Nadezhda Kodaneva
In this work, we study the interlace polynomial as a generalization of a graph invariant to delta-matroids. We prove that the interlace polynomial satisfies the four-term relation for delta-matroids and determines thus a finite type invariant of links in the 3-sphere.
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We generalize theories of graph, matroid, and ribbon-graph activities to delta-matroids. As a result, we obtain an activities based feasible-set expansion for a transition polynomial of delta-matroids defined by Brijder and Hoogeboom. This result yields feasible-set expansions for the two-variable Bollobás-Riordan and interlace polynomials of a delta-matroid. In the former case, the expansion obtained directly generalizes the activities expansions of the Tutte polynomial of graphs and matroids.
We provide a unified framework in which the interlace polynomial and several related graph polynomials are defined more generally for multimatroids and delta-matroids. Using combinatorial properties of multimatroids rather than graph-theoretical arguments, we find that various known results about these polynomials, including their recursive relations, are both more efficiently and more generally obtained. In addition, we obtain several interrelationships and results for polynomials on multimatroids and delta-matroids that correspond to new interrelationships and results for the corresponding g…
Let G be a graph with adjacency matrix A(G). Consider the matrix IA(G)=(I | A(G)), where I is the identity matrix, and let M(IA(G)) be the binary matroid represented by IA(G). Then suitably parametrized versions of the Tutte polynomial of M(IA(G)) yield the interlace polynomials of G, introduced by Arratia, Bollobás and Sorkin [J. Combin. Theory Ser. B 92 (2004) 199-233; Combinatorica 24 (2004) 567-584]. Interlace polynomials subsequently introduced by other authors may be obtained from parametrized Tutte polynomials of the binary matroid represented by (I | A(G) | I+A(G)).
In this paper, we survey results regarding the interlace polynomial of a graph, connections to such graph polynomials as the Martin and Tutte polynomials, and generalizations to the realms of isotropic systems and delta-matroids.
A classic exercise in the topology of surfaces is to show that, using handle slides, every disc-band surface, or 1-vertex ribbon graph, can be put in a canonical form consisting of the connected sum of orientable loops, and either non-orientable loops or pairs of interlaced orientable loops. Motivated by the principle that ribbon graph theory informs delta-matroid theory, we find the delta-matroid analogue of this surface classification. We show that, using a delta-matroid analogue of handle-slides, every binary delta-matroid in which the empty set is feasible can be written in a canonical for…
Multimatroids generalize matroids, delta-matroids, and isotropic systems, and transition polynomials of multimatroids subsume various polynomials for these latter combinatorial structures, such as the interlace polynomial and the Tutte-Martin polynomial. We prove evaluations of the Tutte-Martin polynomial of isotropic systems from Bouchet directly and more efficiently in the context of transition polynomials of multimatroids. Moreover, we generalize some related evaluations of the transition polynomial of 4-regular graphs from Jaeger to multimatroids. These evaluations are obtained in a unifor…
We introduce delta-graphic matroids, which are matroids whose bases form graphic delta-matroids. The class of delta-graphic matroids contains graphic matroids as well as cographic matroids and is a proper subclass of the class of regular matroids. We give a structural characterization of the class of delta-graphic matroids. We also show that every forbidden minor for the class of delta-graphic matroids has at most $48$ elements.
K-classes of delta-matroids and equivariant localization
本研究类比极大正交格拉斯曼流形对格拉斯曼流形的推广，将delta拟阵作为拟阵的B型推广，借助极大正交格拉斯曼流形的K-理论给出delta拟阵的交错多项式的几何解释，并推导了B型置换多面体簇的新型Hirzebruch-Riemann-Roch型公式。
We give upper and lower bounds on the number of delta-matroids, and on the number of even delta-matroids.
We introduce a binary matroid M(IAS(G)) associated with a looped simple graph G. M(IAS(G)) classifies G up to local equivalence, and determines the delta-matroid and isotropic system associated with G. Moreover, a parametrized form of its Tutte polynomial yields the interlace polynomials of G.
