arXiv subjects

Georgios Itsios

Publications and source records attributed to Georgios Itsios.

At least 19 recordsLinked to original sources

arXiv2026

Holographic observables in TsT deformations of confining theories

We construct new families of type-IIB supergravity solutions by employing TsT transformations on the ten-dimensional geometry that arises after the uplift of the five-dimensional soliton solution of Anabal\'on, Nastase, and Oyarzo. In particular, we identify two marginal and two dipole deformations of the uplifted geometry. We then analyse a plethora of holographic observables -- including Wilson loops, `t~Hooft loops, Page charges, entanglement entropy, and central charge -- and compare their behaviour across the different deformed backgrounds.

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arXiv2025

Supergravity realisations of $\lambda$-models

We construct solutions of type-II supergravity based on multiple copies and/or mixings of $\lambda$-deformed coset CFTs on $\mathrm{SO}(n+1)_k/\mathrm{SO}(n)_k$, with $n = 2, 3, 4$. The resulting ten-dimensional geometries contain undeformed $\mathrm{AdS}$ factors, thereby allowing a connection between $\lambda$-deformations and the AdS/CFT correspondence. Imposing reality conditions on the solutions further constrains the deformation parameter. In some cases these bounds exclude the undeformed ($\lambda = 0$) or non-Abelian T-dual ($\lambda \to 1$) limits. This work extends the results of 1911.12371 and 2411.11086.

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arXiv2025

Supersymmetric AdS Solitons, Coulomb Branch Flows and Twisted Compactifications

This work, which accompanies [1], is about constructing smooth solutions in type II and eleven dimensional supergravity which describe supersymmetry preserving RG flows from four-dimensional SCFTs in the UV to three-dimensional SQFTs in the IR, through holography. We show that all the different UV fixed points flow to theories which confine external quarks and have a mass gap. We proceed by presenting extended calculations of a plethora of observables and analyse the dual field theories in great detail. This includes a boundary analysis and application of holographic renormalization methods in the simplest case of the type IIB solution. Many of the observables computed here have a universal behaviour: they factorize into two parts, one of which includes information about the UV SCFTs, and the other describing the dynamics of the RG flow, which is the same regardless of the UV fixed point.

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arXiv2025

Scale without conformal invariance from integrable deformations of coset CFTs

We construct the $\lambda$-model on $SU(3)_k/U(2)_k$ and we compute the one-loop $\beta$-function for the deformation parameter $\lambda$. Its non-compact version for $SU(2,1)_{-k}/U(2)_{-k}$ is also considered, whose target space admits an asymptotic region that can be reached when one of the coordinates becomes large. The asymptotic model can be seen as an integrable deformation of the $SU(2)_k/U(1)$ WZW model together with a linear dilaton and a free boson, where integrability is inherited from the parental $\lambda$-model. By taking an asymptotic double-scaling limit of the $SU(2,1)_{-k}/U(2)_{-k}$ model, we obtain a two-dimensional field theory that is scale-invariant but not conformally invariant at one-loop order. Crucially, this deformation does not admit a Kerr-Schild form, unlike the cases studied in arXiv:2109.05040. However, in a suitable asymptotic regime, scale invariance is enhanced to full conformal invariance. Finally, we construct Type-II supergravity embeddings of the asymptotic model for specific values of the deformation parameter.

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arXiv2025

Universal Observables, SUSY RG-Flows and Holography

We construct and analyse infinite classes of regular supergravity backgrounds dual to four-dimensional superconformal field theories (SCFTs) compactified on a circle with a supersymmetry-preserving twist. These flows lead to three-dimensional gapped QFTs preserving four supercharges. The solutions arise in Type IIB, Type IIA, and eleven-dimensional supergravity, and generalise known constructions by incorporating deformations that avoid typical singularities associated with the holographic description of the Coulomb branch of the CFT. We examine several observables: Wilson loops, holographic central charges, and complexity. We show they exhibit a universal factorisation, with each observable decomposing into a UV-CFT contribution times a flow-dependent factor. We also explore the parameter regimes where higher-curvature corrections become relevant, affecting the physical interpretation of certain observables. Our findings provide new insights into universal features of holographic RG flows and resolve a puzzle related to complexity in these systems.

