# Thread: Show to be injective *-homomorphism

1. ## Show to be injective *-homomorphism

$\gamma : \left[0, 1\right]\rightarrow \mathbb{T},t\mapsto e^{i2\pi t}$
Let $S$ be the closed ideal consisting of functions $\{f\in C_{0}(\left[0,1\right],\mathbb{T}):f(1)=0\}$
Where $C_{0}(\left[0,1\right],\mathbb{T})$ denotes the continuous functions vanishing at infinity
from $\left[0,1\right]$ to the unit circle, $\mathbb{T}$

Show that the map $\gamma_A:A\otimes_{*}S\rightarrow S(A)$
where $S(A)=\{f\in C_{0}(\left[0,1\right],\mathbb{T}):f(1)=0=f(0)\}$
is an injective *-homomorphism

Linearity is easy, so is multiplicativity, but how will I show that the adjoint is preserved and that the map is injective?

2. Wouldn't you just use the standard thing where you map elements a and b to the same value in the image and then show that a and b must be the same? That is f(a) = f(b) implies a = b.

3. I see I forgot to put in how $\gamma_A$ is defined

$\gamma_A(a\otimes f)=(f\circ \gamma)a$

so if $\gamma_A(a\otimes f)=\gamma_A(b\otimes f)$ we must have
$(f\circ \gamma)a=(g\circ\gamma)b$ so
$(f\circ\gamma)a-(g\circ\gamma)b=0$ then
$(fa\circ\gamma)-(gb\circ\gamma)=((fa)-(gb))\circ\gamma=0$
but $\gamma\neq 0$ for any $t\in\left[0,1\right]$

Now I can say $fa=gb$, but what I would like to show is $a\otimes f=b\otimes g$

Im I doing something wrong here?

$\gamma_A(a^*\otimes f^*)=(f^*\circ\gamma)a^*=\left(a(\gamma^*\circ f)\right)^*$