Twin-width is a structural parameter in graph theory that is used to measure the complexity of a graph in terms of how it can be decomposed into simpler components. It is particularly useful for understanding certain classes of graphs and can provide insights into their properties and potential algorithmic approaches for solving problems on them. The concept of twin-width was introduced in a paper by Bui-Xuan, Dolecek, and Fomin in 2020.

In graph theory, a **bramble** is a concept used to describe a certain type of structure in a graph related to covering and dominating sets. Specifically, a bramble is a collection of subsets of vertices that captures the idea of a "tangled" set of vertices that cannot be separated from each other without removing some edges from the graph.

The concept of a graph minor is a fundamental notion in graph theory, particularly in the study of graph structure and graph algorithms. A graph \( H \) is said to be a **minor** of another graph \( G \) if \( H \) can be formed from \( G \) by performing a series of operations that includes: 1. **Edge Deletion**: Removing edges from the graph. 2. **Vertex Deletion**: Removing vertices and incident edges from the graph.

Halin's Grid Theorem is a result in graph theory that describes the structure of certain infinite graphs. Specifically, it focuses on a type of infinite graph known as a "grid" graph, which is a graph that resembles a two-dimensional grid or lattice. Halin's theorem provides conditions under which such infinite grid graphs can be embedded into three-dimensional space without crossings.

The Kelmans–Seymour conjecture is a conjecture in graph theory that relates to the structure of certain types of graphs. Specifically, it deals with the behavior of complete graphs and the existence of specific subgraphs within them. Formulated by Paul Kelmans and Neil Seymour, the conjecture states that every 2-edge-connected graph can be represented as a graph obtained from a complete graph by the contraction of edges.

A Partial k-tree is a data structure used primarily in the field of combinatorial optimization and computer science, particularly in topics related to the representation of combinatorial objects or configurations, such as combinations, subsets, or sequences. In general, a k-tree is a tree structure that represents all possible configurations of k elements chosen from a larger set, and it can be used for various applications, including generating combinations or permutations.

The term "Petersen family" can refer to different contexts depending on the specific area of interest. Here are a few possibilities: 1. **Cultural or Historical Context**: The Petersen family could refer to a family of historical or cultural significance in a specific region or country. 2. **Literary or Film Reference**: There might be fictional works, books, or movies that feature a "Petersen family" as characters.

In graph theory, a **Blossom** refers to a specific structure that is relevant in the context of matching algorithms, particularly in the matching of general graphs. The Blossom structure is utilized to handle situations where augmenting paths may be of odd length, which can complicate the process of finding maximum matchings. The concept of Blossoms is associated with the **Edmonds' Blossom Algorithm**, developed by Jack Edmonds in the 1960s.

"Bipartite half" might refer to concepts within graph theory, particularly regarding bipartite graphs. A **bipartite graph** is a type of graph where the set of vertices can be divided into two distinct sets such that no two graph vertices within the same set are adjacent.

A **clique graph** is a concept in graph theory that pertains to representing cliques within a given graph. A **clique** in a graph is a subset of its vertices such that every two distinct vertices in the subset are adjacent, meaning there is an edge connecting each pair of vertices. In simpler terms, a clique is a complete subgraph.

An acyclic orientation of a directed graph (digraph) is an assignment of directions to the edges of the graph such that there are no directed cycles.

Time-sharing systems represent a significant evolution in computing, allowing multiple users to interact with a computer simultaneously. This concept emerged from the need for more efficient use of computing resources, which were, at the time, expensive and limited. ### Key Stages in the Evolution of Time-Sharing Systems: 1. **Early Computing (1950s)**: - Computers were large, expensive, and primarily used for batch processing.

In graph theory, the complement of a graph is a graph that contains the same set of vertices but has edges that are not present in the original graph.

The disjoint union of graphs is a concept in graph theory that combines two or more graphs into a new graph in such a way that the original graphs do not share any vertices or edges. Here's how it works: 1. **Graphs Involved**: Suppose you have two or more graphs \( G_1, G_2, \ldots, G_n \).

The Goldberg–Coxeter construction is a method used in geometry, particularly in the study of polyhedra and polyhedral structures. It provides a systematic way to generate a class of convex polyhedra, particularly those that can be described as geometric realizations of certain types of combinatorial structures known as "spherical polyhedra.

A line graph is a type of chart used to display information that changes over time. It consists of a series of data points, called "markers," connected by straight line segments. Line graphs are particularly useful for showing trends, patterns, and relationships between two variables. ### Key Features of Line Graphs: 1. **Axes**: - The horizontal axis (x-axis) typically represents the independent variable (often time).

A **moral graph** is a concept used in the fields of graph theory and probabilistic graphical models, particularly in the context of Bayesian networks and Markov networks. The moral graph is derived from a directed acyclic graph (DAG) representing a Bayesian network. ### How to Construct a Moral Graph: 1. **Start with a Directed Graph:** Begin with a Bayesian network, which is typically represented as a directed acyclic graph (DAG).

In mathematics and graph theory, a Mycielski graph, or Mycielski construction, is a method for constructing new graphs from existing ones. The Mycielski construction is used primarily to create triangle-free graphs, which are graphs that do not contain any cycles of length three (triangles). The construction works as follows: 1. **Start with a graph \( G \)**: This can be any simple graph.

A Type-in program refers to a type of computer program where the user is expected to manually enter (or "type in") the code into a computer or programming environment. This practice was particularly popular in the early days of personal computing, especially in the 1980s and 1990s, when magazines and books would publish source code listings for users to type into their own computers. Type-in programs often serve as a way to teach programming concepts, allowing users to learn by doing.