The Orbifolds of Permutation-Type as Physical String Systems at Multiples of c=26 IV. Orientation Orbifolds Include Orientifolds

Abstract

In this fourth paper of the series, I clarify the somewhat mysterious relation between the large class of {\it orientation orbifolds} (with twisted open-string CFT's at $\hat{c}=52$) and {\it orientifolds} (with untwisted open strings at $c=26$), both of which have been associated to division by world-sheet orientation-reversing automorphisms. In particular -- following a spectral clue in the previous paper -- I show that, even as an {\it interacting string system}, a certain half-integer-moded orientation orbifold-string system is in fact equivalent to the archetypal orientifold. The subtitle of this paper, that orientation orbifolds include and generalize standard orientifolds, then follows because there are many other orientation orbifold-string systems -- with higher fractional modeing -- which are not equivalent to untwisted string systems.

22 pages, typos corrected

References in corpus (18)

• Matrix String Theory
• Systematic approach to cyclic orbifolds
• The Operator Algebra and Twisted KZ Equations of WZW Orbifolds
• Chern-Simons Gauge Theory on Orbifolds: Open Strings from Three Dimensions
• General Virasoro Construction on Orbifold Affine Algebra
• Two Large Examples in Orbifold Theory: Abelian Orbifolds and the Charge Conjugation Orbifold on su(n)
• The General Twisted Open WZW String
• The General Coset Orbifold Action
• The Outer-Automorphic WZW Orbifolds on so(2n), including Five Triality Orbifolds on so(8)
• More About All Current-Algebraic Orbifolds
• Cyclic Coset Orbifolds
• On the Target-Space Geometry of Open-String Orientation-Orbifold Sectors
• Extended Operator Algebra and Reducibility in the WZW Permutation Orbifolds
• Twisted Einstein Tensors and Orbifold Geometry
• Twisted Open Strings from Closed Strings: The WZW Orientation Orbifolds
• A Basic Class of Twisted Open WZW Strings
• New Duality Transformations in Orbifold Theory
• The Orbifolds of Permutation-Type as Physical String Systems at Multiples of c=26. I.Extended Actions and New Twisted World-Sheet Gravities

Cited by in corpus (5)

• The Orbifold-String Theories of Permutation-Type: I. One Twisted BRST per Cycle per Sector
• The Orbifolds of Permutation-Type as Physical String Systems at Multiples of $\mathbf{c}=26$ V. Cyclic Permutation Orbifolds
• The orbifold-string theories of permutation-type: II. Cycle dynamics and target space-time dimensions
• The Lorentzian Space-Times of the Orientation-Orbifold String Systems
• The Orbifold-String Theories of Permutation-Type: III. Lorentzian and Euclidean Space-Times in a Large Example