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arXiv2024

Type-II backgrounds from deformed coset CFTs

We construct a plethora of type-II supergravity solutions featuring AdS factors in their geometries, derived from integrable deformations of coset CFTs. Specifically, we uplift the $\lambda$-deformed models of $SO(4)_k/SO(3)_k$ and $SO(5)_k/SO(4)_k$, including the non-compact version of the latter. Requiring reality for the backgrounds imposes bounds on the deformation parameter. As a result, some of the solutions do not admit non-Abelian T-dual limit.

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arXiv2024

Integrability of the $\lambda$-deformation of the PCM with spectators

We construct a generalisation of the $\lambda$-deformation of the Principal Chiral Model (PCM) where we deform just a subgroup $F$ of the full symmetry group $G$. We find that demanding Lax integrability imposes a crucial restriction, namely that the coset $F\backslash G$ must be symmetric. Surprisingly, we also find that (when $F$ is non-abelian) integrability requires that the term in the action involving only the spectator fields should have a specific $\lambda$-dependence, which is a curious modification of the procedure expected from the known $F=G$ case. The resulting Lax connection has a novel analytical structure, with four single poles as opposed to the two poles of the cases of the PCM and of the standard $\lambda$-deformation. We also explicitly work out the example of $G=SU(2)$ and $F=U(1)$, discussing its renormalisation group flow to two loops.

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arXiv2023

Supersymmetric solutions of type-II supergravity from $\lambda$-deformations and zoom-in limits

We construct the embedding of the $\lambda$-model on $SL(2, \mathbb{R}) \times SU(2) \times SU(2)$ in type-II supergravity. In the absence of deformation, the ten-dimensional background corresponds to the near-horizon limit of the NS1-NS5-NS5 brane intersection. We show that when the deformation is turned on, supersymmetry breaks by half, and the solution preserves 8 supercharges. The Penrose limits along two null geodesics of the deformed geometry are also considered. It turns out that none of the associated plane-wave backgrounds exhibit supernumerary supercharges.

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arXiv2023

Supersymmetric backgrounds from $\lambda$-deformations

We provide the first supersymmetric embedding of an integrable $\lambda$-deformation to type-II supergravity. Specifically, that of the near horizon of the NS1-NS5 brane intersection, geometrically corresponding to $AdS_3 \times S^3 \times T^4$. We show that the deformed background preserves 1/4 of the maximal supersymmetry. In the Penrose limit we show that it preserves no-more than one half of the maximal supersymmetry.

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arXiv2022

Marginally deformed Schr\"{o}dinger/dipole CFT correspondence

We construct and thoroughly study a new integrable example of the AdS/CFT correspondence with Schr\"{o}dinger symmetry. On the gravity side, the supergravity solution depends on two parameters and is obtained by marginally deforming the internal space of the Schr\"{o}dinger background through a series of TsT transformations. On the field theory side, we identify the dual field theory which also depends on two parameters. We find a point-like string solution and derive its dispersion relation. A non-trivial test of the correspondence is provided by using the Landau-Lifshitz coherent state approach to reproduce the leading, in the deformation parameters, terms of that relation. Then, we calculate the Wilson loop, describing the quark/anti-quark potential at strong coupling. It exhibits confining behaviour when the separation length is much less than the Schr\"{o}dinger parameter. When the separation length is much greater than the Schr\"{o}dinger parameter the behaviour is that of a conformal theory. Subsequently, we take the Penrose limit along a certain null geodesic of the constructed background and calculate the bosonic spectrum. Based on that spectrum, we make an educated guess for the exact, in the 't Hooft coupling, dispersion relation of the magnon excitations in the original doubly deformed background. This provides us with an exact prediction for the dimensions of the dual field theory operators.

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arXiv2021

Kerr-Schild perturbations of coset CFTs as scale invariant integrable $\sigma$-models

Kerr-Schild perturbations in General Relativity provide a fruitful way of constructing new exact solutions starting from known ones, elucidating also the structure of the spacetimes. We initiate such a study in the context of string theory and supergravity. Specifically, we explicitly construct Kerr-Schild perturbations of coset CFTs based on low dimensionality orthogonal groups. We show that these give rise to scale, but not Weyl, invariant integrable $\sigma$-models. We explicitly demonstrate that these models can also be derived from a particular limiting procedure of $\lambda$-deformed coset CFTs based on non-compact groups. The target space of the simplest $\sigma$-model describes a two-dimensional scale invariant black hole for which we also provide two different embeddings to type-II supergravity.

