Journal of Applied Mathematics

Journal of Applied Mathematics / 2012 / Article

Research Article | Open Access

Volume 2012 |Article ID 648067 |

Yulan Wang, Zhaoyin Xiang, Jinsong Hu, "Blowup Analysis for a Nonlocal Diffusion Equation with Reaction and Absorption", Journal of Applied Mathematics, vol. 2012, Article ID 648067, 17 pages, 2012.

Blowup Analysis for a Nonlocal Diffusion Equation with Reaction and Absorption

Academic Editor: Junjie Wei
Received21 Jan 2012
Accepted20 Apr 2012
Published10 Jul 2012


We investigate a nonlocal reaction diffusion equation with absorption under Neumann boundary. We obtain optimal conditions on the exponents of the reaction and absorption terms for the existence of solutions blowing up in finite time, or for the global existence and boundedness of all solutions. For the blowup solutions, we also study the blowup rate estimates and the localization of blowup set. Moreover, we show some numerical experiments which illustrate our results.

1. Introduction

In this paper, we devote our attention to the singularity analysis of the following nonlocal diffusion equation: 𝑒𝑑(ξ€œπ‘₯,𝑑)=Ω𝐽(π‘₯βˆ’π‘¦)(𝑒(𝑦,𝑑)βˆ’π‘’(π‘₯,𝑑))𝑑𝑦+𝑒𝑝(π‘₯,𝑑)βˆ’π‘˜π‘’π‘ž(𝑒π‘₯,𝑑),π‘₯∈Ω,𝑑>0,(π‘₯,0)=𝑒0(π‘₯),π‘₯∈Ω.(1.1) Here Ξ© is a bounded connected and smooth domain, which contains the origin, and π½βˆΆβ„π‘β†’β„ is a nonnegative, bounded, symmetric radially and strictly decreasing function with βˆ«β„π‘π½(𝑧)𝑑𝑧=1, and 𝑝, π‘ž, π‘˜ are all positive constants. We take the initial datum, 𝑒0(π‘₯), nonnegative and nontrivial.

Equation in (1.1) is called a nonlocal diffusion equation in the sense that the diffusion of the density 𝑒 at a point π‘₯ and time 𝑑 does not only depend on 𝑒(π‘₯,𝑑), but on all the values of 𝑒 in a neighborhood of π‘₯ through the convolution term. Maybe the simplest linear version of nonlocal model (1.1) is 𝑒𝑑(ξ€œπ‘₯,𝑑)=𝑅𝑁𝐽(π‘₯βˆ’π‘¦)(𝑒(𝑦,𝑑)βˆ’π‘’(π‘₯,𝑑))𝑑𝑦=π½βˆ—π‘’(π‘₯,𝑑)βˆ’π‘’(π‘₯,𝑑).(1.2) In recent years, the linear equation (1.2) and its variations have been widely used to model diffusion process, for example, in biology, dislocations dynamics, phase transition model, material science, and network model and so forth (see [1–7] and the references therein). The idea hidden inside those model is simple to understand. As stated in [6], if 𝑒(π‘₯,𝑑) is thought of as a density at the point π‘₯ and time 𝑑 and 𝐽(π‘₯βˆ’π‘¦) is thought of as the probability distribution of jumping from location 𝑦 to location π‘₯, then the convolution ∫(π½βˆ—π‘’)(π‘₯,𝑑)∢=ℝ𝑁𝐽(π‘₯βˆ’π‘¦)𝑒(𝑦,𝑑)𝑑𝑦 is the rate at which individuals are arriving at π‘₯ from all other places and βˆ«βˆ’π‘’(π‘₯,𝑑)=βˆ’β„π‘π½(π‘₯βˆ’π‘¦)𝑒(π‘₯,𝑑)𝑑𝑦 is the rate at which they are leaving location π‘₯ to travel to all other sites.

In the past decades, some works have shown that (1.2) shares many properties with the classical heat equation π‘’π‘‘βˆ’Ξ”π‘’=0(1.3) such as the existence of constant bounded stationary solutions and the maximum principle, but there is no regularizing effect in general for the former [8]. Therefore, as mentioned in [9–11], it is an interesting topic to compare the properties of solutions to the nonlocal diffusion equation with that of the corresponding local diffusion cases.

