2026-364

A zombie infection spreads according to the SI model under the homogeneous mixing assumption. Researchers observe that faster zombies encounter healthy individuals more frequently, so the infection rate is proportional to the zombie walking speed:

$$\beta =c{v}_z,$$

where $v_z$ is the average zombie speed and $c$ is a proportionality constant.

A mutation doubles their average speed. The contact network remains unchanged, with

$$⟨k⟩=8$$

and

$$⟨k^2⟩=100.$$

According to the SI model on networks, by what factor does the characteristic time change after the mutation?

A) It is reduced by half.

B) It doubles.

C) It increases by a factor of four.

D) It remains unchanged.

E) None of the above.

Original idea by George Gigilas Junior