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Georgios Linardopoulos

Publications and source records attributed to Georgios Linardopoulos.

At least 19 recordsLinked to original sources
arXiv2026

Heavy holographic correlators in defect conformal field theories

We study holographic defect conformal field theories which are dual to probe branes with bottom-up methods. First we determine the embedding of codimension-1 interface branes in AdS space. Then we compute defect one and two-point functions of heavy scalar operators at strong coupling. We use geodesic approximations to compute reflected two-point functions in two ways, as well as ambient and defect-channel two-point functions. In appropriate limits, our results agree with the operator product expansion (OPE) and the boundary operator expansion (BOE).

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arXiv2025

Holography of a novel codimension-2 defect CFT

We propose and study a new holographic duality between a non-supersymmetric defect conformal field theory (dCFT) and its gravity dual. On the gravity side, the defect is realised by a novel solution of a D5 probe brane embedded in the $AdS_5\times S^5$ geometry. The D5 brane wraps an $S^2\subset S^5$ and accommodates $k$ units of flux through the $S^2$. The symmetry of the induced on the brane metric is $AdS_3\times S^1\times S^2$. The brane ends on an $\mathbb{R}^{(1,1)}$ subspace of the 4-dimensional $AdS_5$ boundary resulting to a codimension-2 defect. We first prove that our brane configuration is stable by showing that the masses of all the fluctuations of the transverse to the brane coordinates respect the B-F bound. On the field theory side, the 2-dimensional defect is described by a classical solution whose precise form we determine. Subsequently, we calculate the one-point functions of the energy-momentum tensor and of the chiral primary operators (CPOs), first at strong and then at weak coupling. In an appropriate limit, we find compelling agreement between the weak and strong coupling results. Furthermore, we also extract one of the B-type Weyl anomaly coefficients.

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arXiv2025

B-type anomaly coefficients for the D3-D7 domain wall

We compute B-type Weyl anomaly coefficients for the two non-supersymmetric codimension-1 domain wall versions of N = 4 super Yang-Mills theory which are holographically dual to the D3-D7 probe-brane system. We compute the two-point function of the (improved) energy-momentum tensor in the presence of the domain wall, to leading order in perturbation theory. From it we determine the two-point function of the corresponding displacement operator and the b2 anomaly coefficient for both domain wall systems.

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arXiv2025

String theory methods for defect CFTs

We discuss string theory methods for the study of strongly coupled holographic defect conformal field theories (CFTs) which are dual to probe-brane systems. First, we examine whether the string theory duals of such defect CFTs are classically integrable. This amounts to identifying all string boundary conditions on probe branes which preserve the integrability of the underlying Green-Schwarz sigma model. Second, we compute holographic defect correlation functions with semiclassical strings. After reviewing the computation of three and higher-point functions in strongly coupled AdS/CFT, and one-point functions in its probe-brane descendants, we outline the computation of two and higher-point correlation functions in strongly coupled defect CFTs.

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arXiv2024

Turbulent aspects of BMN membrane dynamics

We investigate the large-N limit of the BMN matrix model with classical bosonic membranes which have spherical topologies and spin inside the 11-dimensional maximally supersymmetric plane-wave background. First we classify all possible M2-brane configurations based on the distribution of their components inside the SO(3)xSO(6) symmetric plane-wave spacetime. We then formulate a number of simple but very representative ansatzes of dielectric tops that rotate in this space. We examine the leading-order radial and angular/multipole stability for a wide range of these configurations. By analyzing perturbations at the next-to-leading order, we find that they exhibit the phenomenon of turbulent cascading of instabilities. Thereby, long-wavelength perturbations generate higher-order multipole instabilities through their nonlinear couplings.

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arXiv2023

B-type anomaly coefficients for the D3-D5 domain wall

We compute type-B Weyl anomaly coefficients for the domain wall version of N = 4 SYM that is holographically dual to the D3-D5 probe-brane system with flux. Our starting point is the explicit expression for the improved energy momentum tensor of N = 4 SYM. We determine the two-point function of this operator in the presence of the domain wall and extract the anomaly coefficients from the result. In the same process we determine the two-point function of the displacement operator.

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arXiv2023

Holographic correlators of semiclassical states in defect CFTs

We set up the computation of correlation functions for operators that are dual to semiclassical string states in strongly coupled defect conformal field theories (dCFTs). In the dCFT that is dual to the D3-D5 probe-brane system, we calculate the correlation function of two heavy operators perturbatively, in powers of the conformal ratio. We find that the leading term agrees with the prediction of the operator product expansion (OPE). In the case of two heavy BMN operators, we find agreement in subleading orders as well.

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arXiv2023

Finite volume form factors in integrable theories

We develop a new method to calculate finite size corrections for form factors in two-dimensional integrable quantum field theories. We extract these corrections from the excited state expectation value of bilocal operators in the limit when the operators are far apart. We elaborate the finite size effects explicitly up to the 3rd L\"uscher order and conjecture the structure of the general form. We also fully recover the explicitly known massive fermion finite volume form factors.