To motivate our works, we would like to remark that, in recent years, (1.3) and its variations have been extensively studied. In particular, a considerable effort has been devoted to studying the blowup properties of the following classical diffusion equation with reaction (𝛼>0) and/or absorption (π‘˜>0) under Dirichlet or Neumann boundary π‘’π‘‘βˆ’Ξ”π‘’=π›Όπ‘’π‘βˆ’π‘˜π‘’π‘ž,π‘₯∈Ω,𝑑>0,(1.4) which provides a simple biological or physical model. For instance, by constructing the self-similar weak subsolutions, Bedjaoui and Souplet [12] obtained the following conclusion for (1.4) with 𝛼=1 under Dirichlet or Neumann boundary: if 𝑝<max{π‘ž,1}, then all solutions are global. If 𝑝>max{π‘ž,1}, there exist solutions of (1.4) which blow up in finite time. In the critical case 𝑝=max{π‘ž,1}, the results may depend on the size of the coefficient π‘˜. In the Dirichlet boundary case, Xiang et al. [13] also studied the blowup rate estimates and obtained the following results: if 𝑝>max{π‘ž,1} and the solution 𝑒(π‘₯,𝑑) of (1.4) blows up at 𝑇, then there exists constants 𝐢>𝑐>0 such that max[]Ω×0,𝑑𝑒(π‘₯,𝜏)β‰₯𝑐(π‘‡βˆ’π‘‘)1/(π‘βˆ’1),max[]Ω×0,𝑑𝑒(π‘₯,𝜏)≀𝐢(π‘‡βˆ’π‘‘)1/(π‘βˆ’1)2if1<𝑝<1+.𝑁+1(1.5)

In this paper, we will deal with the blowup properties of the nonlocal diffusion problem (1.1) and compare them with that of problem (1.4). In our model (1.1), the absorption term βˆ’π‘˜π‘’π‘ž(π‘₯,𝑑) represents a rate of consumption due to an internal reaction, and we are integrating in Ξ© and thus imposing the condition that the diffusion takes place only in Ξ©, which means that the individual may enter or leave the domain. This is so called Neumann boundary conditions, see [14, 15]. We remark that GarcΓ­a-MeliΓ‘n and QuirΓ³s [16] recently proved the existence of a critical exponent of Fujita type for the nonlocal diffusion problem 𝑒𝑑(ξ€œπ‘₯,𝑑)=𝑅𝑁𝐽(π‘₯βˆ’π‘¦)(𝑒(𝑦,𝑑)βˆ’π‘’(π‘₯,𝑑))𝑑𝑦+𝑒𝑝(π‘₯,𝑑)=π½βˆ—π‘’(π‘₯,𝑑)βˆ’π‘’(π‘₯,𝑑)+𝑒𝑝(π‘₯,𝑑).(1.6) As mentioned in [17], nonlocal diffusion systems are more accurate than the classical diffusion systems in modeling the spatial diffusion of the individuals in some biology areas, such as embryological development process. For more study about the nonlocal diffusion operator, we refer to [8, 18–22] and references therein.

It is noteworthy that the method used in [12, 13] for problem (1.4) is invalid in our current setting due to the appearance of the nonlocal diffusion term. For example, instead of constructing self-similar weak subsolutions, we will use technique of integration to prove the finite time blowup. As far as the blowup rate is concerned, the scaling argument in [13] is not applicable.

We now state our main results. Our first result determines the complete classification of the parameters for which the solution blows up in finite time or exists globally.

Theorem 1.1. (i) If 𝑝≀max{π‘ž,1}, then all solutions of (1.1) are global. Moreover, if 𝑝<π‘ž or 𝑝=π‘ž and π‘˜β‰₯1, all solutions are uniformly bounded, while if 𝑝=π‘ž and π‘˜<1, there exist unbounded global solutions.
(ii) If 𝑝>max{π‘ž,1}, then (1.1) with large initial data have solutions blowing up in finite time, while the solutions of (1.1) with small initial data exist globally.

Once we have obtained the values of the parameters for which blowup occurs, the next step is to concern the blowup rate, that is the speed at which solutions are blowing up. Different from the result of problem (1.4), we could have a unified upper and low estimate here.

Theorem 1.2. Let 𝑝>max{π‘ž,1} and 𝑒(π‘₯,𝑑) be a solution of (1.1) blowing up at time 𝑇. Then lim𝑑→𝑇(π‘‡βˆ’π‘‘)1/(π‘βˆ’1)maxπ‘₯βˆˆΞ©π‘’(π‘₯,𝑑)=(π‘βˆ’1)βˆ’1/(π‘βˆ’1).(1.7)

Remark 1.3. From this result we find that the nonlocal diffusion term plays no role when determining the blowup rate and the blowup rate is just same as that of the ODE 𝑒𝑑=𝑒𝑝. And this phenomena is the same as that of local diffusion case.

Next we consider the spacial location of the blowup set. As usual, the blowup set of solution 𝑒(π‘₯,𝑑) is defined as follows: 𝐡(𝑒)=π‘₯βˆˆξ€·π‘₯Ξ©;thereexist𝑛,𝑑𝑛π‘₯⟢(π‘₯,𝑇)suchthat𝑒𝑛,π‘‘π‘›ξ€Έξ‚‡βŸΆβˆž,(1.8) where 𝑇 is the maximal existence time of 𝑒. For a general domain Ξ© we can localize the blowup set near any pint in Ξ© just by taking an initial condition being very large near that point and not so large in the rest of the domain. This is the following result.

