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Superspace Sigma Models. IST String Fest Volker Schomerus. based on work w. C. Candu, C.Creutzig, V. Mitev, T Quella, H. Saleur; 2 papers in preparation. Superspace Sigma Models. Aim: Study non-linear sigma models with target space supersymmetry not world-sheet.
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Superspace Sigma Models IST String Fest Volker Schomerus based on work w. C. Candu, C.Creutzig, V. Mitev, T Quella,H. Saleur; 2 papers in preparation
Superspace Sigma Models Aim: Study non-linear sigma models with target space supersymmetry not world-sheet Strings in AdS backgrounds [pure spinor] c = 0 CFTs; symmetry e.g. PSU(2,2|4) ... Focus on scale invariant QFT, i.e. 2D CFT Properties:Weird: logarithmic Conformal Field Theories! Remarkable: Many families with cont. varying exponents
Plan of 2nd Lecture M O D E L S • SM on CP0|1 - Symplectic Fermions • Sigma Model on Superspace CP1|2 • Properties of the Chiral Field on CP1|2 • Conclusion & Some Open Problems Bulk and twisted Neumann boundary conditions M E T H O D S Exact boundary partition functions Quasi-abelian evolution; Lattice models; Symplectic fermions as cohomology
1.1 Symplectic Fermions - Bulk Only global u(1) sym. is manifest Has affine psu(1|1) sym: Action rewritten in terms of currents: U(1) x U(1) Possible modification: θ-angle trivial in bulk
1.1 Symplectic Fermions - Bulk Has affine psu(1|1) sym: Action rewritten in terms of currents: U(1) x U(1) Possible modification: θ-angle trivial in bulk
ΘΘ x 1.2 SF – Boundary Conditions boundary term Implies twisted Neumann boundary conditions: A with currents: Results: 4 ground states In P0 of u(1|1) Θ1Θ2 -1 Ground states: λ(Θ1,Θ2) = λ(tr(A1A2 )) x twist fields [Creutzig,Quella,VS] [Creutzig,Roenne]
1.3 SF – Spectrum/Partition fct. c/24 U(1) gauging constraint branching functions characters
2.1 The Sigma Model on CPN-1|N zα, ηα→ ωzα, ωηα = → 2 parameter family of 2D CFTs;c = -2 a - non-dynamical gauge field D = ∂ - ia θ term non-trivial; θ=θ+2π Non-abelian extension of symplectic fermion
2.2 CPN-1|N – Boundary Conditions Boundary condition in σ-Model on target X is hypersurface Y + bundle with connection A Dirichlet BC ┴ to Y; Neumann BC || to Y; U(N|N) symmetric boundary cond. for CPN-1|N line bundles on Y = CPN-1|N with monopole Aμ Spectrum of sections e.g. N=2; μ = 0 μ integer ~ (1+14+1) + 48 + 80 + ... + (2n+1) x 16 + superspherical harmonics atypicals typicals of U(2|2)
U(1) gauging constraint 2.3 Spectra/Partition Function Count boundary condition changing operators at R = ∞ (free field theory) Built from Zα,Zα,∂xZα, ... fermionic contr. monopole numbers Euler fct bosonic contr. u(2|2) characters for N=2 and μ = ν ~ χ(1+14+1) + χ48 + χ80 + ... q χad + ...
Result: Spectrum at finite R universal indep of Λ,N fμν|μ-ν| ~ λ Characters of u(2|2) reps Branching fcts from R = ∞ λ = λ(Θ1,Θ2) from symplectic Fermions Casimir of U(2|2)
3.1 Quasi-abelian Evolution Free Boson: In boundary theory bulk more involved Prop.: Boundary spectra of CP1|2 chiral field : quadratic Casimir Deformation of conf. weights is `quasi-abelian’ [Bershadsky et al] [Quella,VS,Creutzig] [Candu, Saleur] e.g. (1+14+1) remains at Δ=0; 48, 80, .... are lifted
3.1 Quasi-abelian Evolution Free Boson: In boundary theory bulk more involved at R=R0 universal U(1) charge Prop.: Boundary spectra of CP1|2 chiral field : quadratic Casimir Deformation of conf. weights is `quasi-abelian’ [Bershadsky et al] [Quella,VS,Creutzig] [Candu, Saleur] e.g. (1+14+1) remains at Δ=0; 48, 80, .... are lifted
3.2 Lattice Models and Numerics boundary term f00 acts on states space: level 1 level 2 level 3 Extract fνμ(R) from Δhk= fνμ(R)(Clk-Cl0) l = μ - ν no sign of instanton effects w=w(R)
3.3 SFermions as Cohomology U(2|2): U(1) x U(1|2) in 3 of U(1|2) Result: [Candu,Creutzig,Mitev,VS] Cohomology of Q arises from states in atypical modules with sdim ≠ 0 all multiplets of ground states contribute → λ(Θ1,Θ2) from SF
Conclusions and Open Problems • Exact Boundary Partition Functions for CP1|2 • For S2S+1|S there is WZ-point at radius R = 1 • Is there WZ-point in moduli space of CPN-1|N? • Much generalizes to PCM on PSU(1,1|2)! Techniques: QA evolution; Lattice; Q-Cohomology [Candu,H.Saleur] [Mitev,Quella,VS] osp(2S+2|2s) at level k=1 e.g. psu(N|N) at level k=1 CP0|1 = PSU(1|1)k=1 AdS3 x S3 QA evolution, simple subsector
Examples: Super-Cosets [Candu] [thesis] Familiesv w. compact form, w.o. H-flux: cpct symmetric superspaces volume G/GZ 2 OSP(2S+2|2S) OSP(2S+1|2S) → S2S+1|2S OSP(2S+2|2S) OSP(2S+2-n|2S) x SO(n) c = 1 U(N|N) U(N-1|N)xU(1) → CPN-1|N U(N|N) U(N-n|N) x U(n) c = -2 . . • note: cv (GL(N|N)) = 0 = cv (OSP(2S+2|2S))