What is the Proof for the Jacobi Symbol Property (ii)?

In summary, the conversation discusses a theorem about Jacobi symbols, stating that for odd and positive numbers n and m, (a/nm)=(a/n)(a/m) and (ab/n)=(a/n)(b/n). It also mentions two additional statements regarding gcd, stating that if gcd(a,n)=1, then (a^2/n) = 1 = (a/n^2), and if gcd(ab,nm)=1, then (ab^2/nm^2)=(a/n). The speaker is seeking help understanding the proof for the second statement.
  • #1
kingwinner
1,270
0
This is a theorem about Jacobi symbols in my textbook:
Let n and m be ODD and positive. Then (a/nm)=(a/n)(a/m) and (ab/n)=(a/n)(b/n)
Moreover,
(i) If gcd(a,n)=1, then ([tex]a^2/n[/tex]) = 1 = ([tex]a/n^2[/tex])
(ii) If gcd(ab,nm)=1, then ([tex]ab^2/nm^2[/tex])=(a/n)
=====================================

(i) is easy and follows from the definition, but how can we prove (ii)? My textbook stated the theorem without proof and just says the proofs are easy, but I have no idea why (ii) is true.

Any help is appreciated!
 
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  • #2
(a^2/n) = (a/n)(a/n). So what is it supposed to be?
 

1. What is the Jacobi symbol?

The Jacobi symbol is a mathematical symbol used to determine whether a given integer is a quadratic residue modulo a particular odd prime number. It is denoted by (a/n) and is defined as the Legendre symbol when n is a prime number, and as the Kronecker symbol for any positive odd integer n.

2. What are the properties of the Jacobi symbol?

The Jacobi symbol has several important properties, including linearity, multiplicativity, and quadratic reciprocity. Linearity means that (ab/n) = (a/n)(b/n) for any integers a and b, while multiplicativity states that (a/n)^k = (a^k/n) for any integer k. Quadratic reciprocity is a key property that relates the Jacobi symbol to the Legendre symbol and is used to determine whether an integer is a quadratic residue modulo a particular prime number.

3. How is the Jacobi symbol calculated?

To calculate the Jacobi symbol (a/n), we first express the integer n as a product of prime numbers. Then, we apply the properties of the Jacobi symbol to simplify the expression and determine the value of (a/n). In some cases, we may need to use the law of quadratic reciprocity to evaluate the symbol.

4. What is the significance of the Jacobi symbol?

The Jacobi symbol is an important tool in number theory and is used to solve various mathematical problems, including determining whether an integer is a quadratic residue modulo a particular prime number and finding the solutions to certain types of quadratic congruences. It also has applications in cryptography and coding theory.

5. Are there any limitations to the Jacobi symbol?

While the Jacobi symbol is a useful mathematical tool, it does have some limitations. It can only be used for odd integers, and it does not have the same properties as the Legendre symbol when n is a composite number. Additionally, it can only be used to determine whether an integer is a quadratic residue modulo an odd prime number, not for any general modulus.

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