Matroid theory is often thought of as a generalization of graph theory. In this paper we propose an analogous correspondence between embedded graphs and delta-matroids. We show that delta-matroids arise as the natural extension of graphic matroids to the setting of embedded graphs. We show that various basic ribbon graph operations and concepts have delta-matroid analogues, and illustrate how the connections between embedded graphs and delta-matroids can be exploited. Also, in direct analogy with the fact that The Tutte polynomial is matroidal, we show that several polynomials of embedded grap…
In this work, we study the operations of handle slides introduced recently for delta-matroids by Iain Moffatt and Eunice Mphako-Banda. We then prove that the class of binary delta-matroids is the only class of delta-matroids closed under handle slides.
Delta-matroids whose twist polynomials are monomials
本文将Yan和Jin关于二元Delta-拟阵扭转单项式的刻画推广到一般情形，证明任何具有扭转单项式的Delta-拟阵都必然是二元的。
Recently, we introduced the twist polynomials of delta-matroids and gave a characterization of even normal binary delta-matroids whose twist polynomials have only one term and posed a problem: what would happen for odd binary delta-matroids? In this paper, we show that a normal binary delta-matroid whose twist polynomials have only one term if and only if each connected component of the intersection graph of the delta-matroid is either a complete graph of odd order or a single vertex with a loop.
A q-analogue of delta-matroids and related concepts
本文定义并研究了有限域上向量空间的q-delta-拟阵和q-g-拟阵，并比较了其公理化描述与基于q-拟阵强映射的定义。
The width of a delta-matroid is the difference in size between a maximal and minimal feasible set. We give a Rough Structure Theorem for delta-matroids that admit a twist of width one. We apply this theorem to give an excluded minor characterisation of delta-matroids that admit a twist of width at most one.
Delta-matroids as subsystems of sequences of Higgs lifts
本文围绕由希格斯提升序列得到的全希格斯提升Delta-拟阵，给出其及两类相关子式闭类的排除子式刻画，并刻画了可通过移除可行集得到Delta-拟阵的集系结构。
Whitney's 2-Isomorphism Theorem characterises when two graphs have isomorphic cycle matroids. We present an analogue of this theorem for graphs embedded in surfaces by characterising when two graphs in surface have isomorphic delta-matroids.
Real-rootedness of Kazhdan--Lusztig polynomials of sparse paving matroids
本文证明稀疏铺砌拟阵的非常数Kazhdan--Lusztig多项式仅有简单负零点，并给出均匀拟阵多项式与稀疏铺砌拟阵多项式的严格交错关系。
The mutually enriching relationship between graphs and matroids has motivated discoveries in both fields. In this paper, we exploit the similar relationship between embedded graphs and delta-matroids. There are well-known connections between geometric duals of plane graphs and duals of matroids. We obtain analogous connections for various types of duality in the literature for graphs in surfaces of higher genus and delta-matroids. Using this interplay, we establish a rough structure theorem for delta-matroids that are twists of matroids, we translate Petrie duality on ribbon graphs to loop com…
Delta-matroid theory is often thought of as a generalization of topological graph theory. It is well-known that an orientable embedded graph is bipartite if and only if its Petrie dual is orientable. In this paper, we first introduce the concepts of Eulerian and bipartite delta-matroids and then extend the result from embedded graphs to arbitrary binary delta-matroids. The dual of any bipartite embedded graph is Eulerian. We also extend the result from embedded graphs to the class of delta-matroids that arise as twists of binary matroids. Several related results are also obtained.
In contrast to matroids, vf-safe delta-matroids have three kinds of minors and are closed under the operations of twist and loop complementation. We show that the delta-matroids representable over GF(4) with respect to the nontrivial automorphism of GF(4) form a subclass of the vf-safe delta-matroids closed under twist and loop complementation. In particular, quaternary matroids are vf-safe. Using this result, we show that the matroid of a bicycle space of a quaternary matroid M is obtained from M by using loop complementation. As a consequence, the matroid of a bicycle space of a quaternary m…
Recently, Gross, Mansour and Tucker introduced the partial duality polynomial of a ribbon graph and posed a conjecture that there is no orientable ribbon graph whose partial duality polynomial has only one non-constant term. We found an infinite family of counterexamples for the conjecture and showed that essentially these are the only counterexamples. This is also obtained independently by Chumutov and Vignes-Tourneret and they posed a problem: it would be interesting to know whether the partial duality polynomial and the related conjectures would make sence for general delta-matroids. In thi…
Rank functions and invariants of delta-matroids
本文通过秩函数公理化δ-拟阵，研究其秩生成函数，并利用洛伦兹多项式理论证明相关取值的对数凹性。
We prove a splitter theorem for tight multimatroids, generalizing the corresponding result for matroids, obtained independently by Brylawski and Seymour. Further corollaries give splitter theorems for delta-matroids and ribbon graphs.
