Andrea Dei
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
Andrea Dei has a total of 12 co-authors. Here are the top co-authors by number of shared publications:
- Lorenz Eberhardt
Institute for Theoretical Physics Amsterdam
8 shared publications - Alessandro Sfondrini
University of Birmingham
6 shared publications - Kiarash Naderi
ETH Zurich
5 shared publications - Matthias R. Gaberdiel
Institut für Theoretische Physik, ETH Zürich
5 shared publications - Bob Knighton
University of Cambridge
3 shared publications - Emil J. Martinec
University of Chicago
3 shared publications
Latest Publications
- Open Access
- 22 October 2026
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2026 (10) , 224
$ T\overline{T} $ correlators from tensionless stringsA bstract: Motivated by earlier approaches, we develop a worldsheet framework for computing correlation functions in the single trace $$ T\overline{T} $$ -deformed tensionless AdS 3 /CFT 2 duality. By describing the deformed bulk theory as a Berkovits-Vafa $$ \mathcal{N} $$ = 4 topological string, we obtain a consistent definition of physical states and correlation functions, yielding a tractable setup for testing aspects of holography beyond AdS/CFT. We construct deformed physical vertex operators and compute their tree-level two-point functions exactly. We discuss the relation of our results to previous proposals for $$ T\overline{T} $$ -deformed two-point functions obtained from alternative worldsheet approaches, JT gravity, and perturbative field theory computations.- 22 October 2026
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2026 (10) , 224
Open Access$ T\overline{T} $ correlators from tensionless stringsA bstract: Motivated by earlier approaches, we develop a worldsheet framework for computing correlation functions in the single trace $$ T\overline{T} $$ -deformed tensionless AdS 3 /CFT 2 duality. By describing the deformed bulk theory as a Berkovits-Vafa $$ \mathcal{N} $$ = 4 topological string, we obtain a consistent definition of physical states and correlation functions, yielding a tractable setup for testing aspects of holography beyond AdS/CFT. We construct deformed physical vertex operators and compute their tree-level two-point functions exactly. We discuss the relation of our results to previous proposals for $$ T\overline{T} $$ -deformed two-point functions obtained from alternative worldsheet approaches, JT gravity, and perturbative field theory computations. - Open Access
- 15 September 2026
- Published by Elsevier in Nuclear Physics B
- Vol. 1031
The on-shell gravity action and linear dilaton holography
- 15 September 2026
- Published by Elsevier in Nuclear Physics B
- Vol. 1031
Open AccessThe on-shell gravity action and linear dilaton holography
- Open Access
- 8 October 2025
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2025 (10) , 1-50
On the string theory of a single NS5-brane
A bstract: We formulate a worldsheet description of string theory in the background of a single decoupled NS5-brane, which is a particularly simple example of “little string” holography. The worldsheet theory involves a gauged Wess-Zumino-Witten model for the group coset $$\mathcal{G}/\mathcal{H}$$ , where $$\mathcal{G}= \text{PSU}(1, 1|2)\times {\mathbb{R}}^{\text{5,1}}$$ and $$\mathcal{H}=\text{U}(1)\times \text{U}(1)$$ . A variant of the embedding of $$\mathcal{H}$$ into $$\mathcal{G}$$ describes a background that interpolates between the fivebrane throat in the UV and AdS 3 in the IR, which is dual to the (single trace) $$T\overline{T }$$ -deformed symmetric product orbifold $${\left({\mathbb{T}}^{4}\right)}^{N}/{S}_{N}$$ . Well-known difficulties with a worldsheet theory for n 5 = 1 fivebranes are bypassed by the incorporation of an extra constraint on the dynamics. This constraint arises naturally from consideration of the effects of deforming the theory by one of the four Ramond-Ramond moduli of the spacetime background, which for n 5 = 1 imposes the constraint that our analysis has identified. Along the way, we construct a map between the supergroup formulation of the n 5 = 1 worldsheet theory and the more conventional RNS worldsheet formalism.- 8 October 2025
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2025 (10) , 1-50
Open AccessOn the string theory of a single NS5-brane
