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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2601.17294 |
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| _version_ | 1866911396155883520 |
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| author | Misawa, Ryutaro |
| author_facet | Misawa, Ryutaro |
| contents | In this paper, we study conditions under which a finite subset $Z$ of the unit sphere $S^{d-1}\subset \mathbb{R}^{d}$ becomes a spherical $t$-design, when $Z$ is constructed by the following procedure: starting from a finite set of $k$-dimensional subspaces in the real Grassmannian $G_{k,d}$, we place, for each such $k$-dimensional subspace, a finite set on its unit sphere, and then take the union of these sets in $S^{d-1}$. For this construction problem -- namely, obtaining spherical designs in higher dimensions by distributing point sets on lower-dimensional spheres subspace by subspace -- we provide a sufficient condition based on the framework of tight $t$-fusion frames ($\mathrm{TFF}_t$) due to Bachoc--Ehler. As a preparation for applications, we moreover give an explicit construction of equal-weight tight $2$-fusion frames on $G_{2,d}$ for infinitely many dimensions $d$, via unions of orbits of the hyperoctahedral group. We also derive necessary conditions for the existence of highly symmetric tight $t$-fusion frames, namely equi-chordal and equi-isoclinic tight $t$-fusion frames ($\mathrm{ECTFF}_t$ and $\mathrm{EITFF}_t$), on $G_{2,d}$, and in particular obtain bounds on the number of points. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_17294 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Constructing spherical designs using tight $t$-fusion frames Misawa, Ryutaro Combinatorics Metric Geometry 05B30, 42C15, 52C17 In this paper, we study conditions under which a finite subset $Z$ of the unit sphere $S^{d-1}\subset \mathbb{R}^{d}$ becomes a spherical $t$-design, when $Z$ is constructed by the following procedure: starting from a finite set of $k$-dimensional subspaces in the real Grassmannian $G_{k,d}$, we place, for each such $k$-dimensional subspace, a finite set on its unit sphere, and then take the union of these sets in $S^{d-1}$. For this construction problem -- namely, obtaining spherical designs in higher dimensions by distributing point sets on lower-dimensional spheres subspace by subspace -- we provide a sufficient condition based on the framework of tight $t$-fusion frames ($\mathrm{TFF}_t$) due to Bachoc--Ehler. As a preparation for applications, we moreover give an explicit construction of equal-weight tight $2$-fusion frames on $G_{2,d}$ for infinitely many dimensions $d$, via unions of orbits of the hyperoctahedral group. We also derive necessary conditions for the existence of highly symmetric tight $t$-fusion frames, namely equi-chordal and equi-isoclinic tight $t$-fusion frames ($\mathrm{ECTFF}_t$ and $\mathrm{EITFF}_t$), on $G_{2,d}$, and in particular obtain bounds on the number of points. |
| title | Constructing spherical designs using tight $t$-fusion frames |
| topic | Combinatorics Metric Geometry 05B30, 42C15, 52C17 |
| url | https://arxiv.org/abs/2601.17294 |