What is the correct formula for [AB,C] in terms of A, B, and C?

In summary, the conversation discusses a problem involving operators and their equations, specifically the momentum and position operators. The attempt at a solution involves using the commutator identity to simplify the problem and then considering the wavefunction to find the correct formula for [AB,C].
  • #1
Caulfield
11
0

Homework Statement


I am solving a problem and I arrived near the end, and can't figure out what to do here:

(1/(2m)) [P^2,X]+[P^2,X]

m - mass
P - Momentum operator
X - Position operator


Homework Equations



P = -iħ(∂/∂x)
[A,B]=AB-BA
[AB,C]=A[B,C]+B[A,C] where A, B and C are any operators

The Attempt at a Solution



I used [AB,C]=A[B,C]+B[A,C] to get 1/2m (P(PX-XP) + (PX-XP)P) and blocked
 
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  • #2
Caulfield said:
I used [AB,C]=A[B,C]+B[A,C] to get 1/2m (P(PX-XP) + (PX-XP)P) and blocked
For an arbitrary wavefunction ##\psi(x)##, what is ##P\psi## and ##X\psi##? If you can figure those out, then you should be able to figure out ##[X,P]\psi## ...
 
  • #3
The correct formula is
[tex][AB,C]=A[B,C]+[A,C]B.[/tex]
 

1. What are operator properties?

Operator properties are characteristics or qualities of mathematical operators, such as addition, subtraction, multiplication, and division. These properties define how operators behave and interact with numbers or other mathematical expressions.

2. What are the four basic operator properties?

The four basic operator properties are commutative, associative, distributive, and identity. The commutative property states that the order of operands does not affect the result of an operation. The associative property states that the grouping of operands does not affect the result of an operation. The distributive property states that multiplication distributes over addition and subtraction. The identity property states that the result of an operation with an identity element (e.g. 0 for addition, 1 for multiplication) is equal to the other operand.

3. How do operator properties affect mathematical expressions?

Operator properties can simplify and transform mathematical expressions, making them easier to solve. For example, the commutative and associative properties allow us to rearrange the order and grouping of terms in an expression without changing the result. The distributive property can help us expand or factor expressions. The identity property can help us simplify expressions by canceling out certain terms.

4. Are operator properties only applicable to numbers?

No, operator properties can also be applied to other mathematical objects, such as matrices, vectors, and functions. For example, the commutative and associative properties still hold for matrix addition and multiplication. However, not all operator properties may apply to every mathematical object, so it's important to understand the properties specific to the type of object being used.

5. How can understanding operator properties improve problem-solving in math?

Understanding operator properties can help us simplify and manipulate complex expressions, making them easier to solve. It can also provide shortcuts and strategies for solving problems more efficiently. By understanding these properties, we can also avoid common mistakes and errors in calculations.

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