Positive definite matrix / negative definite matrix / Indefinite Matrix / Hessian matrix

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Positive definite matrix / negative definite matrix / Indefinite Matrix / Hessian matrix

• Hessian matrix
  $f(x)$ About $x$ a square is called second derivative Hesse (or Hessian) matrix (Hessian Matrix), which first $i$ row $j$ elements on the column to the $(\nabla^2f(x))_{ij}=\frac{\partial^2f(x)}{\partial x_i\partial y_j}$Hessian matrix of nature: Symmetry $A^T=A$

See also:
https://baike.baidu.com/item/ Hesse matrix