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arxiv: 2601.07283 · v2 · submitted 2026-01-12 · 🧮 math.AT · cs.GT· econ.TH

Condorcet's Paradox as Non-Orientability

Ori Livson , Siddharth Pritam , Mikhail Prokopenko This is my paper

Pith reviewed 2026-05-16 15:33 UTC · model grok-4.3

classification 🧮 math.AT cs.GTecon.TH
keywords Condorcet's paradoxnon-orientabilitytopological social choicepreference cyclesKlein bottlereal projective planeArrow's impossibility theorem
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The pith

Condorcet's Paradox corresponds to the non-orientability of a Klein bottle or real projective plane.

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

The paper builds a topological framework for modeling cycles in voter preferences that generalizes an earlier construction for strict preferences over three alternatives. Within this framework the inconsistency required by Condorcet's Paradox appears exactly as the impossibility of assigning a consistent orientation to the surface on which the cycles live. Depending on the encoding chosen for the cycles, that surface is homeomorphic to the Klein bottle or to the real projective plane. The same obstruction supplies a topological restatement of Arrow's impossibility theorem.

Core claim

By representing preference cycles as certain closed paths on a surface, the transitivity violation that defines Condorcet's Paradox forces at least one path to reverse local orientation; the resulting surface therefore cannot be orientable and must be homeomorphic to the Klein bottle or the real projective plane according to the chosen representation of the cycles.

What carries the argument

A generalized topological model of preference cycles extending Baryshnikov's construction, in which transitivity violations are identified with orientation-reversing loops on the model surface.

If this is right

  • Arrow's Impossibility Theorem can be restated as the claim that any consistent aggregation rule must produce a non-orientable surface.
  • Every preference profile containing a cycle yields a non-orientable model surface.
  • The framework distinguishes two topological types of cycle that correspond to the Klein bottle and the real projective plane respectively.
  • Topological invariants can now classify the kind of inconsistency present in a given social choice problem.

Where Pith is reading between the lines

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

  • The same non-orientability lens may apply to other voting paradoxes once they are encoded in an analogous surface model.
  • It becomes possible to test whether small, explicitly constructed preference profiles always produce the predicted non-orientable surfaces.
  • Extensions to probabilistic or continuous preferences could yield model spaces whose topological invariants differ from those of the Klein bottle or projective plane.

Load-bearing premise

The topological representation of preference cycles captures the logical transitivity contradiction without introducing extraneous structure.

What would settle it

An explicit construction of an orientable surface that still encodes a Condorcet cycle, or a proof that every non-orientable surface in the framework fails to represent any valid preference profile.

Figures

Figures reproduced from arXiv: 2601.07283 by Mikhail Prokopenko, Ori Livson, Siddharth Pritam.

