Pith. sign in

REVIEW 2 major objections 6 minor 58 references

Recovering a group from few orbits

T0 review · 2 major / 6 minor · reviewed 2026-08-12 · deepseek-v4-flash

Pith's one-line read One generic orbit of an unknown finite unitary group on a complex Hilbert space determines the group up to isomorphism, and two suffice on real Hilbert spaces.

desk verdict Genuinely new one-orbit theorem over C, a plausible two-orbit theorem over R with a fixable proof gap, and an overstated sharpness claim; worth reviewing after revision. read the letter →

arxiv 2411.17434 v1 pith:AZZ5BW5H submitted 2024-11-26 math.RT cs.ITmath.IT

classification math.RTcs.ITmath.IT MSC 20C15
keywords finitegrouprecoverygenericorbitsHilbertspaceautomorphismsGramgraphCayleyrepresentationtheoryorbitsymmetrylearning
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper asks what an unknown finite group of symmetries of a finite-dimensional Hilbert space can be recovered from a small number of its orbits, with 'generic' meaning open and dense. On a complex Hilbert space one generic orbit is enough: the inner products among points of the orbit form an edge-labeled graph isomorphic to the group's complete Cayley graph, so its label-preserving automorphism group is isomorphic to the original group. On a real Hilbert space two generic orbits suffice to identify the isomorphism class, and one suffices in special cases, such as prime order or dimension two. If the goal is not just the isomorphism class but the concrete set of unitary or orthogonal transformations, the paper gives a sharp representation-theoretic bound on the number of generic orbits needed, with matching lower and constructive upper bounds.

What carries the argument

The load-bearing object is the Gram graph of an orbit: the edge-labeled directed graph whose vertices are the orbit's points and whose edge $s \to t$ carries label $\langle s, t \rangle$. For a generic complex orbit this graph is isomorphic to the complete Cayley graph of $G$ (edge $h \to k$ labeled by $h^{-1}k$), which follows from the fact that a generic $x$ makes the level sets of $g \mapsto \langle x, gx \rangle$ coincide with those of $g \mapsto g$ (or $g + g^{-1}$ in the real case). Since every label-preserving automorphism of a complete Cayley graph is left multiplication by a group element, $\operatorname{Aut}(Gv) \cong G$ follows. In real spaces the same graph is too coarse, so the paper pairs two generic orbits and uses the orbit pairing lemma: the map sending each point of the first orbit to its nearest point in the second is a well-defined bijection that is equivariant with respect to every symmetry of the union, transferring the action between orbits and yielding $\operatorname{Aut}(Gv \cup Gw) \cong G$. For concrete recovery the mechanism is representation-theoretic: orbits are viewed as images of equivariant linear maps from $k$ copies of the regular representation, and Schur's lemma translates 'the spans of the orbits have codimension smaller than $r$' into the multiplicity bound $k \ge \max_\pi (n_\pi(V)-(r-1)[\pi=1])/n_\pi(R)$.

What would settle it

Sample a random pair of orbits of the quaternion group $Q_8$ acting by left multiplication on $\mathbb{R}^4$ and count the automorphisms of their union; Theorem 2.12 predicts exactly 8 for every pair in its generic set, so finding a pair with more symmetries, particularly one that preserves distances but is not a single complexified isometry, would disprove the two-orbit theorem.

Watch

Extended reading notes

Core claim

The paper establishes that, for a finite group $G$ acting by unitary automorphisms on a finite-dimensional complex Hilbert space $V$, a single generic orbit determines $G$ up to isomorphism: the canonical map $G \to \operatorname{Aut}(Gv)$ is an isomorphism (Theorem 2.6). On a real Hilbert space, two generic orbits suffice, with $G \to \operatorname{Aut}(Gv \cup Gw)$ an isomorphism (Theorem 2.12). For concrete recovery, Corollary 3.5(b) states that if $k \ge [\mathbb{C}:F]$ and $k$ meets the multiplicity bound $k \ge \max_\pi (n_\pi(V)-(r-1)[\pi=1])/n_\pi(R)$, where $r$ is the smallest dimension of a nontrivial representation, then $k$ generic orbits determine $G$ as a subset of $\operatorname{Aut}(V)$; conversely, if $k$ fails that bound, every collection of $k$ orbits can be realized by another subgroup of $\operatorname{Aut}(V)$.

