arXiv subjects

Chawakorn Maneerat

Publications and source records attributed to Chawakorn Maneerat.

10 recordsLinked to original sources

arXiv2026

Undulating Conformal Boundaries in 3D Gravity

We consider three-dimensional Einstein gravity in Euclidean signature with a finite boundary of torus topology endowed with an induced metric of fixed conformal class and a constant trace of extrinsic curvature $K$. For vanishing, positive, and negative cosmological constant $Λ$, we analytically determine boundaries enclosing different patches of locally flat, de Sitter (dS$_3$), and Anti-de Sitter (AdS$_3$) spaces. We find solutions that depend non-trivially on either cycle of the torus, noting that some of them exhibit self-intersections. Adapting the Gibbons-Hawking prescription of interpreting the Euclidean gravitational path integral as a thermal partition function, we explore the rich semi-classical thermodynamic phase space of the problem. While most saddles are found to be either thermally unstable or metastable compared to those with uniform boundaries, we find inhomogeneous solutions that are thermodynamically favourable in the case of $Λ< 0$ and $2<K|Λ|^{-1/2}<3/\sqrt{2}$. Moreover, for all values of $Λ$, there exist patches of space with a non-contractible thermal circle and a macroscopic entropy. We comment on a recasting of the problem in terms of classical strings. We further analyse the problem in both the stretched dS$_3$ horizon limit and the AdS$_3$ boundary limit. Using the results for the latter, we find limitations to a proposed holographic dual that consists of a two-dimensional holographic conformal field theory coupled to timelike Liouville, deformed by a marginal $T\bar{T}$-type operator.

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arXiv2026

General Relativity with Finite Boundaries

In this thesis, we consider general relativity on a manifold with a timelike boundary of finite size, across all signs of the cosmological constant $Λ$. We impose conformal boundary conditions, whereby the conformal class of the induced metric and the trace of the extrinsic curvature $K$ are fixed at the boundary. In Lorentzian signature, we analyse the linearised Einstein equations about Minkowski, de Sitter (dS), and anti-de Sitter (AdS) space for a variety of boundaries, employing the Kodama-Ishibashi formalism adapted to manifolds with a boundary. In Euclidean signature, we study the thermodynamics of black hole and cosmological horizons enclosed by the boundary, computing the leading semiclassical approximation of the gravitational path integral, for which the boundary data define a conformal canonical ensemble of fixed conformal temperature and $K$.

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arXiv2026

Conformal boundaries near extremal black holes

We examine four dimensional, near-extremal black hole solutions in the presence of a finite boundary obeying conformal boundary conditions, where the conformal class of the induced metric and the trace of the extrinsic curvature are fixed. Working in Euclidean signature and at fixed charge, we find the near-extremal regime is dominated by a double-scaling limit which reveals new scaling laws for the quasi-local conformal entropy at low temperatures. Upon spherical dimensional reduction, we obtain the effective two-dimensional dilaton-gravity theory that describes the near-extremal regime. In contrast to Dirichlet boundaries, for conformal boundaries a linear dilaton potential is not sufficient to capture the leading correction away from extremality and higher orders are needed. We also examine near-Nariai solutions and the spherical reduction of pure three-dimensional gravity in (Anti-) de Sitter space. In the latter, provided the boundary is placed near the conformal boundary of three-dimensional Anti-de Sitter space, the dynamics of the spherically symmetric boundary mode is governed by a Liouville equation that descends from a (minus) Schwarzian effective action.

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arXiv2026

The Stretched Horizon Limit

We consider four-dimensional general relativity with a positive cosmological constant, $Λ$, in the presence of a boundary, $Γ$, of finite spatial size. The boundary is located near a cosmological event horizon, and is subject to boundary conditions that fix the conformal class of the induced metric, and, $K$, the trace of the extrinsic curvature along $Γ$. The proximity of $Γ$ to the horizon is controlled by the dimensionless parameter ${K}{Λ^{-\frac{1}{2}}}$. We provide an exhaustive analysis of linearised gravitational perturbations for the setup. This is performed both for a $Γ$ encasing a portion of the static patch that ends just before the cosmological horizon (pole patch), as well as a $Γ$ containing only the region near the cosmological horizon (cosmic patch). In the pole patch, we uncover a layered hierarchy of modes: ordinary normal modes, a novel type of boundary gapless mode, and boundary soft modes of frequency $ω\approx \pm 2πi T_{\text{dS}}$, with $T_{\text{dS}}$ the horizon temperature. Minkowskian behaviour is recovered only for angular momenta $l \gtrsim {K}{Λ^{-\frac{1}{2}}}$ which can be made parametrically large, thus attenuating previously found growing modes. In the cosmic patch, we uncover sound and shear fluid-dynamical modes that we interpret in terms of a conformal fluid with shear viscosity over entropy density ratio $\tfracη{s} = \tfrac{1}{4π}$ and vanishing bulk viscosity $ζ=0$. The fluid dynamical sector is shown to admit a non-linear treatment. We describe a scaling regime in which the stretched horizon gravitational dynamics is dictated by a universal Rindler geometry, independent to the details of the infilling horizon. We briefly discuss quantitative features that distinguish cosmological and black hole horizons away from the Rindler regime.