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arXiv2021

Novel integrable interpolations

A novel class of integrable $\sigma$-models interpolating between exact coset conformal field theories in the IR and hyperbolic spaces in the UV is constructed. We demonstrate the relation to the asymptotic limit of $\lambda$-deformed models for cosets of non-compact groups. An integrable model interpolating between two spacetimes with cosmological and black hole interpretations and exact conformal field theory descriptions is also provided. In the process of our work, a new zoom-in limit, distinct from the well known non-Abelian T-duality limit, is found.

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arXiv2021

On the stability of $AdS$ backgrounds with $\lambda$-deformed factors

We investigate the stability of the non-supersymmetric solutions of type-IIB supergravity having an unwarped $AdS$ factor and $\lambda$-deformed subspaces found in arXiv:1911.12371. Among the plethora of solutions we study the perturbative stability of backgrounds with an $AdS_n$, with $n = 3,4,6$, factor. Our analysis is performed from a lower dimensional effective theory which we construct. We uncover the regions and isolated points in the parameter space of potential perturbative stability.

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arXiv2019

AdS solutions and $\lambda$-deformations

We elevate $\lambda$-deformed $\sigma$-models into full type-II supergravity backgrounds. We construct several solutions which contain undeformed $AdS_n$ spaces, with $n=2,3,4$ and $6$, as an integrable part. In that respect, our examples are the first in the literature in this context and bring $\lambda$-deformations in contact with the AdS/CFT correspondence. The geometries are supported by appropriate dilaton and RR-fields. Most of the solutions admit non-Abelian T-dual limits.

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arXiv2019

Spin-2 excitations in Gaiotto-Maldacena solutions

In this paper we study spin-2 excitations for a class of $\mathcal{N} = 2$ supersymmetric solutions of type-IIA supergravity found by Gaiotto and Maldacena. The mass spectrum of these excitations can be derived by solving a second order partial differential equation. As specific examples of this class we consider the Abelian and non-Abelian T-dual versions of the $AdS_5 \times S^5$ and we study the corresponding mass spectra. For the modes that do not "feel" the (non-)Abelian T-duality transformation we provide analytic formulas for the masses, while for the rest we were only able to derive the spectra numerically. The numerical values that correspond to large masses are compared with WKB approximate formulas. We also find a lower bound for the masses. Finally, we study the field theoretical implications of our results and propose dual spin-2 operators.

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arXiv2018

Low-energy modes in anisotropic holographic fluids

In this work we will study the low-energy collective behavior of spatially anisotropic dense fluids in four spacetime dimensions. We will embed a massless flavor D7-brane probe in a generic geometry which has a metric possessing anisotropy in the spatial components. We work out generic formulas of the low-energy excitation spectra and two-point functions for charged excitations at finite baryon chemical potential. In addition, we specialize to a certain Lifshitz geometry and discuss in great detail the scaling behavior of several different quantities.

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arXiv2018

A note on defect Mellin amplitudes

We generalize the Mellin representation for a generic co-dimension flat defect CFT. We study the analytic structure of the Mellin amplitudes. We also compute Witten diagrams for a generic co-dimension flat defect CFT.

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arXiv2017

Penrose limits of Abelian and non-Abelian T-duals of $AdS_5\times S^5$ and their field theory duals

We consider the backgrounds obtained by Abelian and non-Abelian T-duality applied on $AdS_5\times S^5$. We study geodesics, calculate Penrose limits and find the associated plane-wave geometries. We quantise the weakly coupled type-IIA string theory on these backgrounds. We study the BMN sector, finding operators that wrap the original quiver CFT. For the non-Abelian plane wave, we find a 'flow' in the frequencies. We report some progress to understand this, in terms of deconstruction of a higher dimensional field theory. We explore a relation with the plane-wave limit of the Janus solution, which we also provide.

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