Last month witnessed two new property testing papers go online, which May be of interest to the community.

Reducing testing affine spaces to testing linearity, by Oded Goldreich (ECCC). In his recent guest post, the author outlined a reduction between testing if a Boolean function is an \((n-k)\)-dimensional affine subspace of \(\{0,1\}^n\), and testing linearity of functions \(f\colon\{0,1\}^n\to \{0,1\}\). This preprint encompasses details of this reduction, as part as a general approach to testing monomials (resolving along the way one of the open problems from April). Namely, it shows that testing if \(f\) is a \(k\)-monomial can be reduced to testing two properties, of \(f\) and of a (related) function \(g\colon\{0,1\}^n\to \{0,1\}^k\). Moreover, it establishes that the general case (\(k\geq 1\)) of the second part  can itself be reduced to the simpler case (\(k=1\)), giving a unified argument.

Testing Equality in Communication Graphs, by Noga Alon, Klim Efremenko, Benny Sudakov (ECCC). Given a connected graph on \(k\) nodes, where each node has an \(n\)-bit string, how many bits of communication are needed to test if all strings are equal? This paper investigates this problem for many interesting graphs, resolving the complexity up to lower order terms. For example, if the graph is Hamiltonian, they show that \(\frac{kn}{2} + o(n)\) bits are sufficient, while at least \(\frac{kn}{2}\) bits are required.

Edit (06/16): updated the description of the first preprint, which was not entirely accurate.