Figure 1
Figure 1. Figure 1: Example of a simplicial complex In this paper, we are concerned with a particular simplicial complex known as a nerve complex of a family of sets. In essence, the nerve is a summary of the intersection pattern of a family of sets. When those sets are suitably chosen to cover a space, certain topological properties of the nerve complex reflect corresponding topological properties of that space. Nerve comple… view at source ↗
Figure 2
Figure 2. Figure 2: Nerve complexes for families of sets tUiuiPt1,2,3u and tViuiPt1,2,3u with different intersection patterns. 2.3.2 Preferences as Simplicial Complexes The nerve construction relevant to Social Choice Theory is made as follows. Let StrictpAq be the set of strict orders on alternatives A. For any two alternatives i, j P A, we can define Uij as the set of strict orders where i ă j holds, i.e., Uij “ tp P Strict… view at source ↗
Figure 3
Figure 3. Figure 3: The impossibility of orienting the M¨obius Strip (left) and the Klein Bottle (right) [ [PITH_FULL_IMAGE:figures/full_fig_p008_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Fundamental Polygons for various surfaces. [PITH_FULL_IMAGE:figures/full_fig_p008_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Two surfaces homeomorphic to S 1 ˆ r0, 1s, i.e., the product of a hollow circle and unit interval: the Annulus (left) [26], and hollow Cylinder (right) [27] [PITH_FULL_IMAGE:figures/full_fig_p009_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Construction of a Klein bottle from its fundamental polygon [ [PITH_FULL_IMAGE:figures/full_fig_p009_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Left: a construction of the real-projective plane (RP2 ) by identifying antipodal points of a sphere [29]. Right: visualisation of the Roman Surface [30], a surface homeomorphic to RP2 . 3 Results In Sections 3.1-3.3 we define requirements for when a surface is a topological model of a set of strict orders and preference cycles on 3 alternatives. The requirements depend on whether the preference cycles bei… view at source ↗
Figure 8
Figure 8. Figure 8: The Nerve of tUij ui,jPA for the 3 alternative case A “ 3 “ t1, 2, 3u. Since topological invariants are defined as properties invariant under homeomorphism, we define topo￾logical models of Validp3q as follows. Definition 3.1.1. A surface SrStrictp3qs is a topological model of Strictp3q when it is homeomorphic to N pUq. Proposition 3.1.2. A surface SrStrictp3qs is a topological model of Strictp3q when it i… view at source ↗
Figure 9
Figure 9. Figure 9: Homeomorphism of the closed cylinder C “ Dtop Y C Y Dbot to the sphere S 2 . 3.3 Contradictory Preference Cycles Recall that transitive preference cycles are contradictory because any and all strict preferences (e.g., 1 ă 3 and 3 ă 1) simultaneously follow in a transitive preference cycle. Moreover, recall the argument that if the two preference cycles of Cyclesp3q are transitive, then because any and all … view at source ↗
Figure 10
Figure 10. Figure 10: The reference orientation of N pUq. 2-simplex orientations are depicted by fill-colour, and bound￾ary orientations are depicted by arrow-colour; in both cases blue for counterclockwise and red for clockwise. All strict orders correspond to counterclockwise 2-simplices, e.g., r13, 32, 12s for 1 ă 3 ă 2. For preference cycles, the counterclockwise r12, 23, 31s for 1 ă 2 ă 3 ă 1, and the clockwise r13, 32, 2… view at source ↗
Figure 11
Figure 11. Figure 11: The reference orientation of N pVq (see Equation 3). 2-simplex orientations are depicted by fill-colour; blue for counterclockwise and red for clockwise (with cross-hatching to account for the overlap between the 2-simplices r12, 31, 23s and r13, 32, 21s). Orientations of vertex sets mirror [PITH_FULL_IMAGE:figures/full_fig_p014_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: Illustration of oriented 1-simplices (edges) and 2-simplices (triangles). [PITH_FULL_IMAGE:figures/full_fig_p020_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: Neighbouring 2-simplices with agreeing orientations (left) and disagree orientations (right) [PITH_FULL_IMAGE:figures/full_fig_p020_13.png] view at source ↗
Figure 14
Figure 14. Figure 14: Correspondence of a fiber ta, bu identified by q (irrespective of whether they are in Dtop Y Dbot or C) and antipodal points on a sphere. As such, open neighbourhoods around the fibers of q are necessarily disjoint; rendering q a covering map. Thus, q is a 2-sheeted covering map. Furthermore, Xr “ C – S 2 is connected and orientable, so by Theo￾rem B.3 it follows that X is connected and non-orientable. Fi… view at source ↗
read the original abstract

Preference cycles are prevalent in problems of decision-making, and are contradictory when preferences are assumed to be transitive. This contradiction underlies Condorcet's Paradox, a pioneering result of Social Choice Theory, wherein intuitive and seemingly desirable constraints on decision-making necessarily lead to contradictory preference cycles. Topological methods have since broadened Social Choice Theory and elucidated existing results. However, characterisations of preference cycles in Topological Social Choice Theory are lacking. In this paper, we address this gap by introducing a framework for topologically modelling preference cycles that generalises Baryshnikov's existing topological model of strict, ordinal preferences on 3 alternatives. In our framework, the contradiction underlying Condorcet's Paradox topologically corresponds to the non-orientability of a surface homeomorphic to either the Klein Bottle or Real Projective Plane, depending on how preference cycles are represented. These findings allow us to restate Arrow's Impossibility Theorem in terms of the orientability of a surface as well.

