arXiv subjects

Ankit Aggarwal

Publications and source records attributed to Ankit Aggarwal.

13 recordsLinked to original sources

arXiv2026

Hexagon-MLIR: An AI Compilation Stack For Qualcomm's Neural Processing Units (NPUs)

In this paper, we present Hexagon-MLIR,an open-source compilation stack that targets Qualcomm Hexagon Neural Processing Unit (NPU) and provides unified support for lowering Triton kernels and PyTorch models . Built using the MLIR framework, our compiler applies a structured sequence of passes to exploit NPU architectural features to accelerate AI workloads. It enables faster deployment of new Triton kernels (hand-written or subgraphs from PyTorch 2.0), for our target by providing automated compilation from kernel to binary. By ingesting Triton kernels, we generate mega-kernels that maximize data locality in the NPU's Tightly Coupled Memory (TCM), reducing the bandwidth bottlenecks inherent in library-based approaches. This initiative complements our commercial toolchains by providing developers with an open-source MLIR-based compilation stack that gives them a path to advance AI compilation capabilities through a more flexible approach. Hexagon-MLIR is a work-in-progress, and we are continuing to add many more optimizations and capabilities in this effort.

cs.PL↗

arXiv2025

Universal sectors of two-dimensional Carrollian CFTs

We revisit modular invariance in two-dimensional Carrollian conformal field theories from a geometric perspective. Focusing on the characters of the induced and highest-weight representations of the theory, we show that there are regions of parameter space where the vacuum character dominates in the dual channel. We use this property to zoom into different subsectors of the Carrollian theory. One of them is reminiscent of the Schwarzian sector of a relativistic CFT2 and has a flat space holographic interpretation as O-plane orbifold. It exists only for the highest-weight representation. We prove that for all sectors with vacuum dominance in the dual channel, the specific heat is negative, concurrent with the holographic interpretation of the negative specific heat of asymptotically flat spacetimes with horizons.

hep-th↗

arXiv2025

Modular matrices of 2d Carrollian and warped CFTs

We derive the modular S and T matrices that generate the modular transformations on the characters of two dimensional Carrollian and warped CFT algebras. We verify that they satisfy some of their defining properties.

hep-th↗

arXiv2024

Modular properties of massive scalar partition functions

We compute the exact thermal partition functions of a massive scalar field on flat spacetime backgrounds of the form $\mathbb R^{d-q}\times \mathbb T^{q+1}$ and show that they possess an ${\rm SL}(q+1,\mathbb Z)$ symmetry. Non-trivial relations between equivalent expressions for the result are obtained by doing the computation using functional, canonical and worldline methods. For $q=1$, the results exhibit modular symmetry and may be expressed in terms of massive Maass-Jacobi forms. In the complex case with chemical potential for ${\rm U}(1)$ charge turned on, the usual discussion of relativistic Bose-Einstein condensation is modified by the presence of the small dimensions.

hep-th↗

arXiv2024

Carroll Hawking effect

Carroll black holes with an associated Carroll temperature were introduced recently. So far, it is unclear if they exhibit a Hawking-like effect. To solve this, we study scalar fields on Carroll black hole backgrounds. Inspired by anomaly methods, we derive a Hawking-like energy-momentum tensor compatible with the Carroll temperature and the Stefan-Boltzmann law. Key steps in our derivation are the finiteness of energy at the Carroll extremal surface and compatibility with the Carroll Ward identities, thereby eliminating, respectively, the Carroll-analogs of the Boulware and Unruh vacua.

hep-th↗

arXiv2023

All near-horizon symmetries of the Schwarzschild black hole in linearised gravity

Asymptotic symmetries are known to constrain the infrared behaviour of scattering processes in asymptotically flat spacetimes. By the same token, one expects symmetries of the black hole horizon to constrain near-horizon gravitational scattering. In this paper, we take a step towards establishing this connection. We find all near-horizon symmetries that can be potentially relevant to gravitational scattering near the horizon of the Schwarzschild black hole. We study large diffeomorphisms of linearised perturbations of the Schwarzschild black hole in a partial wave basis and in a gauge that allows for gravitational radiation crossing the event horizon. This setup is ideally suited for studying processes involving near-horizon gravitons like scattering and black hole evaporation. We find the most general near-horizon symmetries that are consistent with finite perturbations at the horizon. Since we do not impose any further boundary conditions, these symmetries represent the biggest set of symmetries in this setting. We find the associated covariant charges to be finite and non-zero showing that these symmetries are physical. Interestingly, for a large black hole, the dominant symmetries are just two copies of $ u(1)$.

