I'll be applying to graduate schools this fall, and I've been doing quite a bit of research into my various options (of course I've been looking into grad schools for the duration of my undergraduate degree, but now I need to actually fill in the minutia and avoid making any gaffs that hurt my chances, if possible); in any event, I'm a bit unsure of
(a) How much weight (if much at all) is given to the statement of purpose
(b How much detail should be included in the way of interests, interest in faculty research specialties etc.
My primary concern is with length, and due to the breadth of my interests I can only include so much. To give you an idea, my primary areas of interests are
Algebraic Areas: algebraic geometry (I'm presently part way through Eisenbud, and Atiyah McDonald, and I've covered a significant amount of material in the book Ideals Varieties and Algorithms and have had an independent study in the basics of the area), algebraic cryptanalysis (I've done some research in this), arithmetic geometry, category theory (specifically categorical logic and the application of category theory to cognitive science, though there are only a few researchers looking into the latter), Geometric complexity theory is super fascinating to me
Logic Areas: Game semantics in proof theory, Girard's linear logic and "Ludics" programme and Japaridze's work in computability logic, constructive mathematics and Martin-Löf type theory (a large part of this is due to the work by Voevodsky and Awodey in homotopy type theory, which seems very interesting to me), applications of model theory to algebraic geometry and tropical geometry, reverse mathematics (I've been reading Simpson's book on subsystems of second order arithmetic and it is fascinating to me)
Applied Areas: Machine learning, specifically reinforcement learning and Bayesian methodologies in pattern recognition (I've been reading Barto and Sutton as well as Bishop), Computational cognitive science and computational neuroscience, specifically representational learning
Some of these areas are more recent interests and some are surely irrelevant to certain departments, so I would probably not include my interest in linear logic or machine learning in the case of a school that has no researchers doing anything related to either area.
So now that I've blasted you with a wall of boring self indulgence, can anyone tell me whether I should include as many interersts as possible, if the school has people working in a lot of them? Or should I totally avoid doing that? Basically, I need to know how to write a statement of purpose.