Frobenius morphisms and representations of algebras
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- by Bangming Deng and Jie Du PDF
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Abstract:
By introducing Frobenius morphisms $F$ on algebras $A$ and their modules over the algebraic closure ${\overline {\mathbb {F}}}_q$ of the finite field ${\mathbb {F}}_q$ of $q$ elements, we establish a relation between the representation theory of $A$ over $\overline {\mathbb {F}}_q$ and that of the $F$-fixed point algebra $A^F$ over ${\mathbb {F}}_q$. More precisely, we prove that the category $\text {\textbf {mod}-}A^F$ of finite-dimensional $A^F$-modules is equivalent to the subcategory of finite-dimensional $F$-stable $A$-modules, and, when $A$ is finite dimensional, we establish a bijection between the isoclasses of indecomposable $A^F$-modules and the $F$-orbits of the isoclasses of indecomposable $A$-modules. Applying the theory to representations of quivers with automorphisms, we show that representations of a modulated quiver (or a species) over ${\mathbb {F}}_q$ can be interpreted as $F$-stable representations of the corresponding quiver over $\overline {\mathbb {F}}_q$. We further prove that every finite-dimensional hereditary algebra over ${\mathbb {F}}_q$ is Morita equivalent to some $A^F$, where $A$ is the path algebra of a quiver $Q$ over $\overline {\mathbb {F}}_q$ and $F$ is induced from a certain automorphism of $Q$. A close relation between the Auslander-Reiten theories for $A$ and $A^F$ is established. In particular, we prove that the Auslander-Reiten (modulated) quiver of $A^F$ is obtained by “folding" the Auslander-Reiten quiver of $A$. Finally, by taking Frobenius fixed points, we are able to count the number of indecomposable representations of a modulated quiver over ${\mathbb {F}}_q$ with a given dimension vector and to generalize Kac’s theorem for all modulated quivers and their associated Kac–Moody algebras defined by symmetrizable generalized Cartan matrices.References
- Maurice Auslander, Idun Reiten, and Sverre O. Smalø, Representation theory of Artin algebras, Cambridge Studies in Advanced Mathematics, vol. 36, Cambridge University Press, Cambridge, 1995. MR 1314422, DOI 10.1017/CBO9780511623608
- D. J. Benson, Representations and cohomology. I, Cambridge Studies in Advanced Mathematics, vol. 30, Cambridge University Press, Cambridge, 1991. Basic representation theory of finite groups and associative algebras. MR 1110581
- Roger W. Carter, Finite groups of Lie type, Pure and Applied Mathematics (New York), John Wiley & Sons, Inc., New York, 1985. Conjugacy classes and complex characters; A Wiley-Interscience Publication. MR 794307
- E. Cline, B. Parshall, and L. Scott, Finite-dimensional algebras and highest weight categories, J. Reine Angew. Math. 391 (1988), 85–99. MR 961165
- Charles W. Curtis and Irving Reiner, Methods of representation theory. Vol. I, Pure and Applied Mathematics, John Wiley & Sons, Inc., New York, 1981. With applications to finite groups and orders. MR 632548
- Bangming Deng and Jie Du, Monomial bases for quantum affine $\mathfrak {sl}_n$, Adv. Math. 191 (2005), no. 2, 276–304. MR 2103214, DOI 10.1016/j.aim.2004.03.008
- B. Deng and J. Du, Bases of quantized enveloping algebras, Pacific J. Math. 220 (2005), 33–48.
- Bangming Deng and Jie Xiao, A new approach to Kac’s theorem on representations of valued quivers, Math. Z. 245 (2003), no. 1, 183–199. MR 2023959, DOI 10.1007/s00209-003-0541-z
- François Digne and Jean Michel, Representations of finite groups of Lie type, London Mathematical Society Student Texts, vol. 21, Cambridge University Press, Cambridge, 1991. MR 1118841, DOI 10.1017/CBO9781139172417
- Vlastimil Dlab and Claus Michael Ringel, On algebras of finite representation type, J. Algebra 33 (1975), 306–394. MR 357506, DOI 10.1016/0021-8693(75)90125-8
- Vlastimil Dlab and Claus Michael Ringel, Indecomposable representations of graphs and algebras, Mem. Amer. Math. Soc. 6 (1976), no. 173, v+57. MR 447344, DOI 10.1090/memo/0173
- Peter Donovan and Mary Ruth Freislich, The representation theory of finite graphs and associated algebras, Carleton Mathematical Lecture Notes, No. 5, Carleton University, Ottawa, Ont., 1973. MR 0357233
- Yurij A. Drozd and Vladimir V. Kirichenko, Finite-dimensional algebras, Springer-Verlag, Berlin, 1994. Translated from the 1980 Russian original and with an appendix by Vlastimil Dlab. MR 1284468, DOI 10.1007/978-3-642-76244-4
- Peter Gabriel, Unzerlegbare Darstellungen. I, Manuscripta Math. 6 (1972), 71–103; correction, ibid. 6 (1972), 309 (German, with English summary). MR 332887, DOI 10.1007/BF01298413
- Peter Gabriel, Indecomposable representations. II, Symposia Mathematica, Vol. XI (Convegno di Algebra Commutativa, INDAM, Rome, 1971) Academic Press, London, 1973, pp. 81–104. MR 0340377
- Peter Gabriel, Auslander-Reiten sequences and representation-finite algebras, Representation theory, I (Proc. Workshop, Carleton Univ., Ottawa, Ont., 1979), Lecture Notes in Math., vol. 831, Springer, Berlin, 1980, pp. 1–71. MR 607140
- P. Gabriel and A. V. Roiter, Representations of finite-dimensional algebras, Springer-Verlag, Berlin, 1997. Translated from the Russian; With a chapter by B. Keller; Reprint of the 1992 English translation. MR 1475926, DOI 10.1007/978-3-642-58097-0
- J. Hua, Representations of quivers over finite fields, Ph.D. thesis, University of New South Wales, 1998.
