Symmetry, Integrability and Geometry: Methods and Applications (SIGMA)


SIGMA 19 (2023), 076, 43 pages      arXiv:2203.03633      https://doi.org/10.3842/SIGMA.2023.076

Tensors and Algebras: An Algebraic Spacetime Interpretation for Tensor Models

Dennis Obster
Yukawa Institute for Theoretical Physics, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan

Received April 24, 2022, in final form September 30, 2023; Published online October 18, 2023

Abstract
The quest for a consistent theory for quantum gravity is one of the most challenging problems in theoretical high-energy physics. An often-used approach is to describe the gravitational degrees of freedom by the metric tensor or related variables, and finding a way to quantise this. In the canonical tensor model, the gravitational degrees of freedom are encoded in a tensorial quantity $P_{abc}$, and this quantity is subsequently quantised. This makes the quantisation much more straightforward mathematically, but the interpretation of this tensor as a spacetime is less evident. In this work we take a first step towards fully understanding the relationship to spacetime. By considering $P_{abc}$ as the generator of an algebra of functions, we first describe how we can recover the topology and the measure of a compact Riemannian manifold. Using the tensor rank decomposition, we then generalise this principle in order to have a well-defined notion of the topology and geometry for a large class of tensors $P_{abc}$. We provide some examples of the emergence of a topology and measure of both exact and perturbed Riemannian manifolds, and of a purely algebraically-defined space called the semi-local circle.

Key words: algebraic tensor model; quantum gravity; canonical tensor model; interpretation.

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