Exercise · ZW-KERNEL-OF-A-HOMOMORPHISM-001 · ★☆☆ Basic
Let \(\varphi\colon\mathbb{Z}_{12}\to\mathbb{Z}_4\) be given by \(\varphi(x)=x \bmod 4\). What is the kernel of \(\varphi\)?
Choose one option.
Show answer
- C. \(\{0,4,8\}\)
Explanation
The \(x\) in \(\mathbb{Z}_{12}\) with \(x\equiv0\pmod 4\) are \(0,4,8\). Those are exactly the elements sent to the identity \(0\) of \(\mathbb{Z}_4\).
Review the concept: Kernel of a homomorphism
The kernel of a group homomorphism \(\varphi\colon G\to H\) is the set of elements of \(G\) that \(\varphi\) sends to the identity \(e_H\) of \(H\).
\[\ker\varphi=\{g\in G:\ \varphi(g)=e_H\}\]
More practice problems: kernel of a homomorphism
- ZW-KERNEL-OF-A-HOMOMORPHISM-002 Let φcolon(ℝ,+)→(ℝ_>0,·) with φ(x)=e^x. What is its kernel?
- ZW-KERNEL-OF-A-HOMOMORPHISM-003 Which element belongs to the kernel of every homomorphism φcolon G→ H?
- ZW-KERNEL-OF-A-HOMOMORPHISM-004 Let φcolonℤ_18→ℤ_6 with φ(x)=4x bmod 6. How many elements does its kernel have?
- ZW-KERNEL-OF-A-HOMOMORPHISM-005 Let φcolon(ℤ_7^*,·)→(ℤ_7^*,·) with φ(x)=x^2. What is its kernel?
- ZW-KERNEL-OF-A-HOMOMORPHISM-006 A homomorphism φcolon G→ H is injective. What can be stated for sure?
- ZW-KERNEL-OF-A-HOMOMORPHISM-007 Let φcolonℤ_8→ℤ_8 with φ(x)=6x bmod 8. How many distinct elements does its image have?
- ZW-KERNEL-OF-A-HOMOMORPHISM-008 How many homomorphisms φcolonℤ_12→ℤ_18 have a kernel with exactly 2 elements?
- ZW-KERNEL-OF-A-HOMOMORPHISM-009 A group G of order 15 maps onto ℤ_5 by a surjective homomorphism. How many elements does the kernel…