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Nirmalya Kajuri

Publications and source records attributed to Nirmalya Kajuri.

At least 19 recordsLinked to original sources

Holographic One-Point Function and Geodesics in SdS$_3$

Grinberg and Maldacena showed that heavy thermal one-point functions in AdS/CFT can encode complex geodesics reaching a black hole singularity. We study the de Sitter analogue in three-dimensional Schwarzschild--de Sitter space, restricting to the finite cyclic quotients $\mathrm{dS}_3/\mathbb Z_q$. We define a one-point function through a differentiate dictionary and show that an analogous result holds for the Bunch--Davies-prepared integral. Using the exact light field Green function, the bulk integral reduces exactly to a convergent one-dimensional transform, whose large-mass limit is controlled by the near-defect region and governed by a complex saddle. Its action reproduces a complex geodesic length from future infinity to the conical defect, whose real part is the renormalized boundary-to-horizon proper time and whose imaginary part is the horizon-to-defect distance. The imaginary part appears in the one-point coefficient normalized in the Lorentzian source basis; in the Euclidean basis the same saddle contributes only the real part, the two being related by a fixed connection factor.

hep-th

Black Hole Interior Operators and Dilatation Symmetry in Planar Black Branes

Planar AdS black branes have a scaling symmetry that maps a brane solution at one temperature to a solution at another. It is natural to expect that boundary representations of bulk field modes should inherit this symmetry i.e. their correlators should transform covariantly under boundary dilatations. We derive a covariance condition that any boundary representation of interior modes in a planar AdS black brane should satisfy. We then show that Papadodimas-Raju mirror operators satisfy this condition. Thus the Papadodimas-Raju reconstruction of the bulk interior, although state-dependent, inherits the scaling symmetry of planar AdS black holes.

hep-th

Asymptotic Algebras and Holography of Information in CGHS Model

Holography of Information (HoI) and the island formula are two recent approaches to the black hole information loss paradox that yield different Page curves. The difference between the Page curves has been argued to be rooted in the algebra that each approach focuses on. In this paper, we study the candidate algebras for the CGHS model. Making the usual assumptions that are made in HoI literature, we establish HoI for the CGHS model coupled to a massless scalar by constructing the radiative phase space and asymptotic algebras at future null infinity. We prove that the quantum state of the right-moving modes can be recovered from an arbitrarily small neighbourhood of the right future null infinity. We then argue that island reconstruction is incompatible with exact commutativity of the left and right radiative algebras. We discuss the possible distinction between the HoI and island approaches for the CGHS model.

hep-th

Conformally mapping HKLL to flat space

We study two conformal images of the HKLL reconstruction problem for a conformally coupled scalar on AdS$_3$. The first mapping is to a Dirichlet problem on one half of the Einstein static universe. A further conformal transformation maps this half-ESU problem to a massless scalar in a region of $(2+1)$-dimensional Minkowski space bounded by an uniformly accelerated circular Dirichlet mirror. However, the global HKLL problem, the resulting flat-space problem is not a generic local mirror problem with arbitrary boundary data. Rather, the mirror response data must belong to a restricted spectral class inherited from normalizable global AdS modes. We formulate and solve this restricted mirror problem intrinsically in flat space. In the process, we find an example of a valid smearing function which itself does not satisfy the equations of motion. We further consider AdS-Rindler wedge reconstruction. By conformal mapping to an appropriate coordinate system in flat space, we find a simple way to see the blow-up of the smearing function.

hep-th

Geodesics, One Point Functions and Black Hole Perturbations

Holographic black holes exhibit a striking relation between thermal boundary one-point functions and bulk geodesic lengths. In the large conformal-dimension limit, the one-point function of a primary operator is given by the exponential of the geodesic length from its boundary insertion point to the horizon. We test the robustness of this relation under perturbations by considering a class of deformations of an Euclidean BTZ black hole and working to first order in the perturbation.We find that, at leading order in the large conformal-dimension limit and to first order in the radial horizon-preserving perturbation, the logarithmic variation of the one-point function is governed by the variation of the renormalized boundary-to-horizon geodesic length. The result is established using WKB and saddle-point methods, and WKB expressions at large conformal dimension are checked against the exact Green function and bulk-boundary propagator.

hep-th

Lectures on Bulk Reconstruction

If the AdS/CFT conjecture holds, every question about bulk physics can be answered by the boundary CFT. But we still don't know how to translate all the questions about bulk physics to questions about the boundary CFT. Completing this bulk-boundary dictionary is the aim of the bulk reconstruction program, which we review in these lectures. We cover the HKLL construction, bulk reconstruction in AdS/Rindler, mirror operator construction of Papadodimas and Raju and the Marolf-Wall paradox. These notes are based on lectures given at ST4 2018.

hep-th

Unruh-DeWitt Detector Response in Toroidal Spacetime

The global topology of spacetime, though invisible to local curvature measurements, leaves signatures on the correlation functions of quantum fields. We study these signatures using an Unruh-DeWitt particle detector operating in four-dimensional Minkowski spacetime with two spatial directions periodically identified, yielding a spatial topology $\mathbb{R}\times T^2$. We compute detector transition rates for three trajectories: uniform inertial motion, uniform proper acceleration directed along one of the compact axes, and uniform proper acceleration along the non-compact axis. Our results show how a local quantum measurement can reveal features of the large-scale spatial topology.

