Journal of Inequalities in Pure and Applied Mathematics SOME NEW INEQUALITIES SIMILAR TO HILBERT-PACHPATTE TYPE INEQUALITIES volume 4, issue 2, article 33, 2003. ZHONGXUE LÜ Department of Basic Science of Technology College, Xuzhou Normal University, 221011, People’s Republic of China. E-Mail: lvzx1@163.net Received 25 May, 2002; accepted 7 April, 2003. Communicated by: S.S. Dragomir Abstract Contents JJ J II I Home Page Go Back Close c 2000 Victoria University ISSN (electronic): 1443-5756 059-02 Quit Abstract In this paper, some new inequalities similar to Hilbert-Pachpatte type inequalities are given. 2000 Mathematics Subject Classification: 26D15. Key words: Inequalities, Hilbert-Pachpatte inequalities, Hölder inequality. Contents 1 2 3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Main Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Discrete Analogues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities Zhongxue Lü Title Page Contents JJ J II I Go Back Close Quit Page 2 of 19 J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au 1. Introduction In [1, Chap. 9], the well-known Hardy-Hilbert inequality is given as follows. P p Theorem 1.1. Let p > 1, q > 1, p1 + 1q = 1, am , bn ≥ 0, 0 < ∞ n=1 an < ∞, P∞ q 0 < n=1 bn < ∞. Then ! p1 ∞ ! 1q ∞ X ∞ ∞ X X X π am b n p (1.1) ≤ a bqn m λ (m + n) sin(π/p) m=1 n=1 m=1 n=1 where π sin(π/p) Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities is best possible. The integral analogue of the Hardy-Hilbert inequality can be stated as follows R∞ Theorem 1.2. Let p > 1, q > 1, p1 + 1q = 1, f (x), g(y) ≥ 0, 0 < 0 f p (x)dx < R∞ ∞, 0 < 0 g q (y)dy < ∞. Then 1q Z ∞ p1 Z ∞ Z ∞Z ∞ π f (x)g(y) p q dxdy ≤ f (x)dx g (y)dy , (1.2) x+y sin(π/p) 0 0 0 0 where π sin(π/p) is best possible. In [1, Chap. 9] the following extension of Hardy-Hilbert’s double-series theorem is given. Theorem 1.3. Let p > 1, q > 1, Then ∞ X ∞ X am b n m=1 n=1 (m + n)λ 1 p + ≤K 1 q 1 p ≥ 1, 0 < λ = 2 − − ∞ X m=1 ! p1 apm ∞ X n=1 1 q + 1 q ≤ 1. Title Page Contents JJ J II I Go Back Close Quit Page 3 of 19 ! 1q bqn = 1 p Zhongxue Lü , J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au where K = K(p, q) depends on p and q only. The following integral analogue of Theorem 1.3 is also given in [1, Chap. 9]. Theorem 1.4. Under the same conditions as in Theorem 1.1 we have Z ∞ p1 Z ∞ 1q Z ∞Z ∞ f (x)g(y) p q dxdy ≤ K f dx g dy , (x + y)λ 0 0 0 0 where K = K(p, q) depends on p and q only. The inequalities in Theorems 1.1 and 1.2 were studied by Yang and Kuang (see [2, 3]). In [4, 5], some new inequalities similar to the inequalities given in Theorems 1.1, 1.2, 1.3 and 1.4 were established. In this paper, we establish some new inequalities similar to the HilbertPachpatte inequality. Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities Zhongxue Lü Title Page Contents JJ J II I Go Back Close Quit Page 4 of 19 J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au 2. Main Results In what follows we denote by R the set of real numbers. Let N = {1, 2, . . . }, N0 = {0, 1, 2, . . . }. We define the operator ∇ by ∇u(t) = u(t) − u(t − 1) for any function u defined on N . For any function u(t) : [0, ∞) → R, we denote by u0 the derivatives of u. First we introduce some Lemmas. Lemma 2.1. (see [2]). Let p > 1, q > 1, p1 + 1q = 1, λ > 2 − min{p, q}, define the weight function ω1 (q, x) as 2−λ Z ∞ x q 1 dy, x ∈ [0, ∞). ω1 (q, x) := (x + y)λ y 0 Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities Zhongxue Lü Then (2.1) ω1 (q, x) = B q+λ−2 p+λ−2 , q p Title Page x1−λ , Contents where B(p, q) is β-function. Lemma 2.2. (see [3]). Let p > 1, q > 1, p1 + 1q = 1, λ > 2 − min{p, q}, define the weight function ω2 (q, x) as 2−λ Z ∞ x q 1 ω2 (q, x) := dy, x ∈ [0, ∞). xλ + y λ y 0 Then (2.2) 1 ω2 (q, x) = B λ q+λ−2 p+λ−2 , qλ pλ JJ J II I Go Back Close Quit Page 5 of 19 x 1−λ . J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au Lemma 2.3. Let p > 1, q > 1, weight function ω3 (q, m) as ω3 (q, m) := ∞ X n=1 1 p + 1 q = 1, λ > 2 − min{p, q}, define the m 2−λ 1 q , m ∈ {1, 2, . . . }. λ (m + n) n Then (2.3) ω3 (q, m) < B q+λ−2 p+λ−2 , q p m1−λ , where B(p, q) is β-function. Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities Zhongxue Lü Proof. By Lemma 2.1,we have 2−λ m q 1 ω3 (q, m) < dy (m + y)λ y 0 q+λ−2 p+λ−2 =B , m1−λ . q p Z ∞ Contents JJ J II I Go Back The proof is completed. Lemma 2.4. Let p > 1, q > 1, weight function ω4 (q, m) as ω4 (q, m) := Title Page ∞ X n=1 1 p + 1 q = 1, λ > 2 − min{p, q}, define the m 2−λ 1 q , m ∈ {1, 2, . . . }. λ λ m +n n Close Quit Page 6 of 19 J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au Then 1 ω4 (q, m) < B λ (2.4) q+λ−2 p+λ−2 , qλ pλ m1−λ . Proof. By Lemma 2.2, we have 2−λ m q 1 ω4 (q, m) < dy mλ + y λ y 0 1 q+λ−2 p+λ−2 = B , m1−λ . λ qλ pλ Z ∞ Zhongxue Lü The proof is completed. Our main result is given in the following theorem. 1 p 1 q Theorem 2.5. Let p > 1, + = 1, and f (x), g(y) be real-valued continuous functions defined on [0, ∞), respectively, and let f (0) = g(0) = 0, and Z ∞Z x Z ∞Z y p q 0 0< |f (τ )| dτ dx < ∞, 0 < |g 0 (δ)| dδdy < ∞. 0 0 Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities 0 Title Page Contents JJ J II I 0 Go Back Then Close ∞ ∞ |f (x)| |g(y)| dxdy (2.5) p−1 (qx + py q−1 )(x+y) 0 0 Z ∞ Z x p1 Z ∞ Z y 1q π p q 0 0 ≤ |f (τ )| dτ dx |g (δ)| dδdy . sin(π/p)pq 0 0 0 0 Z Z Quit Page 7 of 19 J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au In particular, when p = q = 2, we have Z ∞ Z (2.6) 0 0 ∞ |f (x)| |g(y)| dxdy (x + y)2 Z ∞ Z x 12 Z ∞ Z y 12 π 2 2 0 0 ≤ |f (τ )| dτ dx |g (δ)| dδdy . 