We summarize our recent construction [1,2,3] of new fuzzy hyperspheres SdΛ of arbitrary dimension d∈N covariant under the {\it full} orthogonal group O(D), D=d+1. We impose a suitable energy cutoff on a quantum particle in RD 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 Λ∈N. Consequently, the commutators of the Cartesian coordinates ¯xi are proportional to the angular momentum components Lij, as in Snyder's noncommutative spaces. The ¯xi generate the whole algebra of observables AΛ and thus the whole Hilbert space HΛ when applied to any state.
HΛ carries a reducible representation of O(D) isomorphic to the space of harmonic homogeneous polynomials of degree Λ in the Cartesian coordinates of (commutative) RD+1; the latter carries an irreducible representation πΛ of O(D+1)⊃O(D).
Moreover, AΛ is isomorphic to πΛ(Uso(D+1)).
We identify the subspace CΛ⊂AΛ spanned by fuzzy spherical harmonics. We interpret {HΛ}Λ∈N, {CΛ}Λ∈N as fuzzy deformations of
the space Hs≡L2(Sd) of square integrable functions and the space C(Sd) of continuous functions on Sd respectively, {AΛ}Λ∈N as fuzzy deformation of the associated algebra As of observables, because they resp. go to Hs,C(Sd),As as Λ diverges (with fixed ℏ).
With suitable ℏ=ℏ(Λ)Λ→∞⟶0, in the same limit AΛ goes to the (algebra of functions on the) Poisson manifold T∗Sd;
more formally, {AΛ}Λ∈N yields a fuzzy quantization of a coadjoint orbit of O(D+1) that goes to the classical phase space T∗Sd.
These models might be useful in quantum field theory, quantum gravity or condensed matter physics.