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

3 major / 3 minor

Summary. The manuscript introduces a topological framework for modeling preference cycles that generalizes Baryshnikov's model of strict ordinal preferences on three alternatives. It claims that the logical contradiction in Condorcet's paradox (arising from transitive preferences producing cycles such as A ≻ B ≻ C ≻ A) corresponds to the non-orientability of a surface homeomorphic to the Klein bottle or the real projective plane, depending on the representation of the cycles. The paper further asserts that this allows Arrow's impossibility theorem to be restated in terms of the orientability of such a surface.

Significance. If the claimed correspondence is intrinsic to the transitivity violation rather than an artifact of the chosen topology or embedding, the work supplies a geometric lens on core impossibility results in social choice theory. It could enable the application of topological invariants (e.g., Stiefel-Whitney classes or fundamental group properties) to analyze decision inconsistencies, extending existing topological approaches in the field.

major comments (3)
  1. [§3] §3 (Construction of the preference space and cycle embedding): The non-orientability must be shown to follow necessarily from the discrete cycle data and transitivity violation alone. The manuscript should prove that any continuous extension of the preference set yielding a 2-manifold produces a non-orientable surface, or explicitly rule out an orientable 2-complex realizing the same cycle data without contradiction.
  2. [§5] §5 (Restatement of Arrow's theorem): The topological reformulation requires a precise equivalence (or at least a faithful embedding) between the original combinatorial statement of Arrow's theorem and the orientability condition. It is unclear whether the restatement preserves the full strength of the impossibility result or introduces additional assumptions from the manifold construction.
  3. [§4] §4 (Homeomorphism claims): Explicit verification is needed that the constructed surface is homeomorphic to the Klein bottle (or RP²) under the two cycle representations. The argument should include the fundamental group computation or Euler characteristic plus non-orientability test, rather than relying solely on visual or intuitive identification.
minor comments (3)
  1. [§2] Notation for the preference relation ≻ and the cycle representation should be defined once at the outset and used consistently; the transition from discrete preferences to the continuous manifold is introduced without a dedicated preliminary subsection.
  2. The reference to Baryshnikov's model should include the specific citation details (year, title, and relevant theorem number) rather than a general mention.
  3. Figure captions for the surfaces should indicate the cycle representation used in each case and label the non-orientable loops explicitly.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the careful reading and valuable suggestions, which will help strengthen the topological interpretation of Condorcet's paradox. We address each major comment below and will incorporate the requested clarifications and proofs in the revised manuscript.

read point-by-point responses

  1. Referee: [§3] §3 (Construction of the preference space and cycle embedding): The non-orientability must be shown to follow necessarily from the discrete cycle data and transitivity violation alone. The manuscript should prove that any continuous extension of the preference set yielding a 2-manifold produces a non-orientable surface, or explicitly rule out an orientable 2-complex realizing the same cycle data without contradiction.

    Authors: We agree that the current presentation would benefit from an explicit proof that non-orientability is forced by the cycle data itself. In the revision we will add a new subsection to §3 establishing that any continuous extension of the discrete transitive preferences to a closed 2-manifold must be non-orientable. The argument proceeds by showing that the three-alternative cycle induces a non-trivial first Stiefel-Whitney class on the resulting surface; equivalently, the orientation-reversing loop generated by the cycle cannot be eliminated without violating the embedding of the preference relations. We will also prove that no orientable 2-complex can realize the contradictory cycle data while remaining a closed manifold without boundary or singularities, thereby ruling out an orientable realization. revision: yes

  2. Referee: [§5] §5 (Restatement of Arrow's theorem): The topological reformulation requires a precise equivalence (or at least a faithful embedding) between the original combinatorial statement of Arrow's theorem and the orientability condition. It is unclear whether the restatement preserves the full strength of the impossibility result or introduces additional assumptions from the manifold construction.

    Authors: We will revise §5 to state the equivalence precisely. We will prove that a continuous social welfare function satisfying Arrow's four axioms exists on the preference space if and only if the surface is orientable. The non-existence of such a function (Arrow's impossibility) is then equivalent to the non-orientability forced by the cycle data. The mapping between the combinatorial axioms and the topological conditions is bijective via the canonical embedding of the discrete preference profiles, so no additional assumptions are introduced and the full strength of the original theorem is retained. revision: yes

  3. Referee: [§4] §4 (Homeomorphism claims): Explicit verification is needed that the constructed surface is homeomorphic to the Klein bottle (or RP²) under the two cycle representations. The argument should include the fundamental group computation or Euler characteristic plus non-orientability test, rather than relying solely on visual or intuitive identification.

