arXiv:2004.01437v1 [math.CA] 3 Apr 2020 on h egtdBrmnOlc space Bergman-Orlicz weighted The od o any for holds inequality following the ntds,fr0 for disk, unit (1) (quasi)-norm Luxembourg endby defined l ooopi ucin on functions holomorphic all otnosadnndcesn.W oeta hsipisth implies this that note We non-decreasing. and continuous L itn falhlmrhcfntos edfieon define We functions. holomorphic all of sisting f ie rwhfnto ,w eoeby denote we Φ, function growth a Given measure. ftepstv measures positive the of eosrethat observe We sdfie stesto all of set the as defined is Moreover, q uhthat such ujciefnto [0 : Φ function surjective A For ( e od n phrases. and words Key ie 0 Given 1991 h sa egtdBrmnspace Bergman weighted usual The u etn steui ball unit the is setting Our B B n n EGA-RIZSAE FTEUI BALL UNIT THE OF SPACES BERGMAN-ORLICZ . dµ , || > α ahmtc ujc Classification. Subject Mathematics fteui alta xedtelwrtinl siae for estimates triangle lower the extend that spaces. ball Bergman unit the of Abstract. f ALSNEBDIG IHLS FOR LOSS WITH EMBEDDINGS CARLESON || scniuu.Ta s hr xssaconstant a exists there is, That continuous. is ) Φ lux dν || ,q< q p, < − ,α f α || ,w eoeby denote we 1, f ( = Φ lux || z ∈ ,α p < f = ) || || A f || epoeCreo mednsfrBrmnOlc spaces Bergman-Orlicz for embeddings Carleson prove We mle that implies 0 = Φ || f α p ,α c ≤ L lux || ( || α ∞ B α Φ Φ lux f = (1 < q ,α n || =inf := ecnie h usino h characterization the of question the consider we , Z ), ega pc;Brmnmti;Olc pc;Carleson space; Orlicz metric; Bergman space; Bergman −| || p,α p µ B f sfiieif finite is f n > α z on || ∞ | := ∈ | 1. f L B 2 hsqeto a nwrdb .Hastings W. by answered was question this , α Φ ) ( B n H B ν α z , Z − Introduction e sdnt by denote us Let . n > λ := α ∞ ) dν n B ( | .I h etn fBrmnsae fthe of spaces Bergman of setting the In 1. B q n of h omlzdLbsu esr on measure Lebesgue normalized the ) uhta h embedding the that such dµ ( Z n | f z f → uhthat such ) B : 0 C A ,where ), ( 1 ( n se[5 ae569]). Page [15, (see 0 = f rmr 23;Scnay32A10,46E30. Secondary 32A36; Primary z n z α Φ A Φ( ) ednt by denote We . ) Z [0 ( α p ∈ | B B ≤ p , ( | n dν f n L B ∞ A C Φ stesbpc of subspace the is ) ( α Φ n α z α Φ sagot ucin fi is it if function, growth a is ) orsod oΦ( to corresponds ) k ( c ( ) ( B f α z | B ) | ) k n f dν stenraiigconstant. normalizing the is n p,α q h pc falfunctions all of space the ) < ( λ se[5 eak1.4]). Remark [15, (see ) z α dν ) ∞ ( | z A h eegemeasure Lebesgue the ) . < dν α Φ H ( α B ( ∞ B ( > C n z . h usual the n h following the ) I tΦ0 0. = Φ(0) at ) ,tesaeof space the ), µ ≤ L : uhthat such 0 t α Φ 1 A = ) ( α p B ( . n B t con- ) p n ) and B → n 2CARLESON EMBEDDINGS WITH LOSS FOR BERGMAN-ORLICZ SPACES OF THE UNIT BALL
[7] and the answer to the case 0 0 : Φ dµ(z) ≤ 1 . Bn λ Z In the setting of Bergman-Orlicz spaces, the definition of Carleson measures is as follows.
Definition 1.1. Let Φ1 and Φ2 be two growth functions, and let α > −1. n Let µ be a positive measure on B . We say µ is a Φ2-Carleson measure for Φ1 Bn Φ1 Bn Aα ( ), if there exists a constant C > 0 such that for any f ∈ Aα ( ),
(2) AΦ2,µ(f) ≤ CkfkΦ1,α. Remark 1. We observe that (2) is equivalent to saying that there is a Φ1 Bn constant C > 0 such that for any f ∈ Aα ( ), f 6= 0, |f(z)| (3) Φ2 dµ(z) ≤ C. Bn kfk Z Φ1,α Our concern in this paper is the characterization of the positive measures µ such that (3) holds, when Φ1 and Φ2 are in some appropriate sub-classes of −1 growth functions and such that Φ2 ◦Φ1 is non-increasing. This corresponds exactly to the case 0 mathematical analysis and its applications. Among these problems, one has the questions of the boundedness of Composition operators and Toeplitz operators to name a few.
