“…On the other hand, in [3], Bandeira, Fickus, Mixon and Wong conjectured that the Paley matrix, a (p + 1)/2 × (p + 1) matrix defined by quadratic residues modulo an odd prime p, satisfies the (K, δ)-RIP with K ≥ C 1 • p/ log C 2 p and some δ < √ 2 − 1, where C 1 , C 2 > 0 are universal constants. Under a number-theoretic conjecture in [10], Bandeira, Mixon and Moreira [4] proved that when p ≡ 1 (mod 4), the Paley matrix has the (K, o(1))-RIP with K = Ω(p γ ) for some γ > 1/2, which provides a conditional solution to Problem 2; recently, assuming that the Paley graph conjecture (see Remark 9) holds, Satake [21] extended the result in [4] for general odd primes p, and also gave some implications to a Ramsey-theoretic problem proposed by Erdős and Moser [11]. Also, under another type of number-theoretic conjecture, Arian and Yilmaz [1] proved that for a sufficiently large prime p ≡ 3 (mod 4), a (p + 1)/2 × p matrix obtained by deleting the last column from the Paley matrix (see Remark 14) has the (K, δ)-RIP for any K < p 5/7 /2 and δ < 1/ √ 2.…”