Musical Isomorphism Article Index for
Musical
Website Links For
Musical
 

Information About

Musical Isomorphism





INTRODUCTION

A metric ''g'' on a Riemannian manifold ''M'' is a Tensor Field g \in \mathcal{T}_2(M) which is Symmetric , Nondegenerate and Positive-definite . If we fix one parameter as a vector v_p \in T_p M, we have an isomorphism of vector spaces:

  • }_p M

  • given by

:\hat{g}_p(v_p) = g(v_p,-)
i.e.
: \langle\hat{g}_p(v_p),\omega_p angle = g_p(v_p,\omega_p).

Globally the map



MOTIVATION OF THE NAME

The isomorphism \hat{g} and its inverse \hat{g}^{-1} are called ''musical isomorphisms'' because they move up and down the indexes of the vectors. For instance, a vector of ''TM'' is written as \alpha^i rac{\partial}{\partial x^i} and a covector as \alpha_i dx^i, so the index ''i'' is moved up and down in \alpha just as the symbols Sharp (\sharp) and Flat ( lat) move up and down the Pitch of a Tone .


GRADIENT

The musical isomorphisms can be used to define the Gradient of a Smooth Function over a Riemannian manifold ''M'' as follows:

:\mathrm{grad}\;f=\hat{g}^{-1} \circ df = (df)^{\sharp}