Event Category: String Seminar

String Seminar:
Tuesdays at 3:40pm on campus

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Abstract: Black holes have large classical entropy, with the nature of the underlying microstates remaining a longstanding subject of interest. Among other expected properties, these microstates are expected to be chaotic. Recently, it has been conjectured that they are also`fortuitous’: they change erratically as one tunes the parameters of the theory.  In this talk (based on work in progress with … Read More

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Abstract: Embedding a dS universe into an AdS spacetime is easy but identifying its CFT dual is nontrivial. In this talk, I focus on AdS3 gravity coupled to dS2 end-of-the-world branes, and identify its holographic dual to be a unitary holographic CFT2 with non-unitary conformal boundary conditions. These boundary conditions have complex g-functions and appear in conjugate pairs. The associated … Read More

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Abstract: We provide a proposal generalizing the asymptotic Euclidean state preparation to a state preparation by the deformation of a partial Cauchy slice in Lorentzian spacetime. With a proper choice of boundary conditions, we claim that the state forms a Hilbert space $\bf{H}_\sigma$ associated to the boundary $\sigma$ of the partial Cauchy slice.  Assuming that $\bf{H}_\sigma$ factorises over connected components of … Read More

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Abstract: The OSV conjecture relates a black-hole partition function in four-dimensional $\mathcal{N}=2$ supergravity to the absolute square of the topological-string partition function. I will revisit the conjecture using modern gravitational path-integral techniques. Using finite-temperature Bates–Denef geometries and equivariant localization, we show that the higher-derivative supergravity on-shell action is a sum of prepotentials evaluated at the two poles of the Euclidean horizon; … Read More

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Abstract: ‘Recent works have proposed that pure gravity in $AdS_3$ may be understood as an ensemble average over approximate $\mathrm{CFT}_2$ data. We explore the spectral content of this idea by constructing a “Cardy random matrix theory”: an RMT whose only bootstrap input is coarse-grained $\mathbb{S}$-modular invariance. When we prescribe the vacuum to be the only state below the black-hole threshold, … Read More

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Abstract:   We explain the necessary and sufficient conditions for the gravitational path integral (GPI) to admit an interpretation in terms of (i) an inner product in the Hilbert space of open/closed universes or (ii) a statistical average of boundary observables. The conditions needed for (i) are necessary but not sufficient for (ii).  The conditions are  are equivalent to  positivity constraints … Read More

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Abstract Motivated by the surprising and mysterious utility of inserting line defects in the gravitational path integral, we introduce a conformal line defect in Liouville CFT that realizes a “localized cosmological constant.” This is a non-topological extended operator in the Liouville path integral that is tractable at both weak and strong defect coupling. At weak coupling, we analyze the defect … Read More

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Abstract: Statistical functions such as the moment-generating, characteristic, cumulant-generating, and second characteristic functions are standard tools in classical statistics and probability theory. They provide a systematic means to analyze the statistical properties of a system and find applications in diverse fields. While these functions are ubiquitous in classical theory, a quantum counterpart has remained underdeveloped because of the noncommutativity of … Read More

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Abstract: Gravitational sums over spacetime topology suggest a baby-universe field theory whose quanta are entire universes. We further develop such a description starting from group-averaged amplitudes that impose gravitational constraints and define physical inner products in the single-universe theory. To sharpen the contrast with ordinary QFT, we start with gravity on one-dimensional worldlines, which can arise from reducing higher-dimensional cylinders. … Read More

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Hydrodynamics captures the slow dynamics of thermal systems, and in holography these modes are encoded in black-hole geometries. The hydrodynamic fields can be viewed as keeping track of the relative coordinate frame between the asymptotic boundary and the horizon. Rather than integrating out these degrees of freedom, one keeps them explicit and solves only the bulk dynamics of the remaining … Read More