Definition:Jacobian/Determinant
Definition
Let $U$ be an open subset of $\R^n$.
Let $\mathbf f = \paren {f_1, f_2, \ldots, f_m}^\intercal: U \to \R^m$ be a vector valued function, differentiable at $\mathbf x = \paren {x_1, x_2, \ldots, x_n}^\intercal \in U$.
The Jacobian determinant of $\mathbf f$ at $\mathbf x$ is defined to be the determinant of the Jacobian matrix:
- $\map \det {\mathbf J_{\mathbf f} } := \begin {vmatrix} \map {\dfrac {\partial f_1} {\partial x_1} } {\mathbf x} & \cdots & \map {\dfrac {\partial f_1} {\partial x_n} } {\mathbf x} \\ \vdots & \ddots & \vdots \\ \map {\dfrac {\partial f_m} {\partial x_1} } {\mathbf x} & \cdots & \map {\dfrac {\partial f_m} {\partial x_n} } {\mathbf x} \end {vmatrix}$
Also defined as
Sometimes the absolute value of the determinant of the Jacobian matrix is the intended meaning.
Also known as
This concept is often called just the Jacobian of $\mathbf f$ at $\mathbf x$.
However, this can allow it to be confused with the Jacobian matrix, so it is advised to use the full name unless context establishes which is meant.
Some sources present this as $\map \det {J_f}$, but boldface for matrices is usual, and standard on $\mathsf{Pr} \infty \mathsf{fWiki}$.
Other sources present it as either $\mathbf J_{\mathbf f}$ or $J_f$, allowing a further source of confusion between this and the Jacobian matrix.
Also see
Source of Name
This entry was named for Carl Gustav Jacob Jacobi.
Sources
- 1926: E.L. Ince: Ordinary Differential Equations ... (previous) ... (next): Chapter $\text I$: Introductory: $\S 1.22$ A Property of Jacobians
- 1989: Ephraim J. Borowski and Jonathan M. Borwein: Dictionary of Mathematics ... (previous) ... (next): Jacobian or Jacobian determinant
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): Jacobian
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): Jacobian
- 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): Jacobian
- 2021: Richard Earl and James Nicholson: The Concise Oxford Dictionary of Mathematics (6th ed.) ... (previous) ... (next): Jacobian (Jacobian determinant)