Eigenvectors eigenvalues and constant of motion

In summary, the conversation discusses the Hamiltonian H for the motion of a particle in 3-dimensional space, which is composed of the operators Hx, Hy, and Hz. The question is to check if the standard angular momentum operator Lx is a constant of motion. The conversation also mentions the ground state wavefunction for Hx, which is proportional to e-x2/2, and asks for the wavefunction Y0(x,y,z) representing the ground state for H. The discussion includes tips on how to approach the problem, such as using the Heisenberg equation of motion and assuming the wavefunction can be separated in its variables.
  • #1
umagongdi
19
0

Homework Statement



a.) The motion of a particle in the 3-dimensional space is described by the Hamiltonian H = Hx+Hy+Hz, where

Hx=1/2*(px2+x2), Hy=1/2*(py2+y2), Hz=1/2*(pz2+z2)

Check that the standard angular momentum operators Lx, is a constant of motion.

b.) By knowing that the ground state wavefunction for Hx is proportional to e-x2/2, write the wavefunction Y0(x,y,z) representing the ground state for H (you are not required to fix the normaliszation of the wavefunctions in this problem).

Homework Equations





The Attempt at a Solution



a.) Do you need to check if L and H commute?
b.) I really don't have a clue any tips?
 
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  • #2
umagongdi said:

Homework Statement



a.) The motion of a particle in the 3-dimensional space is described by the Hamiltonian H = Hx+Hy+Hz, where

Hx=1/2*(px2+x2), Hy=1/2*(py2+y2), Hz=1/2*(pz2+z2)

Check that the standard angular momentum operators Lx, is a constant of motion.

b.) By knowing that the ground state wavefunction for Hx is proportional to e-x2/2, write the wavefunction Y0(x,y,z) representing the ground state for H (you are not required to fix the normaliszation of the wavefunctions in this problem).

Homework Equations


The Attempt at a Solution



a.) Do you need to check if L and H commute?
b.) I really don't have a clue any tips?
a.) Do you need to check if L and H commute?

Can you relate that commutator to the equations of motions. HINT: Look up the Heisenberg equation of motion.

b.) I really don't have a clue any tips?

Assume the wave function can be separated in its variables.
 
  • #3
G01 said:
Assume the wave function can be separated in its variables.

Oh i think i get it now thanks. You can just separate the wave function like this?

Y0(x,y,z)=e-x2/2+e-y2/2+e-z2/2
 

Related to Eigenvectors eigenvalues and constant of motion

1. What are eigenvectors and eigenvalues?

Eigenvectors and eigenvalues are mathematical concepts used in linear algebra to describe the behavior of a matrix. An eigenvector is a vector that, when multiplied by a matrix, produces a new vector that is parallel to the original vector. An eigenvalue is a scalar value that represents the amount by which the eigenvector is scaled during this transformation.

2. How are eigenvectors and eigenvalues related to each other?

Eigenvectors and eigenvalues are related through a matrix equation known as the eigenvalue equation. This equation states that when a matrix is multiplied by its corresponding eigenvector, the result is equal to the eigenvalue multiplied by the eigenvector. In other words, the eigenvector is an invariant direction of the transformation represented by the matrix, and the eigenvalue is the scale factor of this transformation in that direction.

3. What is the significance of eigenvectors and eigenvalues?

Eigenvectors and eigenvalues are important in various areas of mathematics and science, including physics, engineering, and computer science. They are used to analyze and understand the behavior of linear systems, such as in quantum mechanics, signal processing, and data analysis. They also have applications in determining stable solutions to differential equations and in finding optimal solutions in optimization problems.

4. What is the constant of motion in relation to eigenvectors and eigenvalues?

The constant of motion, also known as the integral of motion, is a concept in physics that refers to a quantity that remains constant throughout a specific physical process. In the context of eigenvectors and eigenvalues, the constant of motion is a property of a system that is conserved in time, meaning it does not change over time. This is because the eigenvalues and eigenvectors of a system represent the underlying symmetries and invariants of the system, leading to the preservation of certain quantities.

5. How are eigenvectors and eigenvalues calculated?

Eigenvectors and eigenvalues can be calculated through a process called diagonalization, where the matrix is transformed into a diagonal matrix with the eigenvalues along the main diagonal. This process involves finding the roots of the characteristic polynomial of the matrix, which is a polynomial equation that describes the relationship between the matrix's eigenvalues and its determinant. The eigenvectors can then be found by solving a system of linear equations using the eigenvalues as coefficients.

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