In heterotic string theory, the Strominger's equations are the set of equations that are necessary and sufficient conditions for spacetime supersymmetry.
It is derived by requiring the 4-dimensional spacetime to be maximally symmetric, and adding a warp factor on the internal 6-dimensional manifold.
However, there are topological obstructions in obtaining the solutions to the equations; In case V is the tangent bundle
is Kähler, we can obtain a solution of these equations by taking the Calabi–Yau metric on
Once the solutions for the Strominger's equations are obtained, the warp factor