Let: $INF = \{ w \in \Sigma^* | \quad |L(M_w)| = \infty \} $.
It is easy to show with Rices theorem that $INF$ is not decidable. ($INF$ is non-trivial because of $\emptyset$ and $\Sigma^*$).
How can you show this with a reduction onto the halting problem (for example)?
Here are my thoughts:
I had an idea of running the decider of $INF$ in its own input, but couldnt get very far.
Another idea that I just had was:
Construct a Turing machine TM M' that halts if the language is finite, and loops endlessly if it is infinite:
M'(w):
for i=0,1,...
simulate M_w on w_i
Knowing the halting problem we cannot know if that turing machine will halt or not. We have supposedly reduced $HALT$ on $INF$. Is this correct ? (Since we take an instance of $HALT$
Can I get some feedback on my solutions ?