Understanding 2x2 Matrices: Representation and Dot Product

In summary, the conversation is about representing a 2x2 matrix X using a shorthand notation involving a dot product between sigma and a, where a0 and a1, a2 and a3 are numbers. The speaker questions how this notation can represent a matrix, and the expert explains that it is shorthand for a combination of numbers and matrices, resulting in a 2x2 matrix.
  • #1
Josh Conneely
1
0

Homework Statement


Suppose a 2x2 matrix X (not necessarily hermitian, nor unitary) is written as

X = a0 + sigma . a (the sigma . a is a dot product between sigma and a)

where a0 and a1, a2 and a3 are numbers.

How on Earth does X represent a matrix? it's a number added to another number (dot product).

Homework Equations

The Attempt at a Solution

 
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  • #2
Josh Conneely said:

Homework Statement


Suppose a 2x2 matrix X (not necessarily hermitian, nor unitary) is written as

X = a0 + sigma . a (the sigma . a is a dot product between sigma and a)

where a0 and a1, a2 and a3 are numbers.

How on Earth does X represent a matrix? it's a number added to another number (dot product).

Homework Equations

The Attempt at a Solution


I suspect this is a question about Pauli matrices. That notation is shorthand for X=a0*I+sigma1*a1+sigma2*a2+sigma3*a3 where I is the 2x2 identity matrices and sigma1, sigma2 and sigma3 are 2x2 matrices collectively referred to as sigma. The result X is a 2x2 matrix.
 

Related to Understanding 2x2 Matrices: Representation and Dot Product

1. What are matrices?

Matrices are rectangular arrays of numbers, symbols or expressions arranged in rows and columns. They are used in mathematics, science, engineering and other fields to represent and manipulate data and equations.

2. How are matrices used in science?

Matrices are used in a variety of scientific fields, including physics, chemistry, biology, and computer science. They are particularly useful for solving systems of equations, representing data sets, and analyzing complex systems.

3. What is the purpose of matrices?

The main purpose of matrices is to organize and manipulate data in a structured way. They can be used to solve equations, perform transformations, and analyze relationships between variables.

4. Can matrices be used to solve real-world problems?

Yes, matrices are widely used to solve real-world problems in various fields such as economics, social sciences, and engineering. They can be used to model and predict complex systems and make informed decisions based on data analysis.

5. Are there different types of matrices?

Yes, there are several types of matrices, including square matrices, identity matrices, diagonal matrices, and symmetric matrices. Each type has its own properties and uses in mathematical and scientific applications.

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