Logarithmic Derivative - The Multiplicative Group

The Multiplicative Group

Behind the use of the logarithmic derivative lie two basic facts about GL1, that is, the multiplicative group of real numbers or other field. The differential operator

is invariant under 'translation' (replacing X by aX for a constant). And the differential form

dX/X

is likewise invariant. For functions F into GL1, the formula

dF/F

is therefore a pullback of the invariant form.

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