A bstract: We formulate a worldsheet description of string theory in the background of a single decoupled NS5-brane, which is a particularly simple example of “little string” holography. The worldsheet theory involves a gauged Wess-Zumino-Witten model for the group coset $$\mathcal{G}/\mathcal{H}$$ , where $$\mathcal{G}= \text{PSU}(1, 1|2)\times {\mathbb{R}}^{\text{5,1}}$$ and $$\mathcal{H}=\text{U}(1)\times \text{U}(1)$$ . A variant of the embedding of $$\mathcal{H}$$ into $$\mathcal{G}$$ describes a background that interpolates between the fivebrane throat in the UV and AdS 3 in the IR, which is dual to the (single trace) $$T\overline{T }$$ -deformed symmetric product orbifold $${\left({\mathbb{T}}^{4}\right)}^{N}/{S}_{N}$$ . Well-known difficulties with a worldsheet theory for n 5 = 1 fivebranes are bypassed by the incorporation of an extra constraint on the dynamics. This constraint arises naturally from consideration of the effects of deforming the theory by one of the four Ramond-Ramond moduli of the spacetime background, which for n 5 = 1 imposes the constraint that our analysis has identified. Along the way, we construct a map between the supergroup formulation of the n 5 = 1 worldsheet theory and the more conventional RNS worldsheet formalism. - Open Access
- 22 January 2025
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2025 (1) , 1-96
On supergravity and noncritical strings
A bstract: Motivated by the long-term goal of finding holographic descriptions for $$ \mathcal{N} $$ = 1 and $$ \mathcal{N} $$ = 2 super QCD, we revisit the subject of “noncritical” superstring theory. Focusing on string models with 6d super Poincaré invariance, we provide a careful worldsheet derivation of the leading-order effective theories for the lowest modes. We identify them as seven -dimensional, maximally supersymmetric gauged supergravities: the SO(4) theory for noncritical IIA and the ISO(4) theory for noncritical IIB. The same theories also arise as consistent truncations on S 3 of the 10d IIB and IIA supergravities, respectively, where the chirality flip is as expected from T-duality. These effective supergravities should be interpreted in the following sense. The noncritical string can be viewed as a special case of a discrete series of backgrounds labelled by an integer k (which counts the number of NS5 branes in a certain duality frame); the “noncritical” value is k = 2, while for k → ∞ one recovers a weakly-curved 10d target space. The effective supergravities described here give an accurate description of the interactions among the lowest modes for k → ∞, with higher derivative corrections suppressed by powers of 1/ k . We discuss BPS solutions of the 7d gauged supergravities and their uplift to 10d solutions. In particular, we find a novel class of solutions with RR flux, parametrized by a function of three variables that solves an elegant PDE. While we cannot solve the PDE in closed form except in trivial cases, we confirm that our solutions correspond to a 10d IIA Hanany-Witten setup with continuous distributions of both “color” D4 branes and “flavor” D6 branes.- 22 January 2025
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2025 (1) , 1-96
Open AccessOn supergravity and noncritical strings
A bstract: Motivated by the long-term goal of finding holographic descriptions for $$ \mathcal{N} $$ = 1 and $$ \mathcal{N} $$ = 2 super QCD, we revisit the subject of “noncritical” superstring theory. Focusing on string models with 6d super Poincaré invariance, we provide a careful worldsheet derivation of the leading-order effective theories for the lowest modes. We identify them as seven -dimensional, maximally supersymmetric gauged supergravities: the SO(4) theory for noncritical IIA and the ISO(4) theory for noncritical IIB. The same theories also arise as consistent truncations on S 3 of the 10d IIB and IIA supergravities, respectively, where the chirality flip is as expected from T-duality. These effective supergravities should be interpreted in the following sense. The noncritical string can be viewed as a special case of a discrete series of backgrounds labelled by an integer k (which counts the number of NS5 branes in a certain duality frame); the “noncritical” value is k = 2, while for k → ∞ one recovers a weakly-curved 10d target space. The effective supergravities described here give an accurate description of the interactions among the lowest modes for k → ∞, with higher derivative corrections suppressed by powers of 1/ k . We discuss BPS solutions of the 7d gauged supergravities and their uplift to 10d solutions. In particular, we find a novel class of solutions with RR flux, parametrized by a function of three variables that solves an elegant PDE. While we cannot solve the PDE in closed form except in trivial cases, we confirm that our solutions correspond to a 10d IIA Hanany-Witten setup with continuous distributions of both “color” D4 branes and “flavor” D6 branes. - Open Access
- 26 November 2024
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2024 (11) , 1-44
Tensionless AdS3/CFT2 and single trace $ T\overline{T} $One of the few cases of AdS/CFT where both sides of the duality are under good control relates tensionless k = 1 strings on AdS3 to a two-dimensional symmetric product CFT. Building on prior observations, we propose an exact duality between string theory on a spacetime which is not asymptotically AdS and a non-conformal field theory. The bulk theory is constructed as a marginal deformation of the k = 1 AdS3 string while the spacetime dual is a single trace $$ T\overline{T} $$ -deformed symmetric orbifold theory. As evidence for the duality, we match the one-loop bulk and boundary torus partition functions. This correspondence provides a framework to both learn about quantum gravity beyond AdS and understand how to define physical observables in $$ T\overline{T} $$ -deformed field theories.- 26 November 2024
