RST model - Alchetron, The Free Social Encyclopedia

The Russo–Susskind–Thorlacius model or RST model in short is a modification of the CGHS model to take care of conformal anomalies. In the CGHS model, if we include Faddeev-Popov ghosts to gauge-fix diffeomorphisms in the conformal gauge, they contribute an anomaly of -24. Each matter field contributes an anomaly of 1. So, unless N=24, we will have gravitational anomalies. To the CGHS action

S CGHS = 1 2 π ∫ d 2 x − g { e − 2 ϕ [ R + 4 ( ∇ ϕ ) 2 + 4 λ 2 ] − ∑ i = 1 N 1 2 ( ∇ f i ) 2 } , the following term S RST = − κ 8 π ∫ d 2 x − g [ R 1 ∇ 2 R − 2 ϕ R ]

is added, where κ is either ( N − 24 ) / 12 or N / 12 depending upon whether ghosts are considered. The nonlocal term leads to nonlocality. In the conformal gauge,

S RST = − κ π ∫ d x + d x − [ ∂ + ρ ∂ − ρ + ϕ ∂ + ∂ − ρ ] .

It might appear as if the theory is local in the conformal gauge, but this overlooks the fact that the Raychaudhuri equations are still nonlocal.

References

RST model Wikipedia

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