Load-bearing premise

The two-orbit theorem assumes that the two real orbits are permuted in lockstep—that every symmetry of their union also gives a symmetry of the complexified orbit $G(v+iw)$—an assumption supplied by the later orbit pairing lemma but not cited there.

Editorial extensions

If this is right

  • In the complex case, an observer who receives one generic orbit can compute the Gram graph and read off the isomorphism class of $G$ without prior knowledge of the dimension or order.
  • In the real case, two generic orbits recover the abstract group as $\operatorname{Aut}(Gv \cup Gw)$; one orbit already suffices when $G$ has prime order or $V$ has dimension two.
  • The concrete recovery threshold is sharp: if $k$ fails the multiplicity bound, any $k$ orbits can be reinterpreted as orbits of a different subgroup of $\operatorname{Aut}(V)$, while if $k$ meets both the bound and $k \ge [\mathbb{C}:F]$, $k$ generic orbits determine $G$ exactly.
  • For $V$ equal to the regular representation over $\mathbb{C}$, a single generic orbit determines the concrete group action; for $G = \{\pm I\}$, genericity lets a single orbit determine the group even though the general bound asks for $d$ orbits.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • The Gram graph plus automorphism computation gives a concrete algorithmic route to symmetry discovery from unlabeled point clouds: collect one generic complex orbit, build inner-product labels, and compute the label-preserving automorphism group; the two-orbit theorem supplies the synchronization rule that makes the same pipeline work for real data.
  • The orbit pairing lemma's nearest-point bijection is a natural target for numerical experiments: it suggests that approximate orbits can be matched by nearest neighbours before estimating the group, and its equivariance could be checked statistically.
  • If the real one-orbit conjecture is true, the distinction between complex and real cases in abstract recovery would vanish entirely, and the second orbit in Theorem 2.12 would be an artifact of the proof rather than an information-theoretic necessity.
  • The concrete-recovery bound is a worst-case generic threshold, but Example 3.8 shows genericity itself can carry extra information (such as nonzero centroid), so the number of orbits actually needed in structured families may be far smaller.
Share X Bluesky LinkedIn Reddit HN

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

2 major / 6 minor

Summary. The paper studies the inverse problem of recovering an unknown finite group G of automorphisms (linear isometries) of a finite-dimensional real or complex Hilbert space V from one or more generic G-orbits. In the complex case, it proves (Theorem 2.6) that a single generic orbit determines G up to isomorphism, and that the canonical map G to Aut(Gv) is an isomorphism. In the real case, it proves (Theorem 2.12) that two generic orbits determine G up to isomorphism via the automorphism group of their union. For concrete recovery, Theorem 3.4 and Corollary 3.5 give a representation-theoretic bound on the number of generic orbits needed to determine G as a subset of Aut(V), together with a converse. The paper also provides examples, open problems, and a table of bounds.

