pith. sign in

arxiv: 2606.27008 · v1 · pith:YZKTO62Pnew · submitted 2026-06-25 · 🧮 math.FA

Plancherel Identities for unbounded subsets of mathbb R^d

Pith reviewed 2026-06-26 02:26 UTC · model grok-4.3

classification 🧮 math.FA
keywords Plancherel identityFourier transformunbounded subsetsR^dlattice invarianceisometric isomorphismharmonic analysis
0
0 comments X

The pith

Pairs of subsets of R^d invariant under translations by dual full-rank lattices have their restricted Fourier transform as an isometric isomorphism.

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

The paper introduces a class of pairs of unbounded subsets in R^d, each invariant under translations by a pair of dual full-rank lattices. For these pairs the Fourier transform restricts to an isometric isomorphism between the L2 spaces supported on each subset. This yields a Plancherel identity equating the L2 norm of a function on one subset to the L2 norm of its Fourier transform on the other. The construction extends the classical Plancherel theorem from the full space to certain proper unbounded subsets. The lattice-invariance condition supplies the structure that makes the restriction isometric.

Core claim

We present a class of pairs of subsets of R^d for which the Fourier transform, when restricted to these subsets, is an isometric isomorphism, and thus the Plancherel identity is satisfied. The sets are invariant under translations by dual full-rank lattices.

What carries the argument

Invariance of the subsets under translations by dual full-rank lattices, which supplies the structural condition enabling the restricted Fourier transform to act as an isometric isomorphism.

If this is right

  • The Plancherel identity holds exactly for functions whose support lies in one member of such a pair.
  • The Fourier transform maps the L2 space on the first subset isometrically onto the L2 space on the second.
  • The subsets may be unbounded while still satisfying the identity.
  • The result applies in every dimension d.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same lattice-invariance condition might be used to produce spectral sets or orthonormal bases supported on the subsets.
  • The construction could be tested numerically in low dimensions by taking explicit lattices and checking norm preservation on sample functions.
  • Analogous statements may hold for other integral transforms that interact with lattice translations.

Load-bearing premise

Invariance under translations by dual full-rank lattices is sufficient for the restricted Fourier transform to be an isometric isomorphism.

What would settle it

An explicit pair of dual-lattice-invariant subsets together with a square-integrable function on one whose L2 norm differs from the L2 norm of its Fourier transform on the other would falsify the claim.

Figures

Figures reproduced from arXiv: 2606.27008 by Dorin Ervin Dutkay, Piyali Chakraborty.

Figure 1
Figure 1. Figure 1: The nonperiodic set Ω = (0, 1)2 + Γ [PITH_FULL_IMAGE:figures/full_fig_p014_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: The set FB +AZ 2 together with the lattice BZ 2 shown by the intersection points of the thin grey lines. The highlighted parallelogram is the fundamental domain FB. The dots represent the lattice AZ 2 [PITH_FULL_IMAGE:figures/full_fig_p018_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: The translates (AT ) −1 h − 1 2 , 1 2 i2 +(BT ) −1Z 2 . The thin grey lines represent the lattice (AT ) −1Z 2 . The dots represent the lattice (BT ) −1Z 2 . Lemma 5.5. The following statements are equivalent: (i) (BT ) −1Z d ⊆ (AT ) −1Z d . (ii) B−1A has integer entries. (iii) A = BM for some integer d × d matrix M. (iv) The lattice AZ d is contained in the lattice BZ d . In this case a fundamental domain … view at source ↗
Figure 4
Figure 4. Figure 4: R =  1 1 −1 1 , D = { 0 0  , 1 0  }, Γ = Z 2 , Γ =˜ R(Z 2 ) [PITH_FULL_IMAGE:figures/full_fig_p021_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: R =  1 −2 2 1  , D = { 0 0  , 1 0  , 2 0  , 3 0  , 4 0  }, Γ = Z × 2Z, Γ =˜ R(Z × 2Z) [PITH_FULL_IMAGE:figures/full_fig_p022_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: R =  2 1 0 2 , D = { 0 0  , 3 0  , 0 1  , 3 1  }, Γ = 3Z × Z, Γ =˜ R(3Z × Z) References [CD26] Piyali Chakraborty and Dorin Dutkay. Some Plancherel identities for unbounded subsets of R in duality. Journal of Mathematical Sciences, 2026. [CM99] Ethan M. Coven and Aaron Meyerowitz. Tiling the integers with translates of one finite set. J. Algebra, 212(1):161–174, 1999. [FMM06] Bálint Farkas, Máté Mato… view at source ↗
read the original abstract

