What kind of tool will loosen this nut holding a chainwheel on a one piece crank? Can someone tell me how to remove this nut that is holding the chainwheel in place on this one piece crank? In the picture below, the red arrows are pointing to three slots in the nut that a tool would fit into to remove the nut. 

Is there a name for a too like that? I looked on the park tools web site but I didn't see anything.

Is there a way to loosen it without having to buy a specialized tool? 

Thanks in advance,
Such a tool may be called hook spanner.

The nut is holding the inner race of the bottom bracket bearing.

A web search with "bottom bracket" and "hook spanner" produces a couple of hits. (For instance, the tool mentioned by Klaster in the comments.) You may use a vernier caliper to determine the dimensions of your nut and find the right tool for you.