What Are Shankar's Inner Product Axioms in Quantum Mechanics?

In summary, the conversation discusses the concept of the inner product and its axioms as explained in "Principles of Quantum Mechanics" by Shankar. The inner product is defined as obeying three axioms and can be represented using basis vectors. The formula for calculating the inner product is also provided. The individual asking the question struggles to understand the concept, but eventually comes to understand it with the help of a friend.
  • #1
Identity
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I was reading "Principles of Quantum Mechanics" - Shankar, and I'm having trouble understanding the inner product. Can someone help me or link me to a site that explains it?

The axioms of the inner product are

1. [tex]\langle V|W\rangle = \langle W|V\rangle^*[/tex]

2. [tex]\langle V|V\rangle \geq 0\ \ \ \ \ 0 \ \ iff\ \ |V\rangle = |0\rangle[/tex]

3. [tex]\langle V|(a|W\rangle +b|Z\rangle ) \equiv \langle V|aW+bZ\rangle = a\langle V|W \rangle +b\langle V|Z \rangle[/tex]

Given that [tex]|V\rangle[/tex] and [tex]|W \rangle[/tex] can be expressed in terms of their basis vectors,

[tex]|V \rangle = \sum_i v_i |i \rangle[/tex]

[tex]|W \rangle = \sum_j w_j|j \rangle[/tex]

Shankar says "we follow the axioms obeyed by the inner product to obtain"

[tex]\langle V|W \rangle = \sum_i \sum_j v_i^*w_j\langle i|j \rangle[/tex]

I don't understand how this comes about?

thanks
 
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  • #2
Identity said:
I was reading "Principles of Quantum Mechanics" - Shankar, and I'm having trouble understanding the inner product. Can someone help me or link me to a site that explains it?

The axioms of the inner product are

1. [tex]\langle V|W\rangle = \langle W|V\rangle^*[/tex]

2. [tex]\langle V|V\rangle \geq 0\ \ \ \ \ 0 \ \ iff\ \ |V\rangle = |0\rangle[/tex]

3. [tex]\langle V|(a|W\rangle +b|Z\rangle ) \equiv \langle V|aW+bZ\rangle = a\langle V|W \rangle +b\langle V|Z \rangle[/tex]

Given that [tex]|V\rangle[/tex] and [tex]|W \rangle[/tex] can be expressed in terms of their basis vectors,

[tex]|V \rangle = \sum_i v_i |i \rangle[/tex]

[tex]|W \rangle = \sum_j w_j|j \rangle[/tex]

Shankar says "we follow the axioms obeyed by the inner product to obtain"

[tex]\langle V|W \rangle = \sum_i \sum_j v_i^*w_j\langle i|j \rangle[/tex]

I don't understand how this comes about?

thanks

What is your mathematical background? In most basic abstract algebra courses and even some linear algebra courses you will go into inner products and inner product spaces.
 
  • #3
Oh I just finished high school and I'm trying to occupying myself in the holidays

(actually nevermind I was able to get it with some help from a friend)
 

Related to What Are Shankar's Inner Product Axioms in Quantum Mechanics?

1. What is Shankar's Inner Product Axioms?

Shankar's Inner Product Axioms is a set of mathematical rules that define how inner products should behave in vector spaces. An inner product is a mathematical operation that takes two vectors and produces a scalar value. This concept is used in many fields, such as physics, engineering, and computer science.

2. Why are Shankar's Inner Product Axioms important?

Shankar's Inner Product Axioms are important because they provide a rigorous and consistent way of defining inner products in vector spaces. This allows for the development of mathematical models and theories that can be applied to real-world problems.

3. What are the four axioms in Shankar's Inner Product Axioms?

The four axioms in Shankar's Inner Product Axioms are Additivity, Homogeneity, Symmetry, and Positivity. Additivity states that the inner product of two vectors added together is equal to the sum of their individual inner products. Homogeneity states that scaling a vector by a constant also scales the inner product by the same constant. Symmetry states that the inner product of two vectors is the same regardless of their order. Positivity states that the inner product of a vector with itself is always greater than or equal to zero.

4. How are Shankar's Inner Product Axioms used in real-world applications?

Shankar's Inner Product Axioms are used in a variety of fields, such as physics, engineering, and computer science. They are used to define inner products in vector spaces, which are then used to model and solve real-world problems. For example, in physics, inner products are used to calculate work and energy, while in computer science, they are used in machine learning algorithms.

5. How can one apply Shankar's Inner Product Axioms in their own research or work?

To apply Shankar's Inner Product Axioms in your own research or work, you must first understand the concept of inner products and the four axioms. Then, you can use them to define inner products in your vector space and apply them in your mathematical models or problem-solving. It is important to carefully follow the axioms to ensure accurate and consistent results.

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