We present a class of pairs of subsets of $\mathbb R^d$ for which the Fourier transform, when restricted to these subsets, is an isometric isomorphism, and thus the Plancherel identity is satisfied. The sets are invariant under translations by dual full-rank lattices.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 0 minor

Summary. The manuscript asserts the existence of a class of pairs of unbounded subsets of R^d, invariant under translations by dual full-rank lattices, such that the Fourier transform restricted to these subsets forms an isometric isomorphism and thus satisfies the Plancherel identity.

Significance. If the claimed construction and isometry were established with explicit examples and proofs, the result would extend Plancherel theory to new families of unbounded lattice-symmetric domains, potentially relevant to harmonic analysis on periodic structures or sampling on irregular sets.

major comments (1)
  1. [Abstract] Abstract: the abstract asserts the existence of such pairs and the isometric property but supplies no derivation, explicit construction, or verification; the central claim cannot be assessed from available text.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for reviewing our manuscript. We respond to the single major comment below.

read point-by-point responses
  1. Referee: [Abstract] Abstract: the abstract asserts the existence of such pairs and the isometric property but supplies no derivation, explicit construction, or verification; the central claim cannot be assessed from available text.

    Authors: Abstracts are designed to state the main result concisely; derivations, constructions, and verifications appear in the body of the manuscript. The full text defines an explicit class of dual-lattice-invariant subset pairs in R^d and proves that the restricted Fourier transform is an isometric isomorphism, thereby establishing the Plancherel identity on those sets. If the referee had access only to the abstract, the complete arXiv manuscript supplies the requested details. revision: no

Circularity Check

0 steps flagged

No significant circularity; result is a structural existence claim

full rationale

The paper claims existence of lattice-invariant unbounded subsets of R^d on which the restricted Fourier transform is an isometric isomorphism. The abstract and provided description present this as a new class defined by the invariance condition under dual full-rank lattices, without any fitted parameters, self-referential predictions, or load-bearing self-citations that reduce the claim to its inputs by construction. No equations are shown that equate a derived quantity to a fitted input, and the central result is not renamed from a known pattern or smuggled via prior ansatz. The derivation chain is therefore self-contained against external benchmarks and does not exhibit any of the enumerated circularity patterns.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

No information available from the abstract to identify free parameters, axioms, or invented entities; the result is stated at the level of existence of a class.

pith-pipeline@v0.9.1-grok · 5556 in / 1086 out tokens · 55547 ms · 2026-06-26T02:26:16.930656+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

78 extracted references · 58 canonical work pages

  1. [1]

    2024 , eprint=

    Orthogonal Fourier Analysis on Domains , author=. 2024 , eprint=

  2. [2]

    , TITLE =

    Sands, Arthur D. , TITLE =. Acta Math. Acad. Sci. Hungar. , FJOURNAL =. 1957 , PAGES =. doi:10.1007/BF02025232 , URL =

  3. [3]

    2010 , eprint=

    Tilings by translation , author=. 2010 , eprint=

  4. [4]

    and Wang, Yang , TITLE =

    Lagarias, Jeffrey C. and Wang, Yang , TITLE =. J. Fourier Anal. Appl. , FJOURNAL =. 1997 , NUMBER =. doi:10.1007/s00041-001-4051-2 , URL =

  5. [5]

    and Meyerowitz, Aaron , TITLE =

    Coven, Ethan M. and Meyerowitz, Aaron , TITLE =. J. Algebra , FJOURNAL =. 1999 , NUMBER =. doi:10.1006/jabr.1998.7628 , URL =

  6. [6]

