Doubly stochastic matrix

A **doubly stochastic matrix** is a special type of square matrix that has non-negative entries and each row and each column sums to 1. In other words, for a matrix \( A \) of size \( n \times n \), the following conditions must hold: 1. \( a_{ij} \geq 0 \) for all \( i, j \) (all entries are non-negative).