# Re: Paper and slides on indefiniteness of CH

Dear Bob,

On Sun, 26 Oct 2014, Robert Solovay wrote:

Dear Sy,

In the last conjecture of your letter what does ” rigid” mean?

The only elementary embedding from the Stable Core to itself is the identity. I’m thinking of embeddings $j$ such that $(V,j)$ models ZF.

Best,
Sy

# Re: Paper and slides on indefiniteness of CH

Dear Sy,

In the last conjecture of your letter what does ” rigid” mean?

Thanks,
Bob