JEE Exam » JEE Study Material » Physics » Skew Symmetric Determinant

Skew Symmetric Determinant

A square matrix equal to the negative of its transpose is skew-symmetric. Read this article to learn about skew-symmetric determinants, their examples, types, etc.

One can write a transpose of a matrix by interchanging the rows into columns or vice-versa. For a matrix where the matrices are equal to the negative of its transpose, the matrix formed is the skew-symmetric matrix. However, the determinant of such a matrix is defined as the skew-symmetric determinant. Suppose, if a matrix A is defined and its skew-symmetric transpose is given as -AT, then the determinant of this matrix shall be written as det(-AT). A determinant is any scalar quantity (real or complex) associated with any matrix. In the article, the reader will understand the concepts of such matrices, along with examples. 

Skew-symmetric determinant meaning 

  1. The skew-symmetric determinant meaning implies that a determinant is a scalar associated with each matrix, enabling scaling/ characterisation of the matrix and holding physical significance.
  2. It can be understood if one tries to understand the concept of determinants in matrices. However, for a skew-symmetric matrix, its determinant can be calculated as per the same procedure for any matrix, and thus the value would be a scalar quantity. Consider a 2 x 2 matrix A written as, 4 7 0  -2 . Then the skew-symmetric matrix of A will be written as the negative transpose, which will be, 

-AT = 4 0 7  -2 .

Now the determinant of this matrix will be written as,

4  0 7  -2 as (4 x -2) – (7 x 0) = -8-0= -8

Therefore, the skew-symmetric determinant of the present given matrix is -8. 

Skew-symmetric determinant properties 

There are many interesting properties for the skew-symmetric determinant. Take a look: 

  1. If given the order of a matrix as odd, then the determinant of that matrix shall be zero, for example, given a 3 x 3 matrix implying that the order is 3, which is an odd number. Then the determinant of its skew-symmetric form shall come out to be negative. 
  2. If given the order of a matrix as even, then the determinant of that matrix shall be non-zero, for example, given a 2 x 2 matrix implying that the order is 2, which is an even number. Then the skew-symmetric determinant form shall be a non-zero perfect square. 

Consider a matrix A= 0 2 -2  0 , then its transpose is AT= 0 -2 2  0 , and 

Det (AT) = (0 x 0)- (2 x -2) = 0 + 4 = 4, which is a perfect square since the order of the matrix is even. 

Skew-symmetric determinant value 

  1. A set of linear equations can be solved using the matrix method. For every linear equation, there is a scalar quantity known as the eigenvalue of that equation. 
  2. The eigenvalue can have a positive or negative value or can even be an imaginary number. For a matrix M, the Eigen equation may be written as MX = λX, where λ is the eigenvalue of matrix M, and X is the corresponding eigenvector. 
  3. For a skew-symmetric matrix, the value of λ will be either 0 or an imaginary number. The eigenvalue concept is essential for the examination point of view as these come in skew-symmetric determinant hot questions. 

Skew-symmetric determinant theorem

  1. Suppose M is a skew-symmetric matrix of the order N x N, then the determinant det (MT)= det (-M) = (-1)N det (M). Therefore, for N= odd, the determinant shall be zero, such matrices all called singular according to Jabobi’s theorem. 

Suppose a skew matrix is defined as M= a -b b a, then the det (M) shall be a perfect square according to the properties. 

  1. For N=even, then the det (M) = P(M)2, which implies that the skew-symmetric determinant value for an even matrix shall come out to be a perfect square which is always positive. 

Suppose a skew matrix is defined as M= 0 a b -a 0 k -b -k 0, then the det (M) shall be 0 according to the properties. The skew-symmetric determinant hot questions are essential from an exam point of view. 

Conclusion

When a transpose negative is written, the resulting matrix is a skew-symmetric matrix with a unique set of properties. However, when one finds out the determinant of such a matrix, the value can differ as per the order of the matrix. An odd order matrix has determinant zero, while an even order matrix has a determinant non-zero perfect square. The skew-symmetric determinant is described in the text thoroughly, along with a few solved examples. Upon reading the article, the reader shall understand the concepts deeply, along with a few solved examples for the same. The understanding of these concepts is vital in physics and mathematics. 

faq

Frequently asked questions

Get answers to the most common queries related to the IIT JEE Examination Preparation.

What are some of the properties of a skew-symmetric matrix?

Ans. The trace for a skew-symmetric matrix is always zero. When you add any skew-symmetric matrix, the resul...Read full

What will be the symmetric matrix's determinant?

Ans. A symmetric matrix is written as the positive transpose of a matrix. The determinant of such a matrix c...Read full

What are the theorems for the skew-symmetric and symmetric matrix?

Ans. Any given matrix M can be written as the sum of symmetric as well as skew-symmetric matrix written as ...Read full

What is the significance of symmetric and skew-symmetric matrices?

Ans. Since a matrix is a collection of numbers in a rectangular array, therefore, for a matrix whose transpo...Read full