/** \brief Compute linearization of the determinant of a deformation gradient
/** \brief Compute linearization of the determinant of a deformation gradient. Multiplication with a test function(scalar) gradient, gives the linearization in the direction of the test function.
*
*
* \param u The displacement gradient(!) at which the determinant is evaluated
* \param u The displacement gradient(!) at which the determinant is evaluated
/** \brief Compute linearization of the determinant of a deformation gradient
/** \brief Compute linearization of the determinant of a deformation gradient. Multiplication with a test function(scalar) gradient, gives the linearization in the direction of the test function.
*
*
* \param u The displacement gradient(!) at which the determinant is evaluated
* \param u The displacement gradient(!) at which the determinant is evaluated