Monomial web basis for the SL(N) skein algebra of the twice punctured sphere
Pith reviewed 2026-05-23 23:03 UTC · model grok-4.3
The pith
The SL(n) skein algebra of the twice punctured sphere is a commutative polynomial algebra on n-1 explicit crossing-free webs.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
We construct a linear basis for the SL(n) skein algebra of the twice punctured sphere consisting of monomials in n-1 explicit SL(n) webs without crossings. This shows the skein algebra is a commutative polynomial algebra in these n-1 generators. The result holds for any non-zero complex q except finitely many roots of unity of small order, and at q=1 identifies the algebra with the coordinate ring of the SL(n) character variety of the surface. Both spanning and independence follow from properties of the SL(n) quantum trace map.
What carries the argument
The SL(n) quantum trace map, which supplies the spanning and linear-independence arguments for the monomial web basis.
If this is right
- The quantum trace map embeds the polynomial algebra into the Fock-Goncharov quantum higher Teichmüller space of the annulus.
- The splitting map embeds the polynomial algebra into the Lê-Sikora stated skein algebra of the annulus.
- The construction yields a relationship with Fock-Goncharov duality.
Where Pith is reading between the lines
- The explicit monomial basis may make concrete calculations of invariants on the twice punctured sphere feasible in cases previously limited to abstract descriptions.
- The method could extend to produce bases for skein algebras on surfaces with additional punctures or different topologies.
Load-bearing premise
The SL(n) quantum trace map has the required embedding and trace properties to prove both spanning and linear independence of the proposed webs.
What would settle it
A linear dependence among the n-1 proposed basis webs whose image under the quantum trace map is nonzero for generic q would falsify linear independence.
Figures
read the original abstract
We give a new proof of a slightly modified version of a result of Queffelec--Rose, by constructing a linear basis for the $\mathrm{SL}(n)$ skein algebra of the twice punctured sphere for any non-zero complex number $q$, excluding finitely many roots of unity of small order. In particular, the skein algebra is a commutative polynomial algebra in $n-1$ generators, where each generator is represented by an explicit $\mathrm{SL}(n)$ web, without crossings, on the surface. This includes the case $q=1$, where the skein algebra is identified with the coordinate ring of the $\mathrm{SL}(n)$ character variety of the twice punctured sphere. The proof of both the spanning and linear independence properties of the basis depends on the so-called $\mathrm{SL}(n)$ quantum trace map, due originally to Bonahon--Wong in the case $n=2$. Two consequences of our method are that the quantum trace map and the so-called splitting map embed the polynomial algebra into the Fock--Goncharov quantum higher Teichm\"uller space and the L\^{e}--Sikora stated skein algebra, respectively, of the annulus. We end by discussing the relationship with Fock--Goncharov duality.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper gives a new proof of a slightly modified version of a result of Queffelec--Rose by exhibiting an explicit set of n-1 crossing-free SL(n) webs that form a linear basis for the SL(n) skein algebra of the twice-punctured sphere (for q not a small root of unity). It shows that the skein algebra is the commutative polynomial algebra on these generators and identifies the q=1 case with the coordinate ring of the SL(n) character variety. Both spanning and linear independence are deduced from properties of the SL(n) quantum trace map (an extension of the Bonahon--Wong construction); two corollaries are embeddings of the polynomial algebra into the Fock--Goncharov quantum higher Teichmüller space and the Lê--Sikora stated skein algebra of the annulus.
Significance. If the central claim holds, the work supplies an explicit monomial basis for a family of skein algebras that had previously been known only abstractly, together with concrete embeddings into quantum Teichmüller spaces. The explicit web generators and the identification at q=1 are concrete contributions to the study of higher Teichmüller theory and quantum cluster algebras.
major comments (2)
- [sections developing the quantum trace map and the spanning/independence proofs] The spanning and linear-independence arguments (stated in the abstract and developed in the sections on the quantum trace map) both rest on the claim that the SL(n) quantum trace map is an algebra homomorphism that is injective on the polynomial subalgebra generated by the proposed n-1 webs and lands inside the appropriate completion of the skein algebra. The manuscript must supply or cite a self-contained verification that these three properties hold for the generalized map when n>2; without that verification the basis theorem is not established.
- [introduction and statement of main theorem] The paper announces a 'slightly modified version' of the Queffelec--Rose result. The precise statement of the modification (e.g., any change in the allowed roots of unity or in the definition of the skein algebra) should be stated explicitly before the proof, so that the reader can see exactly which prior claim is being reproved.
minor comments (2)
- Notation for the n-1 generators (e.g., how they are indexed and drawn) should be fixed early and used consistently in all subsequent figures and statements.
- A short table or diagram summarizing the n-1 explicit webs for small n (n=3,4) would improve readability.