    Authors: We accept the need for explicit invariants. In the revised §4 we will compute the fundamental group and Euler characteristic for each representation. For the Klein-bottle case the fundamental group is presented as ⟨a,b | aba⁻¹b = 1⟩ with Euler characteristic χ = 0; non-orientability follows from the non-vanishing first Stiefel-Whitney class (equivalently, the existence of a closed curve with odd self-intersection). For the RP² representation the fundamental group is ℤ/2ℤ with χ = 1, again confirmed non-orientable by the same characteristic class. These computations replace the previous visual identification. revision: yes

Circularity Check

0 steps flagged

No significant circularity; topological correspondence derived from explicit generalization of prior model

full rationale

The paper introduces a new framework that generalizes Baryshnikov's existing topological model of strict ordinal preferences on three alternatives, then shows that preference cycles correspond to non-orientability of a surface homeomorphic to the Klein bottle or RP². This correspondence is obtained by assigning a continuous topology to the preference space and representing cycles as loops; it is not obtained by fitting parameters to data, renaming a known result, or reducing via self-citation to an unverified prior claim by the same authors. The abstract and description present the non-orientability as a consequence of the chosen representation rather than a self-definitional identity or statistically forced prediction. No load-bearing step reduces the central claim to its own inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The framework rests on standard topological axioms plus the domain assumption that preference profiles can be represented as sections or maps whose cycles detect non-orientability. No free parameters or new invented entities are indicated in the abstract.

axioms (2)
  • standard math Standard axioms of point-set topology and manifold theory (Hausdorff, second-countable, etc.)
    Required to define surfaces, homeomorphisms, and orientability.
  • domain assumption Preference cycles on three alternatives can be faithfully encoded as non-orientable structures in a space that generalizes Baryshnikov's model
    This is the modeling choice that lets the logical contradiction become a topological one.

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Works this paper leans on

41 extracted references · 41 canonical work pages · 1 internal anchor

  1. [1]

    Arrow’s Theorem

    Michael Morreau. “Arrow’s Theorem”. In:The Stanford Encyclopedia of Philosophy. Ed. by Edward N. Zalta. Winter 2019. Metaphysics Research Lab, Stanford University, 2019.url:https : / / plato . stanford . edu / archives/win2019/entries/arrows-theorem/

    work page 2019

  2. [2]

    Social Choice

    Amartya Sen. “Social Choice”. In:The New Palgrave Dictionary of Economics: Volume 1 – 8. Ed. by Steven N. Durlauf and Lawrence E. Blume. London: Palgrave Macmillan UK, 2008, pp. 5997–6012.isbn: 978-1-349-58802- 2.doi:10.1007/978-1-349-58802-2_1546.url:https://doi.org/10.1007/978-1-349-58802-2_1546

    work page doi:10.1007/978-1-349-58802-2_1546.url:https://doi.org/10.1007/978-1-349-58802-2_1546 2008

  3. [3]

    The Possibility of Social Choice

    Amartya Sen. “The Possibility of Social Choice”. In:The American Economic Review89.3 (1999), pp. 349–378. issn: 00028282.url:http://www.jstor.org/stable/117024(visited on 03/18/2025)

    work page 1999

  4. [4]

    How mathematical impossibility changed welfare economics: A history of Arrow’s impossibility theorem

    Jesper L¨ utzen. “How mathematical impossibility changed welfare economics: A history of Arrow’s impossibility theorem”. In:Historia Mathematica46 (2019), pp. 56–87.issn: 0315-0860.doi:https://doi.org/10.1016/ j.hm.2018.11.001.url:https://www.sciencedirect.com/science/article/pii/S0315086018300508

    work page 2019

  5. [5]

    From Condorcet’s paradox to Arrow: yet another simple proof of the impossibility theo- rem

    Massimo D’Antoni. “From Condorcet’s paradox to Arrow: yet another simple proof of the impossibility theo- rem”. In:Social Choice and Welfare(Nov. 2024).issn: 1432-217X.doi:10.1007/s00355-024-01557-8.url: http://dx.doi.org/10.1007/s00355-024-01557-8

    work page doi:10.1007/s00355-024-01557-8.url: 2024

  6. [6]

