Sparsest solutions of underdetermined linear systems via -minimization for

We present a condition on the matrix of an underdetermined linear system which guarantees that the solution of the system with minimal ℓ_q-quasinorm is also the sparsest one. This generalizes, and slightly improves, a similar result for the ℓ₁-norm. We then introduce a simple numerical scheme to compute solutions with minimal ℓ_q-quasinorm, and we study its convergence. Finally, we display the results of some experiments which indicate that the ℓ_q-method performs better than other available methods.