Significance. The problem is natural and well motivated by symmetry learning in data science. The complex one-orbit theorem and the representation-theoretic concrete recovery bound are elegant and appear correct; the derivations use generic polynomial arguments and Schur's lemma with no free parameters or fitting. The paper also offers instructive examples showing real-orbit behavior (e.g., Example 2.11) and a counterexample to possible over-strong sharpness (Example 3.8). The main caveat is that the proof of the two-orbit theorem is incomplete as written; however, the gap is local and can be repaired using the paper's own orbit-pairing lemma. If that repair is made, the results constitute a solid contribution.

major comments (2)
  1. [Section 2, Theorem 2.12 (proof)] The proof defines alpha(sigma)(x+iy)=sigma(x)+i sigma(y) and argues that because sigma extends to a linear isometry M, alpha(sigma) extends to the linear isometry x+iy maps to Mx+iMy and hence belongs to Aut(G(v+iw)). This only shows alpha(sigma) is a linear isometry of the complexification; it does not show that alpha(sigma) maps the finite set G(v+iw) into itself, as required by the definition of Aut. One needs synchronization: for each g in G, the same group element h_g must satisfy sigma(gv)=h_g gv and sigma(gw)=h_g gw. This synchronization follows from Lemma 3.1 because beta(gv)=gw and sigma(gw)=beta sigma(gv), but Lemma 3.1 is neither stated nor cited before Theorem 2.12. The proof should be reorganized to use Lemma 3.1 (or to prove the synchronization directly) before constructing alpha; with that addition the remainder of the argument is valid.
  2. [Section 3, Corollary 3.5(a)] The proof is only a sketch. The sentence 'we cannot determine whether G acts trivially on the orthogonal complement' does not verify the claim that every combination of k orbits can be realized as orbits of another subgroup. A construction is needed: for arbitrary v_1,...,v_k put S=span(union_i Gv_i); since k fails (1), Theorem 3.4 gives codim S >= r >= 1. Choose a nonzero u in S^perp and let R be the orthogonal reflection in the line through u (fixing u^perp). Then H={g direct sum r : g in G, r in <R>} is a proper subgroup of Aut(V) different from G, and H v_i = G v_i for all i. Inserting this construction would make the lower bound rigorous.
minor comments (6)
  1. [Section 2, Theorem 2.12] The displayed equation in the injectivity argument contains a typo: the equality should involve alpha(sigma)(g(v+iw)) = sigma(gv) + i sigma(gw), not alpha(sigma)(v+iw) on the right-hand side.
  2. [Section 3, Lemma 3.1] The chain proving beta sigma = sigma beta for arbitrary sigma implicitly assumes sigma^{-1}(Gw)=Gw, which is established only later in the proof via the norm inequality ||v|| != ||w||. The proof should establish the norm inequality first, or explicitly note that for the G-equivariance step the chain is applied only to sigma in G.
  3. [Abstract and Table 1] The phrase 'sharp bounds' overstates the real abstract-recovery case: the paper proves an upper bound of 2 and leaves Conjecture 2.7 (one orbit suffices) open. Consider saying 'we give sharp bounds in the complex case and bounds in the real case.'
  4. [Theorem 2.6(a)] The assertion that the label-preserving automorphism group of the complete Cayley graph is isomorphic to G is stated without proof; a one-line verification (phi(h)=phi(1)h follows from label preservation on edges from 1 to h) would make the proof self-contained.
  5. [Section 1.2] In the definition of Aut(S), the permutation is first called pi and then sigma in 'M|S=sigma'; the notation should be unified.
  6. [Example 3.8] The wording 'Corollary 3.5 reports that k orbits determine G as a concrete group only if k>=d' is slightly imprecise because Corollary 3.5(b) is a sufficient condition and part (a) concerns arbitrary combinations; the genericity caveat in the following sentence is important and should be integrated into the phrasing.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: group recovery is derived from generic Gram-graph and representation-theoretic arguments; self-citations are background only.

