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Ana-Maria Raclariu

Publications and source records attributed to Ana-Maria Raclariu.

At least 19 recordsLinked to original sources
arXiv2026

Higher-spin charges and the $L_Λ w_{1 + \infty}$ algebra in (A)dS$_4$

We consider $(3+1)$-dimensional asymptotically locally (anti-)de Sitter ((A)dS$_4$) spacetimes with boundary conditions allowing for gravitational flux. We construct an infinite tower of higher-spin charges as perturbative solutions in the cosmological constant $Λ$ to a hierarchy of evolution equations resulting from an asymptotic expansion of the Einstein equations. We show that these charges canonically realize the $Λ$-deformed $w_{1+\infty}$ algebra ($L_Λ w_{1+\infty}$) on a restricted gravitational phase space, thereby extending the higher-spin symmetry structure of asymptotically flat spacetimes to asymptotically (A)dS spacetimes. We further construct the curved-space counterparts of conformally soft gravitons directly in terms of spacetime data. We show that they are primaries with respect to an $\mathfrak{sl}(2,\mathbb{R})$ subalgebra of the (A)dS$_4$ isometry algebra and that their Poisson brackets with the quadratic higher-spin charges reproduce the $Λ$-deformed celestial operator product expansion proposed by Taylor and Zhu. Our results establish the bulk gravitational origin of the $L_Λw_{1+\infty}$ symmetry and extend the celestial bulk-boundary dictionary to asymptotically (A)dS$_4$ gravity.

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arXiv2026

On bulk reconstruction in Lorentzian AdS and its flat space limit

We revisit the reconstruction of a free quantum field in 4-dimensional Lorentzian Anti-de-Sitter (AdS$_4$) spacetime in terms of primary operators in the boundary 3d CFT (CFT$_3$). We show that the positive and negative energy subspaces of solutions to the Klein-Gordon equation in AdS can be spanned with bulk-to-boundary propagators with appropriate time orderings. As a result, free scalar fields on a codimension-1 bulk hypersurface $Σ_τ$ can be expressed in terms of operators integrated over boundary regions in the past or future of $Σ_τ$ with kernels given by time-ordered or anti-time-ordered propagators. We present various equivalent representations for the bulk field in terms of either CFT primaries or their shadows. We show from both a representation theoretic perspective and by direct computation of various flat space limits that our construction is the AdS analog of the canonical quantization of a free scalar in flat space. Depending on the choice of $Δ$ and the location of the boundary insertions one obtains a decomposition of the scalar in either a plane wave basis ($Δ\rightarrow \infty$) or a Carrollian basis (fixed $Δ$). Finally, we show that the free scalar in AdS$_4$ can be alternatively decomposed in terms of wavefunctions associated with principal series representations of dimension $δ= 1 + iλ$ of an $\mathfrak{so}(3,1)$ subalgebra of the AdS$_4$ isometry algebra. We demonstrate that the latter become, in the limit of large AdS radius and for fixed $δ$, scalar conformal primary wavefunctions in flat space.

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arXiv2025

Null quantization, shadows and boost eigenfunctions in Lorentzian AdS

We revisit the quantization of a free scalar in 4-dimensional (4d) Lorentzian Anti-de-Sitter spacetime (AdS$_4$). We derive solutions to the wave equation that diagonalize time translations in a foliation of AdS$_4$ with null cones. We show that time-translation eigenmodes of arbitrary mass fields that admit a flat space limit must contain both normalizable and non-normalizable fall-offs as one approaches the boundary along a null leaf. We then show that AdS bulk-to-boundary propagators with suitable time orderings provide alternative bases of solutions to the wave equation. We propose an AdS bulk reconstruction formula relating an on-shell free scalar at a spacetime point to CFT primary operators and their shadow transforms. In the flat space limit, this formula reduces to the Carrollian expansion of a free field in flat space. We finally construct Lorentz boost eigenfunctions in AdS in both hyperbolic and null foliations and show that they respectively become massive and massless conformal primary wavefunctions in the flat space limit.

