>>16700850It was kind of uninspiring, but it's a solid 8. A friend that is smarter than me liked Judson's when I let him borrow it from me (https://judsonbooks.org/aata/). It goes into the applications in coding theory in some chapters.
>>16700855>No. For example the rational functions (polynomialis dividing other polynomials) form a field.Yes, now I remember when you mention it, we saw that by the end of the course.
>Or you can just think about the solution space as the space of algebraic varieties and use the tools of algebraic geometry.Well that sounds more of a motivation than "number theory" or "cryptography", but still quite niche IMO. "Introductory" PDE books like Evans won't go into it as a requirement, not even the 4 volume work on PDEs by Lars Hormander I remember going into anything related to abstract algebra. And PDEs is past the first year of graduate mathematics after you've taken the obligatory courses, there are a lot more courses that justify themselves immediately regarding this path.
That said Group and Ring theory are low hanging fruit of course it doesn't hurt to take the courses.