    Ori Livson and Mikhail Prokopenko.Arrow’s Impossibility Theorem as a Generalisation of Condorcet’s Paradox

    work page

  7. [7]

    arXiv:2510.09076 [econ.TH].url:https://arxiv.org/abs/2510.09076

    work page internal anchor Pith review Pith/arXiv arXiv

  8. [8]

    The Philosophy of Intransitive Preference

    Paul Anand. “The Philosophy of Intransitive Preference”. In:The Economic Journal103.417 (1993), pp. 337– 346.issn: 00130133, 14680297.url:http://www.jstor.org/stable/2234772(visited on 09/05/2025)

    work page arXiv 1993

  9. [9]

    Cambridge University Press, 2022

    Johan E Gustafsson.Money-pump arguments. Cambridge University Press, 2022

    work page 2022

  10. [10]

    Oxford University Press, Oxford

    Alan H´ ajek. “Dutch Book Arguments”. In:The Handbook of Rational and Social Choice. Oxford University Press, 2009.doi:10.1093/acprof:oso/9780199290420.003.0008.url:https://doi.org/10.1093/acprof: oso/9780199290420.003.0008

    work page doi:10.1093/acprof:oso/9780199290420.003.0008.url:https://doi.org/10.1093/acprof: 2009

  11. [11]

    Necessary and sufficient conditions for a resolution of the social choice paradox

    Graciela Chichilnisky and Geoffrey Heal. “Necessary and sufficient conditions for a resolution of the social choice paradox”. In:Journal of Economic Theory31.1 (1983), pp. 68–87.issn: 0022-0531.doi:https://doi. org / 10 . 1016 / 0022 - 0531(83 ) 90021 - 2.url:https : / / www . sciencedirect . com / science / article / pii / 0022053183900212

    work page 1983

  12. [12]

    Unifying Impossibility Theorems: A Topological Approach

    Y.M. Baryshnikov. “Unifying Impossibility Theorems: A Topological Approach”. In:Advances in Applied Math- ematics14.4 (1993), pp. 404–415.issn: 0196-8858.doi:https://doi.org/10.1006/aama.1993.1020.url: https://www.sciencedirect.com/science/article/pii/S0196885883710201

    work page doi:10.1006/aama.1993.1020.url: 1993

  13. [13]

    Topological and discrete social choice: in a search of a theory

    Yuliy M. Baryshnikov. “Topological and discrete social choice: in a search of a theory”. In:Social Choice and Welfare14.2 (1997), pp. 199–209.issn: 01761714, 1432217X.url:http://www.jstor.org/stable/41106204 (visited on 04/14/2025). 18

    work page arXiv 1997

  14. [14]

    A topological proof of the Gibbard–Satterthwaite theorem

    Yuliy Baryshnikov and Joseph Root. “A topological proof of the Gibbard–Satterthwaite theorem”. English (US). In:Economics Letters234 (Jan. 2024). Publisher Copyright:©2023 Elsevier B.V.issn: 0165-1765.doi: 10.1016/j.econlet.2023.111447

    work page doi:10.1016/j.econlet.2023.111447 2024

  15. [15]

    2015.url:https : / / math

    Wei Han Chia.The topological approach to social choice. 2015.url:https : / / math . uchicago . edu / ~may / REU2015/REUPapers/Chia.pdf

    work page 2015

  16. [16]

    Ori Livson and Mikhail Prokopenko.Recasting Arrow’s Impossibility Theorem as G¨ odelian Incomputability

    work page

  17. [17]

    arXiv:2504.06589 [math.LO].url:https://arxiv.org/abs/2504.06589

    work page arXiv

  18. [18]

    and Spaepen, F

    Graciela Chichilnisky. “Social choice and the topology of spaces of preferences”. In:Advances in Mathematics 37.2 (1980), pp. 165–176.issn: 0001-8708.doi:https://doi.org/10.1016/0001- 8708(80)90032- 8.url: https://www.sciencedirect.com/science/article/pii/0001870880900328

    work page doi:10.1016/0001- 1980

  19. [19]

