arXiv subjects

Ilija Burić

Publications and source records attributed to Ilija Burić.

9 recordsLinked to original sources

arXiv2026

Stringy resolution of bouncing singularities

We study the near-horizon geometry of near-extremal NS5 branes, which admits an exact worldsheet description in terms of the $SL(2,\mathbb{R})_k/U(1)$ coset. In the supergravity limit, the analytically continued time-domain reflection amplitude exhibits a singularity associated with a null geodesic bouncing off the black-hole singularity, analogous to the bouncing singularities of boundary correlators in asymptotically AdS spacetimes. We show that finite-string-length effects render this amplitude an entire function of complex time, completely resolving the bouncing singularity. This resolution is nonperturbative in the inverse coset level: the singularity persists at every finite order in the expansion.

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arXiv2026

Holographic Correlators from Thermal Bootstrap

Holographic thermal two-point functions can be analyzed using the operator product expansion which contains contributions from both multi-stress-tensor and double-trace operators. The former can be computed by analyzing the bulk equation of motion in a near-boundary expansion, but the latter has remained elusive-in practice, one resorts to solving a partial differential equation with limited accuracy. We show that imposing the Euclidean periodicity condition on the holographic correlator (also known as the KMS condition or thermal bootstrap), followed by Padé-Borel resummation, provides an efficient method for computing double-trace thermal coefficients. The resulting series converges rapidly and yields numerical values in excellent agreement with those obtained from solving the partial differential equation.

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arXiv2026

Spin-resolved double-trace thermal coefficients in holography

It was previously shown that the stress-tensor sector of the OPE, together with the KMS condition, fixes holographic thermal two-point functions at vanishing spatial separation. We extend this construction to nonzero spatial separation, where the KMS condition leaves a residual ambiguity that depends only on the spatial separation. We show that this ambiguity is fixed by the zero-frequency bulk wave equation, which can be solved analytically in terms of Heun functions. This gives an efficient method for computing thermal coefficients of double-trace operators resolved by spin. We also study the Lorentzian analytic structure of the resulting correlator and show that complex bulk-cone singularities which appear at spacelike separation in the stress-tensor sector do not persist in the full two-point function; they are resolved by the double-trace contribution.

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arXiv2026

Thermal two-point functions in SYK and complex-time singularities

We analyze the finite-temperature two-point function of the large-$N$ SYK model at intermediate couplings away from the infrared fixed point. Specifically, we examine its analytic structure in the complex time plane, tracking the complex-time singularities over a range of temperatures. The location of the leading singularity lies on the imaginary axis. It controls the short-time dynamics of operator complexity, defining an `effective temperature' for the correlator. The next-to-leading singularity lies outside the thermal strip set by the above effective temperature. It has been argued that this could be interpreted in terms of bouncing null geodesics in the emergent black hole geometry. Both these singularities persist all the way down to zero temperature. We discuss our observations and motivate the related emergent geometry using a kinematic space perspective.

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arXiv2026

Thermal One-point Functions and Asymptotic CFT Data: QFT in AdS

We investigate the thermal partition and one-point functions of the three-dimensional conformal field theory dual to a massive interacting scalar field in AdS$_4$. Using thermal inversion formulas, we determine the asymptotic behaviour of the spectral density and OPE coefficients involving heavy operators at fixed spin. We first analyse these CFT data for the generalised free field, corresponding to the non-interacting bulk theory. Then we compute the first-order perturbative corrections induced by the cubic and quartic bulk interactions. The thermal observables considered here probe a sector associated with operators of large dimension and, in the bulk description, a regime dominated by states with large particle number. This regime remains comparatively unexplored even in generalised free field theory. Remarkably, the asymptotic formulas obtained from thermal inversion remain quantitatively accurate far from the asymptotic regime, describing CFT data reliably already at intermediate conformal weights. Our results show that this feature survives the inclusion of bulk interactions and provide new analytic control over heavy-state data in conformal field theories.

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arXiv2025

QFT on Fuzzy AdS Spaces: Classical Limit and Boundary Correlation Functions

Quantum field theory on two- and three-dimensional fuzzy anti-de Sitter spaces is introduced and studied. We find a complete set of solutions to the fuzzy Klein-Gordon equation and identify the commutative limit in which they reduce to classical scalar field modes. After introducing the noncommutative boundary via semi-classical states, the fuzzy modes are used to obtain the boundary two-point function. In both two and three dimensions, this gives an interesting two-parameter deformation of the conformal two-point function. For the fuzzy AdS$_2$, the two-point function is given explicitly in terms of the Appell function $F_1$.

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arXiv2025

Thermal holographic correlators and KMS condition

Thermal two-point functions in holographic CFTs receive contributions from two parts. One part comes from the identity, the stress tensor and multi-stress tensors and constitutes the stress-tensor sector. The other part consists of contributions from double-trace operators. The sum of these two parts must satisfy the KMS condition -- it has to be periodic in Euclidean time. The stress-tensor sector can be computed by analyzing the bulk equations of motions near the AdS boundary and is not periodic by itself. We show that starting from the expression for the stress-tensor sector one can impose the KMS condition to fix the double-trace part, and hence the whole correlator. We perform explicit calculations in the asymptotic approximation, where the stress-tensor sector can be computed exactly. One can either sum over the thermal images of the stress-tensor sector and subtract the singularities or solve for the KMS condition directly and perform the Borel resummation of the resulting double-trace data -- the results are the same.

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arXiv2025

Heavy-Heavy-Light Asymptotics from Thermal Correlators

We revisit the calculation of spectral densities and heavy-heavy-light (HHL) operator product expansion (OPE) coefficients in three-dimensional conformal field theories using thermal one-point functions on $S^1 \times S^2$. A central element of our analysis is a new inversion formula for one-point functions which is derived via Casimir differential equations. We develop systematic expansions of the spectral density and HHL OPE coefficients in the regime of large $Δ_H$. We validate our analytic tools by comparing the results with the partial wave expansions of thermal one-point functions in free field theories. The algorithms developed for these expansions make full use of Casimir recursion relations, thereby extending their applicability into the heavy exchange regime. In the end, we observe excellent agreement with our analytic predictions and an improvement of up to three orders of magnitude compared to all previous leading order estimates of the CFT data even for moderate values of $Δ_H$.

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arXiv2020

The Superconformal Xing Equation

Crossing symmetry provides a powerful tool to access the non-perturbative dynamics of conformal and superconformal field theories. Here we develop the mathematical formalism that allows to construct the crossing equations for arbitrary four-point functions in theories with superconformal symmetry of type I, including all superconformal field theories in $d=4$ dimensions. Our advance relies on a supergroup theoretic construction of tensor structures that generalizes an approach which was put forward in \cite{Buric:2019dfk} for bosonic theories. When combined with our recent construction of the relevant superblocks, we are able to derive the crossing symmetry constraint in particular for four-point functions of arbitrary long multiplets in all 4-dimensional superconformal field theories.

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