Complex sentence: The implication of the above relation is the conservation of momentum,\\ nabla\\ cdot\\ mathbf is the momentum flux density and plays a role similar to\\ mathbf in Poynting's theorem.
Split into simpler sentences: The implication of the above relation is the conservation of momentum. Here,\\ nabla\\ cdot\\ mathbf is the momentum flux density and plays a role similar to\\ mathbf in Poynting's theorem.