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6

Supergravity: The Principles

Table 6.4 Field content of type IIB supergravity

 

 

 

 

 

 

Field in SU(1, 1) basis

SU(1, 1) repres.

U(1) charge

Superstring zero modes

 

 

 

 

Vμa

J = 0

0

graviton hμν

ψμ

J = 0

1

gravitinos ψ

2

Aμνα

J = 21

0

B[2], C[2]

Cμνρσ

J = 0

0

C[4]

λ

J = 0

3

dilatinos λA

2

Lα β

J = 21

±1

ϕ, C[0]

The early Greek indices α, β, . . . = 1, 2 run in the fundamental representation of SU(1, 1), while the early capital Latin indices A, B, . . . = 1, 2 run in the fundamental representation of SL(2, R). The p-gauge forms of the Ramond Ramond sector are denoted by C[p] .

6.8.2The Free Differential Algebra, the Supergravity Fields and the Curvatures

Following Castellani and Pesando the field content of type IIB supergravity is organized into representations of SU(1, 1) as displayed in Table 6.4. In order to write down the free differential algebra the critical issue is the correct identification of the fermionic terms contributing to the curvature of the complex 2-form doublet Aαμν . These latter transform in the 2-dimensional representation of SU(1, 1) and are related by the Cayley matrix of (6.8.4) to a doublet of real 2-forms AΛμν that transform in the 2-dimensional representation of SL(2, R):

2 A2

3

= C

2 A2

3

(6.8.8)

A1

 

 

A1

 

 

μν

 

 

μν

 

 

μν

 

 

μν

 

 

We introduce a doublet of Majorana-Weyl spinor 1-forms (the gravitinos) having the same chirality:

Γ11ψA = −ψA; C

ψ

A = ψA, A = 1, 2

(6.8.9)

In terms of these we define the complex doublet of gravitinos:

 

ψ

= C

 

ψ

 

(6.8.10)

ψ

ψ2

 

 

 

 

1

 

 

and we introduce the following doublet made by a complex 3-form current and its complex conjugate:

 

i

 

 

 

 

 

V a

; (x = ±)

 

 

ψ

 

Γ ψ

(6.8.11)

JSU = iψ

 

Γ ψ

V a

x

 

 

 

 

 

a

 

 

 

 

 

 

 

 

a

 

 

 

6.8 Type IIB Supergravity

257

By means of an inverse Cayley transformation we get a doublet of real currents:

 

 

 

1 A

 

 

 

 

 

 

 

 

 

 

 

 

JA

 

C

Jx

 

i

1

 

Γa ψ1 ψ2 Γa ψ2) V a

 

SL

=

 

 

x

SU

=

 

 

 

 

2i

 

 

 

 

 

2

V a

 

 

 

 

ψ

1

Γ

ψ

 

 

 

 

 

 

 

 

 

a

 

 

 

 

dA|BC i

 

B Γa ψC V a

 

 

 

 

 

 

 

 

 

 

 

(6.8.12)

 

ψ

 

 

 

 

 

 

 

 

 

 

 

The formula (6.8.12) is understood as follows. Recall that the fermions transform only with respect to the isotropy subgroup H = U(1) O(2) of the scalar coset (are neutral under G) and that all irreducible representations of O(2) are 2-dimensional. The coefficients dA|BC defined by (6.8.12) are the Clebsch Gordon coefficients that extract the doublet of helicity s = 2 from the tensor product of two representations of helicity s = 1. Relying on these notations we can write the type IIB curvature definitions in two equivalent bases related by a Cayley transformation:

1.the complex SU(1, 1) basis originally used by Castellani and Pesando [34],

2.the real SL(2, R), introduced here and best suited for comparison with string theory massless modes.

The Curvatures of the Free Differential Algebra in the Complex Basis

Using

the complex basis the curvatures are as follows12

 

 

 

 

 

 

 

 

 

 

 

 

Γ a ψ

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(6.8.13)

Ta = D V a

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Rab = ab ωac ωdbηcd

 

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

ωab Γabψ

 

iQ ψ

 

 

 

 

 

 

 

ρ = D ψ

 

 

 

 

 

 

 

 

(6.8.14)

4

2

 

 

 

 

 

 

H α

 

dAα

2α

 

 

 

ψ

 

V a

+

2iΛα

 

 

 

 

 

V a

 

2

 

 

 

(6.8.15)

ψ

Γ

ψ

Γ ψ

[3] =

[2] +

 

 

+

 

a

 

 

 

 

 

a

 

 

 

 

 

 

 

1

 

 

 

 

α

β

 

1

 

 

 

 

 

 

 

a

 

b

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

F[5] = dC[4] +

 

 

 

iεαβ

2A[2] H[3]

+

 

 

ψ

Γabcψ V

 

