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\n\n \n \n Wilson, M. C.\n\n\n \n \n \n \n \n Research publishing for the nonexpert.\n \n \n \n \n\n\n \n\n\n\n
New Zealand Mathematical Society Newsletter, 137: 14-18. 2019.\n
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@article{wilson2019dummies,\n title={Research publishing for the nonexpert},\n author={Wilson, Mark C.},\n journal={New Zealand Mathematical Society Newsletter},\n year={2019},\n volume={137},\n pages={14-18},\n publisher={},\n keywords={publication reform, advocacy},\n url_Paper={https://markcwilson.site/Research/Outputs/oa_dummies.pdf},\n abstract={}\n}\n\n
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\n\n \n \n Aref, S.; and Wilson, M. C.\n\n\n \n \n \n \n \n Balance and frustration in signed networks.\n \n \n \n \n\n\n \n\n\n\n
Journal of Complex Networks, 7(2): 163-189. 2019.\n
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@article{aref2019balance,\n title={Balance and frustration in signed networks},\n author={Aref, Samin and Wilson, Mark C.},\n journal={Journal of Complex Networks},\n volume={7},\n number={2},\n pages={163-189},\n year={2019},\n publisher={Oxford University Press},\n keywords={network science, graphs},\n url_Paper= {https://academic.oup.com/comnet/article-abstract/7/2/163/5074195},\n abstract={The frustration index is a key measure for analysing signed networks,\nwhich has been underused due to its computational complexity. We use an\nexact optimisation-based method to analyse frustration as a global\nstructural property of signed networks coming from diverse application\nareas. In the classic friend-enemy interpretation of balance theory, a\nby-product of computing the frustration index is the partitioning of\nnodes into two internally solidary but mutually hostile groups. The main\npurpose of this paper is to present general methodology for answering\nquestions related to partial balance in signed networks, and apply it to\na range of representative examples that are now analysable because of\nadvances in computational methods. We provide exact numerical results on\nsocial and biological signed networks, networks of formal alliances and\nantagonisms between countries, and financial portfolio networks.\nMolecular graphs of carbon and Ising models are also considered. We\npoint out several mistakes in the signed networks literature caused by\ninaccurate computation, implementation errors or inappropriate\nmeasures.}\n}\n\n
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\n The frustration index is a key measure for analysing signed networks, which has been underused due to its computational complexity. We use an exact optimisation-based method to analyse frustration as a global structural property of signed networks coming from diverse application areas. In the classic friend-enemy interpretation of balance theory, a by-product of computing the frustration index is the partitioning of nodes into two internally solidary but mutually hostile groups. The main purpose of this paper is to present general methodology for answering questions related to partial balance in signed networks, and apply it to a range of representative examples that are now analysable because of advances in computational methods. We provide exact numerical results on social and biological signed networks, networks of formal alliances and antagonisms between countries, and financial portfolio networks. Molecular graphs of carbon and Ising models are also considered. We point out several mistakes in the signed networks literature caused by inaccurate computation, implementation errors or inappropriate measures.\n
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\n\n \n \n Melczer, S.; and Wilson, M. C.\n\n\n \n \n \n \n \n Higher dimensional lattice walks: Connecting combinatorial and analytic behavior.\n \n \n \n \n\n\n \n\n\n\n
SIAM Journal on Discrete Mathematics, 33(4): 2140-2174. 2019.\n
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@Article{melczer2019higher,\n author = {Melczer, Stephen and Wilson, Mark C.},\n title = {Higher dimensional lattice walks: Connecting combinatorial and analytic behavior},\n number = {4},\n pages = {2140-2174},\n volume = {33},\n abstract = {We consider the enumeration of walks on the non-negative lattice\n$\\mathbb{N}^d$, with steps defined by a set $\\mathcal{S} \\subset \\{ -1,\n0, 1 \\}^d \\setminus \\{\\mathbf{0}\\}$. Previous work in this area has\nestablished asymptotics for the number of walks in certain families of\nmodels by applying the techniques of analytic combinatorics in several\nvariables (ACSV), where one encodes the generating function of a lattice\npath model as the diagonal of a multivariate rational function. Melczer\nand Mishna obtained asymptotics when the set of steps $\\mathcal{S}$ is\nsymmetric over every axis; in this setting one can always apply the\nmethods of ACSV to a multivariate rational function whose set of\nsingularities is a smooth manifold (the simplest case). Here we go\nfurther, providing asymptotics for models with generating functions that\nmust be encoded by multivariate rational functions having non-smooth\nsingular sets. In the process, our analysis connects past work to\ndeeper structural results in the theory of analytic combinatorics in\nseveral variables. One application is a closed form for asymptotics of\nmodels defined by step sets that are symmetric over all but one axis. As\na special case, we apply our results when $d=2$ to give a rigorous proof\nof asymptotics conjectured by Bostan and Kauers; asymptotics for walks\nreturning to boundary axes and the origin are also given.