    , TITLE =

    Tijdeman, R. , TITLE =. Number theory (. 1995 , ISBN =. doi:10.1017/CBO9780511661990.016 , URL =

  7. [7]

    , TITLE =

    Newman, Donald J. , TITLE =. J. Number Theory , FJOURNAL =. 1977 , NUMBER =. doi:10.1016/0022-314X(77)90054-3 , URL =

  8. [8]

    Fuglede, Bent , TITLE =. J. Functional Analysis , FJOURNAL =. 1974 , PAGES =. doi:10.1016/0022-1236(74)90072-x , URL =

  9. [9]

    1960 , PAGES =

    Fuglede, Bent , TITLE =. 1960 , PAGES =

  10. [10]

    Li, Qian and Zhang, Min-Min , TITLE =. Rev. Un. Mat. Argentina , FJOURNAL =. 2024 , NUMBER =

  11. [11]

    Cao, Yong-Shen and Deng, Qi-Rong and Li, Ming-Tian and Wu, Sha , TITLE =. Bull. Malays. Math. Sci. Soc. , FJOURNAL =. 2024 , NUMBER =. doi:10.1007/s40840-024-01720-5 , URL =

  12. [12]

    Li, Wenxia and Miao, Jun Jie and Wang, Zhiqiang , TITLE =. J. Funct. Anal. , FJOURNAL =. 2024 , NUMBER =. doi:10.1016/j.jfa.2024.110539 , URL =

  13. [13]

    Li, Wenxia and Wang, Zhiqiang , TITLE =. J. Fourier Anal. Appl. , FJOURNAL =. 2024 , NUMBER =. doi:10.1007/s00041-024-10094-y , URL =

  14. [14]

    Chaos Solitons Fractals , FJOURNAL =

    Liu, Zong-Sheng , TITLE =. Chaos Solitons Fractals , FJOURNAL =. 2024 , PAGES =. doi:10.1016/j.chaos.2024.114926 , URL =

  15. [15]

    Yin, Fengli and Zhang, Minmin , TITLE =. J. Anhui Univ. Nat. Sci. , FJOURNAL =. 2024 , NUMBER =

  16. [16]

    Forum Math

    Wang, Cong and Yin, Feng-Li and Zhang, Min-Min , TITLE =. Forum Math. , FJOURNAL =. 2024 , NUMBER =. doi:10.1515/forum-2023-0114 , URL =

  17. [17]

    1967 , PAGES =

    Maurin, Krzysztof , TITLE =. 1967 , PAGES =

  18. [18]

    Nonlinearity , FJOURNAL =

    Li, Wenxia and Miao, Jun Jie and Wang, Zhiqiang , TITLE =. Nonlinearity , FJOURNAL =. 2024 , NUMBER =. doi:10.1088/1361-6544/ad0d70 , URL =

  19. [19]

    Dutkay, Dorin Ervin and Jorgensen, Palle E. T. , TITLE =. Sampl. Theory Signal Process. Data Anal. , FJOURNAL =. 2023 , NUMBER =. doi:10.1007/s43670-023-00072-8 , URL =

  20. [20]

    Dutkay, Dorin Ervin and Jorgensen, Palle E. T. , TITLE =. Proc. Amer. Math. Soc. , FJOURNAL =. 2015 , NUMBER =. doi:10.1090/S0002-9939-2015-12656-1 , URL =

  21. [21]

    2025 , eprint=

    Commuting self-adjoint extensions of the partial differential operators on disconnected sets , author=. 2025 , eprint=

  22. [22]

    Journal of Mathematical Sciences , author=

    Some. Journal of Mathematical Sciences , author=. 2026 , eprint=

  23. [23]

    and Wang, Yang , TITLE =

    Lagarias, Jeffrey C. and Wang, Yang , TITLE =. Invent. Math. , FJOURNAL =. 1996 , NUMBER =. doi:10.1007/s002220050056 , URL =

  24. [24]

    Jorgensen , keywords =

    Piyali Chakraborty and Dorin Ervin Dutkay and Palle E.T. Jorgensen , keywords =. Fuglede’s conjecture, differential operators and unitary groups of local translations , journal =. 2025 , issn =. doi:https://doi.org/10.1016/j.exmath.2025.125662 , url =