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2024 (11) , 1-44
Open AccessTensionless AdS3/CFT2 and single trace $ T\overline{T} $One of the few cases of AdS/CFT where both sides of the duality are under good control relates tensionless k = 1 strings on AdS3 to a two-dimensional symmetric product CFT. Building on prior observations, we propose an exact duality between string theory on a spacetime which is not asymptotically AdS and a non-conformal field theory. The bulk theory is constructed as a marginal deformation of the k = 1 AdS3 string while the spacetime dual is a single trace $$ T\overline{T} $$ -deformed symmetric orbifold theory. As evidence for the duality, we match the one-loop bulk and boundary torus partition functions. This correspondence provides a framework to both learn about quantum gravity beyond AdS and understand how to define physical observables in $$ T\overline{T} $$ -deformed field theories. - Open Access
- 19 September 2024
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2024 (9) , 1-63
Solving AdS3 string theory at minimal tension: tree-level correlators
We revisit the minimal tension (k = 1) string theory on AdS3 × S3 × 𝕋4. We propose a new free-field description of the worldsheet theory and show how localization of string amplitudes emerges from the path integral. We exemplify our proposal by reproducing the worldsheet partition function of the $$ \mathfrak{psu} $$ (1, 1|2)1 WZW model and providing explicit expressions for spectrally-flowed vertex operators and DDF operators. We compute string correlators in the path integral formalism and obtain a precise tree-level match with correlation functions of the boundary symmetric orbifold.- 19 September 2024
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2024 (9) , 1-63
Open AccessSolving AdS3 string theory at minimal tension: tree-level correlators
We revisit the minimal tension (k = 1) string theory on AdS3 × S3 × 𝕋4. We propose a new free-field description of the worldsheet theory and show how localization of string amplitudes emerges from the path integral. We exemplify our proposal by reproducing the worldsheet partition function of the $$ \mathfrak{psu} $$ (1, 1|2)1 WZW model and providing explicit expressions for spectrally-flowed vertex operators and DDF operators. We compute string correlators in the path integral formalism and obtain a precise tree-level match with correlation functions of the boundary symmetric orbifold. - Open Access
- 21 June 2024
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2024 (6) , 1-76
NS5-brane backgrounds and coset CFT partition functions
Worldsheet string theory is solvable for a variety of backgrounds involving Neveu-Schwarz fivebranes, in terms of gauged nonlinear sigma models on group manifolds. We compute the worldsheet torus partition function of these models, and propose gauging of null isometries as a unifying principle and conceptual framework for this large family of string backgrounds. In the process, we explain how partition functions of asymmetrically gauged Wess-Zumino-Witten models can be computed from the path integral, and organize and systematize various results scattered throughout the literature.
- 21 June 2024
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2024 (6) , 1-76
Open AccessNS5-brane backgrounds and coset CFT partition functions
Worldsheet string theory is solvable for a variety of backgrounds involving Neveu-Schwarz fivebranes, in terms of gauged nonlinear sigma models on group manifolds. We compute the worldsheet torus partition function of these models, and propose gauging of null isometries as a unifying principle and conceptual framework for this large family of string backgrounds. In the process, we explain how partition functions of asymmetrically gauged Wess-Zumino-Witten models can be computed from the path integral, and organize and systematize various results scattered throughout the literature.
- Open Access
NS5-brane backgrounds and coset CFT partition functions
Worldsheet string theory is solvable for a variety of backgrounds involving Neveu-Schwarz fivebranes, in terms of gauged nonlinear sigma models on group manifolds. We compute the worldsheet torus partition function of these models, and propose gauging of null isometries as a unifying principle and conceptual framework for this large family of string backgrounds. In the process, we explain how partition functions of asymmetrically gauged Wess-Zumino-Witten models can be computed from the path integral, and organize and systematize various results scattered throughout the literature.
