Journal of Inequalities in Pure and Applied Mathematics ENERGY DECAY OF SOLUTIONS OF A WAVE EQUATION OF p−LAPLACIAN TYPE WITH A WEAKLY NONLINEAR DISSIPATION volume 7, issue 1, article 15, 2006. ABBÈS BENAISSA AND SALIMA MIMOUNI Université Djillali Liabès Faculté des Sciences Déepartement de Mathématiques B. P. 89, Sidi Bel Abbès 22000, ALGERIA. Received 03 November, 2005; accepted 15 November, 2005. Communicated by: C. Bandle EMail: benaissa_abbes@yahoo.com EMail: bbsalima@yahoo.fr Abstract Contents JJ J II I Home Page Go Back Close c 2000 Victoria University ISSN (electronic): 1443-5756 329-05 Quit Abstract In this paper we study decay properties of the solutions to the wave equation of p−Laplacian type with a weak nonlinear dissipative. 2000 Mathematics Subject Classification: 35B40, 35L70. Key words: Wave equation of p−Laplacian type, Decay rate. Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Preliminaries and Main Results . . . . . . . . . . . . . . . . . . . . . . . . . References 3 5 Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni Title Page Contents JJ J II I Go Back Close Quit Page 2 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 1. Introduction We consider the initial boundary problem for the nonlinear wave equation of p−Laplacian type with a weak nonlinear dissipation of the type 0 l−2 0 0 0 (|u | u ) − ∆p u + σ(t)g(u ) = 0 in Ω × [0, +∞[, u = 0 on ∂Ω × [0, +∞[, (P) u(x, 0) = u0 (x), u0 (x, 0) = u1 (x) in Ω. where ∆p u = div(|∇x u|p−2 ∇x u), p, l ≥ 2, g : R → R is a continuous nondecreasing function and σ is a positive function. When p = 2, l = 2 and σ ≡ 1, for the case g(x) = δx (δ > 0), Ikehata and Suzuki [5] investigated the dynamics, showing that for sufficiently small initial data (u0 , u1 ), the trajectory (u(t), u0 (t)) tends to (0, 0) in H01 (Ω) × L2 (Ω) as t → +∞. When g(x) = δ|x|m−1 x (m ≥ 1), Nakao [8] investigated the decay property of the problem (P ). In [8] the author has proved the existence of global solutions to the problem (P ). For the problem (P ) with σ ≡ 1, l = 2, when g(x) = δ|x|m−1 x (m ≥ 1), p Yao [1] proved that the energy decay rate is E(t) ≤ (1 + t)− (mp−m−1) for t ≥ 0 by using a general method introduced by Nakao [8]. Unfortunately, this method does not seem to be applicable in the case of more general functions σ and is more complicated. Our purpose in this paper is to give energy decay estimates of the solutions to the problem (P ) for a weak nonlinear dissipation. We extend the results obtained by Yao and prove in some cases an exponential decay when p > 2 and the dissipative term is not necessarily superlinear near the origin. Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni Title Page Contents JJ J II I Go Back Close Quit Page 3 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 We use a new method recently introduced by Martinez [7] (see also [2]) to study the decay rate of solutions to the wave equation u00 − ∆x u + g(u0 ) = 0 in Ω × R+ , where Ω is a bounded domain of Rn . This method is based on a new integral inequality that generalizes a result of Haraux [4]. Throughout this paper the functions considered are all real valued. We omit the space variable x of u(t, x), ut (t, x) and simply denote u(t, x), ut (t, x) by u(t), u0 (t), respectively, when no confusion arises. Let l be a number with 2 ≤ l ≤ ∞. We denote by k · kl the Ll norm over Ω. In particular, the L2 norm is denoted by k · k2 . (·) denotes the usual L2 inner product. We use familiar function spaces W01,p . Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni Title Page Contents JJ J II I Go Back Close Quit Page 4 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 2. Preliminaries and Main Results First assume that the solution exists in the class (2.1) u ∈ C(R+ , W01,p (Ω)) ∩ C 1 (R+ , Ll (Ω)). λ(x), σ(t) and g satisfy the following hypotheses: (H1) σ : R+ → R+ is a non increasing function of class C 1 on R+ satisfying Z +∞ (2.2) σ(τ )dτ = +∞. 0 (H2) Consider g : R → R a non increasing C 0 function such that g(v)v > 0 for all v 6= 0. Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni and suppose that there exist ci > 0; i = 1, 2, 3, 4 such that (2.3) 1 c1 |v|m ≤ |g(v)| ≤ c2 |v| m if |v| ≤ 1, Title Page Contents (2.4) c3 |v|s ≤ |g(v)| ≤ c4 |v|r for all |v| ≥ 1, where m ≥ 1, l − 1 ≤ s ≤ r ≤ n(p−1)+p . n−p We define the energy associated to the solution given by (2.1) by the following formula l−1 0 l 1 ku kl + k∇x ukpp . E(t) = l p We first state two well known lemmas, and then state and prove a lemma that will be needed later. JJ J II I Go Back Close Quit Page 5 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 Lemma 2.1 (Sobolev-Poincaré inequality). Let q be a number with 2 ≤ q < np +∞ (n = 1, 2, . . . , p) or 2 ≤ q ≤ (n−p) (n ≥ p + 1), then there is a constant c∗ = c(Ω, q) such that kukq ≤ c∗ k∇ukp for u ∈ W01,p (Ω). Lemma 2.2 ([6]). Let E : R+ → R+ be a non-increasing function and assume that there are two constants q ≥ 0 and A > 0 such that Z +∞ E q+1 (t) dt ≤ AE(S), 0 ≤ S < +∞, S then we have E(t) ≤ cE(0)(1 + t) −1 q ∀t ≥ 0, if q > 0 and Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni Title Page E(t) ≤ cE(0)e−ωt ∀t ≥ 0, if q = 0, where c and ω are positive constants independent of the initial energy E(0). Lemma 2.3 ([7]). Let E : R+ → R+ be a non increasing function and φ : R+ → R+ an increasing C 2 function such that φ(0) = 0 and φ(t) → +∞ as t → +∞. Assume that there exist q ≥ 0 and A > 0 such that Z +∞ E(t)q+1 (t)φ0 (t) dt ≤ AE(S), 0 ≤ S < +∞, Contents JJ J II I Go Back Close Quit Page 6 of 19 S J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 then we have E(t) ≤ cE(0)(1 + φ(t)) −1 q ∀t ≥ 0, if q > 0 and E(t) ≤ cE(0)e−ωφ(t) ∀t ≥ 0, if q = 0, where c and ω are positive constants independent of the initial energy E(0). Proof of Lemma 2.3. Let f : R+ → R+ be defined by f (x) := E(φ−1 (x)). f is non-increasing, f (0) = E(0) and if we set x := φ(t) we obtain Z φ(T ) Z φ(T ) q+1 q+1 f (x) dx = E φ−1 (x) dx φ(S) φ(S) T Z Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni E(t)q+1 φ0 (t) dt = S ≤ AE(S) = Af (φ(S)) 0 ≤ S < T < +∞. Title Page Contents Setting s := φ(S) and letting T → +∞, we deduce that Z +∞ f (x)q+1 dx ≤ Af (s) 0 ≤ s < +∞. s JJ J II I Go Back By Lemma 2.2, we can deduce the desired results. Our main result is the following W01,p Close Quit l Theorem 2.4. Let (u0 , u1 ) ∈ × L (Ω) and suppose that (H1) and (H2) hold. Then the solution u(x, t) of the problem (P ) satisfies Page 7 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 (1) If l ≥ m + 1, we have Z E(t) ≤ C(E(0)) exp 1 − ω t σ(τ ) dτ ∀t > 0. 0 (2) If l < m + 1, we have E(t) ≤ C(E(0)) Rt σ(τ ) dτ 0 p ! (mp−m−1) ∀t > 0. Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Examples 1) If σ(t) = 1 (0 ≤ θ ≤ 1), by applying Theorem 2.4 we obtain tθ 1−θ E(t) ≤ C(E(0))e1−ωt if θ ∈ [0, 1[, l ≥ m + 1, (1−θ)p E(t) ≤ C(E(0))t− mp−m−1 if 0 ≤ θ < 1, l < m + 1 and p E(t) ≤ C(E(0))(ln t)− (mp−m−1) if θ = 1, l < m + 1. Abbès Benaissa and Salima Mimouni Title Page Contents JJ J II I Go Back 1 2) If σ(t) = θ , where k is a positive integer and t ln t ln2 t . . . lnk t ( ln1 (t) = ln(t) Close Quit Page 8 of 19 lnk+1 (t) = ln(lnk (t)), J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 by applying Theorem 2.4, we obtain p E(t) ≤ C(E(0))(lnk+1 t)− (mp−m−1) (1−θ)p if θ = 1, l < m + 1, p E(t) ≤ C(E(0))t− mp−m−1 (ln t ln2 t . . . lnk t) mp−m−1 if 0 ≤ θ < 1, l < m+1. 3) If σ(t) = 1 tθ (ln t)γ , by applying Theorem 2.4, we obtain (1−θ)p γp E(t) ≤ C(E(0))t− mp−m−1 (ln t) mp−m−1 (1−γ)p E(t) ≤ C(E(0))(ln t)− mp−m−1 p − mp−m−1 E(t) ≤ C(E(0))(ln2 t) if 0 ≤ θ < 1, l < m + 1, if θ = 1, 0 ≤ γ < 1, l < m + 1, if θ = 1, γ = 1, l < m + 1. Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni Title Page Proof of Theorem 2.4. First we have the following energy identity to the problem (P ) Lemma 2.5 (Energy identity). Let u(t, x) be a local solution to the problem (P ) on [0, ∞) as in Theorem 2.4. Then we have Z Z t E(t) + σ(s)u0 (s)g(u0 (s)) ds dx = E(0) Ω for all t ∈ [0, ∞). 0 Contents JJ J II I Go Back Close Quit Page 9 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 Proof of the energy decay. From now on, we denote by c various positive constants which may be different at different occurrences. We multiply the first equation of (P ) by E q φ0 u, where φ is a function satisfying all the hypotheses of Lemma 2.3 to obtain Z T Z q 0 0= E φ u((|u0 |l−2 u0 )t − ∆p u + σ(t)g(u0 )) dx dt S Ω T Z T Z Z q 0 0 0 l−2 0 q−1 0 q 00 = E φ uu |u | dx − (qE E φ + E φ ) uu0 |u0 |l−2 dxdt Ω S Ω S Z T Z Z T Z 3l − 2 l − 1 02 1 q 0 0 2 q 0 p E φ |u | dxdt + 2 E φ u + |∇u| dxdt − l l p Ω Ω S S Z T Z T Z 2 + E q φ0 k∇ukpp dxdt. E q φ0 σ(t)ug(u0 ) dxdt + 1 − p S S Ω T (2.5) 2 E T Z q 0 0 0 l−2 φ dt ≤ − E φ uu |u | dx q+1 0 Ω S Z + Abbès Benaissa and Salima Mimouni Title Page We deduce that Z Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation T 0 q 00 Z φ + E φ ) uu0 |u0 |l−2 dxdt S Ω Z Z Z T Z 3l − 2 T q 0 0 l q 0 + E φ |u | dxdt − E φ σ(t)ug(u0 ) dxdt. l S Ω S Ω (qE E q−1 0 S Contents JJ J II I Go Back Close Quit 0 Since E is nonincreasing, φ is a bounded nonnegative function on R+ (and we Page 10 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 denote by µ its maximum), using the Hölder inequality, we have Z + p1 E(t)q φ0 uu0 |u0 |l−2 dx ≤ cµE(S)q+ l−1 l ∀t ≥ S. Ω Z T 0 (qE E S q−1 0 Z q 00 φ + E φ ) uu0 |u0 |l−2 dxdt Ω Z T Z q− 1l + p1 0 ≤ cµ −E (t)E(t) dt + c S T E(t)q+ l−1 + p1 l (−φ00 (t)) dt S + p1 q+ l−1 l ≤ cµE(S) . Using these estimates we conclude from the above inequality that Z T 2 (2.6) E(t)1+q φ0 (t) dt S Z T Z 1 3l − 2 q+ l−1 + q 0 ≤ cE(S) l p + E φ |u0 |l dxdt l S Ω Z T Z − E q φ0 σ(t)ug(u0 ) dxdt S Ω Z Z 3l − 2 T q 0 q+ l−1 + p1 l ≤ cE(S) + E φ |u0 |l dxdt l S Ω Z T Z q 0 − E φ σ(t)ug(u0 ) dxdt |u0 |≤1 S Z − S T E q φ0 Z Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni Title Page Contents JJ J II I Go Back Close Quit σ(t)ug(u0 ) dxdt. Page 11 of 19 |u0 |>1 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 