- J. Hua, Numbers of representations of valued quivers over finite fields, preprint, Universität Bielefeld, 2000 (www.mathematik.uni-bielefeld.de/$^\sim$sfb11/vquiver.ps).
- Jiuzhao Hua and Zongzhu Lin, Generalized Weyl denominator formula, Representations and quantizations (Shanghai, 1998) China High. Educ. Press, Beijing, 2000, pp. 247–261. MR 1802176
- Andrew Hubery, Quiver representations respecting a quiver automorphism: a generalisation of a theorem of Kac, J. London Math. Soc. (2) 69 (2004), no. 1, 79–96. MR 2025328, DOI 10.1112/S0024610703004988
- Jens Carsten Jantzen, Representations of algebraic groups, Pure and Applied Mathematics, vol. 131, Academic Press, Inc., Boston, MA, 1987. MR 899071
- Christian U. Jensen and Helmut Lenzing, Homological dimension and representation type of algebras under base field extension, Manuscripta Math. 39 (1982), no. 1, 1–13. MR 672397, DOI 10.1007/BF01312441
- V. G. Kac, Infinite root systems, representations of graphs and invariant theory, Invent. Math. 56 (1980), no. 1, 57–92. MR 557581, DOI 10.1007/BF01403155
- Victor G. Kac, Root systems, representations of quivers and invariant theory, Invariant theory (Montecatini, 1982) Lecture Notes in Math., vol. 996, Springer, Berlin, 1983, pp. 74–108. MR 718127, DOI 10.1007/BFb0063236
- Victor G. Kac, Infinite-dimensional Lie algebras, 3rd ed., Cambridge University Press, Cambridge, 1990. MR 1104219, DOI 10.1017/CBO9780511626234
- Stanisław Kasjan, Auslander-Reiten sequences under base field extension, Proc. Amer. Math. Soc. 128 (2000), no. 10, 2885–2896. MR 1670379, DOI 10.1090/S0002-9939-00-05382-X
- I. G. Macdonald, Symmetric functions and Hall polynomials, 2nd ed., Oxford Mathematical Monographs, The Clarendon Press, Oxford University Press, New York, 1995. With contributions by A. Zelevinsky; Oxford Science Publications. MR 1354144
- George Lusztig, Introduction to quantum groups, Progress in Mathematics, vol. 110, Birkhäuser Boston, Inc., Boston, MA, 1993. MR 1227098
- George Lusztig, Canonical bases and Hall algebras, Representation theories and algebraic geometry (Montreal, PQ, 1997) NATO Adv. Sci. Inst. Ser. C: Math. Phys. Sci., vol. 514, Kluwer Acad. Publ., Dordrecht, 1998, pp. 365–399. MR 1653038
- L. A. Nazarova, Representations of quivers of infinite type, Izv. Akad. Nauk SSSR Ser. Mat. 37 (1973), 752–791 (Russian). MR 0338018
- Claus Michael Ringel, Hall algebras and quantum groups, Invent. Math. 101 (1990), no. 3, 583–591. MR 1062796, DOI 10.1007/BF01231516
- Leonard L. Scott, Simulating algebraic geometry with algebra. I. The algebraic theory of derived categories, The Arcata Conference on Representations of Finite Groups (Arcata, Calif., 1986) Proc. Sympos. Pure Math., vol. 47, Amer. Math. Soc., Providence, RI, 1987, pp. 271–281. MR 933417
- Toshiyuki Tanisaki, Foldings of root systems and Gabriel’s theorem, Tsukuba J. Math. 4 (1980), no. 1, 89–97. MR 597686, DOI 10.21099/tkbjm/1496158795
Additional Information
- Bangming Deng
- Affiliation: Department of Mathematics, Beijing Normal University, Beijing 100875, People’s Republic of China
- Email: dengbm@bnu.edu.cn
- Jie Du
- Affiliation: School of Mathematics, University of New South Wales, Sydney 2052, Australia
- MR Author ID: 242577
- Email: j.du@unsw.edu.au
- Received by editor(s): August 14, 2003
- Received by editor(s) in revised form: August 12, 2004
- Published electronically: January 24, 2006
- Additional Notes: This work was partially supported by the NSF of China (Grant no. 10271014), the Doctoral Program of Higher Education, and the Australian Research Council.
- © Copyright 2006
American Mathematical Society
The copyright for this article reverts to public domain 28 years after publication. - Journal: Trans. Amer. Math. Soc. 358 (2006), 3591-3622
- MSC (2000): Primary 16G10, 16G20, 16G70
- DOI: https://doi.org/10.1090/S0002-9947-06-03812-8
- MathSciNet review: 2218990