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We construct a compactification of the space of circular planar electrical networks studied by Curtis-Ingerman-Morrow and De Verdiere-Gitler-Vertigan, using cactus networks. We embed this compactification as a linear slice of the totally…

Combinatorics · Mathematics 2018-09-03 Thomas Lam

We introduce a new class of "electrical" Lie groups. These Lie groups, or more precisely their nonnegative parts, act on the space of planar electrical networks via combinatorial operations previously studied by Curtis-Ingerman-Morrow. The…

Representation Theory · Mathematics 2016-01-22 Thomas Lam , Pavlo Pylyavskyy

This is the first of a series of papers where we develop a theory of total positivity for loop groups. In this paper, we completely describe the totally nonnegative part of the polynomial loop group GL_n(\R[t,t^{-1}]), and for the formal…

Combinatorics · Mathematics 2009-12-06 Thomas Lam , Pavlo Pylyavskyy

Kenyon and Wilson showed how to test if a circular planar electrical network with $n$ nodes is well-connected by checking the positivity of $\binom{n}{2}$ central minors of the response matrix. Their test is based on the fact that any…

Combinatorics · Mathematics 2018-08-02 Tri Lai

In [LP] we introduced Laurent phenomenon algebras, a generalization of cluster algebras. Here we give an explicit description of Laurent phenomenon algebras with a linear initial seed arising from a graph. In particular, any graph…

Representation Theory · Mathematics 2012-10-19 Thomas Lam , Pavlo Pylyavskyy

As an improvement of the combinatorial realization of totally positive matrices via the essential positive weightings of certain planar network by S.Fomin and A.Zelevisky \cite{[4]}, in this paper, we give the test method of positive…

Rings and Algebras · Mathematics 2014-06-27 Fang Li , Yichao Yang

We discuss several parametrizations of the space of circular planar electrical networks. For any circular planar network we associate a canonical minimal network with the same response matrix, called a "standard" network. The conductances…

Combinatorics · Mathematics 2016-09-20 Richard W. Kenyon , David B. Wilson

We review some important results by Gross, Hacking, Keel, and Kontsevich on cluster algebra theory, namely, the column sign-coherence of $C$-matrices and the Laurent positivity, both of which were conjectured by Fomin and Zelevinsky. We…

Combinatorics · Mathematics 2023-02-23 Tomoki Nakanishi

We consider the inverse boundary value problem in the case of discrete electrical networks containing nonlinear (non-ohmic) resistors. Generalizing work of Curtis, Ingerman, Morrow, Colin de Verdiere, Gitler, and Vertigan, we characterize…

Combinatorics · Mathematics 2012-03-20 Will Johnson

We introduce a new class of combinatorial objects, named tight gradings, which are certain nonnegative integer-valued functions on maximal Dyck paths. Using tight gradings, we derive a manifestly positive formula for any wall-function in a…

Combinatorics · Mathematics 2025-03-06 Amanda Burcroff , Kyungyong Lee , Lang Mou

Landau analysis in momentum twistor space can be formulated as the study of varieties of lines in three-dimensional projective space, together with their projections and discriminants. Within this framework, we define enumerative invariants…

High Energy Physics - Theory · Physics 2026-03-27 Benjamin Hollering , Elia Mazzucchelli , Matteo Parisi , Bernd Sturmfels

Laurent phenomenon algebras, first introduced by Lam and Pylyavskyy, are a generalization of cluster algebras that still possess many salient features of cluster algebras. Graph Laurent phenomenon algebras, defined by Lam and Pylyavskyy,…

Representation Theory · Mathematics 2025-10-07 Guilherme Zeus Dantas e Moura , Ramanuja Charyulu Telekicherla Kandalam , Dora Woodruff

In 2013, Lee, Li, and Zelevinsky introduced combinatorial objects called compatible pairs to construct the greedy bases for rank-2 cluster algebras, consisting of indecomposable positive elements including the cluster monomials.…

Combinatorics · Mathematics 2024-09-24 Amanda Burcroff , Kyungyong Lee , Lang Mou

LP algebras, introduced by Lam and Pylyavskyy, are a generalization of cluster algebras. These algebras are known to have the Laurent phenomenon, but positivity remains conjectural. Graph LP algebras are finite LP algebras encoded by a…

Combinatorics · Mathematics 2022-11-28 Esther Banaian , Sunita Chepuri , Elizabeth Kelley , Sylvester W. Zhang

We provide a new solution to the classical black box problem (the discrete Calderon problem) in the theory of circular electrical networks. Our approach is based on the explicit embedding of electrical networks into non-negative…

Mathematical Physics · Physics 2025-09-29 A. A. Kazakov

We analyze bipartite matrices and linear maps between matrix algebras, which are respectively, invariant and covariant, under the diagonal unitary and orthogonal groups' actions. By presenting an expansive list of examples from the…

Quantum Physics · Physics 2021-08-11 Satvik Singh , Ion Nechita

Leclerc and Zelevinsky described quasicommuting families of quantum minors in terms of a certain combinatorial condition, called weak separation. They conjectured that all maximal by inclusion weakly separated collections of minors have the…

Combinatorics · Mathematics 2015-06-12 Suho Oh , Alex Postnikov , David E Speyer

The Rayleigh property is a negative correlation property of electrical networks, which was generalized to matroids by Choe and Wagner. We prove that positroids, a class of matroid introduced by Postnikov which have seen many recent…

Combinatorics · Mathematics 2016-11-14 Cameron Marcott

Wilson loop diagrams are an important tool in studying scattering amplitudes of SYM $N=4$ theory and are known by previous work to be associated to positroids. We characterize the conditions under which two Wilson loop diagrams give the…

Mathematical Physics · Physics 2021-02-17 Susama Agarwala , Siân Fryer , Karen Yeats

Using the relationship between totally nonnegative matrices and directed acyclic weighted planar networks, we show that $2\times 2$ minors of minor matrices of totally nonnegative matrices are also nonnegative. We give a combinatorial…

Combinatorics · Mathematics 2015-03-17 David A. Cardon , Pace P. Nielsen
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