Open AccessNS5-brane backgrounds and coset CFT partition functions
Worldsheet string theory is solvable for a variety of backgrounds involving Neveu-Schwarz fivebranes, in terms of gauged nonlinear sigma models on group manifolds. We compute the worldsheet torus partition function of these models, and propose gauging of null isometries as a unifying principle and conceptual framework for this large family of string backgrounds. In the process, we explain how partition functions of asymmetrically gauged Wess-Zumino-Witten models can be computed from the path integral, and organize and systematize various results scattered throughout the literature.
- Open Access
Solving AdS$_3$ string theory at minimal tension: tree-level correlators
We revisit the minimal tension ($k=1$) string theory on $\text{AdS}_3\times\text{S}^3\times\mathbb{T}^4$. We propose a new free-field description of the worldsheet theory and show how localization of string amplitudes emerges from the path integral. We exemplify our proposal by reproducing the worldsheet partition function of the $\mathfrak{psu}(1,1|2)_1$ WZW model and providing explicit expressions for spectrally-flowed vertex operators and DDF operators. We compute string correlators in the path integral formalism and obtain a precise tree-level match with correlation functions of the boundary symmetric orbifold.Open AccessSolving AdS$_3$ string theory at minimal tension: tree-level correlators
We revisit the minimal tension ($k=1$) string theory on $\text{AdS}_3\times\text{S}^3\times\mathbb{T}^4$. We propose a new free-field description of the worldsheet theory and show how localization of string amplitudes emerges from the path integral. We exemplify our proposal by reproducing the worldsheet partition function of the $\mathfrak{psu}(1,1|2)_1$ WZW model and providing explicit expressions for spectrally-flowed vertex operators and DDF operators. We compute string correlators in the path integral formalism and obtain a precise tree-level match with correlation functions of the boundary symmetric orbifold. - Open Access
- 6 September 2022
- Published by Stichting SciPost in SciPost Physics
- Vol. 13 (3) , 053
String correlators on $\text{AdS}_3$: Analytic structure and dual CFT
We continue our study of string correlators on Euclidean \text{AdS}_3 AdS 3 with pure NS-NS flux. The worldsheet and spacetime correlators have a rich analytic structure, which we analyse completely for genus 0 four-point functions. We show that correlators exhibit a simple behaviour near their singularities. The spacetime correlators are meromorphic functions in the \mathrm{SL}(2,\mathbb{R}) S L ( 2 , ℝ ) -spins, whose pole structure is shown to agree with the prediction of a recent proposal for the dual \text{CFT}_2 CFT 2 . Moreover, we also compute the residues of the spacetime correlators for some of the poles exactly and find again a perfect match with the proposal for the dual \text{CFT}_2 CFT 2 , thereby checking the duality for some non-trivial four-point functions exactly. Our computations simplify drastically in the tensionless limit of \mathrm{AdS}_3 \times \mathrm{S}^3 \times \mathbb{T}^4 A d S 3 × S 3 × ???? 4 where the behaviour near the poles gives in fact the exact answer. This paper is the third in a series with several installments.
- 6 September 2022
- Published by Stichting SciPost in SciPost Physics
- Vol. 13 (3) , 053
Open AccessString correlators on $\text{AdS}_3$: Analytic structure and dual CFT
We continue our study of string correlators on Euclidean \text{AdS}_3 AdS 3 with pure NS-NS flux. The worldsheet and spacetime correlators have a rich analytic structure, which we analyse completely for genus 0 four-point functions. We show that correlators exhibit a simple behaviour near their singularities. The spacetime correlators are meromorphic functions in the \mathrm{SL}(2,\mathbb{R}) S L ( 2 , ℝ ) -spins, whose pole structure is shown to agree with the prediction of a recent proposal for the dual \text{CFT}_2 CFT 2 . Moreover, we also compute the residues of the spacetime correlators for some of the poles exactly and find again a perfect match with the proposal for the dual \text{CFT}_2 CFT 2 , thereby checking the duality for some non-trivial four-point functions exactly. Our computations simplify drastically in the tensionless limit of \mathrm{AdS}_3 \times \mathrm{S}^3 \times \mathbb{T}^4 A d S 3 × S 3 × ???? 4 where the behaviour near the poles gives in fact the exact answer. This paper is the third in a series with several installments.