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arXiv2025

Gravitational Observatories

We consider four-dimensional general relativity with vanishing cosmological constant defined on a manifold with a boundary. In Lorentzian signature, the timelike boundary is of the form $\boldsymbolσ \times \mathbb{R}$, with $\boldsymbolσ$ a spatial two-manifold that we take to be either flat or $S^2$. In Euclidean signature, we take the boundary to be $S^2\times S^1$. We consider conformal boundary conditions, whereby the conformal class of the induced metric and trace $K$ of the extrinsic curvature are fixed at the timelike boundary. The problem of linearised gravity is analysed using the Kodama-Ishibashi formalism. It is shown that for a round metric on $S^2$ with constant $K$, there are modes that grow exponentially in time. We discuss a method to control the growing modes by varying $K$. The growing modes are absent for a conformally flat induced metric on the timelike boundary. We provide evidence that the Dirichlet problem for a spherical boundary does not suffer from non-uniqueness issues at the linearised level. We consider the extension of black hole thermodynamics to the case of conformal boundary conditions, and show that the form of the Bekenstein-Hawking entropy is retained.

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arXiv2025

Gravitational Observatories in AdS$_4$

We consider four-dimensional general relativity with a negative cosmological constant in the presence of a finite size boundary, $Γ$, for both Euclidean and Lorentzian signature. As our boundary condition, we consider the `conformal' boundary condition that fixes the conformal class of the induced metric at $Γ$ and the trace of the extrinsic curvature, $K(x^m)$. In Lorentzian signature, we must supplement these with appropriate initial data comprising the standard Cauchy data along a spatial slice and, in addition, initial data for a boundary mode that appears due to the presence of the finite size boundary. We perform a linearised analysis of the gravitational field equations for both an $S^2\times \mathbb{R}$ as well as a Minkowskian, $\mathbb{R}^{1,2}$, boundary. In the $S^2\times \mathbb{R}$ case, in addition to the usual AdS$_4$ normal modes, we uncover a novel linearised perturbation, $\boldsymbolω(x^m)$, which can exhibit complex frequencies at sufficiently large angular momentum. Upon moving $Γ$ toward the infinite asymptotic AdS$_4$ boundary, the complex frequencies appear at increasingly large angular momentum and vanish altogether in the strict limit. In the $\mathbb{R}^{2,1}$ case, although we uncover an analogous novel perturbation, we show it does not exhibit complex frequencies. In Euclidean signature, we show that $K(x^m)$ plays the role of a source for $\boldsymbolω(x^m)$. When close to the AdS$_4$ asymptotic boundary, we speculate on the holographic interpretation of $\boldsymbolω(x^m)$.

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arXiv2025

Cosmological Observatories

We study the static patch of de Sitter space in the presence of a timelike boundary. We impose that the conformal class of the induced metric and the trace of the extrinsic curvature, $K$, are fixed at the boundary. We present the thermodynamic structure of de Sitter space subject to these boundary conditions, for static and spherically symmetric configurations to leading order in the semiclassical approximation. In three spacetime dimensions, and taking $K$ constant on a toroidal Euclidean boundary, we find that the spacetime is thermally stable for all $K$. In four spacetime dimensions, the thermal stability depends on the value of $K$. It is established that for sufficiently large $K$, the de Sitter static patch subject to conformal boundary conditions is thermally stable. This contrasts the Dirichlet problem for which the region encompassing the cosmological horizon has negative specific heat. We present an analysis of the linearised Einstein equations subject to conformal boundary conditions. In the worldline limit of the timelike boundary, the underlying modes are linked to the quasinormal modes of the static patch. In the limit where the timelike boundary approaches the cosmological event horizon, the linearised modes are interpreted in terms of the shear and sound modes of a fluid dynamical system. Additionally, we find modes with a frequency of positive imaginary part. Measured in a local inertial reference frame, and taking the stretched cosmological horizon limit, these modes grow at most polynomially.