2. Settings and presentation of the main result We recall that the growth function Φ is of upper type q if we can find q > 0 and C > 0 such that, for s> 0 and t ≥ 1, (4) Φ(st) ≤ CtqΦ(s). We denote by U q the set of growth functions Φ of upper type q, (with Φ(t) q ≥ 1), such that the function t 7→ t is non-decreasing. We write U = U q. q[≥1 We also recall that Φ is of lower type p if we can find p > 0 and C > 0 such that, for s> 0 and 0 We denote by Lp the set of growth functions Φ of lower type p, (with p ≤ 1), Φ(t) such that the function t 7→ t is non-increasing. We write L = Lp. 0 The growth function Φ satisfies the ∆2-condition if there exists a constant K > 1 such that, for any t ≥ 0, (7) Φ(2t) ≤ KΦ(t). A growth function Φ is said to satisfy the ∇2-condition whenever both Φ and its complementary function satisfy the ∆2-conditon. n For z = (z1,...,zn) and w = (w1, . . . , wn) in C , we let hz, wi = z1w1 + · · · + znwn 2 2 2 which gives |z| = hz, zi = |z1| + · · · + |zn| . For z ∈ Bn and δ > 0 define the average function µ(D(z, δ)) µˆδ(z) := vα(D(z, δ)) where D(z, δ) is the Bergman metric ball centered at z with radius δ. The Berezin transformµ ˜ of the measure µ is the function defined for any w ∈ Bn by (1 − |w|2)n+1+α µ˜(w) := dµ(z). Bn |1 − hz, wi|2(n+1+α) Z Our main result can be stated as follows. Theorem 2.1. Let Φ1, Φ2 ∈ L ∪ U , α> −1. Assume that −1 (i) Φ1 ◦ Φ2 satisfies the ∇2-condition; −1 Φ1◦Φ2 (t) (ii) t is non-decreasing. n Let µ be a positive measure on B , and let Φ3 be the complementary function −1 of Φ1 ◦ Φ2 . Then the following assertions are equivalent. Φ1 Bn (a) There is a constant C > 0 such that for any f ∈ Aα ( ), f 6= 0, the inequality (3) holds. Φ3 n (b) For any 0 <δ< 1, the average function µˆδ belongs to L (B , dνα). Φ3 n (c) The Berezin transform µ˜ of the measure µ belongs to L (B , dνα). We observe that the condition (ii) insures that the growth function Φ1 ◦ −1 p Φ1◦Φ (t) −1 −1 U p q 2 q Φ2 belongs to . IfΦ1(t) = t and Φ2(t) = t , then t = t and for this to be non-decreasing, one should have q ≤ p. Hence the above p n q n result is an extension of the embedding Iµ : Aα(B ) → L (B , dµ) when 0 As mentioned previously, the power function version of the above result is due to D. Luecking [8]. In his proof, Luecking used a method that appeals to the atomic decomposition of Bergman spaces and Khintchine’s inequalities. We will use the same approach here. We will prove and use a generaliza- tion of Khintchine’s inequalities to growth functions, and take advantage of the recent characterization of the atomic decomposition of Bergman-Orlicz spaces obtained in [1]. There are some other technicalities that require a good understanding of the properties of growth functions. n n For φ : B → B holomorphic, the composition operator Cφ is the opera- tor defined for any f ∈ H(Bn) by n Cφ(f)(z) = (f ◦ φ)(z), z ∈ B . Φ1 Bn Φ2 Bn We say the operator Cφ : Aα ( ) → L ( , dµ) is bounded, if there is a Φ1 Bn constant K > 0 such that for any f ∈ Aα ( ), f 6= 0, |Cφ(f)(z)| (8) Φ2 dµ(z) ≤ K. Bn kfk Z Φ1,α The characterization of the symbols φ such that (8) holds, relies essentially on the characterization of Carleson embeddings for Bergman-Orlicz spaces (see [2, 3]). Let φ be as above, and let β > −1. Define the measure µφ,β by −1 µφ,β(E)= νβ(φ (E)) for any Borel set E ⊆ Bn. Then it follows from classical arguments (see for example [3]) and Theo- rem 4.3 that the following holds. Corollary 2.2. Let Φ1, Φ2 ∈ L ∪ U , α,β > −1. Assume that −1 (i) Φ1 ◦ Φ2 satisfies the ∇2-condition; −1 Φ1◦Φ2 (t) (ii) t is non-decreasing. −1 Let Φ3 be the complementary function of Φ1◦Φ2 . Then for any holomorphic self mapping φ of Bn, the following conditions are equivalent. Φ1 Bn Φ2 Bn (a) Cφ is bounded from Aα ( ) to Aβ ( ). Φ1 Bn (b) The measure µφ,β is a Φ2-Carleson measure for Aα ( ). (c) For any 0 <δ< 1, the function z → µφ,β (D(z,δ)) belongs to LΦ3 (Bn, dν ). να(D(z,δ)) α The paper is organized as follows. In the next section, we present some useful tools needed to prove our result. Section 3 is devoted to the proof of our result . As usual, given two positive quantities A and B, the notation A . B (resp. A & B) means that there is an absolute positive constant C such that A ≤ CB (resp. A ≥ CB). When A . B and B . A, we write A ≈ B and say A and B are equivalent. Finally, all over the text, C or K will denote a positive constants not necessarily the same at distinct occurrences. CARLESON EMBEDDINGS WITH LOSS FOR BERGMAN-ORLICZ SPACES OF THE UNIT BALL5 3. Preliminary results In this section, we give some fundamental facts about growth functions, Bergman metric and Bergman-Orlicz spaces. These results are needed in the proof our result. 3.1. Growth functions and H¨older-type inequality. Let Φ be a C1 growth function. Then the lower and the upper indices of Φ are respectively defined by tΦ′(t) tΦ′(t) aΦ := inf and bΦ := sup . t>0 Φ(t) t>0 Φ(t) It is well known that if Φ is convex, then 1 ≤ aΦ ≤ bΦ < ∞ and, if Φ is concave, then 0 < aΦ ≤ bΦ ≤ 1. We observe that a convex growth function satisfies the ▽2−condition if and only if 1 < aΦ ≤ bΦ < ∞ (see [6, Lemma 2.6]). 1 Φ(t) We also observe that if Φ is a C growth function, then the functions taΦ Φ−1(t) and 1 are increasing. We then deduce the following. t bΦ Lemma 3.1. Let Φ ∈ Lp. Then the growth function Φp, defined by Φp(t)= Φ(t1/p) is in U q for some q ≥ 1. q When writing Φ ∈ U (resp. Φ ∈ Lp), we will always assume that q (resp. p) is the smallest (resp. biggest) number q1 (resp. p1) such that Φ is of upper type q1 (resp. lower type p1). We note that aΦ (resp. bΦ) coincides with the biggest (resp. smallest) number p such that Φ is of lower (resp. upper) type p. We also make the following observation (see [16, Proposition 2.1]). Proposition 3.2. The following assertion holds: Φ ∈ L if and only if Φ−1 ∈ U . We recall the following H¨older-type inequality (see [13, Page 58]). Lemma 3.3. Let Φ ∈ U , α> −1. Denote by Ψ the complementary function of Φ. Then |f(z)g(z)|dνα(z) ≤ 2 Φ (|f(z)|) dνα(z) Ψ (|g(z)|) dνα(z) . Bn Bn Bn Z Z Z 3.2. The Bergman metric and atomic decomposition. For a ∈ Bn, n a 6= 0, let ϕa denote the automorphism of B taking 0 to a defined by 1 a − P (z) − (1 − |z|2) 2 Q (z) ϕ (z)= a a a 1 − hz, ai n where Pa is the projection of C onto the one-dimensional subspace span of a and Qa = I − Pa where I is the identity. It is easy to see that ϕa(0) = a, ϕa(a) = 0, ϕaoϕa(z)= z. The Bergman metric d on the unit ball Bn is defined by 1 1+ ϕ (w) d(z, w)= log z , z, w ∈ Bn. 2 1 − ϕ (w) z 6CARLESON EMBEDDINGS WITH LOSS FOR BERGMAN-ORLICZ SPACES OF THE UNIT BALL For δ > 0, we denote by D(z, δ)= {w ∈ Bn : d(z, w) < δ}, the Bergman ball centered at z with radius δ. It is well known that for any α> −1, and for w ∈ D(z, δ), n+1+α 2 n+1+α να(D(z, δ)) ≈ |1 − hz, wi| ≈ (1 − |w| ) . n We recall that a sequence a = {ak}k∈N in B is said to be separated in the Bergman metric d, if there is a positive constant r> 0 such that d(ak, aj) > r for k 6= j. We refer to [19, Theorem 2.23] for the following result. Theorem 3.4. Given δ ∈ (0, 1), there exists a sequence {ak} of points of Bn called δ-lattice such that δ (i) the balls D(ak, 4 ) are pairwise disjoint; n (ii) B = ∪kD(ak, δ); (iii) there is an integer N (depending only on Bn) such that each point of n B belongs to at most N of the balls D(ak, 4δ). Let α> −1 and Φ a growth function. For a fixed δ-lattice a = {ak}k∈N in Bn Φ , we define by la,α, the space of all complex sequences c = {ck}k∈N such that 2 n+1+α (1 − |ak| ) Φ(|ck|) < ∞. Xk The following was observed in [17, Proposition 2.8]. Lemma 3.5. Let Φ ∈ U , and α > −1. Assume that Φ satisfies the ∇2- condition and denote by Ψ its complementary function. Then, the dual space Φ ∗ Φ Ψ ℓa,α of the space ℓa,α identifies with ℓa,α under the sum pairing