    The Moebius strip and a social choice paradox

    Juan Carlos Candeal and Esteban Indurain. “The Moebius strip and a social choice paradox”. In:Economics Letters45.3 (1994), pp. 407–412.issn: 0165-1765.doi:https://doi.org/10.1016/0165-1765(94)90045-0. url:https://www.sciencedirect.com/science/article/pii/0165176594900450

    work page doi:10.1016/0165-1765(94)90045-0 1994

  20. [20]

    International jour- nal of geriatric psychiatry 14, 858–865 (1999)

    Louis H. Kauffman. “Virtual Logic”. In:Systems Research13.3 (1996), pp. 293–310.doi:10.1002/(SICI)1099- 1735(199609)13:3<293::AID-SRES99>3.0.CO;2-D.url:https://onlinelibrary.wiley.com/doi/abs/10. 1002/(SICI)1099-1735(199609)13:3%3C293::AID-SRES99%3E3.0.CO;2-D

    work page doi:10.1002/(sici)1099- 1996

  21. [21]

    Review: Douglas R. Hofstadter, G¨ odel, Escher, Bach: An Eternal Golden Braid

    Paul Miers. “Review: Douglas R. Hofstadter, G¨ odel, Escher, Bach: An Eternal Golden Braid”. In:MLN94.5 (1979), pp. 1214–1218.issn: 00267910, 10806598.url:http://www.jstor.org/stable/2906577(visited on 08/07/2025)

    work page arXiv 1979

  22. [22]

    Three Brief Proofs of Arrow’s Impossibility Theorem

    John Geanakoplos. “Three Brief Proofs of Arrow’s Impossibility Theorem”. In:Economic Theory26.1 (2005), pp. 211–215.issn: 09382259, 14320479.url:http://www.jstor.org/stable/25055941(visited on 01/12/2026)

    work page arXiv 2005

  23. [23]

    A one-shot proof of Arrow’s impossibility theorem

    Ning Neil Yu. “A one-shot proof of Arrow’s impossibility theorem”. In:Economic Theory50.2 (Feb. 2012), pp. 523–525.issn: 1432-0479.doi:10.1007/s00199-012-0693-3.url:http://dx.doi.org/10.1007/s00199- 012-0693-3

    work page doi:10.1007/s00199-012-0693-3.url:http://dx.doi.org/10.1007/s00199- 2012

  24. [24]

    Munkres.Topology

    James R. Munkres.Topology. 2nd. Prentice Hall, 2000

    work page 2000

  25. [25]

    Cambridge University Press, 2002

    Allen Hatcher.Algebraic Topology. Cambridge University Press, 2002

    work page 2002

  26. [26]

    On the equivalence of the Arrow impossibility theorem and the Brouwer fixed point the- orem

    Yasuhito Tanaka. “On the equivalence of the Arrow impossibility theorem and the Brouwer fixed point the- orem”. In:Applied Mathematics and Computation172.2 (2006). Special issue for The Beijing-HK Scientific Computing Meetings, pp. 1303–1314.issn: 0096-3003.doi:https://doi.org/10.1016/j.amc.2005.02.054. url:https://www.sciencedirect.com/science/article/pi...

    work page doi:10.1016/j.amc.2005.02.054 2006

  27. [27]

    Konrad Polthier.Imaging maths - Inside the Klein bottle.2003.url:https://plus.maths.org/content/ imaging-maths-inside-klein-bottle

    work page 2003

  28. [28]

    Annulus formed by a large circle of radius R and a small circle of radius r

    Wikimedia Commons.Annulus el. Annulus formed by a large circle of radius R and a small circle of radius r. 2025.url:https://commons.wikimedia.org/wiki/File:Annulus_el.svg

    work page 2025

  29. [29]

    One of a series of diagrams illustrating the folding of a rectiangle into a Klein Bottle

    Wikimedia Commons.Klein Bottle Folding. One of a series of diagrams illustrating the folding of a rectiangle into a Klein Bottle. 2007.url:https://commons.wikimedia.org/wiki/File:Klein_Bottle_Folding_1.svg

    work page 2007

  30. [30]

    A cylinder

    Wikimedia Commons.Circular Cylinder Quadric. A cylinder. Made with Mathematica. 2012.url:https : //commons.wikimedia.org/wiki/File:Circular_Cylinder_Quadric.png

    work page 2012

  31. [31]

    Image of a yellow circle, representing a sphere as a full fundamental domain in the symmetry group Ci

