Besides linear algebra (matrix theory), Friedland does research on a wide variety of mathematics, including
complex dynamics and applied mathematics. With Elizabeth Gross, he proved a set-theoretic version of the salmon conjecture posed by
Elizabeth S. Allman.[4]
with
Walter K. Hayman: "Eigenvalue inequalities for the Dirichlet problem on spheres and the growth of subharmonic functions", Commentarii Mathematici Helvetici 51, no. 1 (1976): 133–161.
doi:
10.1007/BF02568147
"A lower bound for the permanent of doubly stochastic matrices", Annals of Mathematics, vol. 110, 1979, pp. 167–176.
JSTOR1971250
with Nimrod Moiseyev: "Association of resonance states with the incomplete spectrum of finite complex-scaled Hamiltonian matrices", Physical Review A, vol. 22, no. 2, 1980, 618–624.
doi:
10.1103/PhysRevA.22.618
"Convex spectral functions", Linear and Multilinear Algebra, vol. 9, no. 4, 1981, 299–316.
doi:
10.1080/03081088108817381
with Joel W. Robbin and John H. Sylvester: "On the crossing rule", Communications in Pure and Applied Mathematics, vol. 37, 1984, pp. 19–37.
doi:
10.1002/cpa.3160370104
with Vlad Gheorghiu and Gilad Gour: "Universal uncertainty relations", Physical Review Letters, vol. 111, 2013, p. 230401
doi:
10.1103/PhysRevLett.111.230401
with Stéphane Gaubert and Lixing Han: "Perron–Frobenius theorem for nonnegative multilinear forms and extensions", Linear Algebra and its Applications, vol. 438, no. 2, 2013, pp. 738–749.
doi:
10.1016/j.laa.2011.02.042
with Giorgio Ottaviani: "The number of singular vector tuples and uniqueness of best rank one approximation of tensors", Foundations of Computational Mathematics, vol. 14, 2014, pp. 1209–1242.
doi:
10.1007/s10208-014-9194-z