gr-qc

Momentum Space Correlation Functions in 2D Galilean Conformal Algebra

Galilean Conformal Algebra (GCA) arises as a controlled nonrelativistic limit of the relativistic conformal algebra. In this paper, we initiate the study of momentum space correlation functions in two-dimensional GCA. We derive and solve momentum space Ward identities to obtain two-point and three-point functions. However, relating them to position space correlation functions presents a challenge as Fourier transforms of the latter do not exist. This is resolved by analytically continuing the boost eigenvalues to imaginary values. In this regime, the Fourier transform of the position space two-point and three-point functions exist and match exactly with the momentum space two-point and three-point function obtained by solving the Ward identities.

hep-th

Hawking Radiation in Jackiw-Teitelboim Gravity

In this paper, we study Hawking radiation in Jackiw-Teitelboim gravity for minimally coupled massless and massive scalar fields. We employ a holography-inspired technique to derive the Bogoliubov coefficients. We consider both black holes in equilibrium and black holes attached to a bath. In the latter case, we compute semiclassical deviations from the thermal spectrum.

hep-th

Bulk reconstruction in 2D multi-horizon black hole

The goal of the bulk reconstruction program is to construct boundary representations of fields in asymptotically Anti-de Sitter spacetimes. In this paper, we extend the program by computing the boundary representation of massless fields in an Achucarro-Ortiz black hole spacetime. We obtain analytic expressions for smearing functions in both the exterior and interior of the black hole. We also obtain expressions for Papadodimas-Raju mirror operators.

hep-th

Bulk Reconstruction in De Sitter Spacetime

The bulk reconstruction program involves expressing local bulk fields as non-local operators on the boundary. It was initiated in the context of AdS/CFT correspondence. Attempts to extend it to de Sitter have been successful for heavy(principal series) scalar fields. For other fields, the construction ran into issues. In particular, divergences were found to appear for higher spin fields. In this paper, we resolve these issues and obtain boundary representations for scalars of all masses as well as higher spin fields. We trace the origin of the previously discovered divergences and show that the smearing function becomes distributional for certain values of mass, spin and dimension. We also extend the construction from Bunch-Davies vacuum to all $α$-vacua.

hep-th

Symmetry transformation of subregion bulk representations

Different AdS-Rindler wedges can be mapped to each other using bulk isometries. In this paper we address how the boundary representations corresponding to the AdS-Rindler wedges transform under such isometries. We show that when a bulk wedge is mapped to another using a bulk isometry, their boundary representations are mapped by the conformal transformation corresponding to the isometry. We comment on the import of this result on the relation between AdS/CFT and quantum error correction.

hep-th

Bulk reconstruction and Bogoliubov transformations in AdS$_2$

In the bulk reconstruction program, one constructs boundary representations of bulk fields. We investigate the relation between the global/Poincare and AdS-Rindler representations for AdS$_2$. We obtain the AdS-Rindler smearing function for massive and massless fields and show that the global and AdS-Rindler boundary representations are related by conformal transformations. We also use the boundary representations of creation and annihilation operators to compute the Bogoliubov transformation relating global modes to AdS-Rindler modes for both massive and massless particles.

hep-th

Bulk reconstruction in rotating BTZ black hole

The bulk reconstruction program aims to obtain representations of bulk fields as operators in the boundary CFT. In this paper we extend the program by obtaining the boundary representation for a scalar field in a rotating BTZ black hole. We find that the representation of the field near the inner horizon shows novel features. We also obtain a representation for fields inside the horizon as operators in a single boundary CFT using mirror operator construction.

hep-th

Subregion bulk reconstruction and symmetries

How do subregion boundary representations transform under conformal transformations? In this paper we conjecture a transformation rule and provide evidence for it. We also show how this transformation rule helps mitigate the subregion reconstruction paradox presented by Alhmeiri et al.

hep-th

Entanglement entropy of non-local theories in AdS

We investigate the effect of non-locality on entanglement entropy in anti-de Sitter space-time. We compute entanglement entropy of a nonlocal field theory in anti-de Sitter space-time and find several interesting features. We find that area law is followed, but sub-leading terms are affected by non-locality. We also find that the UV finite term is universal. For the massless theory in 3 dimensional AdS we compute it exactly and find the novel feature that it shows oscillatory behavior.

hep-th

Non-local scalar field on deSitter and its infrared behaviour

We investigate free non-local massless and massive scalar field on deSitter (dS) space-time. We compute the propagator for the non-local scalar field for the corresponding theories on flat and deSitter space-times. It is seen that for the non-local theory, the massless limit of massive propagator is smooth for both flat and deSitter. Moreover, this limit matches exactly with the massless propagator of the non-local scalar field for both flat and deSitter space-time. The propagator is seen to respect dS invariance. Furthermore, investigations of the non-local Green's function on deSitter for large time-like separation shows that the propagator has no infrared divergences. The dangerous infrared $\log$-divergent contributions which arise is local massless theories are absent in the corresponding non-local version. Lack of infrared divergences in the propagator hints at the strong role non-localities may play in the dS infrared physics. This study suggest that non-locality can cure IR issues in deSitter.

hep-th