Quick question about bra-ket notation

In summary, the conversation discusses a relation in perturbation theory and how it relates to the Hermitian property of H and E_n. The participants come to the conclusion that the relation is valid and their approach is correct.
  • #1
Observer Two
25
0

Homework Statement



On Wikipedia there is an article about perturbation theory. To understand something I need to understand the following relation. They say:

Homework Equations



[itex]H |n> = E_n |n>[/itex]

So:

[itex]<n| H = <n| E_n[/itex]

H is Hermitian.

So: Why is this?

The Attempt at a Solution



I don't know if this is valid.

[itex](H \cdot |n>)^\dagger = (E_n \cdot |n>)^\dagger[/itex]

[itex]\Leftrightarrow[/itex]

[itex]<n| H^\dagger = <n| E_n^\dagger[/itex]

And since H is Hermitian and E_n is real, I get:

[itex]<n| H = <n| E_n[/itex]

Is this how things work?
 
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  • #2
That looks correct.
 
  • #3
Looks fine to me too.
 

What is bra-ket notation?

Bra-ket notation, also known as Dirac notation, is a mathematical notation used in quantum mechanics to represent quantum states and operators. It consists of a bra, which is represented by the symbol 〉 and a ket, represented by the symbol 〈.

How is bra-ket notation used?

Bra-ket notation is used to describe the relationship between quantum states and operators. The bra represents the complex conjugate of a quantum state, while the ket represents the original state. The notation is also used to calculate inner products and matrix elements.

What are the advantages of using bra-ket notation?

Bra-ket notation allows for a concise and elegant representation of quantum states and operators. It also simplifies calculations involving inner products and matrix elements, making it a useful tool for solving complex quantum mechanics problems.

Can bra-ket notation be used for any quantum system?

Yes, bra-ket notation can be used for any quantum system, including single particles, multi-particle systems, and even continuous systems. It is a universal notation that is widely used in the field of quantum mechanics.

Are there any alternative notations for representing quantum states and operators?

Yes, there are alternative notations such as matrix notation and wave function notation. However, bra-ket notation is the most commonly used and preferred notation in quantum mechanics due to its simplicity and versatility.

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