Meet

Definition

In the context of partially ordered sets and lattice theory, a 'meet' is the greatest lower bound (GLB) of two elements. It represents the largest element that is less than or equal to both elements within a given set. This concept is crucial in understanding how elements relate to each other in a structured way, especially when dealing with lattices where every pair of elements has both a meet and a join.

5 Must Know Facts For Your Next Test

1. The meet of two elements a and b in a partially ordered set is often denoted by a ∧ b.
2. In lattices, the existence of meets for all pairs ensures that the structure supports operations fundamental to combinatorial theories.
3. Meets can be visualized in Hasse diagrams, where they correspond to lower points within the diagram.
4. If one element is less than or equal to another, that element is its own meet with the greater element.
5. The concept of meets extends beyond finite sets and can be applied in infinite contexts as long as the meet exists.

Review Questions

• How does the concept of 'meet' contribute to the structure of partially ordered sets?
  • 'Meet' contributes significantly to the structure of partially ordered sets by providing a way to identify the greatest lower bound of two elements. This allows us to establish relationships between elements and helps create a clearer understanding of their ordering. In a partially ordered set, having a meet helps in defining the overall structure and enables further analysis of how elements interact within that framework.
• Compare and contrast the concepts of 'meet' and 'join' in lattice theory, highlighting their significance.
  • 'Meet' and 'join' are fundamental operations in lattice theory, representing the greatest lower bound and least upper bound of two elements, respectively. While 'meet' focuses on finding an element that is as large as possible but still less than or equal to both elements, 'join' identifies an element that is as small as possible yet greater than or equal to both. Together, they encapsulate the full relational dynamics between pairs of elements in a lattice, making them vital for exploring algebraic properties.
• Evaluate the role of 'meets' in Specht modules and Young's lattice, particularly regarding representation theory.
  • 'Meets' play a critical role in Specht modules and Young's lattice by facilitating the understanding of how these mathematical structures represent symmetric groups. In this context, meets help define how different partitions interact and how their corresponding modules combine. By analyzing meets within Young's lattice, we gain insight into representation theory, particularly how these representations can be constructed and decomposed based on partition relationships.

Related terms

join: The least upper bound (LUB) of two elements, which is the smallest element that is greater than or equal to both elements.

partially ordered set: A set equipped with a binary relation that is reflexive, antisymmetric, and transitive, allowing for comparison between elements.

lattice: A special type of partially ordered set where any two elements have both a meet and a join.