2 0 0 0 0 Proof. From the hypotheses, we have the following identities Z x (2.7) f (x) = f 0 (τ )dτ, Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities 0 Zhongxue Lü and y Z (2.8) Title Page g 0 (δ)dδ g(y) = 0 Contents for x, y ∈ (0, ∞). From (2.7) and (2.8) and using Hölder’s integral inequality, respectively, we have (2.9) |f (x)| ≤ x 1 q x Z 0 p p1 |f (τ )| dτ II I Go Back Close 0 and (2.10) JJ J Quit |g(y)| ≤ y 1 p Z y 0 q 1q Page 8 of 19 |g (δ)| dδ 0 J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au for x, y ∈ (0, ∞). From (2.9) and (2.10) and using the elementary inequality z1 z2 ≤ (2.11) z1p z2q 1 1 + , z1 ≥ 0, z2 ≥ 0, + = 1, p > 1, p q p q we observe that 1 q |f (x)| |g(y)| ≤ x y 1 p Z x p |f 0 (τ )| dτ p1 Z 0 ≤ (2.12) x p−1 p + y q |g 0 (δ)| dδ 1q 0 y q−1 Z q x p |f 0 (τ )| dτ p1 Z y q |g 0 (δ)| dδ 1q Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities 0 0 Zhongxue Lü for x, y ∈ (0, ∞). From (2.12) we observe that 1 |f (x)| |g(y)| ≤ p−1 q−1 qx + py pq (2.13) Z x 0 p p1 Z |f (τ )| dτ 0 y 0 q |g (δ)| dδ Title Page 1q . 0 Hence Z ∞ Z (2.14) 0 0 ∞ |f (x)| |g(y)| dxdy + py q−1 )(x + y) 1 R y 1 Z ∞Z ∞ Rx 0 |f (τ )|p dτ p 0 |g 0 (δ)|q dδ q 1 0 ≤ dxdy. pq 0 x+y 0 (qxp−1 Contents JJ J II I Go Back Close Quit Page 9 of 19 J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au By Hölder’s integral inequality and (2.1), we have Z ∞ ∞ Z 0 0 (2.15) p1 R y 0 1q q p 0 |f (τ )| dτ |g (δ)| dδ 0 0 dxdy x+y p1 1 R y 0 1q 1 Z ∞Z ∞ Rx 0 p q pq (τ )| dτ |f |g (δ)| dδ x y pq 0 0 = dxdy 1 1 y x 0 0 (x + y) p (x + y) q ! p1 1q Z ∞Z ∞ Rx 0 p |f (τ )| dτ x 0 dxdy ≤ x+y y 0 0 1q Z ∞ Z ∞ R y 0 |g (δ)|q dδ y p1 0 dxdy × x+y x 0 0 Z ∞ Z x p1 Z ∞ Z y 1q π p q 0 0 ≤ |f (τ )| dτ dx |g (δ)| dδdy sin(π/p) 0 0 0 0 Rx by (2.14) and (2.15), we get (2.5). The proof of Theorem 2.5 is complete. In a similar way to the proof of Theorem 2.5, we can prove the following theorems. 1 p 1 q Theorem 2.6. Let p > 1, + = 1, λ > 2 − min{p, q}, and f (x), g(y) be real-valued continuous functions defined on [0, ∞),respectively, and let f (0) = g(0) = 0, and Z ∞Z x Z ∞Z y p q 1−λ 0 0< x |f (τ )| dτ dx < ∞, 0 < y 1−λ |g 0 (δ)| dδdy < ∞, 0 0 0 0 Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities Zhongxue Lü Title Page Contents JJ J II I Go Back Close Quit Page 10 of 19 J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au then ∞ Z ∞ |f (x)| |g(y)| dxdy (qxp−1 + py q−1 )(x + y)λ 0 q+λ−2 p+λ−2 Z p1 ∞Z x B , p q p 1−λ 0 ≤ x |f (τ )| dτ dx pq 0 0 Z ∞ Z y 1q q × y 1−λ |g 0 (δ)| dδdy . (2.16) 0 Z 0 0 In particular, when p = q = 2, Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities Zhongxue Lü ∞ Z Z (2.17) 0 0 ∞ |f (x)| |g(y)| dxdy (x + y)1+λ Z ∞ Z x 12 B λ2 , λ2 2 1−λ 0 ≤ x |f (τ )| dτ dx 2 0 0 Z ∞ Z y 12 2 1−λ 0 × y |g (δ)| dδdy . 