Sum-check design philosophy, why it works?

Using an example of 3 variants multilinear polynomial to explain the design idea of sum-check protocol.

A 3 variants multilinear polynomial can be generally represented as

$$g(X,Y,Z)=a_0+a_xX+a_yY+a_zZ+a_{xy}XY+a_{xz}XZ+a_{yz}YZ+a_{xyz}XYZ$$

Understanding Sum-check in reverse order

In the final round of sumcheck protocol, assuming the verifier gets a one degree polynomial

$$h(z)=g(r_1,r_2,\ldots,z )=\alpha_n z …

Upon understanding the attack on Nova — Part 1

To understand the attack on Nova, I figure out I need to understand the role of the hash function and the validation check of hash function in Nova, from the first paper where the “cycle of curves” is not introduced, the circuit is illustrated as

Nova circuit in https://eprint.iacr.org/2021/370.pdf

to …