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arXiv2025

Infinite towers of 2d symmetry algebras from Carrollian limit of 3d CFT

We consider the Carrollian limit of OPE blocks of scalar primaries, spin-1 currents and the stress tensor in 3-dimensional conformal field theory (CFT$_3$). We demonstrate that these OPE blocks decompose into OPE blocks of towers of $\mathfrak{sl}(2,\mathbb{C})$ modes labeled by negative integer dimensions. We present two applications of this construction. We first show that the current-scalar-scalar and stress tensor-scalar-scalar OPE blocks in CFT$_3$ reduce to $\mathfrak{sl}(2,\mathbb{C})$ OPE blocks from which towers of conformally soft photon and graviton theorems can be derived. We then show that the CFT$_3$ OPE blocks of, respectively, current and stress tensor components dual to positive helicity gluons and gravitons in AdS$_4$ become $\mathfrak{sl}(2,\mathbb{C})$ blocks of conformally soft gluons and gravitons which imply the $S$ and $w_{1 + \infty}$ algebras of celestial CFT.

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arXiv2025

An Infrared On-Shell Action and its Implications for Soft Charge Fluctuations in Asymptotically Flat Spacetimes

We study the infrared on-shell action of Einstein gravity in asymptotically flat spacetimes, obtaining an effective, gauge-invariant boundary action for memory and shockwave spacetimes. We show that the phase space is in both cases parameterized by the leading soft variables in asymptotically flat spacetimes, thereby extending the equivalence between shockwave and soft commutators to spacetimes with non-vanishing Bondi mass. We then demonstrate that our on-shell action is equal to three quantities studied separately in the literature: $(i)$ the soft supertranslation charge; $(ii)$ the shockwave effective action, or equivalently the modular Hamiltonian; and $(iii)$ the soft effective action. Finally, we compute the quantum fluctuations in the soft supertranslation charge and, assuming the supertranslation parameter may be promoted to an operator, we obtain an area law, consistent with earlier results showing that the modular Hamiltonian has such fluctuations.

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arXiv2025

Entanglement, Soft Modes, and Celestial Holography

We evaluate the vacuum entanglement entropy across a cut of future null infinity for free Maxwell theory in four-dimensional Minkowski spacetime. The Weyl invariance of 4D Maxwell theory allows us to embed the Minkowski spacetime inside the Einstein static universe. The Minkowski vacuum can then be described as a thermofield double state on the (future) Milne wedges of the original and inverted Minkowski patches. We show that the soft mode contribution to entanglement entropy is due to correlations between asymptotic charges of these Milne wedges or, equivalently, nontrivial conformally soft (or edge) mode configurations at the entangling surface.

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arXiv2024

Celestial amplitudes from conformal correlators with bulk-point kinematics

We show that two- and three-point celestial (C)CFT$_{d-1}$ amplitudes can be directly obtained from correlation functions in a unitary Lorentzian CFT$_d$ on $\mathbb{R}\times S^{d-1}$. The recipe involves a rescaling of the operators, followed by an expansion around a bulk point configuration and a transformation to an $S^{d-1}$ conformal primary basis. The first two steps project the CFT$_d$ correlators onto distributions on $S^{d-1}$. The final step implements a dimensional reduction yielding CCFT$_{d-1}$ amplitudes that are manifestly vanishing for all in/out configurations and Poincaré invariant. The dimensional reduction may be implemented either by evaluating certain time integral transforms around the bulk-point limit, or by analytically continuing the CFT$_d$ operator dimensions and restricting the operators to $S^{d-1}$ time slices separated by $π$ in global time. The latter prescription generates the correct normalization for both two- and three-point functions. On the other hand, the celestial three-point amplitudes obtained via the former prescription are found to only agree after evaluating a residue at an integer linear combination of the CFT$_d$ conformal dimensions. The correct normalization may also be obtained by considering a different integration path in the uplift of the complexified time plane to its universal cover.

