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Meseret Asrat

Publications and source records attributed to Meseret Asrat.

11 recordsLinked to original sources
arXiv2026

An integrable deformation of the sine(sinh)-Gordon model -- Malcev algebra

In this paper we present an integrable model in two dimensions. It is a deformation of the sine(sinh)-Gordon model. We give its Lax connection. We also obtain its (classical) $r$-matrix. It satisfies the classical Yang-Baxter equation. Thus, the model is a classical integrable field theory in two dimensions. The underlying algebra is a ${\cal Z}$-graded non-Lie Malcev algebra. It is a direct sum of $sl(2, {\rm I\!R})$ Lie algebras with a shared common Cartan. A Malcev algebra is the tangent space at the identity of an analytic Moufang loop as a Lie algebra is the tangent space at the identity of a Lie group. We expect the model to be integrable at the quantum level. We also give a family of classically integrable models which are related to the Poisson-Boltzmann equation in two dimensions.

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arXiv2025

Thermal/Black hole phase transition and entanglement entropy in (2 + 1)D

We consider a one parameter family of holographic solutions in classical string theory in three spacetime dimensions. In Euclidean space, the solutions interpolate smoothly without developing a conical singularity between the cigar black hole times a (non contractible) spatial circle and a thermal solution which has a (non contractible) temporal circle. We study the phase transition and the holographic entanglement entropy.

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arXiv2025

Kalb-Ramond field, black holes and black strings in (2 + 1)D

New rotating dilaton black hole and black string solutions in three spacetime dimensions are obtained. The background spacetime interpolates between Anti-de Sitter and a (an asymptotically) flat spacetime. The new black strings are characterized by their masses, angular momenta and axion charges. The uncharged black string solutions have only a single horizon. They contain a curvature singularity enclosed inside their horizons. Thus, they are also black hole solutions of Einstein-scalar gravity. On the other hand, the charged black string solutions have two horizons. They may or may not contain a curvature singularity depending on the ratio of their inner and outer horizons radii. When they contain a singularity, the singularity is either at or enclosed inside their inner horizons. We also obtain, in addition to the uncharged black strings, other new black hole solutions of Einstein-scalar gravity by applying duality transformation on the new charged black strings. The new black holes are described by their masses and angular momenta. We show that their angular momenta do not depend on their horizons radii. We also find that the masses of a class of the black holes can be made negative by adjusting, using the gauge ambiguity, the asymptotic value of the (independent component of the) Kalb-Ramond field in the dual black strings. We also discuss black hole and black string solutions with a curvature singularity at or beyond their outer or event horizons. Black hole solutions with a ring curvature singularity in between their inner and outer horizons are also presented.

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arXiv2024

Moving holographic boundaries

In this paper, we show that for one sign of the deformation coupling single-trace $T{\bar T}$ deformation moves the holographic screen in Gödel universe radially inward. For the other sign of the coupling it moves the holographic screen radially outward. We (thus) argue, on general grounds, that in holography (single-trace) $T{\bar T}$ deformation can be generally thought of as either moving the holographic boundary into the bulk or washing it away to infinity. In Anti-de Sitter this breaks the spacetime conformal symmetry. We further note that moving timelike holographic boundary into bulk creates a curvature singularity. In the boundary the singularity is understood by states with imaginary energies. To make the theory sensible we introduce an ultraviolet cutoff and thereby move the boundary into the bulk. In this paper we first obtain the Penrose limit of the single-trace $T{\bar T}$ deformed string background and then perform $T$-duality along a space-like isometry to obtain a class of (deformed) Gödel universes. The string background we consider is $AdS_3\times S^3\times {\cal M}_4$. The single-trace $T{\bar T}$ deformation is a particular example of the more general $O(d, d)$ transformations.

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arXiv2024

Rotating strings and anomalous dimensions in Non-AdS holography

In this paper we consider certain rigidly rotating closed string configurations in an asymptotically non-AdS string background. The string background is a deformation of $AdS_3 \times {\cal M}_7$. It interpolates between $AdS_3 $ and asymptotically linear dilaton ${\rm I\!R} \times S^1 \times {\rm I\!R}$ spacetime (times the internal compact manifold ${\cal M}_7$). We compute the quantity $E - J$ (in the large $J$ limit) where $E$ is the energy and $J$ is the angular momentum of the spinning strings. In the two dimensional CFT dual to string theory on $AdS_3$ (times ${\cal M}_7$) it gives the anomalous dimensions of certain twist two and higher operators. We show in the deformed background that $E - J$ is bounded. At a special value of the deformation coupling we also show that for spinning closed strings containing $n > 2$ cusps or spikes both $E$ and $J$ are bounded. In the CFT dual to string theory on $AdS_3$ (times ${\cal M}_7$) the spinning cusped strings describe operators with twist $n$ larger than two. In general, at other values of the deformation coupling, we demonstrate that this feature is exhibited only by those cusped strings with $n > n_0$ where $n_0$ is determined only by the deformation coupling. We also give simple exact Regge relations between $E$ and $J$. We also study the closely related cusp anomalous dimension of a light-like Wilson loop. We comment on what $E - J$ measures away from the CFT along the deformation in the coupling space. In the long string sector the deformation is dual to a single trace $T{\bar T}$ deformed orbifold theory. We determine the associated deformed sinh-Gordon model that classically describes the (long) strings near the boundary. This provides an example of single trace $T{\bar T}$ deformation in non-orbifold theories.

