Levi-Civita symbol
The Levi-Civita symbol, usually denoted as εijk equals one if i,j,k = 1,2,3 or any permutation that keeps the same cyclic order,[1] or minus one if the order is different, or zero if any two of the indices are the same. It is named after the Italian mathematician and physicist Tullio Levi-Civita.
The symbol can be generalized to n-dimensions, as completely antisymmetric in its indices with ε123...n = 1. More specifically, the symbol is one for even permutations of the indices, −1 for odd permutations, and 0 otherwise.
Levi-Civita tensor
The Levi-Civita symbol also is used to denote the components of the Levi-Civita tensor, and in n dimensions this tensor is an invariant of the special unitary group SU(n).[2] It also is called the alternating tensor[3] or the completely antisymmetric tensor with n indices in n dimensions. The completely antisymmetric tensor with n indices in n-dimensions has only one independent component, and is denoted in two, three and four dimensions as εij, εijk, εijkl.[4] Consequently, in three dimensions the completely antisymmetric tensor with three indices is entirely specified by stating ε123 = εxyz = 1 in Cartesian coordinates.
Notes
- ↑ The term "cyclic order" imagines the items in a list, say a, b, c, ... arranged in a circle. Then all sequences that could be encountered by going once around the circle in the direction of the sequence a, b, c, ... are in cyclic order, regardless of the starting point. See Scoby McCurdy (1894). “Cyclic order”, An exercise book in algebra. D. C. Heath & Co., p. 59.
- ↑ Michael T. Vaughn (2007). Introduction to mathematical physics. Wiley-VCH, p. 484. ISBN 3527406271.
- ↑ Vinod K. Sharma (2009). “§9.2 Alternating tensor (or Levi-Civita symbol)”, Matrix Methods and Vector Spaces in Physics. Prentice-Hall of India Pvt.Ltd, p. 370. ISBN 8120338669.
- ↑ T. Padmanabhan (2010). Gravitation: Foundations and Frontiers. Cambridge University Press, p. 22. ISBN 0521882230.