Position and Momentum operator in Legendre base

In summary, the problem at hand is to find the matrix elements of the position and momentum operators in the Legendre base on the interval [-1, 1]. The position operator can be written as an integral, while the momentum operator can be written as a differential operator. The integrals can be evaluated using recursive relations and the final solution depends on the Legendre polynomials. The poster is seeking assistance with the integration process and apologizes for any language barriers.
  • #1
Mengahna
1
0
First of all, I don't really know if this problem corresponds to this section, but anyway I have this as a probem in my matemathical physics class.

The problem is stated something like this:

Find the matrix elements of the position and momentum operators in the legendre base (on the interval [-1, 1]).

Ok, I know how to proceed...but I'm having a hard time integrating. Can someone help me with this?... or at least give me the correct answer just to know if I'm doing right.

Sorry for the bad english, I'm not a native speaker. Also I'm new in this so I don't know if I'm posting in the right forum...please tell me.
 
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  • #2
The position and momentum operators can be written as, Position operator: $\hat{x}=\int_{-1}^{1}x|x\rangle\langle x|dx$Momentum operator: $\hat{p}=-i\hbar\int_{-1}^{1}\frac{\partial}{\partial x}|x\rangle\langle x|dx$The matrix elements of the operators in the Legendre base are given by, Position operator: $\langle n|\hat{x}|m\rangle=\int_{-1}^{1}xP_n(x)P_m(x)dx$Momentum operator: $\langle n|\hat{p}|m\rangle=-i\hbar\int_{-1}^{1}\frac{\partial}{\partial x}P_n(x)P_m(x)dx$The integrals can be evaluated using the following recursive relation, $\int_{-1}^{1} xP_n(x)P_m(x)dx = \frac{2}{2n+1}\left[ (n+m+1)\int_{-1}^{1} P_{n+1}(x)P_m(x)dx + (n-m)\int_{-1}^{1} P_{n-1}(x)P_m(x)dx \right]$In a similar way, the integral for the momentum operator can be evaluated using the following recursive relation, $\int_{-1}^{1}\frac{\partial}{\partial x}P_n(x)P_m(x)dx = \frac{2}{2n+1}\left[ (n+m+1)\int_{-1}^{1} \frac{\partial}{\partial x}P_{n+1}(x)P_m(x)dx - (n-m)\int_{-1}^{1} \frac{\partial}{\partial x}P_{n-1}(x)P_m(x)
 

FAQ: Position and Momentum operator in Legendre base

What is the purpose of the Position and Momentum operator in Legendre base?

The Position and Momentum operator in Legendre base is used to determine the position and momentum of a particle in quantum mechanics. It is a mathematical tool that helps to describe the properties of a particle in terms of its position and momentum.

How is the Position operator defined in Legendre base?

The Position operator in Legendre base is defined as the multiplication of the position coordinate with the Legendre polynomial. It is represented by the symbol x.

What is the relationship between the Position and Momentum operator in Legendre base?

The Position and Momentum operator in Legendre base are related by the Fourier transform. This means that the Fourier transform of the position operator is equal to the momentum operator and vice versa.

How is the Momentum operator defined in Legendre base?

The Momentum operator in Legendre base is defined as the derivative of the position coordinate with respect to time multiplied by the Legendre polynomial. It is represented by the symbol p.

What is the significance of using Legendre base for the Position and Momentum operator?

Using Legendre base allows for a more complete and accurate description of a particle's position and momentum in quantum mechanics. It also makes it easier to perform mathematical operations and solve equations involving these operators.

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