  25. [25]

    Jorgensen, Palle E. T. and Pedersen, Steen and Tian, Feng , TITLE =. Complex Anal. Oper. Theory , FJOURNAL =. 2013 , NUMBER =. doi:10.1007/s11785-012-0234-x , URL =

  26. [26]

    Jorgensen, Palle and Pedersen, Steen and Tian, Feng , TITLE =. J. Math. Phys. , FJOURNAL =. 2012 , NUMBER =. doi:10.1063/1.4709770 , URL =

  27. [27]

    Dutkay, Dorin Ervin and Jorgensen, Palle E. T. , TITLE =. J. Funct. Anal. , FJOURNAL =. 2015 , NUMBER =. doi:10.1016/j.jfa.2015.01.018 , URL =

  28. [28]

    Dutkay, Dorin Ervin and Jorgensen, Palle E. T. , TITLE =. Rocky Mountain J. Math. , FJOURNAL =. 2013 , NUMBER =. doi:10.1216/RMJ-2013-43-5-1497 , URL =

  29. [29]

    Dutkay, Dorin Ervin and Jorgensen, Palle E. T. , TITLE =. J. Fourier Anal. Appl. , FJOURNAL =. 2013 , NUMBER =. doi:10.1007/s00041-013-9264-7 , URL =

  30. [30]

    Dutkay, Dorin Ervin and Han, Deguang and Jorgensen, Palle E. T. and Picioroaga, Gabriel , TITLE =. Adv. Math. , FJOURNAL =. 2013 , PAGES =. doi:10.1016/j.aim.2013.02.016 , URL =

  31. [31]

    Dutkay, Dorin Ervin and Jorgensen, Palle E. T. , TITLE =. Math. Comp. , FJOURNAL =. 2012 , NUMBER =. doi:10.1090/S0025-5718-2012-02589-0 , URL =

  32. [32]

    Dutkay, Dorin Ervin and Jorgensen, Palle E. T. , TITLE =. Math. Comp. , FJOURNAL =. 2012 , NUMBER =. doi:10.1090/S0025-5718-2012-02580-4 , URL =

  33. [33]

    Dutkay, Dorin Ervin and Han, Deguang and Jorgensen, Palle E. T. , TITLE =. J. Funct. Anal. , FJOURNAL =. 2009 , NUMBER =. doi:10.1016/j.jfa.2009.05.014 , URL =

  34. [34]

    Dutkay, Dorin Ervin and Jorgensen, Palle E. T. , TITLE =. Radon transforms, geometry, and wavelets , SERIES =. 2008 , MRCLASS =. doi:10.1090/conm/464/09077 , URL =

  35. [35]

    Dutkay, Dorin Ervin and Jorgensen, Palle E. T. , TITLE =. J. Funct. Anal. , FJOURNAL =. 2007 , NUMBER =. doi:10.1016/j.jfa.2007.03.002 , URL =

  36. [36]

    Dutkay, Dorin Ervin and Jorgensen, Palle E. T. , TITLE =. Math. Z. , FJOURNAL =. 2007 , NUMBER =. doi:10.1007/s00209-007-0104-9 , URL =

  37. [37]

    Jorgensen, Palle E. T. , TITLE =. 2018 , PAGES =. doi:10.1090/cbms/128 , URL =

  38. [38]

    Tao, Terence , TITLE =. Math. Res. Lett. , FJOURNAL =. 2004 , NUMBER =. doi:10.4310/MRL.2004.v11.n2.a8 , URL =

  39. [39]

    Jorgensen, Palle E. T. , TITLE =. Adv. in Math. , FJOURNAL =. 1982 , NUMBER =. doi:10.1016/0001-8708(82)90001-9 , URL =

  40. [40]

    Pedersen, Steen , TITLE =. J. Funct. Anal. , FJOURNAL =. 1987 , NUMBER =. doi:10.1016/0022-1236(87)90061-9 , URL =

  41. [41]

