## Posts Tagged ‘**Fundamental Constants**’

## The physical basis of natural units and truly fundamental constants

**Leonardo Hsua, Jong-Ping Hsua**

**Abstract:** The natural unit system, in which the value of fundamental constants such as c and h-bar are set equal to one and all quantities are expressed in terms of a single unit, is usually introduced as a calculational convenience.

However, we demonstrate that this system of natural units has aphysical justification as well. We discuss and review the natural units, including definitions for each of the seven base units in the International System of Units (SI) in terms of a single unit.

We also review the fundamental constants, which can be classified as units-dependent or unitsindependent.

Units-independent constants, whose values are not determined by human conventions

of units, may be interpreted as inherent constants of nature….

Read more: http://arxiv.org/pdf

## Gyromagnetic Factors and Atomic Clock Constraints on the Variation of Fundamental Constants

We consider the effect of the coupled variations of fundamental constants on the nucleon magnetic moment. The nucleon g-factor enters into the interpretation of the measurements of variations in the fine-structure constant, alpha, in both the laboratory (through atomic clock measurements) and in astrophysical systems (e.g. through measurements of the 21 cm transitions). A null result can be translated into a limit on the variation of a set of fundamental constants, that is usually reduced to alpha. However, in specific models, particularly unification models, changes in alpha are always accompanied by corresponding changes in other fundamental quantities such as the QCD scale, Lambda_QCD. This work tracks the changes in the nucleon g-factors induced from changes in Lambda_QCD and the light quark masses. In principle, these coupled variations can improve the bounds on the variation of alpha by an order of magnitude from existing atomic clock and astrophysical measurements. Unfortunately, the calculation of the dependence of g-factors on fundamental parameters is notoriously model-dependent….

Read more: http://arxiv.org/PS_cache/arxiv/pdf/1107/1107.4154v1.pdf