Abstract
It is shown in this paper how a solution for a combinatorial problem obtained from applying the greedy algorithm is guaranteed to be optimal for those instances of the problem that, under an appropriate algebraic representation, satisfy the Cohen-Macaulay property known for rings and modules in Commutative Algebra. The choice of representation for the instances of a given combinatorial problem is fundamental for recognizing the Cohen-Macaulay property. Departing from an exposition of the general framework of simplicial complexes and their associated Stanley-Reisner ideals, wherein the Cohen-Macaulay property is formally defined, a review of other equivalent frameworks more suitable for graphs or arithmetical problems will follow. In the case of graph problems a better framework to use is the edge ideal of Rafael Villarreal. For arithmetic problems it is appropriate to work within the semigroup viewpoint of toric geometry developed by Antonio Campillo and collaborators.
For Antonio Campillo and Miguel Angel Revilla
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Notes
- 1.
The reader is encouraged to prove this equivalence.
- 2.
The dimension of a finitely generated ring is the maximum cardinality of an algebraically independent set. This is equivalent in R Δ to dim(Δ) + 1 and Eq. (2).
References
Björner, A., Wachs, M.: Shellable nonpure complexes and posets I. Trans. Am. Math. Soc. 348(4), 1299–1327 (1996)
Bruns, W., Herzog, J.: Cohen-Macaulay Rings. Cambridge University Press, Cambridge (1993)
Campillo, A., Gimenez, P.: Syzygies of affine toric varieties. J. Algebra 225, 142–161 (2000)
Campillo, A., Pisón, P.: Toric mathematics from semigroup viewpoint. In: Granja, A., et al. (eds.) Ring Theory and Algebraic Geometry. Lecture Notes in Pure and Applied Mathematics, vol. 221, pp. 95–112. CRC Press, Boca Raton (2001)
Campilllo, A., Revilla, M.A.: Coin exchange algorithms and toric projective curves. Commun. Algebra 29(7), 2985–2989 (2001)
Dinur, I., Safra, S.: On the hardness of approximating minimum vertex-cover. Ann. Math. 162(1), 439–485 (2005)
Edmonds, J.: Matroids and the greedy algorithm. Math. Program. 1, 127–136 (1971)
Fröberg, R.: On Stanley-Reisner rings. Topics Algebra 26(2), 57–70 (1990). Banach Center Publications
Fulkerson, D.R., Gross, O.A.: Incidence matrices and interval graphs. Pac. J. Math. 15, 835–855 (1965)
Garey, M.R., Johnson, D.S.: Computers and Intractability. Freeman, San Francisco (1979)
Guo, J., Shen, Y.H., Wu, T.: Strong shellability of simplicial complexes. arXiv preprint arXiv:1604.05412 (2016)
Guo, J., Shen, Y.H., Wu, T.: Edgewise strongly shellable clutters. J. Algebra Appl. 17(1) (2018)
Korte, B., Lovász, L.: Greedoids and linear objective functions. SIAM J. Algebraic Disc. Methods 5(2), 229–238 (1984)
Kozen, D., Zaks, S.: Optimal bounds for the change-making problem. Theor. Comput. Sci. 123, 377–388 (1994)
Kunz, E.: Introduction to Commutative Algebra and Algebraic Geometry. Birkhäuser, Basel (1985)
Miller, E., Sturmfels, B.: Combinatorial Commutative Algebra. Springer, New York (2005)
Papadimitriou, C., Steiglitz, K.: Combinatorial Optimization, Algorithms and Complexity. Dover, Mineola (1998)
Stanley, R.: Combinatorics and Commutative Algebra, 2nd edn. Birkhäuser, Boston (1996)
van Tuyl, A., Villarreal, R.: Shellable graphs and sequentially Cohen–Macaulay bipartite graphs. J. Combin. Theory Ser. A 115(5), 799–814 (2008)
Villarreal, R.: Cohen-Macaulay graphs. Manuscripta Math. 66(3), 277–293 (1990)
Acknowledgements
The author acknowledges the support of the Ministerio de Economía, Industria y Competitividad, Spain, project MACDA [TIN2017-89244-R] and of the Generalitat de Catalunya, project MACDA [SGR2014-890]
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2018 Springer Nature Switzerland AG
About this chapter
Cite this chapter
Arratia, A. (2018). The Greedy Algorithm and the Cohen-Macaulay Property of Rings, Graphs and Toric Projective Curves. In: Greuel, GM., Narváez Macarro, L., Xambó-Descamps, S. (eds) Singularities, Algebraic Geometry, Commutative Algebra, and Related Topics. Springer, Cham. https://doi.org/10.1007/978-3-319-96827-8_17
Download citation
DOI: https://doi.org/10.1007/978-3-319-96827-8_17
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-96826-1
Online ISBN: 978-3-319-96827-8
eBook Packages: Mathematics and StatisticsMathematics and Statistics (R0)