PoS - Proceedings of Science
Volume 436 - Corfu Summer Institute 2022 "School and Workshops on Elementary Particle Physics and Gravity" (CORFU2022) - Workshop on Noncommutative and Generalized Geometry in String Theory, Gauge Theory and Related Physical Models
General O(D)-equivariant fuzzy hyperspheres via confining potentials and energy cutoffs
G. Fiore
Full text: pdf
Published on: November 08, 2023
Abstract
We summarize our recent construction [1,2,3] of new fuzzy hyperspheres $S^d_{\Lambda}$ of arbitrary dimension $d\in\mathbb{N}$ covariant under the {\it full} orthogonal group $O(D)$, $D=d\!+\!1$. We impose a suitable energy cutoff on a quantum particle in $\mathbb{R}^D$ subject to a confining potential well $V(r)$ with a very sharp minimum on the sphere of radius $r=1$; the cutoff and the depth of the well diverge with $\Lambda\in\mathbb{N}$. Consequently, the commutators of the Cartesian coordinates $\overline{x}^i$ are proportional to the angular momentum components $L_{ij}$, as in Snyder's noncommutative spaces. The $\overline{x}^i$ generate the whole algebra of observables ${\cal A}_{\Lambda}$ and thus the whole Hilbert space ${\cal H}_{\Lambda}$ when applied to any state.
$\mathcal{H}_{\Lambda}$ carries a reducible representation of $O(D)$ isomorphic to the space of harmonic homogeneous polynomials of degree $\Lambda$ in the Cartesian coordinates of (commutative) $\mathbb{R}^{D+1}$; the latter carries an irreducible representation ${\bf\pi}_\Lambda$ of $O(D\!+\!1)\supset O(D)$.
Moreover, ${\cal A}_{\Lambda}$ is isomorphic to ${\bf\pi}_\Lambda\left(Uso(D\!+\!1)\right)$.
We identify the subspace ${\cal C}_\Lambda\subset{\cal A}_{\Lambda}$ spanned by fuzzy spherical harmonics. We interpret $\{{\cal H}_\Lambda\}_{\Lambda\in\mathbb{N}}$, $\{{\cal C}_\Lambda\}_{\Lambda\in\mathbb{N}}$ as fuzzy deformations of
the space ${\cal H}_s\equiv {\cal L}^2(S^d)$ of square integrable functions and the space $C(S^d)$ of continuous functions on $S^d$ respectively, $\{{\cal A}_\Lambda\}_{\Lambda\in\mathbb{N}}$ as fuzzy deformation of the associated algebra ${\cal A}_s$ of observables, because they resp. go to ${\cal H}_s,C(S^d),{\cal A}_s$ as $\Lambda$ diverges (with fixed $\hbar$).
With suitable $\hbar=\hbar(\Lambda)\stackrel{\Lambda\to\infty}{\longrightarrow} 0$, in the same limit ${\cal A}_\Lambda$ goes to the (algebra of functions on the) Poisson manifold $T^*S^d$;
more formally, $\{{\cal A}_\Lambda\}_{\Lambda\in\mathbb{N}}$ yields a fuzzy quantization of a coadjoint orbit of $O(D\!+\!1)$ that goes to the classical phase space $T^*S^d$.
These models might be useful in quantum field theory, quantum gravity or condensed matter physics.
DOI: https://doi.org/10.22323/1.436.0344
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