of cosmology ," the universe is thought to be about 5% ordinary matter, 27% dark matter and 68% dark energy. In this new work, researchers refined distance measurements to ... rdv free center