arXiv subjects

Krishnanand Karthikeyan

Publications and source records attributed to Krishnanand Karthikeyan.

4 recordsLinked to original sources

arXiv2026

Observation of gravity-like signatures in holographic codes on a quantum computer

The unification of quantum mechanics and general relativity remains one of the major open problems of theoretical physics. The Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence provides a valuable theoretical framework for this effort via a holographic duality between a theory of quantum gravity in asymptotically AdS spacetime and a conformal quantum field theory on the lower-dimensional boundary. Here, we implement a toy model of this duality called the HaPPY code, a quantum error-correcting code in the form of a tensor network with hyperbolic entanglement patterns, on a trapped-ion quantum computer. We present the first experimental confirmation of the Faulkner-Lewkowycz-Maldacena formula in this model - a key test of the holographic correspondence. We then enrich it with non-stabilizerness, or magic, and observe entropic precursors expected of emergent gravity. Finally, we present and measure a code construction whose entropic behavior is reminiscent of a highly quantum wormhole. Our experiments illustrate how quantum computers can serve as testbeds for modeling the emergence of spacetime.

quant-ph↗

arXiv2026

State-dependent geometries from magic-enriched quantum codes

Quantum error-correcting codes provide a powerful framework for emergent spacetime, yet existing holographic code models describe only quantum fields on a fixed background: in subsystem erasure-correcting codes, the entropic area term is state independent and cannot capture gravitational backreaction. We argue that this limitation is intrinsic to exact subsystem complementary recovery and that incorporating backreaction instead requires approximate quantum error correction. We introduce a Ryu-Takayanagi-like entropy decomposition for approximate subsystem erasure-correcting codes, defining bulk matter entropy via optimal recovery and a complementary proto-area entropy as the difference between boundary entropy and recoverable bulk entropy. For a broad class of skewed quantum codes obtained by small nonlocal perturbations of exact codes, the proto-area increases monotonically with bulk entropy, closely aligning with the behavior of quantum extremal surfaces. We identify the origin of this response as a form of tripartite non-local magic in the Choi state of the encoding map, which vanishes in stabilizer codes and controls the leading matter-geometry coupling in approximate subsystem erasure-correcting codes.

hep-th↗

arXiv2024

Constraint on cosmological constant in generalized Skryme-teleparallel system

The Einstein-Skyrme system is understood to defy the "no hair" conjecture by possessing black-hole solutions with fractional baryon number outside the event horizon. In this article, we extend the study of the Skyrme system to teleparallel gravity framework. We consider two scenarios, the Teleparallel Equivalent of General Relativity (TEGR) and generalized teleparallel gravity $f(T)$. In our analysis, we compute the fractional baryon number beyond the black-hole horizon and its correlation with the cosmological constant ($Λ$). In the TEGR context, where $f(T) = -T - 2Λ$, the results match with the Einstein-Skyrme model, assuming a positive $Λ$. More interestingly, in generalized teleparallel gravity scenario, defined by $f(T) = -T - τT^2 - 2Λ$, we show that the existence of a solution demands that not only must $Λ$ be positive but has to lie in a range, $Λ_{min} < Λ< Λ_{max}$. While the upper bound depends inversely on $τ$, the lower bound is a linear function of it. Hence, in the limiting case with generalized teleparallel gravity converging towards TEGR ($τ\rightarrow 0$), the constraints on the cosmological constant relax to the Einstein Skryme system ($Λ_{min}$ approaches zero and $Λ_{max}$ becomes unbounded). On the other hand, in f(T) gravity, vanishing cosmological constant solution is found only if the lower bound on the energy of the soliton is very large.

gr-qc↗

arXiv2022

Kalb-Ramond field induced cosmological bounce in generalized teleparallel gravity

One of the important open questions in high-energy physics is to understand the lack of evidence of Kalb-Ramond (KR) field, in particular in the present day cosmology. In this paper we aim to address this issue by showing that a bounce scenario in the evolution of the Universe strongly advocates their elusiveness, even if their energy density was very large to start with. We consider the Kalb-Ramond field and its effects in the context of generalized teleparallel gravity in (3+1) dimensions. Teleparallel gravity is a description of gravitation in which the tetrads are the dynamical degrees of freedom, and the torsion arising from fields with spin are accommodated naturally as field strength tensors. In order to describe the coupling prescription, we address the correct generalization of the Fock-Ivanenko derivative operator for an n-form tensor field. By varying with respect to the tetrads, this rank-2 field is shown to source the teleparallel equivalent of Einstein's equations. We study the possibility of reproducing two well-known cosmological bounce scenarios, namely, symmetric bounce and matter bounce in four-dimensional spacetime with with the Friedmann-Lemaitre-Robertson-Walker metric and observe that the solution requires the KR field energy density to be localized near the bounce. The crucial result in our work is that this feature also naturally explains the lack of cosmological evidence of the rank-2 field in the present day Universe for the matter-bounce scenario. Thus, among the bouncing cosmologies, latter is favored over the former.

gr-qc↗