An analysis of helium primordial nucleosynthesis with a variable cosmological coupling

Alvarenga, F. G.; Fabris, J. C.; Gonçalves, S. V. B.; Marinho, J. A. O.

doi:10.1590/s0103-97332001000400004

Cited by 2 publications

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References 15 publications

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“…[1,40,41] for non-gravitational couplings and BBN). Among the constants which are effective during BBN, the gravitational constant plays a key role, and hence there have been many published studies of the effects of a varying G on the primordial abundance of the light elements [42,43,44,45,46,47,48,49,50,51]. However, since G is a dimensional constant, we calculate the abundance of helium synthesized during BBN in an explicit dimensionless way in this section, focusing on the dominant parts of the physics and neglecting some of the finer details.…”

Section: Dimensionless Bbnmentioning

confidence: 99%

Dimensionless cosmology

Narimani

Moss

Scott

2012

Astrophys Space Sci

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Although it is well known that any consideration of the variations of fundamental constants should be restricted to their dimensionless combinations, the literature on variations of the gravitational constant $G$ is entirely dimensionful. To illustrate applications of this to cosmology, we explicitly give a dimensionless version of the parameters of the standard cosmological model, and describe the physics of Big Bang Neucleosynthesis and recombination in a dimensionless manner. The issue that appears to have been missed in many studies is that in cosmology the strength of gravity is bound up in the cosmological equations, and the epoch at which we live is a crucial part of the model. We argue that it is useful to consider the hypothetical situation of communicating with another civilization (with entirely different units), comparing only dimensionless constants, in order to decide if we live in a Universe governed by precisely the same physical laws. In this thought experiment, we would also have to compare epochs, which can be defined by giving the value of any {\it one} of the evolving cosmological parameters. By setting things up carefully in this way one can avoid inconsistent results when considering variable constants, caused by effectively fixing more than one parameter today. We show examples of this effect by considering microwave background anisotropies, being careful to maintain dimensionlessness throughout. We present Fisher matrix calculations to estimate how well the fine structure constants for electromagnetism and gravity can be determined with future microwave background experiments. We highlight how one can be misled by simply adding $G$ to the usual cosmological parameter set

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Section: Dimensionless Bbnmentioning

confidence: 99%

Dimensionless cosmology

Narimani

Moss

Scott

2012

Astrophys Space Sci

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Adventures in Friedmann cosmology: A detailed expansion of the cosmological Friedmann equations

Nemiroff

Patla

2008

American Journal of Physics

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The general relativistic cosmological Friedmann equations which describe how the scale factor of the universe evolves are expanded explicitly to include energy forms not usually seen. The evolution of the universe as predicted by the Friedmann equations when dominated by a single, isotropic, stable, static, perfect-fluid energy form is discussed for different values of its gravitational pressure to density ratio w. These energy forms include phantom energy (w < −1), cosmological constant (w = −1), domain walls (w = −2/3), cosmic strings (w = −1/3), normal matter (w = 0), radiation and relativistic matter (w = 1/3), and a previously little-discussed form of energy called "ultralight" (w > 1/3). A brief history and possible futures of Friedmann universes dominated by a single energy form are discussed. * Electronic address: nemiroff@mtu.edu † Electronic address: brpatla@mtu.edu 1 John A. Peacock, Cosmological Physics (Cambridge University Press, Cambridge, 1999).

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An analysis of helium primordial nucleosynthesis with a variable cosmological coupling

Cited by 2 publications

References 15 publications

Dimensionless cosmology

Dimensionless cosmology

Adventures in Friedmann cosmology: A detailed expansion of the cosmological Friedmann equations

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