I am frequently interested to find less technical proofs of results which already appear in the literature, at least in some special cases of these results. Sometimes a published proof shows that an object with some properties exists, but actually the proof does not (at least not without additional work) *construct* that object in a concrete way. (Here *object* is understood to be in a very general sense, so functors for instance also qualify as objects.) Imagine for example a theorem stating that a certain functor is representable, and the proof uses some adjoint functor theorem: this does not really tell us much about the internal structure of a representing object, and it is often (not always) very useful to write down that representing object directly, including a direct proof that it actually represents the functor which also does not use much machinery.


I believe that it is worthwile to write down and maybe also publish a more direct, easy and constructive argument in case it is available and presumably not published so far. My question is basically how to fit this into the common "definition-theorem-proof" scheme of mathematical publications.


I cannot just have a theorem stating "There is an object with the property ...", since that existence statement is already known and I am actually more interested in the specific construction of that object. Another solution might be to put the construction of that object into a separate section, or a long definition, and then have a theorem stating "The object constructed above has the property ...". Another idea might be to find logical properties of a "concrete construction" which the published existence proof does not have; but I have to admit that this task is nontrivial for someone who is not an expert in mathematical logic, and it might become a bit artificial, and it might turn out that these logical properties actually already follow formally from the published proof. Basically, what I want is a theorem "There is an explicit construction of an object with the property ..." and give the construction in its proof, but the problem is that "explicit construction" is not a well-defined notion, as far as I know, so that it is unclear what qualifies as a proof of it.


Do you have other ideas or guidelines for a good exposition for a "concrete construction"? What are good examples of papers which have a good exposition of this type?



Exposition of concrete constructions
I think the following scheme is quite reasonable, which paraphrases your second option:


**Def.** Object X is...


**Def.** Property Y is...


**Thm.** Object X has Property Y.


**Rmk.** Object X is the first explicit example of Property Y.


You might need to put in quite a bit of effort to prove the Theorem, or to construct of X itself. Moreover, the Remark you are making is more about the state of the literature, rather than a formal statement, which is of course allowed in a remark. If you can also motivate why having an explicit example is important, the nontrivial mathematical content and the motivation make a perfectly reasonable recipe for a paper.


