This similar denomination is not a coincidence ; the Type IIA string theory has the Type IIA supergravity theory as its low-energy limit and the Type IIB string theory gives rise to Type IIB supergravity .
It was discovered that by taking a Type IIA string theory that has a size R and changing the radius to 1\/R the result will end up being what is equivalent to a Type IIB theory of size R . This duality , along with the others , creates connections between all 5 ( or 6 , if supergravity is counted ) theories .