Theorem 1.4. Let 𝑝>max{π‘ž,2}. For any π‘₯0∈Ω and πœ€>0, there exists an initial data 𝑒0 such that the corresponding solution 𝑒(π‘₯,𝑑) of (1.1) blows up at finite time 𝑇 and its blowup set 𝐡(𝑒) is contained in π΅πœ–(π‘₯0)={π‘₯∈Ω;β€–π‘₯βˆ’π‘₯0β€–<πœ–}.

Next we consider the radially symmetric case. In this case, single point blowup occurs.

Theorem 1.5. Let 𝑝>max{π‘ž,2} and Ξ©=𝐡𝑅={|π‘₯|<𝑅}. If the initial data 𝑒0∈𝐢1(𝐡𝑅) is a radial nonnegative function with a unique maximum at the origin, that is, 𝑒0=𝑒0(π‘Ÿ)β‰₯0, π‘’ξ…ž0(π‘Ÿ)<0 for 0<π‘Ÿβ‰€π‘…, 𝑒′(0)=0 and 𝑒0ξ…žξ…ž(0)<0, then the blowup set 𝐡(𝑒) of the solution 𝑒 of (1.1) consists only of the original point π‘₯=0.

The remainder of this paper is organized as follows. In Section 2, we give the existence and uniqueness of the solutions as well as the comparison principle. In Section 3, we prove the blowup and global existence condition. And then we prove the blowup rate and blowup set results in Sections 4 and 5, respectively. And in the last section we will give some numerical experiments to demonstrate our results.

2. Existence, Uniqueness, and Comparison Principle

We begin our study of problem (1.1) with a result of existence and uniqueness of continuous solutions and comparison principle.

Firstly, existence and uniqueness of solutions is a consequence of Banach's fixed point theorem. We look for π‘’βˆˆπΆ1((0,𝑇);𝐢(Ξ©))∩𝐢([0,𝑇);𝐢(Ξ©)) satisfying (1.1). Fix 𝑑0>0, and consider the Banach space 𝑋𝑑0=π‘’βˆˆπΆ1((0,𝑇);𝐢(Ξ©))∩𝐢([0,𝑇);𝐢(Ξ©)) with the norm β€–πœ”β€–π‘‹π‘‘0=max0≀𝑑≀𝑑0β€–β€–πœ”(β‹…,𝑑)𝐢(Ξ©)+max0<𝑑≀𝑑0β€–β€–πœ”π‘‘β€–β€–(β‹…,𝑑)𝐢(Ξ©).(2.1)

We define the following operator π‘‡βˆΆπ‘‹π‘‘0→𝑋𝑑0π‘‡πœ”0(πœ”)(π‘₯,𝑑)=πœ”0(ξ€œπ‘₯)+𝑑0ξ€œΞ©+ξ€œπ½(π‘₯βˆ’π‘¦)(πœ”(𝑦,𝑠)βˆ’πœ”(π‘₯,𝑠))𝑑𝑦𝑑𝑠𝑑0ξ€·|πœ”|π‘βˆ’1πœ”(π‘₯,𝑠)βˆ’π‘˜|πœ”|π‘žβˆ’1ξ€Έπœ”(π‘₯,𝑠)𝑑𝑠.(2.2)

Similar to [10, 15] we could prove the solution to (1.1) is a fixed point of operator 𝑇 in a convenient ball of 𝑋𝑑0. Thus, we could obtain the following result.

Theorem 2.1. For every 𝑒0∈𝐢(Ξ©) there exists a unique solution 𝑒 of (1.1) such that π‘’βˆˆπΆ1((0,𝑇);𝐢(Ξ©))∩𝐢([0,𝑇);𝐢(Ξ©)) and 𝑇 (finite or infinite) is the maximal existence time of solution.

Next, we will study the comparison principle. As usual we first give the definition of supersolution and subsolution.

Definition 2.2. A function π‘’βˆˆπΆ1((0,𝑇);𝐢(Ξ©))∩𝐢([0,𝑇);𝐢(Ξ©)) is a supersolution of (1.1) if it satisfies 𝑒𝑑(ξ€œπ‘₯,𝑑)β‰₯Ω𝐽(π‘₯βˆ’π‘¦)𝑒(𝑦,𝑑)βˆ’ξ€Έπ‘’(π‘₯,𝑑)𝑑𝑦+𝑒𝑝(π‘₯,𝑑)βˆ’π‘˜π‘’π‘ž(π‘₯,𝑑),𝑒(π‘₯,0)β‰₯𝑒0(π‘₯).(2.3) Subsolutions are defined similarly by reversing the inequalities.