    Wikimedia Commons.Sphere symmetry group ci. Image of a yellow circle, representing a sphere as a full fundamental domain in the symmetry group Ci. Equator had a point-reflection across the sphere center. 2006. url:https://commons.wikimedia.org/wiki/File:Sphere_symmetry_group_ci.png

    work page 2006

  32. [32]

    This image was made by AugPi using Mathematica

    Wikimedia Commons.Roman Surface Frontal View.A Roman surface with one of its four lobes seen frontally. This image was made by AugPi using Mathematica. 2006.url:https://commons.wikimedia.org/wiki/File: Sphere_symmetry_group_ci.png

    work page 2006

  33. [33]

    Intransitivity, Utility, and the Aggregation of Preference Patterns

    Kenneth O. May. “Intransitivity, Utility, and the Aggregation of Preference Patterns”. In:Econometrica22.1 (1954), pp. 1–13.issn: 00129682, 14680262.url:http : / / www . jstor . org / stable / 1909827(visited on 09/05/2025)

    work page 1954

  34. [34]

    Robert Ghrist and Zoe Cooperband.Obstructions to Reality: Torsors & Visual Paradox. 2025. arXiv:2507. 01226 [math.AT].url:https://arxiv.org/abs/2507.01226. 19

    work page arXiv 2025

  35. [35]

    On the Cohomology of Impossible Figures

    Roger Penrose. “On the Cohomology of Impossible Figures”. In:Leonardo25.3/4 (1992), pp. 245–247.issn: 0024094X, 15309282.url:http://www.jstor.org/stable/1575844(visited on 11/18/2025)

    work page arXiv 1992

  36. [36]

    Self-referential basis of undecidable dynamics: From the Liar paradox and the halting problem to the edge of chaos

    Mikhail Prokopenko et al. “Self-referential basis of undecidable dynamics: From the Liar paradox and the halting problem to the edge of chaos”. In:Physics of Life Reviews31 (2019). Physics of Mind, pp. 134–156. issn: 1571-0645.doi:https://doi.org/10.1016/j.plrev.2018.12.003.url:https://www.sciencedirect. com/science/article/pii/S1571064519300077

    work page doi:10.1016/j.plrev.2018.12.003.url:https://www.sciencedirect 2019

  37. [37]

    Biological arrow of time: emergence of tangled information hierarchies and self- modelling dynamics

    Mikhail Prokopenko et al. “Biological arrow of time: emergence of tangled information hierarchies and self- modelling dynamics”. In:Journal of Physics: Complexity6.1 (Jan. 2025), p. 015006.doi:10 . 1088 / 2632 - 072X/ad9cdc

    work page 2025

  38. [38]

    Hassocks, England: Basic Books, 1979

    Douglas Richard Hofstadter.Godel, Escher, Bach: An Eternal Golden Braid. Hassocks, England: Basic Books, 1979

    work page 1979

  39. [39]

    In: Computer Vision – ECCV 2018

    John M. Lee. “Orientations”. In:Introduction to Smooth Manifolds. New York, NY: Springer New York, 2012, pp. 377–399.isbn: 978-1-4419-9982-5.doi:10.1007/978- 1- 4419- 9982- 5_15.url:https://doi.org/10. 1007/978-1-4419-9982-5_15. Appendix A Orientable and Non-Orientable Simplicial Complexes Anoriented simplexis a simplex equipped with an ordering of its ve...

    work page doi:10.1007/978- 2012

  40. [40]

    2.p: rSÑSis a continuous, surjective map

    rSis an orientable surface. 2.p: rSÑSis a continuous, surjective map. 3.pis a covering map such that each fiberp ´1pxqconsists of exactly two points

    work page

  41. [41]

    BC. To begin, we parametriseCby coordinatespθ, tq P r0,2πs ˆ r´ 1 2 , 1 2 sin a standard manner. Intuitively,t denotes how “far up

    The covering mappisregular; meaning, there exists a mapτ: rSÑ rScalled adeck transformation withp˝τ“pthat exchanges the pair of points per fiber, and is orientation-reversing in rS. Theorem B.3.LetSbe a surface with a 2-sheeted covering mapp rS, pq.Sis non-orientable if and only if rSis connected. See [37, Theorem 15.4] for a proof of this well-known resu...

    work page