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arXiv2023

Comments on 1+1d QCD with heavy adjoint quarks

In this paper, we determine at weak coupling the non-relativistic $n$-body Schrödinger equation that describes the low-lying color singlet bound states of two dimensional adjoint $QCD$ with heavy quarks. In the case of three adjoint quarks, we show that the three-body equation reduces equivalently to the Schrödinger equation that describes a point electric dipole in an electric field in a plane angular sector. We conjecture that the three-body problem is solvable. The eigenstates are given in terms of the triconfluent Heun functions. Our conjecture implies that a bound state of three adjoint quarks is described by a particle confined in a two dimensional Cornell potential. We expect the $n$-parton problem also to be solvable in a similar fashion.

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arXiv2020

KdV Charges and the Generalized Torus Partition Sum in $T{\bar T}$ deformation

We consider KdV currents in a quantum field theory obtained by deforming a two dimensional conformal field theory on a cylinder via the irrelevant operator $T{\bar T}$. In this paper we determine their one-point functions modular properties. We find that the one-point functions factorize into two components each with a definite modular weight. We also obtain a general differential equation that the generalized torus partition sum satisfies.

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arXiv2020

Entropic c-functions in $T{\bar T}, J{\bar T}, T{\bar J}$ deformations

We study the holographic entanglement entropy of an interval in a quantum field theory obtained by deforming a holographic two-dimensional conformal field theory via a general linear combination of irrelevant operators that are closely related to, but nonetheless distinct from, $T{\bar T}, \ J{\bar T}$ and $T{\bar J}$, and compute the Casin-Huerta entropic $c$-function. We find that the entropic $c$-function is ultraviolet regulator independent, and along the renormalization group upflow towards the ultraviolet, it is non-decreasing. We show that the entropic $c$-function exhibits a power law divergence as the interval length approaches a minimum finite value determined in terms of the deformation parameters. We also find for a particular combination of the deformation parameters a square root correction of the entanglement entropy area law.

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arXiv2020

$T\bar{T}$, the entanglement wedge cross section, and the breakdown of the split property

We consider fine-grained probes of the entanglement structure of two dimensional conformal field theories deformed by the irrelevant double-trace operator $T\bar{T}$ and its closely related but nonetheless distinct single-trace counterpart. For holographic conformal field theories, these deformations can be interpreted as modifications of bulk physics in the ultraviolet region of anti-de Sitter space. Consequently, we can use the Ryu-Takayanagi formula and its generalizations to mixed state entanglement measures to test highly nontrivial consistency conditions. In general, the agreement between bulk and boundary quantities requires the equivalence of partition functions on manifolds of arbitrary genus. For the single-trace deformation, which is dual to an asymptotically linear dilaton geometry, we find that the mutual information and reflected entropy diverge for disjoint intervals when the separation distance approaches a minimum, finite value that depends solely on the deformation parameter. This implies that the mutual information fails to serve as a geometric regulator which is related to the breakdown of the split property at the inverse Hagedorn temperature. In contrast, for the double-trace deformation, which is dual to anti-de Sitter space with a finite radial cutoff, we find all divergences to disappear including the standard quantum field theory ultraviolet divergence that is generically seen as disjoint intervals become adjacent. We furthermore compute reflected entropy in conformal perturbation theory. While we find formally similar behavior between bulk and boundary computations, we find quantitatively distinct results. We comment on the interpretation of these disagreements and the physics that must be altered to restore consistency. We also briefly discuss the $T{\bar J}$ and $J{\bar T}$ deformations.

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arXiv2017

Holography Beyond AdS

We continue our study of string theory in a background that interpolates between $AdS_3$ in the infrared and a linear dilaton spacetime $R^{1,1}\times R_ϕ$ in the UV. This background corresponds via holography to a $CFT_2$ deformed by a certain irrelevant operator of dimension $(2,2)$. We show that for two point functions of local operators in the infrared CFT, conformal perturbation theory in this irrelevant operator has a finite radius of convergence in momentum space, and one can use it to flow up the renormalization group. The spectral density develops an imaginary part above a certain critical value of the spectral parameter; this appears to be related to the non-locality of the theory. In position space, conformal perturbation theory has a vanishing radius of convergence; the leading non-perturbative effect is an imaginary part of the two point function.

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