Define Z φ(t) = t σ(s) ds. 0 It is clear that φ is a non decreasing function of class C 2 on R+ . The hypothesis (2.2) ensures that (2.7) φ(t) → +∞ as t → +∞. Now, we estimate the terms of the right-hand side of (2.6) in order to apply the results of Lemma 2.3: Using the Hölder inequality, we get for l < m + 1 Z T Z q 0 E φ |u0 |l dxdt S Ω Z T Z 1 0 q 0 ≤C E φ u ρ(t, u0 ) dx dt σ(t) S Ω l (m+1) Z T Z 1 0 0 q 0 0 dx dt +C E φ u ρ(t, u ) σ(t) S Ω Z T Z T 0 l φ0 q φ 0 0 q ≤C E (−E ) dt + C (Ω) E (−E 0 ) m+1 dt l σ(t) S S σ m+1 (t) l 0 m+1 Z T l φ q+1 0 q 0 m+1−l ≤ CE (S) + C (Ω) E φ m+1 (−E 0 ) m+1 dt. σ(t) S Now, fix an arbitrarily small ε > 0 (to be chosen later). By applying Young’s Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni Title Page Contents JJ J II I Go Back Close Quit Page 12 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 inequality, we obtain T Z q 0 Z |u0 |l dxdt E φ (2.8) S Ω ≤ CE q+1 (m+1) m + −l (m+1−l) (S) + C (Ω) ε m+1 0 Z T m+1 E q m+1−l φ0 dt S + C 0 (Ω) 1 l E(S). (m+1) m+1ε l If l ≥ m + 1, we easily obtain from (2.3) and (2.4) Z T Z q 0 (2.9) E φ |u0 |l dxdt ≤ CE q+1 (S). S Abbès Benaissa and Salima Mimouni Ω Next, we estimate the third term of the right-hand of (2.6). We get for l < m + 1 Z T Z q 0 (2.10) E φ σ(t)ug(u0 ) dxdt |u0 |≤1 S T Z E q φ0 ≤ ε1 |u0 |≤1 S Z ≤ cε1 kukpp dt + C(ε1 ) T E S Z q+1 0 T Z E q φ0 S Z φ dt + C(ε1 ) T q 0 Z E φ S |u0 |≤1 Z Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation (σg(u0 )) |u0 |≤1 p (σg(u0 )) p−1 dx. p p−1 dx Title Page Contents JJ J II I Go Back Close Quit Page 13 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 We now estimate the last term of the above inequality to get Z T Z p q 0 (2.11) E φ (σg(u0 )) p−1 dx dt |u0 |≤1 T S Z Z q 0 ≤ p (u0 g(u0 )) (m+1)(p−1) dx dt E φ |u0 |≤1 S T Z ≤ E φ σ S Z ≤ C(Ω) Z 1 q 0 p (m+1)(p−1) T |u0 |≤1 1 E q φ0 p (σu0 g(u0 )) (m+1)(p−1) dx dt p (m+1)(p−1) (−E 0 ) p (m+1)(p−1) Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation dt. σ Set ε2 > 0; due to Young’s inequality, we obtain Z T Z p q 0 (2.12) E φ (σg(u0 )) p−1 dxdt S S ≤ C(Ω) Abbès Benaissa and Salima Mimouni Title Page |u0 |≤1 (m + 1)(p − 1) − p ε (m + 1)(p − 1) 2 (m+1)(p−1) (m+1)(p−1)−p Z T (m+1)(p−1) E q (m+1)(p−1)−p φ0 dt S C(Ω) p + (m + 1)(p − 1) 1 (m+1)(p−1) p E(S), ε2 JJ J II I Go Back we chose q such that Close (m + 1)(p − 1) = q + 1. q (m + 1)(p − 1) − p thus we find q = Contents mp−m−1 p m+1 and thus q m+1−l = q + 1 + α with α = Quit (m+1)(p l−p−l) . p(m+1−l) Page 14 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 Using the Hölder inequality, the Sobolev imbedding and the condition (2.4), we obtain Z T Z q 0 E φ σ(t)ug(u0 ) dxdt |u0 |≥1 S T Z Z q 0 ≤ r+1 |u| E φ σ(t) S 1 Z (r+1) |g(u )| dx T ≤c E q+ p1 0 φσ 1 (r+1) Z ≤c 0 0 σu g(u ) dx (t) r r+1 dx dt r r+1 dt |u0 |>1 S Z r+1 r |u0 |>1 Ω Z 0 T 1 1 r E q+ p φ0 σ (r+1) (t)(−E 0 ) r+1 dt. Abbès Benaissa and Salima Mimouni S Applying Young’s inequality, we obtain Z T Z q 0 (2.13) E φ σ(t)ug(u0 ) dxdt S |u0 |≥1 Z T 1 Title Page Contents Z 1 T (E q+ p φ0 σ (r+1) (t))r+1 dt + c(ε3 ) (−E 0 ) dt S S Z T (p−1)(mr−1) p ≤ ε3 µr+1 E (0) E q+1 φ0 dt + c(ε3 )E(S). ≤ ε3 Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation JJ J II I Go Back S If l ≥ m + 1, the last inequality is also valid in the domain {|u0 | < 1} and with m instead of r. Choosing