We show that the symmetric difference distance measure for set systems, and more specifically for delta-matroids, corresponds to the notion of nullity for symmetric and skew-symmetric matrices. In particular, as graphs (i.e., symmetric matrices over GF(2)) may be seen as a special class of delta-matroids, this distance measure generalizes the notion of nullity in this case. We characterize delta-matroids in terms of equicardinality of minimal sets with respect to inclusion (in addition we obtain similar characterizations for matroids). In this way, we find that, e.g., the delta-matroids obtain…
Given a map $\mathcal M$ on a connected and closed orientable surface, the delta-matroid of $\mathcal M$ is a combinatorial object associated to $\mathcal M$ which captures some topological information of the embedding. We explore how delta-matroids associated to dessins d'enfants behave under the action of the absolute Galois group. Twists of delta-matroids are considered as well; they correspond to the recently introduced operation of partial duality of maps. Furthermore, we prove that every map has a partial dual defined over its field of moduli. A relationship between dessins, partial dual…
Partial-twuality polynomials of delta-matroids
本文针对Chumutov等人提出的部分对偶多项式对一般delta-拟阵是否成立的问题，研究delta-拟阵的部分对偶多项式类似物，分析其性质，证明交图可确定两类delta-拟阵的该多项式，并刻画了多项式仅含一项的vf-safe delta-拟阵特征。
The handle slide operation, originally defined for ribbon graphs, was extended to delta-matroids by I. Moffatt and E. Mphako-Bandab, who show that, using a delta-matroid analogue of handle slides, every binary delta-matroid in which the empty set is feasible can be written in a canonical form analogous to the canonical form for one-vertex maps on a surface. We provide a canonical form for binary delta-matroids without restriction on the feasibility of the empty set.
The excluded 3-minors for vf-safe delta-matroids
本文通过寻找最小障碍即排除3-minors来刻画vf-safe delta-matroids和ribbon-graphic delta-matroids，并解释了binary delta-matroids中3-minors与图vertex minors的等价性。
$Γ$-graphic delta-matroids and their applications
本文定义了$Γ$-图示delta-拟阵，提出了求解分离问题的多项式时间算法，并利用对称贪婪算法寻找最大权可行集，展示了其在树包装问题中的算法应用。
Stanley's symmetrized chromatic polynomial is a generalization of the ordinary chromatic polynomial to a graph invariant with values in a ring of polynomials in infnitely many variables. The ordinary chromatic polynomial is a specialization of the Stanley's one. Our goal is to extend Stanley's chromatic polynomial to embedded graphs. In contrast to well-known extensions of, say, the Tutte polynomial from abstract to embedded graphs [5], we do not treat an embedded graph as an abstract graph endowed with additional information about the embedding. Instead, we consider the binary delta-matroid a…
Twist polynomial interpolation for binary delta-matroids
本文基于delta-矩阵框架，证明了二元delta-矩阵的扭多项式要么是偶多项式，要么是奇多项式，或两者皆是。应用于ribbon图时，得出其部分对偶多项式具有相同性质。
Real-rootedness of the $Z$-polynomials of sparse paving matroids and strict interlacing for uniform matroids
本文证明稀疏铺砌拟阵的$Z$-多项式仅有负实零点，证实实根性猜想，并证明固定余秩下均匀拟阵的$Z$-多项式严格交错，方法是通过$\gamma$-多项式转移性质。
Lattice Path Delta Matroids
本文研究格路拟阵的 $C_n$ 型推广，即沿主对角线对称的格路 delta 拟阵，描述其组合运算并证明其可行多面体可分解为具有单模三角剖分的特殊多面体，体积与特定上升集的排列比例相关。