0 0 0 Contents JJ J II I 0 Theorem 2.7. Let p > 1, p1 + 1q = 1, λ > 2 − min{p, q}, and f (x), g(y) be real-valued continuous functions defined on [0, ∞), respectively, and let f (0) = g(0) = 0, and Z ∞Z x Z ∞Z y p q 1−λ 0 0< x |f (τ )| dτ dx < ∞, 0 < y 1−λ |g 0 (δ)| dδdy < ∞. 0 Title Page 0 Go Back Close Quit Page 11 of 19 J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au Then Z (2.18) 0 ∞ ∞ |f (x)| |g(y)| dxdy (qxp−1 + py q−1 )(xλ + y λ ) 0 q+λ−2 p+λ−2 Z p1 ∞Z x B , pλ qλ p 1−λ 0 ≤ x |f (τ )| dτ dx λpq 0 0 Z ∞ Z y 1q q × y 1−λ |g 0 (δ)| dδdy . Z 0 0 In particular, when p = q = 2, Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities Zhongxue Lü Z ∞ Z (2.19) 0 0 ∞ |f (x)| |g(y)| dxdy + y λ )(x + y) Z ∞ Z x 12 π 2 1−λ 0 ≤ x |f (τ )| dτ dx 2λ 0 0 Z ∞ Z y 12 2 1−λ 0 × y |g (δ)| dδdy . (xλ 0 Title Page Contents JJ J II I 0 Go Back Close Quit Page 12 of 19 J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au 3. Discrete Analogues Theorem 3.1. Let p > 1, p1 + 1q = 1, and {a(m)} and {b(n)} be two sequences where m, N0 , and a(0) = b(0) = 0, and 0 < P∞ Pofm real numbers Pn∞ ∈ P p n q |∇a(τ )| < ∞, 0 < m=1 τ =1 n=1 δ=1 |∇b(δ)| < ∞, then (3.1) ∞ X ∞ X m=1 n=1 (qmp−1 |am | |bn | + pnq−1 )(m + n) π ≤ sin(π/p)pq ∞ X m X ! p1 apk m=1 k=1 ∞ X n X ! 1q bqr . n=1 r=1 Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities Zhongxue Lü In particular, when p = q = 2, we have (3.2) ∞ X ∞ X |am | |bn | π ≤ 2 (m + n) 2 m=1 n=1 ∞ X m X ! 12 a2k m=1 k=1 ∞ X n X ! 12 b2r Title Page . n=1 r=1 Proof. From the hypotheses, it is easy to observe that the following identities hold (3.3) am = m X Contents JJ J II I Go Back ∇a(τ ), Close τ =1 Quit and (3.4) bn = n X δ=1 Page 13 of 19 ∇b(δ) J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au for m, n ∈ N. From (3.3) and (3.4) and using Hölder’s inequality, we have 1 q |am | ≤ m (3.5) m X ! p1 |∇a(τ )|p , τ =1 and |bn | ≤ n (3.6) 1 p n X ! 1q |∇b(δ)|q Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities δ=1 for m, n ∈ N. From (3.5) and (3.6) and using the elementary inequality (2.11), we observe that ! p1 ! 1q m n X X 1 1 p q |∇b(δ)| |am | |bn | ≤ m q n p |∇a(τ )| τ =1 (3.7) ≤ δ=1 mp−1 nq−1 + p q X m ! p1 p |∇a(τ )| τ =1 n X ! 1q q |∇b(δ)| δ=1 (3.8) |am | |bn | p−1 qm + pnq−1 ≤ 1 pq τ =1 Contents JJ J II I Close ! p1 |∇a(τ )|p Title Page Go Back for m, n ∈ N. From (3.7), we observe that m X Zhongxue Lü n X δ=1 ! 