},\n journal = {SIAM Journal on Discrete Mathematics},\n keywords = {ACSV applications},\n publisher = {Society for Industrial and Applied Mathematics},\n url_paper = {https://arxiv.org/abs/1810.06170},\n url_slides = {https://www.youtube.com/watch?v=o5SOHJbGO4g},\n year = {2019},\n}\n\n
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\n We consider the enumeration of walks on the non-negative lattice $ℕ^d$, with steps defined by a set $\\mathcal{S} ⊂ \\{ -1, 0, 1 \\}^d ∖ \\{\\mathbf{0}\\}$. Previous work in this area has established asymptotics for the number of walks in certain families of models by applying the techniques of analytic combinatorics in several variables (ACSV), where one encodes the generating function of a lattice path model as the diagonal of a multivariate rational function. Melczer and Mishna obtained asymptotics when the set of steps $\\mathcal{S}$ is symmetric over every axis; in this setting one can always apply the methods of ACSV to a multivariate rational function whose set of singularities is a smooth manifold (the simplest case). Here we go further, providing asymptotics for models with generating functions that must be encoded by multivariate rational functions having non-smooth singular sets. In the process, our analysis connects past work to deeper structural results in the theory of analytic combinatorics in several variables. One application is a closed form for asymptotics of models defined by step sets that are symmetric over all but one axis. As a special case, we apply our results when $d=2$ to give a rigorous proof of asymptotics conjectured by Bostan and Kauers; asymptotics for walks returning to boundary axes and the origin are also given.\n
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\n\n \n \n Ianovski, E.; and Wilson, M. C.\n\n\n \n \n \n \n \n Manipulability of consular election rules.\n \n \n \n \n\n\n \n\n\n\n
Social Choice and Welfare, 52(2): 363-393. 2019.\n
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@article{ianovski2019manipulability,\n title={Manipulability of consular election rules},\n author={Ianovski, Egor and Wilson, Mark C.},\n journal={Social Choice and Welfare},\n volume={52},\n number={2},\n pages={363-393},\n year={2019},\n publisher={Springer Berlin Heidelberg},\n keywords={social choice, voting},\n url_Paper={https://arxiv.org/abs/1611.07102},\n url_Link={https://link.springer.com/article/10.1007/s00355-018-1152-2},\n abstract={The Gibbard-Satterthwaite theorem is a cornerstone of social choice\ntheory, stating that an onto social choice function cannot be both\nstrategy-proof and non-dictatorial if the number of alternatives is at\nleast three. The Duggan-Schwartz theorem proves an analogue in the case\nof set-valued elections: if the function is onto with respect to\nsingletons, and can be manipulated by neither an optimist nor a\npessimist, it must have a weak dictator. However, the assumption that\nthe function is onto with respect to singletons makes the\nDuggan-Schwartz theorem inapplicable to elections which necessarily\nselect a committee with multiple members. In this paper we make a start\non this problem by considering elections which elect a committee of size\ntwo (such as the consulship of ancient Rome). We establish that if such\na \\emph{consular election rule} cannot be expressed as the union of two\ndisjoint social choice functions, then strategy-proofness implies the\nexistence of a dictator. Although we suspect that a similar result holds\nfor larger sized committees, there appear to be many obstacles to\nproving it, which we discuss in detail.}\n}\n\n