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arXiv2022

String integrability of the ABJM defect

ABJM theory in the presence of a half-BPS domain wall is dual to the D2-D4 probe brane system with nonzero worldvolume flux. The ABJM domain wall was recently shown to be integrable to lowest order in perturbation theory and bond dimension. In the present paper we show that the string theory dual of this system is integrable, namely that the string boundary conditions on the probe D4-brane preserve the integrability of the Green-Schwarz sigma model. Our result suggests that the ABJM domain wall is integrable to all loop orders and for any value of the bond dimension.

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arXiv2021

Cascade of instabilities in the classical limit of the BMN matrix model

We study the leading (LO) and the next-to-leading order (NLO) stability of multipole perturbations for a static dielectric M2-brane with spherical topology in the 11-dimensional maximally supersymmetric plane-wave background. We observe a cascade of instabilities that originates from the dipole (j=1) and quadrupole (j=2) sectors (the only unstable sectors of the LO) and propagates towards all the multipoles of the NLO.

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arXiv2021

String integrability of defect CFT and dynamical reflection matrices

The D3-D5 probe-brane system is holographically dual to a defect CFT which is known to be integrable. The evidence comes mainly from the study of correlation functions at weak coupling. In the present work we shed light on the emergence of integrability on the string theory side. We do so by constructing the double row transfer matrix which is conserved when the appropriate boundary conditions are imposed. The corresponding reflection matrix turns out to be dynamical and depends both on the spectral parameter and the string embedding coordinates.

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arXiv2020

M-theory as a dynamical system generator

We review our recent work on ellipsoidal M2-brane solutions in the large-N limit of the BMN matrix model. These bosonic finite-energy membranes live inside SO(3)xSO(6) symmetric plane-wave spacetimes and correspond to local extrema of the energy functional. They are static in SO(3) and stationary in SO(6). Chaos appears at the level of radial stability analysis through the explicitly derived spectrum of eigenvalues. The angular perturbation analysis is suggestive of the presence of weak turbulence instabilities that propagate from low to high orders in perturbation theory.

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arXiv2020

Solving holographic defects

Defect conformal field theories (dCFTs) have been attracting increased attention recently, mainly because they enable us to bridge the gap between idealistic, highly symmetric models of our world (such as the particle/string duality) and real-world systems. This talk is about the AdS/defect CFT correspondence, an exciting new proposal that joins the forces of holography, integrability, supersymmetric localization and the conformal bootstrap program in a framework that is appropriate for the study of defects in real-world systems. After introducing dCFTs and some of their holographic realizations, we will present some recent results for the one-point functions of the integrable dCFTs that are the holographic duals of the D3-probe-D5 and the D3-probe-D7 systems of intersecting branes.

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arXiv2019

Spin Chain Overlaps and the Twisted Yangian

Using considerations based on the thermodynamical Bethe ansatz as well representation theory of twisted Yangians we derive an exact expression for the overlaps between the Bethe eigenstates of the $SO(6)$ spin chain and matrix product states built from matrices whose commutators generate an irreducible representation of $\mathfrak{so}(5)$. The latter play the role of boundary states in a domain wall version of ${\cal N}=4$ SYM theory which has non-vanishing, $SO(5)$ symmetric vacuum expectation values on one side of a co-dimension one wall. This theory, which constitutes a defect CFT, is known to be dual to a D3-D7 probe brane system. We likewise show that the same methodology makes it possible to prove an overlap formula, earlier presented without proof, which is of relevance for the similar D3-D5 probe brane system.

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arXiv2018

Scalar one-point functions and matrix product states of AdS/dCFT

We determine in a closed form all scalar one-point functions of the defect CFT dual to the D3-D5 probe brane system with k units of flux which amounts to calculating the overlap between a Bethe eigenstate of the integrable SO(6) spin chain and a certain matrix product state of bond dimension k. In particular, we show that the matrix product state is annihilated by all the parity odd charges of the spin chain which has recently been suggested as the criterion for such a state to correspond to an integrable initial state. Finally, we discuss the properties of the analogous matrix product state for the SO(5) symmetric D3-D7 probe brane set-up.

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arXiv2017

M2-brane Dynamics in the Classical Limit of the BMN Matrix Model

We investigate the large-N limit of the BMN matrix model by analyzing the dynamics of ellipsoidal M2-branes that spin in the 11-dimensional maximally supersymmetric SO(3)xSO(6) plane-wave background. We identify finite-energy solutions by specifying the local minima of the corresponding energy functional. These configurations are static in SO(3) due to the Myers effect and rotate in SO(6) with an angular momentum that is bounded from above. As a first step towards studying their chaotic properties, we evaluate the Lyapunov exponents of their radial fluctuations.

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arXiv2016

One-Point Functions of Non-protected Operators in the SO(5) symmetric D3-D7 dCFT

We study tree level one-point functions of non-protected scalar operators in the defect CFT, based on N=4 SYM, which is dual to the SO(5) symmetric D3-D7 probe brane system with non-vanishing instanton number. Whereas symmetries prevent operators from the SU(2) and SU(3) sub-sectors from having non-vanishing one-point functions, more general scalar conformal operators, which in particular constitute Bethe eigenstates of the integrable SO(6) spin chain, are allowed to have non-trivial one-point functions. For a series of operators with a small number of excitations we find closed expressions in terms of Bethe roots for these one-point functions, valid for any value of the instanton number. In addition, we present some numerical results for operators with more excitations.

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