1q |∇b(δ)|q . Quit Page 14 of 19 J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au Hence (3.9) ∞ X ∞ X |am | |bn | + pnq−1 )(m + n) m=1 n=1 P ∞ ∞ p p1 Pn q 1q 1 XX( m τ =1 |∇a(τ )| ) ( δ=1 |∇b(δ)| ) ≤ . pq m=1 n=1 m+n (qmp−1 By the Hölder inequality and (2.3) P ∞ X ∞ p p1 Pn q 1q X ( m δ=1 |∇b(δ)| ) τ =1 |∇a(τ )| ) ( m+n m=1 n=1 1 P P ∞ X ∞ p p1 X ( m m pq1 ( nδ=1 |∇b(δ)|q ) q n pq1 τ =1 |∇a(τ )| ) = 1 1 m n (m + n) q (m + n) p m=1 n=1 !1 ∞ X ∞ Pm p 1q p X |∇a(τ )| m τ =1 ≤ m+n n m=1 n=1 !1 ∞ X ∞ Pn q p1 q X |∇b(δ)| n δ=1 × m+n m m=1 n=1 ! p1 ∞ n ! 1q ∞ X m X X X π (3.10) < |∇a(τ )|p |∇b(δ)|q sin(π/p) m=1 τ =1 n=1 δ=1 by (3.9) and (3.10), we get (3.1). The proof of Theorem 3.1 is complete. Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities Zhongxue Lü Title Page Contents JJ J II I Go Back Close Quit Page 15 of 19 J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au In a similar manner to the proof of Theorem 3.1, we can prove the following theorems. Theorem 3.2. Let p > 1, p1 + 1q = 1, λ > 2−min{p, q}, and {a(m)} and {b(n)} be two sequences of real numbers where m, n ∈ N0 ,and a(0) = b(0) = 0, and 0< ∞ X m X m1−λ |∇a(τ )|p < ∞, m=1 τ =1 0< n ∞ X X Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities n1−λ |∇b(δ)|q < ∞, n=1 δ=1 Zhongxue Lü then (3.11) ∞ X ∞ X m=1 n=1 ≤ |am | |bn | (qmp−1 + pnq−1 )(m + n)λ q+λ−2 p+λ−2 ∞ X m B , p X q pq Title Page Contents ! p1 m=1 τ =1 × ∞ X n X n=1 δ=1 In particular, when p = q = 2, we have (3.12) ∞ X ∞ X |am | |bn | (m + n)1+λ m=1 n=1 JJ J m1−λ |∇a(τ )|p ! 1q n1−λ |∇b(δ)|q . II I Go Back Close Quit Page 16 of 19 J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au ≤ B λ λ , 2 2 2 ∞ X m X ! 12 ∞ X n X 2 m1−λ |∇a(τ )| m=1 τ =1 ! 12 2 n1−λ |∇b(δ)| . n=1 δ=1 Theorem 3.3. Let p > 1, p1 + 1q = 1, λ > 2−min{p, q}, and {a(m)} and {b(n)} be two sequences of real numbers where m, n ∈ N0 , and a(0) = b(0) = 0, and 0< m ∞ X X m1−λ |∇a(τ )|p < ∞, m=1 τ =1 0< ∞ X n X Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities q n1−λ |∇b(δ)| < ∞, n=1 δ=1 Zhongxue Lü then (3.13) ∞ X ∞ X m=1 n=1 ≤ |am | |bn | + pnq−1 )(mλ + nλ ) p+λ−2 ∞ X m B q+λ−2 , X qλ pλ Title Page (qmp−1 λpq Contents ! p1 JJ J m1−λ |∇a(τ )|p m=1 τ =1 × ∞ X n X ! 1q n1−λ |∇b(δ)|q II I Go Back . Close n=1 δ=1 In particular, when p = q = 2, we have (3.14) ∞ X ∞ X m=1 n=1 Quit Page 17 of 19 |am | |bn | (m + n)(mλ + nλ ) J. Ineq. Pure and Appl. Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au π ≤ 2λ ∞ X m X m=1 τ =1 ! 12 2 m1−λ |∇a(τ )| ∞ X n X ! 12 2 n1−λ |∇b(δ)| . n=1 δ=1 Some New Inequalities Similar to Hilbert-Pachpatte Type Inequalities Zhongxue Lü Title Page Contents JJ J II I Go Back Close Quit Page 18 of 19 J. Ineq. Pure and Appl. 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Math. 4(2) Art. 33, 2003 http://jipam.vu.edu.au