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arXiv2024

Entanglement, Soft Modes, and Celestial CFT

We revisit the calculation of vacuum entanglement entropy in free Maxwell theory in four-dimensional Minkowski spacetime. Weyl invariance allows for this theory to be embedded as a patch inside the Einstein static universe. We use conformal inversions to extend the conformal primary solutions of the equations of motion labelled by a boost-weight $Δ= 1 + iλ$ to an inverted Minkowski patch centered at spacelike infinity of the original patch. For $λ\neq 0$ these solutions admit an expansion in terms of wavefunctions supported in the (future) Milne wedges of the original and inverted Minkowski patches, that diagonalize the respective Milne times. The Minkowski vacuum can then be described as a thermofield double state on these two Milne wedges. We characterize the soft sectors of $λ= 0$ modes supported in the two Milne wedges. Upon reinterpreting the non-pure gauge $λ= 0$ wavefunctions as sourced by image charges in the inverse Minkowski patch, we construct an appropriate entangling constraint in the Minkowski theory, thereby characterizing the physical state space. We show that the edge mode contribution to the vacuum entanglement entropy is due to correlations between the soft charges of the two Milne patches, or equivalently non-trivial conformally soft mode configurations at the entangling surface.

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arXiv2024

A discrete basis for celestial holography

Celestial holography provides a reformulation of scattering amplitudes in four dimensional asymptotically flat spacetimes in terms of conformal correlators of operators on the two dimensional celestial sphere in a basis of boost eigenstates. A basis of {massless particle} states has previously been identified in terms of conformal primary wavefunctions labeled by a boost weight $Δ= 1 + iλ$ with $λ\in \mathbb{R}$. Here we show that a {\it discrete} orthogonal and complete basis exists for $Δ\in \mathbb{Z}$. This new basis consists of a tower of discrete memory and Goldstone observables, which are conjugate to each other and allow to reconstruct gravitational signals belonging to the Schwartz space. We show how generalized dressed states involving the whole tower of Goldstone operators can be constructed and evaluate the higher spin Goldstone 2-point functions. Finally, we recast the tower of higher spin charges providing a representation of the $w_{1+\infty}$ loop algebra (in the same helicity sector) in terms of the new discrete basis.

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arXiv2023

From Shockwaves to the Gravitational Memory Effect

We study the relationship between shockwave geometries and the gravitational memory effect in four-dimensional asymptotically flat spacetime. In particular, we show the 't Hooft commutation relations of shockwave operators are equivalent to the commutation relation between soft and Goldstone modes parametrizing a sector of the gravitational phase space. We demonstrate this equivalence via a diffeomorphism that takes a shockwave metric to a metric whose transverse traceless component is the gravitational memory. The shockwave momentum in 't Hooft's analysis is related to the soft graviton mode, which is responsible for the memory effect, while the shift in the shockwave position is related to the Goldstone mode. This equivalence opens new directions to utilize the gravitational memory effect to explore the observational implications of shockwave geometries in flat space.

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arXiv2023

On infinite symmetry algebras in Yang-Mills theory

Similar to gravity, an infinite tower of symmetries generated by higher-spin charges has been identified in Yang-Mills theory by studying collinear limits or celestial operator products of gluons. This work aims to recover this loop symmetry in terms of charge aspects constructed on the gluonic Fock space. We propose an explicit construction for these higher spin charge aspects as operators which are polynomial in the gluonic annihilation and creation operators. The core of the paper consists of a proof that the charges we propose form a closed loop algebra to quadratic order. This closure involves using the commutator of the cubic order expansion of the charges with the linear (soft) charge. Quite remarkably, this shows that this infinite-dimensional symmetry constrains the non-linear structure of Yang-Mills theory. We provide a similar all spin proof in gravity for the so-called global quadratic (hard) charges which form the loop wedge subalgebra of $w_{1+\infty}$.

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arXiv2023

Celestial Sector in CFT: Conformally Soft Symmetries

We show that time intervals of width $Δτ$ in 3-dimensional conformal field theories (CFT$_3$) on the Lorentzian cylinder admit an infinite dimensional symmetry enhancement in the limit $Δτ\rightarrow 0$. The associated vector fields are approximate solutions to the conformal Killing equations in the strip labelled by a function and a conformal Killing vector on the sphere. An Inonu-Wigner contraction yields a set of symmetry generators obeying the extended BMS$_4$ algebra. We analyze the shadow stress tensor Ward identities in CFT$_d$ on the Lorentzian cylinder with all operator insertions in infinitesimal time intervals separated by $π$. We demonstrate that both the leading and subleading conformally soft graviton theorems in $(d-1)$-dimensional celestial CFT (CCFT$_{d-1}$) can be recovered from the transverse traceless components of these Ward identities in the limit $Δτ\rightarrow 0$. A similar construction allows for the leading conformally soft gluon theorem in CCFT$_{d-1}$ to be recovered from shadow current Ward identities in CFT$_d$.

