Non-BPS Branes in a Type I Orbifold

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We analyse the spectrum of non-BPS branes in the type I theory on the orbifold T⁴/ I₄. We present a detailed analysis of the action of the worldsheet parity Ω on the different D-brane boundary state sectors of type IIB on T⁴/ I₄, using the covariant formulation. Using these results we derive the spectrum of branes in the type I orbifold. We find ₂- and - charged non-BPS branes. A study of the stability of these branes in the type I orbifold is also presented. We find that the type I non-BPS D-particle and D-instanton remain stable in the orbifold. The D-particle carries no charge whereas the non-BPS D-instanton can carry twisted R-R charge.