full rationale

I walked the claimed derivation chain. The central recovery results are constructive and do not assume what they prove. Theorem 2.5 proves, by a generic-polynomial argument, that the Gram graph of a generic complex orbit is isomorphic to the complete Cayley graph of G; Theorem 2.6 then recovers the isomorphism class of G from that graph, using the standard fact that label-preserving automorphisms of the complete Cayley graph are left multiplications. No fitted parameter is involved. The real two-orbit theorem (Theorem 2.12) reduces to the complex one-orbit theorem on the complexification V_C; its proof contains a genuine gap, since showing that alpha(sigma) extends to an isometry does not by itself show that it permutes G(v+iw) unless the two real orbits are permuted in a synchronized way. This is an omitted-support problem, not a circular one: the synchronization is supplied later by Lemma 3.1, which is proved independently by an equivariant nearest-point argument, and no step of the theorem uses its own conclusion as a premise. The concrete-recovery results in Section 3 are likewise first-principles: the equivalence in Theorem 3.4 is a generic-polynomial/representation-theoretic criterion, Corollary 3.5 combines it with the multi-orbit theorem, and Schur's lemma is external to the paper's conclusions. Self-citations (e.g., [17], [18], [23], [34], [40], [41]) appear only in related-work or as background and are not load-bearing. Example 3.8 even exhibits a case where the paper's own sufficient bound is larger than necessary, which is the opposite of a conclusion forced by the analysis. No circular step can be exhibited with the required specificity, so the circularity score is 0.

Assumptions & free parameters 0 free parameters · 4 assumptions · 0 invented entities

The paper introduces no free parameters or invented entities. Its results rest on standard representation theory, the polynomial genericity technique, and a classical fact about group tables that is used without citation (isotopic groups are isomorphic).

assumptions (4)
  • domain assumption Standard facts about finite group representations over R and C: semisimplicity, Schur's lemma, multiplicities in regular representation.
    Used in Theorem 3.4 (c)<->(d) and Corollary 3.5 for the orbit count formula.
  • standard math The complement of the zero set of a nonzero polynomial is open and dense in the Zariski topology.
    Used throughout to define generic conditions (Section 1.2, Lemma 2.2).
  • domain assumption The isomorphism class of the complete Cayley graph / Cayley table of a finite group determines the group up to isomorphism (isotopic groups are isomorphic).
    Used in Theorem 2.6(a) to conclude one orbit's Gram graph determines G; not stated or cited.
  • standard math Finite subgroups of O(2) are cyclic or dihedral (Leonardo da Vinci's theorem).
    Used in Example 2.1 and Example 2.8, but not load-bearing for main theorems.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Recovering a group from few orbits." pith.science (2026). https://pith.science/paper/AZZ5BW5H

@misc{pith2026241117434,
  author       = {Pith},
  title        = {Pith review of: Recovering a group from few orbits},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/AZZ5BW5H}},
  note         = {Machine review of arXiv:2411.17434}
}
abstract

For an unknown finite group $G$ of automorphisms of a finite-dimensional Hilbert space, we find sharp bounds on the number of generic $G$-orbits needed to recover $G$ up to group isomorphism, as well as the number needed to recover $G$ as a concrete set of automorphisms.

Figures

Figures reproduced from arXiv: 2411.17434 by the authors.

Figure 1
Figure 1. Six orbits in R 2 arising from the actions of six different subgroups of the orthogonal group Op2q. The reader is invited to guess the isomorphism class of the group that generated each orbit. In each case, you may assume that the point that generated the orbit was drawn at random according to a continuous probability distribution over R 2 . The solutions can be found in the footnote on the next page.2 To facilitate… view at source ↗
Figure 2
Figure 2. Orbits generated by C8 (left) and D4 (right). As discussed in Example 2.1, the points fall on the vertices of a centered regular octagon and a centered truncated square, respectively, each shown in blue. In Section 3 we turn our attention to Problem 1.1(b). We recover the concrete group G in two steps. We first show that, given enough generic orbits, one can recover the permutations that G induces on the union of or… view at source ↗
Figure 3
Figure 3. An illustration of the orbit pairing lemma (Lemma [PITH_FULL_IMAGE:figures/full_fig_p008_3.png] view at source ↗

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

58 extracted references · 47 canonical work pages

  1. [1]

