D5D_5 elliptic fibrations: non-Kodaira fibers and new orientifold limits of F-theory

Oct, 2011
60 pages
Published in:
  • Commun.Num.Theor.Phys. 09 (2015) 3, 583-642
  • Published: 2015
e-Print:

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Abstract: (International Press)
We present for the first time Sen’s (orientifold) limits for D5D_5 elliptic fibrations. These orientifolds limits describe different weak coupling limits of F-theory to type IIB string theory giving a system of three brane-image-brane pairs in presence of a Z2\mathbb{Z}_2 orientifold. The orientifold theory is mathematically described by the double cover the base of the elliptic fibration. Such orientifold theories are characterized by a transition from a semi-stable singular fiber to an unstable one. In this paper, we describe the first example of a weak coupling limit in F-theory characterized by a transition to a non-Kodaira (and non-ADE) fiber. Inspired by string dualities, we obtain non-trivial topological relations connecting the elliptic fibration and the different loci that appear in its weak coupling limit. Mathematically, these are very surprising relations which relate the total Chern class of the D5D_5 elliptic fibration and those of different loci that naturally appear in the weak coupling limit. We work over bases of arbitrary dimension and our results are independent of any Calabi-Yau hypothesis.
  • duality: string
  • symmetry: Z(2)
  • string model: Type IIB
  • F-theory: topological
  • orientifold
  • weak coupling
  • D-brane: 5
  • singularity
  • fibre bundle