Person: Song, Wei
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Song
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Song, Wei
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Publication New Boundary Conditions for \(AdS_3\)(Springer Science + Business Media, 2013) Compère, Geoffrey; Song, Wei; Strominger, AndrewNew chiral boundary conditions are found for quantum gravity with matter on \(AdS_3\). The associated asymptotic symmetry group is generated by a single right-moving U(1) Kac-Moody-Virasoro algebra with \(c_R=\frac{3ℓ}{2G}\). The Kac-Moody zero mode generates global left-moving translations and equals, for a BTZ black hole, the sum of the total mass and spin. The level is positive about the global vacuum and negative in the black hole sector, corresponding to ergosphere formation. Realizations arising in Chern-Simons gravity and string theory are analyzed. The new boundary conditions are shown to naturally arise for warped \(AdS_3\) in the limit that the warp parameter is taken to zero.Publication Chiral Liouville Gravity(Springer Science + Business Media, 2013) Compère, Geoffrey; Song, Wei; Strominger, AndrewClassical two-dimensional Liouville gravity is often considered in conformal gauge which has a residual left and right Virasoro symmetry algebra. We consider an alternate, chiral, gauge which has a residual right Virasoro Kac-Moody algebra, and no left Virasoro algebra. The Kac-Moody zero mode is the left-moving energy. Dirac brackets of the constrained Hamiltonian theory are derived, and the residual symmetries are shown to be generated by integrals of the conserved chiral currents. The central charge and Kac-Moody level are computed. The possible existence of a corresponding quantum theory is discussed.Publication Warped \(AdS_3\)/Dipole-CFT Duality(Springer-Verlag, 2012) Song, Wei; Strominger, AndrewString theory contains solutions with \(SL(2, \mathbb{R})_R \times U(1)_L\)-invariant warped \(AdS_3\) \((WAdS_3)\) factors arising as continuous deformations of ordinary \(AdS_3\) factors. We propose that some of these are holographically dual to the IR limits of nonlocal dipole-deformed 2D D-brane gauge theories, referred to as “dipole CFTs”. Neither the bulk nor boundary theories are currently well-understood, and consequences of the proposed duality for both sides is investigated. The bulk entropy-area law suggests that dipole CFTs have (at large N) a high-energy density of states which does not depend on the deformation parameter. Putting the boundary theory on a spatial circle leads to closed timelike curves in the bulk, suggesting a relation of the latter to dipole-type nonlocality.Publication Holographic Derivation of Kerr-Newman Scattering Amplitudes for General Charge and Spin(Springer, 2010) Hartman, Thomas; Song, Wei; Strominger, AndrewNear-superradiant scattering of charged scalars and fermions by a near-extreme Kerr-Newman black hole and photons and gravitons by a near-extreme Kerr black hole are computed as certain Fourier transforms of correlators in a two-dimensional conformal field theory. The results agree with the classic spacetime calculations from the 1970s, thereby providing good evidence for a conjectured Kerr-Newman/CFT correspondence.Publication Chiral Gravity, Log Gravity, and Extremal CFT(American Physical Society, 2010) Maloney, Alexander; Song, Wei; Strominger, AndrewWe show that the linearization of all exact solutions of classical chiral gravity around the AdS3 vacuum have positive energy. Non-chiral and negative-energy solutions of the linearized equations are infrared divergent at second order, and so are removed from the spectrum. In other words, chirality is confined and the equations of motion have linearization instabilities. We prove that the only stationary, axially symmetric solutions of chiral gravity are BTZ black holes, which have positive energy. It is further shown that classical log gravity – the theory with logarithmically relaxed boundary conditions – has finite asymptotic symmetry generators but is not chiral and hence may be dual at the quantum level to a logarithmic CFT. Moreover we show that log gravity contains chiral gravity within it as a decoupled charge superselection sector. We formally evaluate the Euclidean sum over geometries of chiral gravity and show that it gives precisely the holomorphic extremal CFT partition function. The modular invariance and integrality of the expansion coefficients of this partition function are consistent with the existence of an exact quantum theory of chiral gravity. We argue that the problem of quantizing chiral gravity is the holographic dual of the problem of constructing an extremal CFT, while quantizing log gravity is dual to the problem of constructing a logarithmic extremal CFT.Publication Black Hole Superradiance From Kerr/CFT(Springer Verlag, 2010) Bredberg, Irene; Hartman, Thomas; Song, Wei; Strominger, AndrewThe superradiant scattering of a scalar field with frequency and angular momentum (w,m) by a near-extreme Kerr black hole with mass and spin (M, J) was derived in the seventies by Starobinsky, Churilov, Press and Teukolsky. In this paper we show that for frequencies scaled to the superradiant bound the full functional dependence on (w,m,M, J) of the scattering amplitudes is precisely reproduced by a dual twodimensional conformal field theory in which the black hole corresponds to a specific thermal state and the scalar field to a specific operator. This striking agreement corroborates a conjectured Kerr/CFT correspondence.Publication Chiral Gravity in Three Dimensions(Springer, 2008) Li, Wei; Song, Wei; Strominger, AndrewThree dimensional Einstein gravity with negative cosmological constant \(-1/\ell^2\) deformed by a gravitational Chern-Simons action with coefficient \(1/\mu\) is studied in an asymptotically \(AdS_3\) spacetime. It is argued to violate unitary or positivity for generic \(\mu\) due to negative-energy massive gravitons. However at the critical value \(\mu\ell=1\), the massive gravitons disappear and BTZ black holes all have mass and angular momentum related by \(\ell M=J\). The corresponding chiral quantum theory of gravity is conjectured to exist and be dual to a purely right-moving boundary CFT with central charges \((c_L,c_R)=(0,3\ell /G)\).Publication The Kerr/CFT Correspondence(American Physical Society, 2009) Guica, Monica; Hartman, Thomas; Song, Wei; Strominger, AndrewQuantum gravity in the region very near the horizon of an extreme Kerr black hole (whose angular momentum and mass are related by \(J = GM^2\)) is considered. It is shown that consistent boundary conditions exist, for which the asymptotic symmetry generators form one copy of the Virasoro algebra with central charge \(c_L = 12J/\hbar\). This implies that the near-horizon quantum states can be identified with those of (a chiral half of) a two-dimensional conformal field theory (CFT). Moreover, in the extreme limit, the Frolov-Thorne vacuum state reduces to a thermal density matrix with dimensionless temperature \(T_L = 1/2\pi\) and conjugate energy given by the zero mode generator, \(L_0\), of the Virasoro algebra. Assuming unitarity, the Cardy formula then gives a microscopic entropy \(S_{micro} = 2\pi J/\hbar\) for the CFT, which reproduces the macroscopic Bekenstein-Hawking entropy \(S_{macro} = Area/4\hbar G\). The results apply to any consistent unitary quantum theory of gravity with a Kerr solution. We accordingly conjecture that extreme Kerr black holes are holographically dual to a chiral two-dimensional conformal field theory with central charge \(c_L = 12J/\hbar\), and, in particular, that the near-extreme black hole GRS 1915+105 is approximately dual to a CFT with \(c_L\sim 2 \times 10^{79}\).