- #1
MathematicalPhysicist
Gold Member
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this is from his website:
"In what class of 4-dimensional spacetimes does there exist a real, non-constant scalar field φ with the following properties:
It obeys the wave equation: ◻φ=0
Its gradient is everywhere null: ∇φ.∇φ=0"
somehow i think it is concerned with his work, but what is its siginificance?
"In what class of 4-dimensional spacetimes does there exist a real, non-constant scalar field φ with the following properties:
It obeys the wave equation: ◻φ=0
Its gradient is everywhere null: ∇φ.∇φ=0"
somehow i think it is concerned with his work, but what is its siginificance?