    T. Amir, S. Gortler, I. Avni, R. Ravina, N. Dym, Neural injective functions for multisets, measures and graphs via a finite witness theorem, NeurIPS 36 (2024)

  2. [2]

    Balan, P

    R. Balan, P. Casazza, D. Edidin, On signal reconstruction without phase, Appl. Comput. Harmon. Anal. 20 (2006) 345–356

  3. [3]

    Balan, E

    R. Balan, E. Tsoukanis, G-invariant representations using coorbits: Bi-lipschitz properties, arXiv:2308.11784 (2023)

  4. [4]

    G-Invariant Representations using Coorbits: Injectivity Properties

    R. Balan, E. Tsoukanis, G-invariant representations using coorbits: Injectivity properties, arXiv:2310.16365 (2023)

  5. [5]

    Stability of sorting based embeddings

    R. Balan, E. Tsoukanis, M. Wellershoff, Stability of sorting based embeddings, arXiv:2410.05446 (2024)

  6. [6]

    A. S. Bandeira, B. Blum-Smith, J. Kileel, J. Niles-Weed, A. Perry, A. S. Wein, Estimation under group actions: recovering orbits from invariants, Appl. Comput. Harmon. Anal. 66 (2023) 236–319

  7. [7]

    Bendory, N

    T. Bendory, N. Dym, D. Edidin, A. Suresh, A transversality theorem for semi-algebraic sets with application to signal recovery from the second moment and cryo-EM, arXiv:2405.04354 (2024)

  8. [8]

    Bendory, N

    T. Bendory, N. Dym, D. Edidin, A. Suresh, Phase retrieval with semi-algebraic and ReLU neural network priors, arXiv:2311.08833 (2023)

Show all 58 references
  1. [9]

    Bendory, D

    T. Bendory, D. Edidin, The Sample Complexity of Sparse Multireference Alignment and Single- Particle Cryo-Electron Microscopy, SIAM J. Math. Data Sci. 6 (2024) 254–282

  2. [10]

    Bendory, D

    T. Bendory, D. Edidin, O. Mickelin, The beltway problem over orthogonal groups, arXiv:2402.03787 (2024)

  3. [11]

    Blum-Smith, N

    B. Blum-Smith, N. Huang, M. Cuturi, S. Villar, Learning functions on symmetric matrices and point clouds via lightweight invariant features, arXiv:2405.08097 (2024)

  4. [12]

    Blum-Smith, S

    B. Blum-Smith, S. Villar, Machine Learning and Invariant Theory, Notices Amer. Math. Soc. 70 (2023) 1205–1213. 12

  5. [13]

    B¨ oker, R

    J. B¨ oker, R. Levie, N. Huang, S. Villar, C. Morris, Fine-grained expressivity of graph neural networks, NeurIPS 36 (2024)

  6. [14]

    Broome, S

    H. Broome, S. Waldron, On the construction of highly symmetric tight frames and complex polytopes, Linear Algebra Appl. 439 (2013) 4135–4151

  7. [15]

    Cahill, A

    J. Cahill, A. Contreras, A. Contreras-Hip, Complete set of translation invariant measurements with Lipschitz bounds, Appl. Comput. Harmon. Anal. 49 (2020) 521–539

  8. [16]

    Cahill, A

    J. Cahill, A. Contreras, A. Contreras-Hip, Stable Separation of Orbits for Finite Abelian Group Actions, J. Fourier Anal. Appl. 30 (2024) 12

  9. [17]

    Cahill, J

    J. Cahill, J. W. Iverson, D. G. Mixon, Towards a bilipschitz invariant theory, Appl. Comput. Harmon. Anal. 72 (2024) 101669

  10. [18]

    Cahill, J

    J. Cahill, J. W. Iverson, D. G. Mixon, D. Packer, Group-invariant max filtering, Found. Comput. Math. (2024) 1–38

  11. [19]