Simulated Author's Rebuttal
We thank the referee for the careful reading and constructive feedback on the manuscript. We address each major comment below and will revise the paper accordingly to strengthen the exposition and completeness of the arguments.
read point-by-point responses
-
Referee: [sections developing the quantum trace map and the spanning/independence proofs] The spanning and linear-independence arguments (stated in the abstract and developed in the sections on the quantum trace map) both rest on the claim that the SL(n) quantum trace map is an algebra homomorphism that is injective on the polynomial subalgebra generated by the proposed n-1 webs and lands inside the appropriate completion of the skein algebra. The manuscript must supply or cite a self-contained verification that these three properties hold for the generalized map when n>2; without that verification the basis theorem is not established.
Authors: We agree that the three properties of the generalized SL(n) quantum trace map (algebra homomorphism, injectivity on the polynomial subalgebra, and landing in the completion) require explicit verification for n>2 to fully support the basis theorem. In the revised manuscript we will add a self-contained verification of these properties in the sections on the quantum trace map, extending the Bonahon--Wong construction with the necessary details for the higher-rank case. revision: yes
-
Referee: [introduction and statement of main theorem] The paper announces a 'slightly modified version' of the Queffelec--Rose result. The precise statement of the modification (e.g., any change in the allowed roots of unity or in the definition of the skein algebra) should be stated explicitly before the proof, so that the reader can see exactly which prior claim is being reproved.
Authors: We will revise the introduction and the paragraph immediately preceding the main theorem to state the precise modifications explicitly. This will include the precise range of q (any nonzero complex number excluding finitely many roots of unity of small order) and confirmation that the skein algebra is defined in the standard way, so the differences from the Queffelec--Rose result are clear to the reader. revision: yes
Circularity Check
No circularity; spanning and independence rest on external quantum trace map from prior literature
full rationale
The paper constructs an explicit monomial web basis and proves it spans and is linearly independent for the SL(n) skein algebra by invoking the SL(n) quantum trace map (originally Bonahon-Wong for n=2). This map is cited as an independent external tool whose embedding and homomorphism properties supply the required arguments; the authors of the cited map do not overlap with Cremaschi-Douglas. No self-definitional equations, fitted inputs renamed as predictions, or load-bearing self-citations appear in the derivation chain. The result is therefore not equivalent to its inputs by construction.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption The SL(n) quantum trace map is well-defined for generic q and supplies both spanning and linear independence for the proposed web basis.
Reference graph
Works this paper leans on
-
[1]
D. G. L. Allegretti and H. K. Kim. A duality map for quantum cluster varieties from surfaces. Adv. Math., 306:1164–1208, 2017
work page 2017
-
[2]
S. Baseilhac, M. Faitg, and P. Roche. Unrestricted quantum moduli algebras, III: Surfaces of arbitrary genus and skein algebras. https://arxiv.org/abs/2302.00396, 2023
-
[3]
B. Beaumont-Gould, E. Brodsky, V. Higgins, A. Hogan, J. M. Melby, and J. Piazza. Power sum elements in the G2 skein algebra. https://arxiv.org/abs/2310.01773, 2023
-
[4]
F. Bonahon and V. Higgins. Central elements in the SL d-skein algebra of a surface. https://arxiv. org/abs/2308.13691, 2023
-
[5]
F. Bonahon and H. Wong. Quantum traces for representations of surface groups in SL 2(C). Geom. Topol., 15:1569–1615, 2011
work page 2011
-
[6]
D. Bullock. Rings of SL2(C)-characters and the Kauffman bracket skein module.Comment. Math. Helv., 72:521–542, 1997
work page 1997
