Superconformal algebra

{{Short description|Algebra combining both supersymmetry and conformal symmetry}}

{{cleanup|date=May 2015|reason=This stub is remarkably poorly written and should be fixed to read in a more pedagogical fashion}}

In theoretical physics, the superconformal algebra is a graded Lie algebra or superalgebra that combines the conformal algebra and supersymmetry. In two dimensions, the superconformal algebra is infinite-dimensional. In higher dimensions, superconformal algebras are finite-dimensional and generate the superconformal group (in two Euclidean dimensions, the Lie superalgebra does not generate any Lie supergroup).

Superconformal algebra in dimension greater than 2

The conformal group of the (p+q)-dimensional space \mathbb{R}^{p,q} is SO(p+1,q+1) and its Lie algebra is \mathfrak{so}(p+1,q+1). The superconformal algebra is a Lie superalgebra containing the bosonic factor \mathfrak{so}(p+1,q+1) and whose odd generators transform in spinor representations of \mathfrak{so}(p+1,q+1). Given Kac's classification of finite-dimensional simple Lie superalgebras, this can only happen for small values of p and q. A (possibly incomplete) list is

  • \mathfrak{osp}^*(2N|2,2) in 3+0D thanks to \mathfrak{usp}(2,2)\simeq\mathfrak{so}(4,1);
  • \mathfrak{osp}(N|4) in 2+1D thanks to \mathfrak{sp}(4,\mathbb{R})\simeq\mathfrak{so}(3,2);
  • \mathfrak{su}^*(2N|4) in 4+0D thanks to \mathfrak{su}^*(4)\simeq\mathfrak{so}(5,1);
  • \mathfrak{su}(2,2|N) in 3+1D thanks to \mathfrak{su}(2,2)\simeq\mathfrak{so}(4,2);
  • \mathfrak{sl}(4|N) in 2+2D thanks to \mathfrak{sl}(4,\mathbb{R})\simeq\mathfrak{so}(3,3);
  • real forms of F(4) in five dimensions
  • \mathfrak{osp}(8^*|2N) in 5+1D, thanks to the fact that spinor and fundamental representations of \mathfrak{so}(8,\mathbb{C}) are mapped to each other by outer automorphisms.

Superconformal algebra in 3+1D

According to {{cite book |doi=10.1007/0-306-47056-X_17|chapter=Introduction to Rigid Supersymmetric Theories |title=Confinement, Duality, and Non-Perturbative Aspects of QCD |series=NATO Science Series: B |year=2002 |last1=West |first1=P. C. |volume=368 |pages=453–476 |arxiv=hep-th/9805055 |isbn=0-306-45826-8 |s2cid=119413468 }}

{{cite journal

| last = Gates | first = S. J.

| last2 = Grisaru | first2 = Marcus T.

| last3 = Rocek | first3 = M.

| author3-link = Martin Rocek

| last4 = Siegel | first4 = W.

| author4-link = Warren Siegel

| year = 1983

| title = Superspace, or one thousand and one lessons in supersymmetry

| journal = Frontiers in Physics

| volume = 58 | pages = 1–548

| arxiv = hep-th/0108200

| bibcode = 2001hep.th....8200G

| doi =

}} the superconformal algebra with \mathcal{N} supersymmetries in 3+1 dimensions is given by the bosonic generators P_\mu, D, M_{\mu\nu}, K_\mu, the U(1) R-symmetry A, the SU(N) R-symmetry T^i_j and the fermionic generators Q^{\alpha i}, \overline{Q}^{\dot\alpha}_i, S^\alpha_i and {\overline{S}}^{\dot\alpha i}. Here, \mu,\nu,\rho,\dots denote spacetime indices; \alpha,\beta,\dots left-handed Weyl spinor indices; \dot\alpha,\dot\beta,\dots right-handed Weyl spinor indices; and i,j,\dots the internal R-symmetry indices.

The Lie superbrackets of the bosonic conformal algebra are given by

:[M_{\mu\nu},M_{\rho\sigma}]=\eta_{\nu\rho}M_{\mu\sigma}-\eta_{\mu\rho}M_{\nu\sigma}+\eta_{\nu\sigma}M_{\rho\mu}-\eta_{\mu\sigma}M_{\rho\nu}

:[M_{\mu\nu},P_\rho]=\eta_{\nu\rho}P_\mu-\eta_{\mu\rho}P_\nu

:[M_{\mu\nu},K_\rho]=\eta_{\nu\rho}K_\mu-\eta_{\mu\rho}K_\nu

:[M_{\mu\nu},D]=0

:[D,P_\rho]=-P_\rho

:[D,K_\rho]=+K_\rho

:[P_\mu,K_\nu]=-2M_{\mu\nu}+2\eta_{\mu\nu}D

:[K_n,K_m]=0

:[P_n,P_m]=0

where η is the Minkowski metric; while the ones for the fermionic generators are:

:\left\{ Q_{\alpha i}, \overline{Q}_{\dot{\beta}}^j \right\} = 2 \delta^j_i \sigma^{\mu}_{\alpha \dot{\beta}}P_\mu

:\left\{ Q, Q \right\} = \left\{ \overline{Q}, \overline{Q} \right\} = 0

:\left\{ S_{\alpha}^i, \overline{S}_{\dot{\beta}j} \right\} = 2 \delta^i_j \sigma^{\mu}_{\alpha \dot{\beta}}K_\mu

:\left\{ S, S \right\} = \left\{ \overline{S}, \overline{S} \right\} = 0

:\left\{ Q, S \right\} =

:\left\{ Q, \overline{S} \right\} = \left\{ \overline{Q}, S \right\} = 0

The bosonic conformal generators do not carry any R-charges, as they commute with the R-symmetry generators:

:[A,M]=[A,D]=[A,P]=[A,K]=0

:[T,M]=[T,D]=[T,P]=[T,K]=0

But the fermionic generators do carry R-charge:

:[A,Q]=-\frac{1}{2}Q

:[A,\overline{Q}]=\frac{1}{2}\overline{Q}

:[A,S]=\frac{1}{2}S

:[A,\overline{S}]=-\frac{1}{2}\overline{S}

:[T^i_j,Q_k]= - \delta^i_k Q_j

:[T^i_j,{\overline{Q}}^k]= \delta^k_j {\overline{Q}}^i

:[T^i_j,S^k]=\delta^k_j S^i

:[T^i_j,\overline{S}_k]= - \delta^i_k \overline{S}_j

Under bosonic conformal transformations, the fermionic generators transform as:

:[D,Q]=-\frac{1}{2}Q

:[D,\overline{Q}]=-\frac{1}{2}\overline{Q}

:[D,S]=\frac{1}{2}S

:[D,\overline{S}]=\frac{1}{2}\overline{S}

:[P,Q]=[P,\overline{Q}]=0

:[K,S]=[K,\overline{S}]=0

Superconformal algebra in 2D

{{main|super Virasoro algebra}}

There are two possible algebras with minimal supersymmetry in two dimensions; a Neveu–Schwarz algebra and a Ramond algebra. Additional supersymmetry is possible, for instance the N = 2 superconformal algebra.

See also

References

{{reflist}}

{{Supersymmetry topics}}

{{String theory topics |state=collapsed}}

{{DEFAULTSORT:Superconformal Algebra}}

Category:Conformal field theory

Category:Supersymmetry

Category:Lie algebras

{{quantum-stub}}