    Cahill, D

    J. Cahill, D. G. Mixon, H. Parshall, Lie PCA: Density estimation for symmetric manifolds, Appl. Comput. Harmon. Anal. 65 (2023) 279–295

  12. [20]

    Chien, S

    T.-Y. Chien, S. Waldron, A characterization of projective unitary equivalence of finite frames and applications, SIAM J. Discrete Math. 30 (2016) 976–994

  13. [21]

    H. Cohn, A. Kumar, Universally optimal distribution of points on spheres, J. Amer. Math. Soc. 20 (2007) 99–148

  14. [22]

    Conca, D

    A. Conca, D. Edidin, M. Hering, C. Vinzant, An algebraic characterization of injectivity in phase retrieval, Appl. Comput. Harmon. Anal. 38 (2015) 346–356

  15. [23]

    C. Cox, E. J. King, D. G. Mixon, H. Parshall, Uniquely optimal codes of low complexity are symmetric, arXiv:2008.12871 (2020)

  16. [24]

    Derksen, Bi-Lipschitz Quotient embedding for Euclidean Group actions on Data, arXiv:2409.06829 (2024)

    H. Derksen, Bi-Lipschitz Quotient embedding for Euclidean Group actions on Data, arXiv:2409.06829 (2024)

  17. [25]

    N. Dym, S. J. Gortler, Low-dimensional invariant embeddings for universal geometric learning, Found. Comput. Math. (2024) 1–41

  18. [26]

    Edidin, J

    D. Edidin, J. Katz, Generic orbit recovery from invariants of very low degree, arXiv:2408.09599 (2024)

  19. [27]

    Edidin, M

    D. Edidin, M. Satriano, Orbit recovery for band-limited functions, SIAM J. Appl. Algebra Geometry 8 (2024) 733–755

  20. [28]

    Ennes, R

    H. Ennes, R. Tinarrage, LieDetect: Detection of representation orbits of compact Lie groups from point clouds, arXiv:2309.03086 (2023)

  21. [29]

    Z. Fan, R. R. Lederman, Y. Sun, T. Wang, S. Xu, Maximum likelihood for high-noise group orbit estimation and single-particle cryo-EM, Ann. Stat. 52 (2024) 52–77

  22. [30]

    Fejes T´ oth, Regular figures, Pergamon, 1964

    L. Fejes T´ oth, Regular figures, Pergamon, 1964

  23. [31]

    Fejes T´ oth, Symmetry induced by economy, Symmetry (1986) 83–91

    L. Fejes T´ oth, Symmetry induced by economy, Symmetry (1986) 83–91

  24. [32]

    Fejes T´ oth,¨Uber die dichteste Kugellagerung, Math

    L. Fejes T´ oth,¨Uber die dichteste Kugellagerung, Math. Z. 48 (1940) 676–684

  25. [33]

    Fickus, E

    M. Fickus, E. Gomez-Leos, J. W. Iverson, Radon-Hurwitz Grassmannian codes, arXiv:2404.06417 (2024)

  26. [34]

    Fickus, J

    M. Fickus, J. W. Iverson, J. Jasper, D. G. Mixon, Equi-isoclinic subspaces from symmetry, arXiv:2406.19542 (2024). 13

  27. [35]

    I. Hadi, T. Bendory, N. Sharon, SE p3q Synchronization by eigenvectors of dual quaternion matrices, Inform. Inference 13 (2024) iaae014

  28. [36]

    Hordan, T

    S. Hordan, T. Amir, N. Dym, Weisfeiler Leman for Euclidean Equivariant Machine Learning, arXiv:2402.02484 (2024)

  29. [37]

    Hoskins, Y

    J. Hoskins, Y. Khoo, O. Mickelin, A. Singer, Y. Wang, Subspace method of moments for ab initio 3-D single-particle Cryo-EM reconstruction, arXiv:2410.06889 (2024)

  30. [38]