- [7]
-
[8]
L. O. Chekhov and V. V. Fock. Observables in 3D gravity and geodesic algebras. Czechoslovak J. Phys., 50:1201–1208, 2000
work page 2000
-
[9]
J. Cooke and A. Lacabanne. Higher Rank Askey-Wilson Algebras as Skein Algebras. https://arxiv. org/abs/2205.04414, 2022
-
[10]
F. Costantino and T. T. Q. Lˆ e. Stated skein algebras of surfaces. J. Eur. Math. Soc. (JEMS) , 24:4063– 4142, 2022
work page 2022
-
[11]
B. Davison. Positivity for quantum cluster algebras. Ann. of Math. (2) , 187:157–219, 2018
work page 2018
-
[12]
B. Davison and T. Mandel. Strong positivity for quantum theta bases of quantum cluster algebras. Invent. Math., 226:725–843, 2021
work page 2021
- [13]
-
[14]
D. C. Douglas. Quantum traces for SL n(C): The case n = 3. J. Pure Appl. Algebra , 228:50 pp., 2024
work page 2024
-
[15]
D. C. Douglas, R. Kenyon, and H. Shi. Dimers, webs, and local systems. Trans. Amer. Math. Soc. , 377:921–950, 2024
work page 2024
- [16]
-
[17]
D. C. Douglas and Z. Sun. Tropical Fock-Goncharov coordinates for SL3-webs on surfaces I: construction. Forum Math. Sigma, 12:Paper No. e5, 55 pp., 2024
work page 2024
-
[18]
C. Florentino and S. Lawton. Topology of character varieties of Abelian groups. Topology and its Ap- plications, 173:32–58, 2014
work page 2014
-
[19]
V. V. Fock. Dual Teichm¨ uller spaces.https://arxiv.org/abs/dg-ga/9702018, 1997
work page internal anchor Pith review Pith/arXiv arXiv 1997
-
[20]
V. V. Fock and A. B. Goncharov. Moduli spaces of local systems and higher Teichm¨ uller theory. Publ. Math. Inst. Hautes ´Etudes Sci., 103:1–211, 2006
work page 2006
-
[21]
V. V. Fock and A. B. Goncharov. Cluster ensembles, quantization and the dilogarithm. Ann. Sci. ´Ec. Norm. Sup´ er., 42:865–930, 2009
work page 2009
- [22]
- [23]
-
[24]
C. Frohman and A. S. Sikora. SU(3)-skein algebras and webs on surfaces. Math. Z., 300:33–56, 2022. 40 T. CREMASCHI AND D. C. DOUGLAS
work page 2022
-
[25]
M. Gabella. Quantum Holonomies from Spectral Networks and Framed BPS States. Comm. Math. Phys., 351:563–598, 2017
work page 2017
-
[26]
Rotation-invariant web bases from hourglass plabic graphs
C. Gaetz, O. Pechenik, S. Pfannerer, J. Striker, and J. P. Swanson. Rotation-invariant web bases from hourglass plabic graphs. https://arxiv.org/abs/2306.12501, 2024
work page internal anchor Pith review Pith/arXiv arXiv 2024
-
[27]
D. Gaiotto, G. W. Moore, and A. Neitzke. Framed BPS states. Adv. Theor. Math. Phys. , 17:241–397, 2013
work page 2013
-
[28]
W. M. Goldman. Invariant functions on Lie groups and Hamiltonian flows of surface group representa- tions. Invent. Math., 85:263–302, 1986
work page 1986
-
[29]
A. B. Goncharov and L. Shen. Geometry of canonical bases and mirror symmetry. Invent. Math. , 202:487–633, 2015
work page 2015
- [30]
- [31]
-
[32]
S. Gunningham, D. Jordan, and P. Safronov. The finiteness conjecture for skein modules. Invent. Math., 232:301–363, 2023
work page 2023
-
[33]
J. Hass and P. Scott. Intersections of curves on surfaces. Israel J. Math. , 51:90–120, 1985
work page 1985
-
[34]
J. Hass and P. Scott. Curve flows on surfaces and intersections of curves. In Differential geometry: Riemannian geometry (Los Angeles, CA, 1990) , volume 54, Part 3 of Proc. Sympos. Pure Math., pages 415–421. Amer. Math. Soc., Providence, RI, 1993
work page 1990
-
[35]
V. Higgins. Triangular decomposition of SL 3 skein algebras. Quantum Topol., 14:1–63, 2023
work page 2023
-
[36]
N. J. Hitchin. Lie groups and Teichm¨ uller space.Topology, 31:449–473, 1992
work page 1992
-
[37]
J. Hoste and J. H. Przytycki. The (2 , ∞)-skein module of lens spaces; a generalization of the Jones polynomial. J. Knot Theory Ramifications, 2:321–333, 1993
work page 1993
-
[38]
L. H. Kauffman. State models and the Jones polynomial. Topology, 26:395–407, 1987
work page 1987
- [39]
- [40]
-
[41]
H. K. Kim. Quantized geodesic lengths for Teichm¨ uller spaces: algebraic aspects.https://arxiv.org/ abs/2405.14727, 2024
work page internal anchor Pith review Pith/arXiv arXiv 2024
-
[42]
H. K. Kim, T. T. Q. Lˆ e, and M. Son. SL 2 quantum trace in quantum Teichm¨ uller theory via writhe. Algebr. Geom. Topol., 23:339–418, 2023