hep-th↗

arXiv2023

Near-Extremal Limits of Warped Black Holes

A holographic description of three-dimensional warped black holes suffers from ambiguities due to a seemingly harmless choice of coordinate system. This gives rise to the notion of ensembles in warped black holes, and we focus on two of them: the canonical and quadratic ensemble. Our aim is to quantify the imprint of these ensembles in the near-extremal limit of a warped black hole. To this end, for each ensemble, we explore the thermodynamic response and evaluate greybody factors. We also set-up a holographic dictionary in their near-AdS$_2$ region, and decode aspects of the dual near-CFT$_1$. This gives us different perspectives of the black hole that we can contrast and compare. On the one hand, we find perfect agreement between the near-extremal limit of the canonical ensemble warped black holes, their near-AdS$_2$ effective analysis, and a warped conformal field theory description. On the other, we are led to rule out the quadratic ensemble due to inconsistencies at the quantum level with the near-AdS$_2$ effective description.

hep-th↗

arXiv2022

Near-Extremal Limits of Warped CFTs

Warped conformal field theories (WCFTs) are two-dimensional non-relativistic systems, with a chiral scaling and shift symmetry. We present a detailed derivation of the near-extremal limit for their torus partition function. This limit requires large values of the central charge, and is only consistent for non-unitary WCFT. We compare our analysis with previous studies of WCFT and its relation to a one-dimensional warped-Schwarzian theory. We discuss different ensembles of warped CFTs and contrast our results with analogous limits in two-dimensional CFTs.

hep-th↗

arXiv2022

Phase transition of photons and gravitons in a Casimir box

A first order phase transition for photons and gravitons in a Casimir box is studied analytically from first principles with a detailed understanding of symmetry breaking due to the boundary conditions. It is closely related to Bose-Einstein condensation and accompanied by a quantum phase transition whose control parameter is the chemical potential for optical helicity.

hep-th↗

arXiv2021

Boundary Conditions for Warped AdS$_3$ in Quadratic Ensemble

In the context of warped conformal field theories (WCFT), the derivation of the warped Cardy formula relies on the zero mode spectrum being bounded from below. Generically, this is not true for holographic WCFTs in "canonical" ensemble, whereas this condition is satisfied in the "quadratic" ensemble, making it more natural in holographic setups. In this work, we find a new set of boundary conditions in three-dimensional Topologically Massive Gravity (TMG) such that the putative dual theory is a WCFT in quadratic ensemble. Surprisingly, imposing the equations of motion, we obtain a closed form metric spanned by two arbitrary chiral functions, analogous to the Ba\~nados metrics in Einstein gravity. Surface charges for these boundary conditions are not a priori integrable and we discuss two choices of boundary conditions to make them so. We obtain the bulk thermodynamic entropy of warped BTZ black holes by making use of the warped Cardy formula, in its regime of validity. We also discuss the issue of identifying the vacuum in our solution space: demanding the enhancement of global symmetries selects only a family of solutions, out of which the unique vacuum must be carefully singled out.

hep-th↗

arXiv2019

Warped Symmetries of the Kerr Black Hole

We propose a set of diffeomorphism that act non-trivially near the horizon of the Kerr black hole. We follow the recent developments of Haco-Hawking-Perry-Strominger to quantify this phase space, with the most substantial difference being our choice of vectors fields. Our gravitational charges are organized into a Virasoro-Kac-Moody algebra with non-trivial central extensions. We interpret this algebra as arising from a warped conformal field theory. Using the data we can infer from this warped CFT description, we capture the thermodynamic properties of the Kerr black hole.

hep-th↗

arXiv2018

Supertranslations in Higher Dimensions Revisited

In this paper, we revisit the question of identifying Soft Graviton theorem in higher (even) dimensions with Ward identities associated with Asymptotic symmetries. Building on the prior work of \cite{strominger}, we compute, from first principles, the (asymptotic) charge associated to Supertranslation symmetry in higher even dimensions and show that (i) these charges are non-trivial, finite and (ii) the corresponding Ward identities are indeed the soft graviton theorems.

hep-th↗

arXiv2017

Quadrupolar power radiation by a binary system in de Sitter Background

Cosmological observations over past couple of decades favor our universe with a tiny positive cosmological constant. Presence of cosmological constant not only imposes theoretical challenges in gravitational wave physics, it has also observational relevance. Inclusion of cosmological constant in linearized theory of gravitational waves modifies the power radiated quadrupole formula. There are two types of observations which can be impacted by the modified quadrupole formula. One is the orbital decay of an inspiraling binary and other is the modification of the waveform at the detector. Modelling a compact binary system in an elliptic orbit on de Sitter background we obtain energy and angular momentum radiation due to emission of gravitational waves. We also investigate evolution of orbital parameters under back reaction and its impact on orbital decay rate. In the limit to circular orbit our result matches to that obtained in ref. [26].

gr-qc↗