    Jorgensen, Palle and Pedersen, Steen and Tian, Feng , TITLE =. Trans. Amer. Math. Soc. , FJOURNAL =. 2015 , NUMBER =. doi:10.1090/S0002-9947-2014-06296-X , URL =

  42. [42]

    Jorgensen, Palle E. T. and Pedersen, Steen , TITLE =. J. Fourier Anal. Appl. , FJOURNAL =. 1999 , NUMBER =. doi:10.1007/BF01259371 , URL =

  43. [43]

    1980 , PAGES =

    Reed, Michael and Simon, Barry , TITLE =. 1980 , PAGES =

  44. [44]

    , TITLE =

    Conway, John B. , TITLE =. 1990 , PAGES =

  45. [45]

    Maurin, Krzysztof , TITLE =. Math. Scand. , FJOURNAL =. 1961 , PAGES =. doi:10.7146/math.scand.a-10641 , URL =

  46. [46]

    von Neumann, John , TITLE =. Ann. of Math. (2) , FJOURNAL =. 1949 , PAGES =. doi:10.2307/1969463 , URL =

  47. [47]

    and Fournier, John J

    Adams, Robert A. and Fournier, John J. F. , TITLE =. 2003 , PAGES =

  48. [48]

    Jorgensen, Palle E. T. and Pedersen, Steen , TITLE =. J. Anal. Math. , FJOURNAL =. 1998 , PAGES =. doi:10.1007/BF02788699 , URL =

  49. [49]

    Jorgensen, Palle E. T. and Pedersen, Steen , TITLE =. Electron. Res. Announc. Amer. Math. Soc. , FJOURNAL =. 1998 , PAGES =. doi:10.1090/S1079-6762-98-00044-4 , URL =

  50. [50]

    Jorgensen, Palle E. T. and Pedersen, Steen , TITLE =. Exposition. Math. , FJOURNAL =. 1993 , NUMBER =

  51. [51]

    Jorgensen, Palle E. T. and Pedersen, Steen , TITLE =. J. Funct. Anal. , FJOURNAL =. 1992 , NUMBER =. doi:10.1016/0022-1236(92)90101-N , URL =

  52. [52]

    Jorgensen, Palle E. T. and Pedersen, Steen , TITLE =. C. R. Acad. Sci. Paris S\'. 1991 , NUMBER =

  53. [53]

    Etkind, Mark Mordechai and Lev, Nir , TITLE =. Proc. Lond. Math. Soc. (3) , FJOURNAL =. 2023 , NUMBER =

  54. [54]

    , TITLE =

    Dunford, Nelson and Schwartz, Jacob T. , TITLE =. 1988 , PAGES =

  55. [55]

    Functional

    Nelson, Edward , TITLE =. Functional. 1970 , MRCLASS =

  56. [56]

    1969 , PAGES =

    Nelson, Edward , TITLE =. 1969 , PAGES =

  57. [57]

    , TITLE =

    Mackey, George W. , TITLE =. Math. Ann. , FJOURNAL =. 1961/62 , PAGES =. doi:10.1007/BF01452360 , URL =

  58. [58]

    , TITLE =

    Mackey, George W. , TITLE =. Proc. 1961 , MRCLASS =

  59. [59]

    Jorgensen, Palle E. T. , TITLE =. Internat. J. Math. , FJOURNAL =. 1991 , NUMBER =. doi:10.1142/S0129167X91000168 , URL =

  60. [60]

    , TITLE =

    J rgensen, Palle T. , TITLE =. Bull. Amer. Math. Soc. , FJOURNAL =. 1976 , NUMBER =. doi:10.1090/S0002-9904-1976-14217-6 , URL =

  61. [61]

    Farkas, B\'. On. J. Fourier Anal. Appl. , FJOURNAL =. 2006 , NUMBER =. doi:10.1007/s00041-005-5069-7 , URL =

  62. [62]

    Lev, Nir , TITLE =. Rev. Mat. Iberoam. , FJOURNAL =. 2022 , NUMBER =. doi:10.4171/RMI/1318 , URL =

  63. [63]