    Huang, R

    N. Huang, R. Levie, S. Villar, Approximately equivariant graph networks, NeurIPS 36 (2024)

  31. [39]

    J. W. Iverson, J. Jasper, D. G. Mixon, More on the optimal arrangement of 2 d lines in Cd, arXiv:2410.17379 (2024)

  32. [40]

    J. W. Iverson, D. G. Mixon, Doubly transitive lines I: Higman pairs and roux, J. Combin. Theory A 185 (2022) 105540

  33. [41]

    J. W. Iverson, D. G. Mixon, Doubly transitive lines II: Almost simple symmetries, Alg. Combin. 7 (2024) 37–76

  34. [42]

    E. J. King, D. G. Mixon, S. Waldron, Testing isomorphism between tuples of subspaces, arXiv:2105.03448 (2021)

  35. [43]

    G. S. Kopp, SIC-POVMs and the Stark conjectures, Int. Math. Res. Not. (2018) rnz153

  36. [44]

    D. G. Mixon, D. Packer, Max filtering with reflection groups, Adv. Comput. Math. 49 (2023) 82

  37. [45]

    D. G. Mixon, Y. Qaddura, Injectivity, stability, and positive definiteness of max filtering, arXiv:2212.11156 (2022)

  38. [46]

    D. G. Mixon, Y. Qaddura, Stable Coorbit Embeddings of Orbifold Quotients, arXiv:2403.14042 (2024)

  39. [47]

    Y. Rong, Y. Wang, Z. Xu, Almost everywhere injectivity conditions for the matrix recovery problem, Appl. Comput. Harmon. Anal. 50 (2021) 386–400

  40. [48]

    Sverdlov, Y

    T. Sverdlov, Y. Davidson, N. Dym, T. Amir, FSW-GNN: A Bi-Lipschitz WL-Equivalent Graph Neural Network, arXiv:2410.09118 (2024)

  41. [49]

    Sverdlov, I

    Y. Sverdlov, I. Springer, N. Dym, Revisiting Multi-Permutation Equivariance through the Lens of Irreducible Representations, arXiv:2410.06665 (2024)

  42. [50]

    R. Vale, S. Waldron, The symmetry group of a finite frame, Linear Algebra Appl. 433 (2010) 248–262

  43. [51]

    R. Vale, S. Waldron, Tight frames and their symmetries, Constr. Approx. 21 (2004) 83–112

  44. [52]

    Villar, D

    S. Villar, D. W. Hogg, K. Storey-Fisher, W. Yao, B. Blum-Smith, Scalars are universal: Equivariant machine learning, structured like classical physics, NeurIPS 34 (2021) 28848–28863

  45. [53]

    Villar, W

    S. Villar, W. Yao, D. W. Hogg, B. Blum-Smith, B. Dumitrascu, Dimensionless machine learning: Imposing exact units equivariance, J. Mach. Learn. Res. 24 (2023) 1–32

  46. [54]

    S. F. D. Waldron, An introduction to finite tight frames, Birkh¨ auser, 2018

  47. [55]

    Y. Wang, Z. Xu, Generalized phase retrieval: Measurement number, matrix recovery and beyond, Appl. Comput. Harmon. Anal. 47 (2019) 423–446

  48. [56]

    Weyl, Symmetry, Princeton U

    H. Weyl, Symmetry, Princeton U. Press, 1952

  49. [57]

    L. Yin, A. Little, M. Hirn, Bispectrum Unbiasing for Dilation-Invariant Multi-reference Alignment, arXiv:2402.14276 (2024)

  50. [58]

    Zhang, O

    A. Zhang, O. Mickelin, J. Kileel, E. J. Verbeke, N. F. Marshall, M. A. Gilles, A. Singer, Moment-based metrics for molecules computable from cryogenic electron microscopy images, Biol. Imag. 4 (2024) e3. 14

Pith tools

Reviewed August 12, 2026 · model on record in the stance chip above.