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\n The Gibbard-Satterthwaite theorem is a cornerstone of social choice theory, stating that an onto social choice function cannot be both strategy-proof and non-dictatorial if the number of alternatives is at least three. The Duggan-Schwartz theorem proves an analogue in the case of set-valued elections: if the function is onto with respect to singletons, and can be manipulated by neither an optimist nor a pessimist, it must have a weak dictator. However, the assumption that the function is onto with respect to singletons makes the Duggan-Schwartz theorem inapplicable to elections which necessarily select a committee with multiple members. In this paper we make a start on this problem by considering elections which elect a committee of size two (such as the consulship of ancient Rome). We establish that if such a \\emphconsular election rule cannot be expressed as the union of two disjoint social choice functions, then strategy-proofness implies the existence of a dictator. Although we suspect that a similar result holds for larger sized committees, there appear to be many obstacles to proving it, which we discuss in detail.\n
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\n\n \n \n Hadjibeyli, B.; and Wilson, M. C.\n\n\n \n \n \n \n \n Distance rationalization of anonymous and homogeneous voting rules.\n \n \n \n \n\n\n \n\n\n\n
Social Choice and Welfare, 52(3): 559-583. 2019.\n
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@article{hadjibeyli2019distance,\n title={Distance rationalization of anonymous and homogeneous voting rules},\n author={Hadjibeyli, Benjamin and Wilson, Mark C.},\n journal={Social Choice and Welfare},\n volume={52},\n number={3},\n pages={559-583},\n year={2019},\n publisher={Springer Berlin Heidelberg},\n keywords={social choice, voting},\n url_Paper={https://link.springer.com/content/pdf/10.1007/s00355-018-1156-y.pdf},\n abstract={The concept of distance rationalizability of voting rules has been\nexplored in recent years by several authors. Most previous work has\ndealt with a definition in terms of preference profiles. However, most\nvoting rules in common use are anonymous and homogeneous. In this case\nthere is a much more succinct representation (using the voting simplex)\nof the inputs to the rule. This representation has been widely used in\nthe voting literature, but rarely in the context of distance\nrationalizability. Recently, the present authors showed, as a special\ncase of general results on quotient spaces, exactly how to connect\ndistance rationalizability on profiles for anonymous and homogeneous\nrules to geometry in the simplex. In this article we develop the\nconnection for the important special case of votewise distances,\nrecently introduced and studied by Elkind, Faliszewski and Slinko in\nseveral papers. This yields a direct interpretation in terms of\nwell-developed mathematical topics not seen before in the voting\nliterature, namely Kantorovich (also called Wasserstein) distances and\nthe geometry of Minkowski spaces. As an application of this approach, we\nprove some positive and some negative results about the decisiveness of\ndistance rationalizable anonymous and homogeneous rules. The positive\nresults connect with the recent theory of hyperplane rules, while the\nnegative ones deal with distances that are not metrics, controversial\nnotions of consensus, and the fact that the $\\ell^1$-norm is not\nstrictly convex. We expect that the above novel geometric interpretation\nwill aid the analysis of rules defined by votewise distances, and the\ndiscovery of new rules with desirable properties.}\n}\n\n
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\n The concept of distance rationalizability of voting rules has been explored in recent years by several authors. Most previous work has dealt with a definition in terms of preference profiles. However, most voting rules in common use are anonymous and homogeneous. In this case there is a much more succinct representation (using the voting simplex) of the inputs to the rule. This representation has been widely used in the voting literature, but rarely in the context of distance rationalizability. Recently, the present authors showed, as a special case of general results on quotient spaces, exactly how to connect distance rationalizability on profiles for anonymous and homogeneous rules to geometry in the simplex. In this article we develop the connection for the important special case of votewise distances, recently introduced and studied by Elkind, Faliszewski and Slinko in several papers. This yields a direct interpretation in terms of well-developed mathematical topics not seen before in the voting literature, namely Kantorovich (also called Wasserstein) distances and the geometry of Minkowski spaces. As an application of this approach, we prove some positive and some negative results about the decisiveness of distance rationalizable anonymous and homogeneous rules. The positive results connect with the recent theory of hyperplane rules, while the negative ones deal with distances that are not metrics, controversial notions of consensus, and the fact that the $\\ell^1$-norm is not strictly convex. We expect that the above novel geometric interpretation will aid the analysis of rules defined by votewise distances, and the discovery of new rules with desirable properties.\n
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