# Mass spectrum of Type I string theory

I understand that the massless fields of the Type I string theory are the described by: [\begin{array}{*{20}{c}} {{\rm{Sector}}}&{{\rm{Massless fields}}}\\ {{\rm{R - R}}}&{{C_0}}\\ {{\rm{NS - NS}}}&{{g_{\mu \nu }},\Phi }\\ {{\rm{R - NS}}}&{{\Psi _\mu }}\\ {{\rm{NS - R}}}&{\lambda'}\\ {\rm{R}}&{}\\ {{\rm{NS}}}&{} \end{array}]

I have 6 questions:

1. Are there any (massless) fields in the R and NS sectors (open strings)?

2. What is the projection of state vectors from the Type IIB string theory to the Type I string theory?

3. Is putting the ' necessary in the NS - R sector massless field?

4. What exactly are the spectra of state vectors (in terms of $\mathbf{8}_s$, $\mathbf{8}_v$ etc.) in the Type I string theory?

5. If the Type I string theory is a projection of the Type IIB string theory, where do the open strings come from?

6. What is the mass spectrum of the Type I string theory?

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1) Yes, the gauginos and gauge bosons, respectively. 2) Orientifold projection, as described in any textbook. 3) It's just a notation, convention. 4) The representations are clear from the indices in the notation and described in any textbook. 5) Open strings aren't considered projections of closed strings here; they're an independent sector. Projected closed strings are unorientable closed string. 6) A Hagedorn tower described in any textbook. – Luboš Motl May 13 '13 at 16:18
@Lubos Motl: Thanks a lot. – centralcharge May 14 '13 at 15:43
@Lubos Motl: However, I have a few questions: (1) When you say "gauge bosons and gauginos, are gravitons (and therefore the field $g_{\mu\nu}$) included? (2) Since the fields $F_{\mu\nu}$ and $g_{\mu\nu}$ are there in the NS-NS sector anyway, are these repeated in both the NS-NS sector (closed bosonic strings) and the NS (open bosonic strings) sector? (3) But doesn't the ' determine the chirality of the field? So putting the ' for the dilatino field would mean that it is of the opposite chirality than the gravitino field while not putting ' would mean same chirality, right? – centralcharge May 14 '13 at 16:04
Oops: In my previous comment, the $F_{\mu\nu}$ shouldn;t have been there. – centralcharge May 15 '13 at 14:51

Let me convert Lubos Motl's comment into a Community Wiki answer.

1. Yes, the gauginos and gauge bosons, respectively.

2. Orientifold projection, as described in any textbook.

3. It's just a notation, convention.

4. The representations are clear from the indices in the notation and described in any textbook.

5. Open strings aren't considered projections of closed strings here; they're an independent sector. Projected closed strings are unorientable closed string.

6. A Hagedorn tower described in any textbook.

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