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arXiv2021

Janus solutions from dyonic ISO(7) maximal gauged supergravity

We give a large class of new supersymmetric Janus solutions in dyonic $ISO(7)$ maximal gauged supergravity encompassing all known solutions appearing recently. We consider $SO(3)$ invariant sector in which the gauged supergravity admits four supersymmetric $AdS_4$ vacua with $N=1,1,2,3$ unbroken supersymmetries and $G_2$, $SU(3)$, $SU(3)\times U(1)$ and $SO(4)$ symmetries, respectively. We find Janus solutions preserving $N=1,2,3$ supersymmetries and interpolating between $AdS_4$ vacua and the $N=8$ SYM phase. These solutions can be interpreted as conformal interfaces between SYM and various conformal phases of the dual field theory in three dimensions. The solutions can also be embedded in massive type IIA theory by a consistent truncation on $S^6$. We also find a number of singular Janus solutions interpolating between $N=8$ SYM or $AdS_4$ vacua and singularities or between singular geometries. It turns out that, apart from the SYM phase on D2-branes, all the singularities arising in these solutions are unphysical in both four- and ten-dimensional frameworks.

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arXiv2021

Supersymmetric Janus solutions in $ω$-deformed N=8 gauged supergravity

We give a large class of supersymmetric Janus solutions in $ω$-deformed (dyonic) $SO(8)$ maximal gauged supergravity with $ω=\fracπ{8}$. Unlike the purely electric counterpart, the dyonic $SO(8)$ gauged supergravity exhibits a richer structure of $AdS_4$ vacua with $N=8,2,1,1$ supersymmetries and $SO(8)$, $U(3)$, $G_2$ and $SU(3)$ symmetries, respectively. Similarly, domain walls interpolating among these critical points show a very rich structure as well. In this paper, we show that this gauged supergravity also accommodates a number of interesting supersymmetric Janus solutions in the form of $AdS_3$-sliced domain walls asymptotically interpolating between the aforementioned $AdS_4$ geometries. These solutions could be holographically interpreted as two-dimensional conformal defects within the superconformal field theories (SCFTs) of ABJM type dual to the $AdS_4$ vacua. We also give a class of solutions interpolating among the $SO(8)$, $G_2$ and $U(3)$ $AdS_4$ vacua in the case of $ω=0$ which have not previously appeared in the presently known Janus solutions of electric $SO(8)$ gauged supergravity.

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arXiv2020

Supersymmetric solutions from N=5 gauged supergravity

We study a large class of supersymmetric solutions in four-dimensional $N=5$ gauged supergravity with $SO(5)$ gauge group. There is only one $N=5$ supersymmetric $AdS_4$ vacuum preserving the full $SO(5)$ symmetry dual to an $N=5$ SCFT in three dimensions. We give a number of domain walls interpolating between this $AdS_4$ fixed point and singular geometries in the IR with $SO(4)$ and $SO(3)$ symmetries. These solutions describe RG flows from the $N=5$ SCFT to non-conformal field theories driven by mass deformations. The $SO(4)$ solutions are precisely in agreement with the previously known mass deformations within the dual $N=5$ SCFT. We also find supersymmetric Janus solutions describing two-dimensional conformal defects in the $N=5$ SCFT with $N=(4,1)$ and $N=(1,1)$ supersymmetries on the defects. Finally, we study supersymmetric solutions of the form $AdS_2\times Σ^2$, with $Σ^2=S^2,H^2$ being a Riemann surface, corresponding to near horizon geometries of $AdS_4$ black holes. We consider both magnetic and dyonic solutions and find that there exists a class of magnetic $AdS_2\times H^2$ solutions with $SO(2)$ symmetry. It is rather remarkable that a complete analytic solution interpolating between $AdS_4$ and $AdS_2\times H^2$ with a running scalar can be obtained. The solution corresponds to a twisted compactification of $N=5$ SCFT to superconformal quantum mechanics. We also show that no purely magnetic or dyonic black holes with $AdS_2\times Σ^2$ horizon from $SO(2)\times SO(2)$ twist exist in $N=5$, $SO(5)$ gauged supergravity.

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