I presume the OP is looking for examples from mathematics. Here is one:

Hadrien De March, Nizar Touzi: <A HREF="https://arxiv.org/abs/1702.08298">Irreducible convex paving for decomposition of multi-dimensional martingale transport plans</A> (submitted February 27, 2017, at 14.23 hours)   

Jan Obłój, Pietro Siorpaes: <A HREF="https://arxiv.org/abs/1702.08433">Structure of martingale transports in finite dimensions</A> (submitted February 27, 2017, at 18.52 hours)

The second paper explains:

> Finally we note that we have hoped to make this paper publicly
> available only after having proved Conjecture 1.3. However we have
> been recently made aware of a parallel and independent work of De
> March and Touzi who study the same problem and obtain similar
> results using different techniques. Consequently, we have agreed to
> simultaneously make our works publicly available.