Conformal Metrics to a Product or Doubly Warped Product on <math xmlns="http://www.w3.org/1998/Math/MathML" id="M1"> <msup> <mrow> <mi mathvariant="double-struck">S</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msup> <mo>×</mo> <msup> <mrow> <mi mathvariant="double-struck">S</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msup> </math> and the Hopf Conjecture
Journal of mathematics