# Is there an open oriented superstring?

Type I superstring theory is unoriented, and it seems that it needs to be so in order to exist.

Now, we always have open-closed duality, that connects at least the ultraviolet sector of a theory with the infrared sector of another, so in principle we should have some oriented open strings coming from it, by duality with a closed oriented theory.

And we have all the D-brane stuff, that surely produces another kinds of open string theories with the restriction of terminating there in the branes.

¿Is some of these D-brane examples an oriented theory? ¿Is there some canonical, well known, example of a consistent oriented theory with open strings?

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In the closed string spectrum, there is an $\mathcal N = 2A$ algebra and and an $\mathcal N = 2B$ algebra which lead to different string theories. Both have 32 supercharges. In each of these,, there are 2 gravitinoes, dilationoes, 1 in the Ramond Neveu-Schwarz Sector and 1 more in the Neveu-Schwarz Ramond Sector. These 2 gravitinos need 2 different supercurrents to couple to. But the $\mathcal N=1$ supersymmetric algebra with only 16 supercharges clearly cannot allow this!