arXiv subjects

Kotaro Shinmyo

Publications and source records attributed to Kotaro Shinmyo.

7 recordsLinked to original sources

arXiv2026

Stokes Phenomena between AdS/CFT and dS/CFT

As parameters are varied, the set of saddle points contributing to a (path) integral may change discontinuously, leading to a corresponding change in the asymptotic expansion of the integral. This behavior is known as the Stokes phenomenon. We explore this phenomenon in the context of the analytic continuation problem relating the AdS/CFT and dS/CFT correspondences. In this paper, we study these correspondences for three-dimensional pure gravity and two-dimensional Liouville theory, using independent calculations in bulk minisuperspace and in the boundary Liouville zero-mode. In the bulk, the dS contour selects a single saddle and yields the tunneling wave function. Upon continuation to AdS, the contour instead selects an infinite family of saddles. The boundary calculation independently reproduces the same Stokes structure at leading semiclassical order, providing a nontrivial holographic consistency check. Our construction also offers a contour prescription for the conformal factor problem in Euclidean AdS$_3$ quantum gravity within minisuperspace.

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arXiv2026

Bulk Reconstruction of Scalar Excitations in Flat$_3$/CCFT$_2$ and the Flat Limit from (A)dS$_3$/CFT$_2$

We explore the reconstruction of bulk local states in three-dimensional flat spacetime (Flat$_3$) using states from two-dimensional Carrollian conformal field theories (CCFT$_2$), proposed as dual field theories in one lower dimension. For massive scalar-type bulk excitations, reconstruction is achieved through states in the induced representation. This method successfully reproduces the bulk massive scalar spectrum and the bulk-to-bulk propagator. Additionally, we identify a new flat limit from AdS$_3$ and dS$_3$ spacetimes, further validating our proposal for scalar reconstruction in Flat$_3$/CCFT$_2$.

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arXiv2026

de Sitter holography from a Lorentzian torus

We show that the quantum entanglement between the conformal field theories (CFTs) living on the future and past boundaries in the de Sitter/conformal field theory (dS/CFT) correspondence can be described by Wick rotating to a geometry with two timelike directions. We propose a new realization of the dS/CFT correspondence in which quantum gravity on this two-time geometry is holographically dual to a CFT defined on a Lorentzian torus. We show that this duality reproduces key features of dS holography, including the dS entropy, correlation functions, and pseudoentropy. Finally, by extending the framework of path-integral optimization, we explain how dS spacetime emerges from the CFT on the Lorentzian torus.

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arXiv2026

More on Bulk Local State Reconstruction in Flat/Carr CFT

We revisit and extend the construction of bulk local states in flat holography, focusing on the induced representation obtained from the flat limit of the AdS highest-weight conditions. In three dimensions we clarify the scaling mismatch between bra and ket states in the flat basis and resolve it by introducing a dual basis, which yields a smooth flat limit and reproduces the correct Green's function. For higher dimensions we construct bulk local states explicitly, both in the momentum basis and in an alternative tilde basis. The flat limit of the AdS$_{d+1}$ construction is shown to be non-uniform in the descendant level and the Riemann-sum treatment over the scaling window $n\sim l$ converts the discrete descendant expansion into the continuum momentum representation, recovering the massive propagator. The tilde basis generalizes seamlessly to any dimension and is related to the three-dimensional flat basis by a sign factor. These results establish the induced representation as the correct algebraic foundation for bulk reconstruction in flat holography and provide a unified framework valid for arbitrary dimension.

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arXiv2025

Entropic Interpretation of Einstein Equation in dS/CFT

In this paper, we demonstrate that the first law of holographic pseudo-entropy, which is a non-Hermitian generalization of entanglement entropy in a two-dimensional conformal field theory (CFT), is equivalent to the perturbative Einstein equation in three-dimensional de Sitter (dS) space, assuming the dS/CFT correspondence. Our analysis reveals that the geodesic that accurately satisfies the first law of holographic pseudo-entropy consists of a timelike curve and a curve whose coordinates are complex. We also demonstrate that infinitesimal changes to the pseudo entropy satisfy a Klein-Gordon equation in two-dimensional de Sitter space. These imply the emergence of a time coordinate from a Euclidean CFT in dS/CFT.

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arXiv2025

Probing de Sitter Space Using CFT States

In this paper we construct CFT states describing a putative holographic dual to local excitations in the three-dimensional de Sitter space (dS), called the bulk local states. We find that the conjugation operation in dS$_3/$CFT$_2$ is notably different from that in AdS$_3/$CFT$_2$. This requires us to combine two bulk local states constructed out of different primary states in a CPT-invariant way. This analysis explains why Green's functions in the dS Euclidean vacuum cannot simply be obtained from the Wick rotation of those in AdS. We also argue that this characteristic feature explains the emergence of a time coordinate from the dual Euclidean CFT. We show that the information metric for the quantum estimation of bulk coordinate values replicates the de Sitter space metric.

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arXiv2023

Pseudo entropy under joining local quenches

We compute the pseudo entropy in two-dimensional holographic and free Dirac fermion CFTs for excited states under joining local quenches. Our analysis reveals two of its characteristic properties that are missing in the conventional entanglement entropy. One is that, under time evolution, the pseudo entropy exhibits a dip behavior as the excitations propagate from the joined point to the boundaries of the subsystem. The other is that the excess of pseudo entropy over entanglement entropy can be positive in holographic CFTs, whereas it is always non-positive in free Dirac fermion CFTs. We argue that the entropy excess can serve as a measure of multi-partite entanglement. Its positivity implies that the vacuum state in holographic CFTs possesses multi-partite entanglement, in contrast to free Dirac fermion CFTs.

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