Vassiliev (finite type) invariants of knots can be described in terms of weight systems. These are functions on chord diagrams satisfying so-called 4-term relations. In the study of the sl2 weight system, it was shown that its value on a chord diagram depends on the intersection graph of the diagram rather than on the diagram itself. Moreover, it was shown that the value of this weight system on an intersection graph depends on the cy- cle matroid of the graph rather than on the graph itself. This result arose the question whether there is a natural way to introduce a 4-term relation on the sp…
A Fano framework for binary delta-matroids
本文为二元delta-拟阵建立了类似嵌入图的Fano平面框架，通过$Z_3$-二部性等性质刻画满足条件的非零向量，并恢复已知结果。
A recursion for the twist polynomial of a one-point join of normal binary delta-matroids
该研究推导了正规二元δ-拟阵单点结合的扭曲多项式的递推公式，将其应用于部分对偶欧拉示性数多项式，得到相关取值关系及可行集刻画，推广了Yan和Jin的成果。
Oriented and Valuated Delta Matroids from Stable Polynomials
本文推广Brändén的支撑定理，证明多仿射实稳定多项式的系数产生定向$\Delta$-拟阵，Puiseux级数上的多仿射稳定多项式的系数产生赋值的$\Delta$-拟阵。
Orbits and self-twuality in set systems and delta-matroids
本文提出集合系统上的新群作用，推广带状群框架，证明自扭曲性在轨道中传播，刻画vf-安全delta-拟阵轨道，并应用于带状图delta-拟阵，回答开放问题。
A polyhedral approach to homotopy theorems in matroid theory
该研究利用多面体方法给出毛雷尔拟阵同伦定理新证，此方法还得出delta - 拟阵同伦定理及相关结果，同时证明了整多拟阵的类似定理。
Monotone maximum partial-twuality widths of vf-safe delta-matroids
研究 vf - 安全 delta - 拟阵由扭转和环补生成的部分对偶性的单调最大宽度序列，证明相关定理，给出所有五个非平凡部分对偶性运算的单调最大宽度定理，还证明了某些运算的可行集达到结果并转化到带状图。
Note on Hamiltonicity of basis graphs of even delta-matroids
本文证明了偶 delta-matroid 基图在顶点数大于二时的 Hamiltonian 性及其环结构性质，并推广了关于 matroids 的相关经典结论。
Signed permutohedra, delta-matroids, and beyond
本文建立了B型排列多面体环面簇的代数几何与delta-拟阵组合学的联系，计算了B型广义排列多面体的体积和格点计数，并利用热带Hodge理论确立了包含可实现delta-拟阵在内的该类拟阵的类Tutte不变量的对数凹性。
Transition polynomial as a weight system for binary delta-matroids
本文将转移多项式特化为弦图上的乘法权系统，满足 4-项关系并给出有限型纽结不变量，同时将类似结果推广到一般带图和二元 delta-拟阵，从而得到有限型链环不变量。
Partial-twuality polynomial interpolation for binary delta-matroids
本文证明了对任意二元delta-拟阵和所有非平凡的部分对偶性算子，部分对偶性多项式要么是偶插值、奇插值，或同时是偶插值和奇插值，并给出反例说明二元性假设的必要性。
Valuated Delta Matroids and Principal Minors of Hermitian matrices
本文提出赋值Δ-拟阵，统一推广赋值拟阵与Δ-拟阵，证明其具有良好性质，并建立其与赋值域上Hermitian矩阵主子式赋值的表示关系。
Finite order invariants (Vassiliev invariants) of knots are expressed in terms of weight systems, that is, functions on chord diagrams satisfying the four-term relations. Weight systems have graph analogues, so-called $4$-invariants of graphs, i.e. functions on graphs that satisfy the four-term relations for graphs. Each $4$-invariant determines a weight system. The notion of weight system is naturally generalized for the case of embedded graphs with an arbitrary number of vertices. Such embedded graphs correspond to links; to each component of a link there corresponds a vertex of an embedded …
On a conjecture of Gross, Mansour and Tucker for $Δ$-matroids
本文研究 Gross、Mansour 和 Tucker 关于 delta-拟阵部分对偶多项式的猜想，证明偶非二元 delta-拟阵均无改变宽度的扭转，扩展了 Yan 和 Jin 对偶正规二元情形的结论。
Representative set statements for delta-matroids and the Mader delta-matroid
本文提出delta-正则集的代表集陈述，并展示了Mader网络的稀疏化结果，扩展了核化工具箱。
The spinor variety is cut out by the quadratic Wick relations among the principal Pfaffians of an n x n skew-symmetric matrix. Its points correspond to n-dimensional isotropic subspaces of a 2n-dimensional vector space. In this paper we tropicalize this picture, and we develop a combinatorial theory of tropical Wick vectors and tropical linear spaces that are tropically isotropic. We characterize tropical Wick vectors in terms of subdivisions of Delta-matroid polytopes, and we examine to what extent the Wick relations form a tropical basis. Our theory generalizes several results for tropical l…
