Erratum to "Asymptotic dimension and boundary dimension of proper CAT(0) spaces"

. The review on [1] in Mathematical Reviews points out that the proof of its main result is incorrect. The aim of this paper is to correct the previous paper’s argument and clarify the statement. In [2] it is stated that the proof of [1, Theorem 1.1] is incorrect, i.e., the map f does not satisfy ð(cid:1)Þ r , as claimed on line 4 of the first paragraph on [1, p. 188]. In fact, diam f ð B ð c i k ð x 0 Þ ; 1 ÞÞ ¼ diam a 1 ð B ð x 0 ; 1 ÞÞ 0 0 for each k A N . In this paper, we redefine the map f ¼ 6 k A N f k : ð Y ; r Þ ! ð B n þ 1 ; s Þ , in particular f k : c i k ð B ð x 0 ; k ÞÞ ! B n þ 1 , where let B ð x 0 ; r Þ ¼ f y A X : d ð x 0 ; y Þ a r g for r > 0. Let ð X ; d Þ be a proper CAT ð 0 Þ space and let c : ð X ; d Þ ! ð X ; d Þ be an isometry satisfying that f c i ð x Þ : i A Z g is unbounded (see [1, Theorem 1.1]). Fix a point x 0 of X . For every x A X , let x x : ½ 0 ; d ð x 0 ; x Þ(cid:2) ! X be the geodesic from x 0 to x in ð X ; d Þ . Recall the projection map p 1 : X ! B ð x 0 ; 1 Þ in [1, p. 187] defined by p 1 ð x Þ ¼ x x ð min f d ð x 0 ; x Þ ; 1 gÞ for each x A X .