ε, ε1 , ε2 and ε3 small enough, we deduce from (2.6), (2.8), (2.10), Close Quit Page 15 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 (2.12) and (2.13) for l < m + 1 Z T l−1 1 E(t)1+q φ0 (t) dt ≤ CE(S)q+1 + C 0 E(S)q+ l + p + C 00 E(S) S + C 000 E(0) (p l−p−l)(m+1) p l E(S) + C 0000 E(0) (m r−1)(p−1) p r E(S), where C, C 0 , C 00 , C 000 , C 000 are different positive constants independent of E(0). Choosing ε3 small enough, we deduce from (2.6), (2.9) and (2.13) for l ≥ m+1 Z T (m2 −1)(p−1) l−1 1 E(t)1+q φ0 (t) dt ≤ CE(S)q+1 + C 0 E(S)q+ l + p + C 00 E(0) p m E(S), S where C, C 0 , C 00 are different positive constants independent of E(0), we may thus complete the proof by applying Lemma 2.3. Remark 1. We obtain the same results for the following problem (|u0 |l−2 u0 )0 − e−Φ(x) div(eΦ(x) |∇x u|p−2 ∇x u) + σ(t)g(u0 ) = 0 in Ω × [0, +∞[, u = 0 on ∂Ω × [0, +∞[, u(x, 0) = u0 (x), u0 (x, 0) = u1 (x) in Ω, where Φ is a positive function such that Φ ∈ L∞ (Ω), in this case (u0 , u1 ) ∈ 1,p W0,Φ × LlΦ , where Z 1,p 1,p Φ(x) p W0,Φ (Ω) = u ∈ W0 (Ω), e |∇x u| dx < ∞ , Ω Z l l Φ(x) l e |u| dx < ∞ . LΦ (Ω) = u ∈ L (Ω), Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni Title Page Contents JJ J II I Go Back Close Quit Page 16 of 19 Ω J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 Thus the energy associated to the solution is given by the following formula E(t) = l − 1 Φ(x)/l 0 l 1 Φ(x)/p ke u kl + ke ∇x ukpp . l p Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni Title Page Contents JJ J II I Go Back Close Quit Page 17 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 References [1] YAO-JUN YE, On the decay of solutions for some nonlinear dissipative hyperbolic equations, Acta Math. Appl. Sin. Engl. Ser., 20(1) (2004), 93– 100. [2] A. BENAISSA AND S. MOKEDDEM, Global existence and energy decay of solutions to the Cauchy problem for a wave equation with a weakly nonlinear dissipation, Abstr. Appl. Anal., 11 (2004), 935–955. [3] Y. EBIHARA, M. NAKAO AND T. NAMBU, On the existence of global classical solution of initial boundary value problem for u00 − ∆u − u3 = f , Pacific J. of Math., 60 (1975), 63–70. [4] A. HARAUX, Two remarks on dissipative hyperbolic problems, in: Research Notes in Mathematics, Pitman, 1985, p. 161–179. [5] R. IKEHATA AND T. SUZUKI, Stable and unstable sets for evolution equations of parabolic and hyperbolic type, Hiroshima Math. J., 26 (1996), 475– 491. [6] V. KOMORNIK, Exact Controllability and Stabilization. The Multiplier Method, Masson-John Wiley, Paris, 1994. Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni Title Page Contents JJ J II I Go Back [7] P. MARTINEZ, A new method to decay rate estimates for dissipative systems, ESAIM Control Optim. Calc. Var., 4 (1999), 419–444. [8] M. NAKAO, A difference inequality and its applications to nonlinear evolution equations, J. Math. Soc. Japan, 30 (1978), 747–762. Close Quit Page 18 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006 [9] M. NAKAO, On solutions of the wave equations with a sublinear dissipative term, J. Diff. Equat., 69 (1987), 204–215. Energy Decay of Solutions of a Wave Equation of p−Laplacian Type with a Weakly Nonlinear Dissipation Abbès Benaissa and Salima Mimouni Title Page Contents JJ J II I Go Back Close Quit Page 19 of 19 J. Ineq. Pure and Appl. Math. 7(1) Art. 15, 2006