Acta mathematica scientia,Series B ›› 2013, Vol. 33 ›› Issue (4): 1031-1048.doi: 10.1016/S0252-9602(13)60061-2

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ON THE CAUCHY PROBLEM FOR A REACTION-DIFFUSION SYSTEM WITH SINGULAR NONLINEARITY

 ZHOU Jun   

  1. School of Mathematics and Statistics, Southwest University, Chongqing 400715, China
  • Received:2012-05-22 Revised:2012-09-26 Online:2013-07-20 Published:2013-07-20
  • Supported by:

    This research was supported by NSFC (11201380), the Fundamental Research Funds for the Central Universities (XDJK2012B007), Doctor Fund of Southwest University (SWU111021) and Educational Fund of Southwest University (2010JY053).

Abstract:

We consider the growth rate and quenching rate of the following problem with singular nonlinearity
ut = △uv−λ, vt = △vuμ, (x, t) ∈ Rn × (0,∞),
u(x, 0) = u0(x), v(x, 0) = v0(x), xRn
for any n ≥ 1, where λ, μ > 0 are constants. More precisely, for any u0(x), v0(x) satisfying A11(1+|x|2α11u0A12(1+|x|2α12 , A21(1+|x|2α21v0A22(1+|x|2α22 for some constants α12 ≥ α11, α22 ≥α 21, A12A11, A22A21, the global solution (u, v) exists and satisfies A11(1+|x|2+b1tα11 uA12(1+|x|2+b2tα12 , A21(1+|x|2+b1tα21 v A22(1+|x|2+b2tα22 for some positive constants b1, b2 (see Theorem 3.3 for the parameters Aijαij , bi, i, j = 1, 2). When (1 − λ)(1 − λμ) > 0, (1 − λ)(1 − λμ) > 0 and 0 < u0A1(b1T +|x|2)1−λ/1−λμ , 0 < v0A2(b2T +|x|2)1−μ/1−λμ in Rn for some constants Ai, bi (i = 1, 2)satisfying A−λ2 > 2nA11−λ/1−λμ , Aμ1 > 2nA21−μ/1−λμ and 0 < b1 ≤ (1−λμ)A−λ2−(1−λ)2nA1/(1−λ)A1, 0 < b2 ≤ (1−λμ)Aμ1−(1−μ)2nA2/(1−μ)A2, we prove that u(x, t) ≤ A1(b1(Tt)+|x|2)1−λ/1−λμ , v(x, t) ≤A2(b2(Tt) + |x|2)1−μ/1−λμ in Rn × (0, T). Hence, the solution (u, v) quenches at the origin x = 0 at the same time T (see Theorem 4.3). We also find various other conditions for the solution to quench in a finite time and obtain the corresponding decay rate of the solution near the quenching time.

Key words: Cauchy problems, singular nonlinearity, growth rate, quenching rate

CLC Number: 

  • 35B35
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