Several exact recovery criteria (ERC) ensuring that orthogonal matching pursuit (OMP) identifies the correct support of sparse signals have been developed in the last few years. These ERC rely on the restricted isometry property (RIP), the associated restricted isometry constant (RIC) and sometimes the restricted orthogonality constant (ROC). In this paper, three of the most recent ERC for OMP are examined. The contribution is to show that these ERC remain valid for a generalization of OMP, entitled simultaneous orthogonal matching pursuit (SOMP), that is capable to process several measurement vectors simultaneously and return a common support estimate for the underlying sparse vectors. The sharpness of the bounds is also briefly discussed in light of previous works focusing on OMP.
Regarding older works, it is also worth pointing out that the ERC @math , first obtained in [Theorem 5.2] liu2012orthogonal for OMP, has been shown to remain valid for SOMP in [Corollary 1] ding2012robustness . Thereby, the authors of @cite_1 also proved that the older ERC @math , initially derived in [Theorem 3.1] davenport2010analysis for OMP, remains correct for SOMP as @math is implied by @math . Very recently, ) was extended to SOMP in [Remark 1] xu2015perturbation . However, the extension to SOMP of both ) and ) is a novel result. In @cite_8 , the author has derived the ERC @math , which is sharper than ). Combining the ideas developed in @cite_8 and our paper could possibly extend this ERC to SOMP.
@cite_1 @cite_8
2169380424 1557195970
Introduction Preliminaries Special linear groups: @math Orthogonal groups: @math Symplectic groups: @math Unitary groups: @math Proofs of Theorems 1.1 and 1.1, and of corollaries 1.2-1.4 Permutation group algorithms Concluding remarks References. In this paper we study general @math l p regularized unconstrained minimization problems. In particular, we derive lower bounds for nonzero entries of the first- and second-order stationary points and hence also of local minimizers of the @math l p minimization problems. We extend some existing iterative reweighted @math l 1 ( @math IRL 1 ) and @math l 2 ( @math IRL 2 ) minimization methods to solve these problems and propose new variants for them in which each subproblem has a closed-form solution. Also, we provide a unified convergence analysis for these methods. In addition, we propose a novel Lipschitz continuous @math ∈ -approximation to @math ? x ? p p . Using this result, we develop new @math IRL 1 methods for the @math l p minimization problems and show that any accumulation point of the sequence generated by these methods is a first-order stationary point, provided that the approximation parameter @math ∈ is below a computable threshold value. This is a remarkable result since all existing iterative reweighted minimization methods require that @math ∈ be dynamically updated and approach zero. Our computational results demonstrate that the new @math IRL 1 method and the new variants generally outperform the existing @math IRL 1 methods (Chen and Zhou in 2012; Foucart and Lai in Appl Comput Harmon Anal 26:395---407, 2009). The seminal complete intersection theorem of Ahlswede and Khachatrian gives the maximum cardinality of a @math -uniform @math -intersecting family on @math points, and describes all optimal families. We extend this theorem to several other settings: the weighted case, the case of infinitely many points, and the Hamming scheme. The weighted Ahlswede-Khachatrian theorem gives the maximal @math measure of a @math -intersecting family on @math points, where @math . As has been observed by Ahlswede and Khachatrian and by Dinur and Safra, this theorem can be derived from the classical one by a simple reduction. However, this reduction fails to identify the optimal families, and only works for @math , using a different technique of Ahlswede and Khachatrian (the case @math is Katona's intersection theorem). We then extend the weighted Ahlswede-Khachatrian theorem to the case of infinitely many points. The Ahlswede-Khachatrian theorem on the Hamming scheme gives the maximum cardinality of a subset of @math in which any two elements @math have @math positions @math such that @math . We show that this case corresponds to @math with @math , extending work of Ahlswede and Khachatrian, who considered the case @math . We also determine the maximum cardinality families. We obtain similar results for subsets of @math , though in this case we are not able to identify all maximum cardinality families. For a > 0, let Wa(t) be the a-neighbourhood of standard Brownian motion in Rd starting at 0 and observed until time t. It is well-known that E|Wa(t)| ?at (t ? 8) for d = 3, with ?a the Newtonian capacity of the ball with radius a. We prove that @math and derive a variational representation for the rate function I?a . We show that the optimal strategy to realise the above moderate deviation is for Wa(t) to look like a Swiss cheese': Wa(t) has random holes whose sizes are of order 1 and whose density varies on scale t1 d. The optimal strategy is such that t-1 dWa(t) is delocalised in the limit as t ? 8. This is markedly different from the optimal strategy for large deviations |Wa(t)| = f(t) with f(t) = o(t), where Wa(t) is known to fill completely a ball of volume f(t) and nothing outside, so that Wa(t) has no holes and f(t)-1 dWa(t) is localised in the limit as t ? 8. We give a detailed analysis of the rate function I?a , in particular, its behaviour near the boundary points of (0, ?a) as well as certain monotonicity properties. It turns out that I?a has an infinite slope at ?a and, remarkably, for d = 5 is nonanalytic at some critical point in (0, ?a), above which it follows a pure power law. This crossover is associated with a collapse transition in the optimal strategy. We also derive the analogous moderate deviation result for d = 2. In this case E|Wa(t)| 2p t log t (t ? 8), and we prove that @math The rate function I2p has a finite slope at 2p.