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arXiv2023

The SAGEX Review on Scattering Amplitudes

This is an introduction to, and invitation to read, a series of review articles on scattering amplitudes in gauge theory, gravity, and superstring theory. Our aim is to provide an overview of the field, from basic aspects to a selection of current (2022) research and developments.

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arXiv2022

Eikonal Approximation in Celestial CFT

We identify an eikonal regime in celestial CFT$_2$ in which massless 2-2 scattering is dominated by t-channel exchange. We derive a formula for the celestial amplitude that resums exchanges of arbitrary integer spin to all orders in the coupling. The resulting eikonal phase takes the same form as in flat space with the powers of center-of-mass energy replaced by weight-shifting operators on the celestial sphere. We independently compute the celestial two-point function for a scalar propagating in a shockwave background and show that to leading order in the gravitational coupling and for a suitable choice of the source, the result agrees with the prediction from the celestial eikonal formula for graviton exchange. We demonstrate that this two-point function can be directly obtained from the corresponding formula in AdS$_4$ in a flat space limit. We finally establish a general relation between scalar celestial amplitudes in celestial CFT$_{d-1}$ and the flat space limit of scalar AdS$_{d+1}$ Witten diagrams.

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arXiv2022

Higher spin dynamics in gravity and $w_{1 + \infty}$ celestial symmetries

In this paper we extract from a large-$r$ expansion of the vacuum Einstein's equations a dynamical system governing the time evolution of an infinity of higher-spin charges. Upon integration, we evaluate the canonical action of these charges on the gravity phase space. The truncation of this action to quadratic order and the associated charge conservation laws yield an infinite tower of soft theorems. We show that the canonical action of the higher spin charges on gravitons in a conformal primary basis, as well as conformally soft gravitons reproduces the higher spin celestial symmetries derived from the operator product expansion. Finally, we give direct evidence that these charges form a canonical representation of a $w_{1+\infty}$ loop algebra on the gravitational phase space.

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arXiv2022

The SAGEX Review on Scattering Amplitudes, Chapter 11: Soft Theorems and Celestial Amplitudes

The soft limits of scattering amplitudes have been extensively studied due to their essential role in the computation of physical observables in collider physics. The universal factorisation that occurs in these kinematic limits has been shown to be related to conservation laws associated with asymptotic, or large, gauge symmetries. This connection has led to a deeper understanding of the symmetries of gauge and gravitational theories and to a reformulation of scattering amplitudes in a basis of boost eigenstates which makes manifest the two-dimensional global conformal symmetry of the celestial sphere. The recast, or celestial, amplitudes possess many of the properties of conformal field theory correlation functions which has suggested a path towards a holographic description of asymptotically flat spacetimes. In this review we consider these interconnected developments in our understanding of soft theorems, asymptotic symmetries and conformal field theory with a focus on the structure and symmetries of the celestial amplitudes and their holographic interpretation.

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arXiv2022

Sub-subleading Soft Graviton Theorem from Asymptotic Einstein's Equations

We identify in Einstein gravity an asymptotic spin-$2$ charge aspect whose conservation equation gives rise, after quantization, to the sub-subleading soft theorem. Our treatment reveals that this spin-$2$ charge generates a non-local spacetime symmetry represented at null infinity by pseudo-vector fields. Moreover, we demonstrate that the non-linear nature of Einstein's equations is reflected in the Ward identity through collinear corrections to the sub-subleading soft theorem. Our analysis also provides a unified treatment of the universal soft theorems as conservation equations for the spin-0,-1,-2 canonical generators, while highlighting the important role played by the dual mass.

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