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A mathematical constant is a key number whose value is fixed by an unambiguous definition, often referred to by a symbol (e.g., an alphabet letter), or by mathematicians' names to facilitate using it across multiple mathematical problems. [1]
A nondimensionalised system commonly used in high energy physics sets ε 0 = c = ħ = 1, where the expression for the fine-structure constant becomes [10] =. As such, the fine-structure constant is chiefly a quantity determining (or determined by) the elementary charge : e = √ 4 πα ≈ 0.302 822 12 in terms of such a natural unit of charge.
These include the Boltzmann constant, which gives the correspondence of the dimension temperature to the dimension of energy per degree of freedom, and the Avogadro constant, which gives the correspondence of the dimension of amount of substance with the dimension of count of entities (the latter formally regarded in the SI as being dimensionless).
The first Feigenbaum constant or simply Feigenbaum constant [5] δ is the limiting ratio of each bifurcation interval to the next between every period doubling, of a one-parameter map + = (), where f (x) is a function parameterized by the bifurcation parameter a. It is given by the limit: [6]
Using the cross product as a Lie bracket, the algebra of 3-dimensional real vectors is a Lie algebra isomorphic to the Lie algebras of SU(2) and SO(3). The structure constants are =, where is the antisymmetric Levi-Civita symbol.
The propagation constant of a sinusoidal electromagnetic wave is a measure of the change undergone by the amplitude and phase of the wave as it propagates in a given direction. The quantity being measured can be the voltage , the current in a circuit , or a field vector such as electric field strength or flux density .
Boltzmann constant: The Boltzmann constant, k, is one of seven fixed constants defining the International System of Units, the SI, with k = 1.380 649 x 10 −23 J K −1. The Boltzmann constant is a proportionality constant between the quantities temperature (with unit kelvin) and energy (with unit joule). [3]
Unit cell definition using parallelepiped with lengths a, b, c and angles between the sides given by α, β, γ [1]. A lattice constant or lattice parameter is one of the physical dimensions and angles that determine the geometry of the unit cells in a crystal lattice, and is proportional to the distance between atoms in the crystal.