String Theory Demystified

CHAPTER 11 Type II String Theories 203
Type II B Theory
We have seen that type II A theory is characterized by opposite chirality. Type II B
theory is characterized by the same chirality. That is, for a state
R ⊗ R 1 2
R and R will have the same chirality. The left and right movers will have
1 2
the same GSO projection:
The spinor fi eld satisfi es
The states
also have the same chirality.
( Γ 0 Γ 0
11 ) = ( 11 )
R left R right (11.27)
a a a a
Γ S = S and Γ S = S
(11.28)
11 11
left right left right
R −12 / NS −12
/ NS R
µ µ
0 ⊗ b 0 and b 0 ⊗ 0
The Massless Spectrum of Different Sectors
We conclude the chapter by noting the spectrum of states seen in the different
sectors, and describing how these are different in type II A and type II B string
theories. For those with a background in differential geometry or general relativity,
forms are odd in type II A theory and even in type II B theory.
THE |NS〉 ⊕ |NS〉 SECTOR
Type II A and type II B string theories have the same NS-NS sector. The spectrum
of states in the NS-NS sector is
• A scalar fi eld ϕ which is the dilaton described in the last chapter (1 state)
• An antisymmetric gauge fi eld with 28 states
• A symmetric traceless rank two tensor G (this is the graviton) with 35 states
µν