I am little bit curious about the following examples

at least two papers appeared on arxiv at the same day solving one and the same problem.

Have you ever seen such a coincidence? If yes, can you provide the links to that papers?

• of course the papers maybe solving one and the same problem in a slightly different generalities, for example, one solved a certain case of the problem, and the other one solved the problem completely.

• the authors should be different, for example, it is not allowed that both papers have one and the same person as an author/co-author.