V

 

16

6

 

 

1

 

 

 

 

 

α

 

 

 

β

 

 

 

 

 

 

 

β

 

 

 

a

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

+

 

εαβ

 

2A[2] Λ+ψΓa ψ

 

+ Λψ

Γa ψ V

 

 

 

 

8

 

 

 

 

 

 

1

 

 

 

 

 

 

 

3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

D λ =

 

ωabΓabλ i

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

D Λα± = α± iα±.

alternatively using the real SL(2, R) basis we can write:

V c

(6.8.16)

(6.8.17)

(6.8.18)

The Curvatures of the Free Differential Algebra in the Real Basis

 

 

A Γ a ψA

 

Ta = D V a

(6.8.19)

12Comparing with the original paper by Castellani and Pesando, note that we have changed the nor-

malization: Aα 2Aα and Bλμνρ = 6Cλμνρ so that eventually the 4-form C[4] will be identified with that used in Polchinski’s book [32, 33].

258

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6 Supergravity: The Principles

 

ab

=

ab

 

 

ac

 

 

db

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R

 

 

 

 

ω

 

 

ω1

 

ηcd

 

 

 

 

 

 

1

 

 

 

ρA = D ψA A

 

 

 

ωab ΓabψA +

 

Q

εAB ψB

(6.8.20)

4

 

2

H[Λ3]

= dA[Λ3] + iLAΛdA|BC

 

 

B Γa ψC V a

 

(6.8.21)

ψ

 

 

 

 

 

 

 

 

 

 

 

 

1

εΛΣ A[Λ3] H[Σ3] + i

1

 

 

 

 

 

 

 

F[5] = dC[4]

 

ψA ΓabcψB εAB V a V b V c

 

 

 

 

16

6

 

 

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

+

i

 

 

ε

 

 

 

 

AΛ

LΣ dA|BC ψ

B

Γ

 

 

ψ

C

V a

(6.8.22)

 

 

 

 

 

 

 

 

 

 

 

 

4

 

 

 

ΛΣ

 

[2]

 

A

 

 

 

 

 

 

 

 

a

 

 

 

D λ =

1

ωab

 

 

 

 

 

 

 

3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Γabλ

 

i

 

 

 

 

 

 

 

 

 

(6.8.23)

4

2

 

 

 

 

 

 

 

 

 

D L±Λ = dLAΛ + εAB QLBΛ.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(6.8.24)

In the above formulae, (6.8.18) and (6.8.24) define the covariant derivative of the coset representative of the scalar coset in the SU(1, 1) and SL(2, R) basis respectively. They follow from the Maurer Cartan equations of G/H.

Next, using the results of Castellani and Pesando [34], we can write the rheonomic parameterizations of the curvatures (6.8.13)–(6.8.18) (alternatively (6.8.19)– (6.8.24)) that determine the supersymmetry transformation rules of all the fields. Prior to that, in order to make contact with superstring massless modes as normalized in Polchinski’s book, it is convenient to introduce the following identifications:

1

 

 

2

 

 

 

2B[2];

 

(6.8.25)

A[2] = 2

 

A[2] = 2

2C[2]

where B[2] is the 2-form gauge field of the Neveu-Schwarz sector that couples to ordinary fundamental strings, while C[2] is the 2-form of the Ramond-Ramond sector that couples to D1-branes. For simplicity we write the rheonomic parameterizations only in the complex basis and we disregard the bilinear fermionic terms calculated by Castellani and Pesando. We have:

Ta = 0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(6.8.26)

ρ = ρabV a V b + 16 iΓ a1

a4 ψV a5 Fa1a5 + 5! εa1a10 Fa6a10

 

 

 

 

 

 

 

 

 

 

 

 

5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

 

 

1

 

Γ a1a4 ψ Va1

+ 9Γ a2a3 ψ V a4 Λ+α Haβ2a4 εαβ

 

 

 

+

 

 

 

 

32

 

 

 

+ fermion bilinears

 

 

 

 

 

 

 

 

λ V a

 

 

 

 

 

(6.8.27)

H α

=

H α

V a

 

V b

 

V c

+

Λα

ψ

Γ

ab

 

V b

 

[3]

abc

 

 

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

+ Λα

 

ΓabλV a V b

 

 

 

 

 

 

 

 

 

 

 

 

 

(6.8.28)

 

 

ψ

 

 

 

 

 

 

 

 

 

 

 

 

 

F[5] = Fa1a5 V a1 · · · V a5

1

 

 

 

 

 

 

 

 

 

 

 

(6.8.29)

D λ

=

Da λV a

+

iPa Γ a ψ

 

iΓ a1

a3 ψεαβ Λα

H β

(6.8.30)

 

 

8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

+

 

a1a3

 

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