    Lev, Nir and Matolcsi, M\'. The. Acta Math. , FJOURNAL =. 2022 , NUMBER =. doi:10.4310/acta.2022.v228.n2.a3 , URL =

  64. [64]

    Extended abstracts fall 2019---spaces of analytic functions: approximation, interpolation, sampling , SERIES =

    Debernardi, Alberto and Lev, Nir , TITLE =. Extended abstracts fall 2019---spaces of analytic functions: approximation, interpolation, sampling , SERIES =. [2021] 2021 , MRCLASS =. doi:10.1007/978-3-030-74417-5\_11 , URL =

  65. [65]

    Greenfeld, Rachel and Lev, Nir , TITLE =. J. Anal. Math. , FJOURNAL =. 2020 , NUMBER =. doi:10.1007/s11854-020-0092-9 , URL =

  66. [66]

    Lev, Nir and Olevskii, Alexander , TITLE =. Adv. Math. , FJOURNAL =. 2017 , PAGES =. doi:10.1016/j.aim.2017.05.015 , URL =

  67. [67]

    and Lev, Nir , TITLE =

    Kolountzakis, Mihail N. and Lev, Nir , TITLE =. Int. Math. Res. Not. IMRN , FJOURNAL =. 2016 , NUMBER =. doi:10.1093/imrn/rnv283 , URL =

  68. [68]

    Iosevich, Alex and Mayeli, Azita and Pakianathan, Jonathan , TITLE =. Anal. PDE , FJOURNAL =. 2017 , NUMBER =. doi:10.2140/apde.2017.10.757 , URL =

  69. [69]

    , TITLE =

    Iosevich, Alex and Kolountzakis, Mihal N. , TITLE =. Anal. PDE , FJOURNAL =. 2013 , NUMBER =. doi:10.2140/apde.2013.6.819 , URL =

  70. [70]

    Iosevich, Alex and Rudnev, Mischa , TITLE =. Int. Math. Res. Not. , FJOURNAL =. 2003 , NUMBER =. doi:10.1155/S1073792803208126 , URL =

  71. [71]

    , TITLE =

    Evans, Lawrence C. , TITLE =. 2010 , PAGES =. doi:10.1090/gsm/019 , URL =

  72. [72]

    and Lions, J

    Deny, J. and Lions, J. L. , TITLE =. Ann. Inst. Fourier (Grenoble) , FJOURNAL =. 1945 , PAGES =

  73. [73]

    Iosevich, Alex and Katz, Nets and Pedersen, Steen , TITLE =. Math. Res. Lett. , FJOURNAL =. 1999 , NUMBER =. doi:10.4310/MRL.1999.v6.n2.a13 , URL =

  74. [74]

    and Jorgensen, Palle E

    Herr, John E. and Jorgensen, Palle E. T. and Weber, Eric S. , TITLE =. From classical analysis to analysis on fractals. [2023] 2023 , MRCLASS =. doi:10.1007/978-3-031-37800-3\_9 , URL =

  75. [75]

    and Jorgensen, Palle E

    Herr, John E. and Jorgensen, Palle E. T. and Weber, Eric S. , TITLE =. Analysis, probability and mathematical physics on fractals , SERIES =. [2020] 2020 , MRCLASS =

  76. [76]

    and Jorgensen, Palle E

    Herr, John E. and Jorgensen, Palle E. T. and Weber, Eric S. , TITLE =. J. Anal. Math. , FJOURNAL =. 2019 , NUMBER =. doi:10.1007/s11854-019-0026-6 , URL =

  77. [77]

    and Jorgensen, Palle E

    Herr, John E. and Jorgensen, Palle E. T. and Weber, Eric S. , TITLE =. Linear Algebra Appl. , FJOURNAL =. 2019 , PAGES =. doi:10.1016/j.laa.2018.02.023 , URL =

  78. [78]

    and Jorgensen, Palle E

    Herr, John E. and Jorgensen, Palle E. T. and Weber, Eric S. , TITLE =. Frames and harmonic analysis , SERIES =. [2018] 2018 , MRCLASS =. doi:10.1090/conm/706/14211 , URL =