On the maximum twist width of delta-matroids
本文研究δ-矩阵的最大扭转宽度，证明其可通过扭转可行集实现，并解决了一个关于带状图欧拉亏格递增的问题。
Regular dyadic triangulations of delta-matroid polytopes
本文证明每个delta-拟阵多面体（及更一般的整B型广义置换多面体）存在正则二进三角剖分，其最大单纯形体积为2的幂，并指出B型中唯一非幺模单纯形例外，基于B型根配置的完全二进性。
If $G$ is a looped graph, then its adjacency matrix represents a binary matroid $M_{A}(G)$ on $V(G)$. $M_{A}(G)$ may be obtained from the delta-matroid represented by the adjacency matrix of $G$, but $M_{A}(G)$ is less sensitive to the structure of $G$. Jaeger proved that every binary matroid is $M_{A}(G)$ for some $G$ [Ann. Discrete Math. 17 (1983), 371-376]. The relationship between the matroidal structure of $M_{A}(G)$ and the graphical structure of $G$ has many interesting features. For instance, the matroid minors $M_{A}(G)-v$ and $M_{A}(G)/v$ are both of the form $M_{A}(G^{\prime}-v)$ wh…
Delta-matroids and toric degenerations in OG(n,2n+1)
本文在极大正交Grassmann流形OG(n,2n+1)中构造了环面轨道闭包到Richardson簇并集的显式退化，由此得到上同调类公式，并揭示退化片段对应delta-拟阵基多面体对单位超立方体的分解。
In unpublished work, Geelen proved that a matroid is near-regular if and only if it has no minor isomorphic to: U2,5; U3,5; the Fano plane and its dual; the non-Fano and its dual; the single-element deletion of AG(2,3), its dual, and the matroid obtained from it with a Delta-Y operation; and P8. We provide a proof of this characterization.
Binary delta-matroids are closed under vertex flips, which consist of the natural operations of twist and loop complementation. In this note we provide an extension of this result from GF(2) to GF(4). As a consequence, quaternary matroids are "safe" under vertex flips (vf-safe for short). As an application, we find that the matroid of a bicycle space of a quaternary matroid is independent of the chosen representation. This extends a result of Vertigan [J. Comb. Theory B (1998)] concerning the bicycle dimension of quaternary matroids.
In this note we generalize the convolution formula for the Tutte polynomial of Kook-Reiner-Stanton and Etienne-Las Vergnas to a more general setting that includes both arithmetic matroids and delta-matroids. As corollaries, we obtain new proofs of two positivity results for pseudo-arithmetic matroids and a combinatorial interpretation of the arithmetic Tutte polynomial at infinitely many points in terms of arithmetic flows and colorings. We also exhibit connections with a decomposition of Dahmen-Micchelli spaces and lattice point counting in zonotopes.
Euler Stratifications of Second Hypersimplices via Delta-matroids
通过Delta-拟阵与主A-行列式的非零因子对应，研究第二超单形缩放环面的欧拉示性数，证明Clarke等人(2024)关于最小ML度数的猜想。
For every finite simple connected graph $G = (V,E)$, we introduce an invariant, its blowup-polynomial $p_G(\{ n_v : v \in V \})$. This is obtained by dividing the determinant of the distance matrix of its blowup graph $G[{\bf n}]$ (containing $n_v$ copies of $v$) by an exponential factor. We show that $p_G({\bf n})$ is indeed a polynomial function in the sizes $n_v$, which is moreover multi-affine and real-stable. This associates a hitherto unexplored delta-matroid to each graph $G$; and we provide a second unexplored one for each tree. As another consequence, we obtain a new characterization …
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