work page 2023
-
[43]
A. Knutson and T. Tao. The honeycomb model of GL n(C) tensor products. I. Proof of the saturation conjecture. J. Amer. Math. Soc. , 12:1055–1090, 1999
work page 1999
- [44]
- [45]
- [46]
-
[47]
T. T. Q. Lˆ e. Triangular decomposition of skein algebras. Quantum Topol., 9:591–632, 2018
work page 2018
-
[48]
T. T. Q. Lˆ e, L. Shen, Z. Sun, and D. Weng. Private communication
- [49]
- [50]
-
[51]
W. B. R. Lickorish. Linear skein theory and link polynomials. Topology Appl., 27:265–274, 1987
work page 1987
-
[52]
W. B. R. Lickorish. The skein method for three-manifold invariants. J. Knot Theory Ramifications , 2:171–194, 1993
work page 1993
-
[53]
T. Mandel and F. Qin. Bracelets bases are theta bases. https://arxiv.org/abs/2301.11101, 2023
-
[54]
H. Morton and P. Samuelson. The HOMFLYPT skein algebra of the torus and the elliptic Hall algebra. Duke Math. J. , 166:801–854, 2017
work page 2017
-
[55]
H. R. Morton and S. G. Lukac. The Homfly polynomial of the decorated Hopf link. J. Knot Theory Ramifications, 12:395–416, 2003. WEB BASIS FOR THE ANNULUS 41
work page 2003
-
[56]
H. R. Morton and P. M. G. Manch´ on. Geometrical relations and plethysms in the Homfly skein of the annulus. J. Lond. Math. Soc. (2) , 78:305–328, 2008
work page 2008
-
[57]
A. Neitzke and F. Yan. q-nonabelianization for line defects. J. High Energy Phys. , 153:65 pp., 2020
work page 2020
-
[58]
A. Neitzke and F. Yan. The quantum UV-IR map for line defects in gl(3)-type class S theories. J. High Energy Phys., pages Paper No. 81, 50 pp., 2022
work page 2022
-
[59]
T. Ohtsuki and S. Yamada. Quantum SU (3) invariant of 3-manifolds via linear skein theory. J. Knot Theory Ramifications, 6:373–404, 1997
work page 1997
- [60]
-
[61]
J. H. Przytycki. Skein Modules of 3-Manifolds. Bull. Polish Acad. Sci. Math. , 39:91–100, 1991
work page 1991
-
[62]
J. H. Przytycki and A. S. Sikora. On skein algebras and Sl2(C)-character varieties. Topology, 39:115–148, 2000
work page 2000
-
[63]
J. H. Przytycki and P. Traczyk. Conway algebras and skein equivalence of links. Proc. Amer. Math. Soc., 100:744–748, 1987
work page 1987
-
[64]
H. Queffelec and D. E. V. Rose. Sutured annular Khovanov-Rozansky homology. Trans. Amer. Math. Soc., 370:1285–1319, 2018
work page 2018
-
[65]
H. Queffelec and P. Wedrich. Extremal weight projectors II, glN case. Algebr. Comb., 7:187–223, 2024
work page 2024
-
[66]
N. Reshetikhin and V. G. Turaev. Invariants of 3-manifolds via link polynomials and quantum groups. Invent. Math., 103:547–597, 1991
work page 1991
- [67]
-
[68]
A. S. Sikora. SL n-character varieties as spaces of graphs.Trans. Amer. Math. Soc., 353:2773–2804, 2001
work page 2001
-
[69]
A. S. Sikora. Skein theory for SU (n)-quantum invariants. Algebr. Geom. Topol., 5:865–897, 2005
work page 2005
-
[70]
A. S. Sikora. Character varieties of abelian groups. Math. Z., 277:241–256, 2014
work page 2014
-
[71]
Z. Sun, A. Wienhard, and T. Zhang. Flows on the PGL(V)-Hitchin component. Geom. Funct. Anal. , 30:588–692, 2020
work page 2020
-
[72]
V. Turaev and H. Wenzl. Quantum invariants of 3-manifolds associated with classical simple Lie algebras. Internat. J. Math. , 4:323–358, 1993
work page 1993
-
[73]
V. G. Turaev. The Conway and Kauffman modules of a solid torus. Zap. Nauchn. Sem. Leningrad. Otdel. Mat. Inst. Steklov. (LOMI) , 167:79–89, 190, 1988
work page 1988
- [74]
- [75]
-
[76]
E. Witten. Quantum Field Theory and the Jones Polynomial. Comm. Math. Phys. , 121:351–399, 1989
work page 1989
-
[77]
D. Xie. Higher laminations, webs and N=2 line operators. https://arxiv.org/abs/1304.2390, 2013
work page internal anchor Pith review Pith/arXiv arXiv 2013
-
[78]
Y. Yokota. Skeins and quantum SU (N) invariants of 3-manifolds. Math. Ann., 307:109–138, 1997. School of Mathematics, Trinity College Dublin, 17 Westland Row, Dublin 2, Ireland Email address : cremasct@tcd.ie Department of Mathematics, Virginia Tech, 225 Stanger Street, Blacksburg, V A 24061, USA Email address : dcdouglas@vt.edu
work page 1997
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