To obtain the comparison principle for problem (1.1), we first give a maximum principle.

Lemma 2.3. Suppose that 𝑀(π‘₯,𝑑)∈𝐢1((0,𝑇);𝐢(Ξ©))∩𝐢([0,𝑇);𝐢(Ξ©)) is nontrivial and satisfies𝑀𝑑(ξ€œπ‘₯,𝑑)β‰₯Ω𝐽(π‘₯βˆ’π‘¦)(𝑀(𝑦,𝑑)βˆ’π‘€(π‘₯,𝑑))𝑑𝑦+𝑐1𝑀(π‘₯,𝑑),π‘₯∈Ω,𝑑>0(2.4) with 𝑀(π‘₯,0)β‰₯0 for π‘₯∈Ω, where 𝑐1 is a bounded function, then 𝑀(π‘₯,𝑑)>0 for π‘₯∈Ω and 𝑑>0.

Proof. We first show 𝑀(π‘₯,𝑑)β‰₯0 for π‘₯∈Ω,𝑑>0. Assume that 𝑀(π‘₯,𝑑) is negative somewhere. Let πœƒ(π‘₯,𝑑)=π‘’βˆ’πœ†π‘‘π‘€(π‘₯,𝑑)(πœ†>0,πœ†β‰₯2sup|𝑐1|). If we take (π‘₯0,𝑑0) a point where πœƒ attains its negative minimum, there holds 𝑑0>0 and πœƒπ‘‘ξ€·π‘₯0,𝑑0ξ€Έ=βˆ’πœ†π‘’βˆ’πœ†π‘‘0𝑀π‘₯0,𝑑0ξ€Έ+π‘’βˆ’πœ†π‘‘0𝑀𝑑π‘₯0,𝑑0ξ€Έβ‰₯π‘’βˆ’πœ†π‘‘0ξ€œΞ©π½ξ€·π‘₯0π‘€ξ€·βˆ’π‘¦ξ€Έξ€·π‘¦,𝑑0ξ€Έξ€·π‘₯βˆ’π‘€0,𝑑0𝑑𝑦+βˆ’πœ†+𝑐1𝑀π‘₯0,𝑑0ξ€Έ>0,(2.5) which is a contradiction. Thus πœƒ(π‘₯,𝑑)β‰₯0 for π‘₯∈Ω,𝑑>0. And so does 𝑀(π‘₯,𝑑).
Now, we suppose πœƒ(π‘₯1,𝑑1)=0 for some (π‘₯1,𝑑1); that is, πœƒ attains its minimum at (π‘₯1,𝑑1) from the first step. Notice that the hypotheses on 𝐽 imply 𝐽(0)>0, so that πœƒ(π‘₯1,𝑑1)=0 implies that πœƒ(π‘₯,𝑑1)=0 for π‘₯ in a neighborhood of π‘₯1. Thus a standard connectedness argument yields πœƒβ‰‘0. This is a contradiction. So we obtain our conclusion.

Lemma 2.4. If 𝑝β‰₯1, π‘žβ‰₯1 and 𝑒,  𝑒_are super and subsolutions to (1.1), respectively then 𝑒(π‘₯,𝑑)β‰₯𝑒_(π‘₯,𝑑) for every (π‘₯,𝑑)βˆˆΞ©Γ—[0,𝑇).

Proof. Letting  𝑀(π‘₯,𝑑)=π‘’βˆ’π‘’_, it is easy to verify that 𝑀(π‘₯,𝑑) satisfies (2.4) when 𝑝β‰₯1,π‘žβ‰₯1. We could obtain our conclusion from Lemma 2.3.

Remark 2.5. When 𝑝<1 or π‘ž<1, the conclusion is also validity if 𝑒 and  𝑒_  are bounded away from 0.

3. Blowup and Global Existence

In this section, we will analyze the blowup condition and give the proof of Theorem 1.1.

Proof of Theorem 1.1. (i) We only need to look for a global supersolution of (1.1). Indeed, it is easy to construct spacial homogeneous global supersolution of (1.1). To see this, we set 𝑒=𝐢𝑒𝛼𝑑, where 𝐢 and 𝛼 are positive constants to be determined.
For any given initial data 𝑒0, we note that 𝑒(𝑑0)β‰₯‖𝑒0β€–βˆž for 𝑑0 sufficiently large and 𝑒 is bounded away from 0. Thus by the comparison principle and Remark 2.5, to make 𝑒 a supersolution of (1.1), we only need to show the existence of 𝐢 and 𝛼 satisfyingπΆπ‘π‘’π‘π›Όπ‘‘β‰€π‘˜πΆπ‘žπ‘’π‘žπ›Όπ‘‘+𝛼𝐢𝑒𝛼𝑑.(3.1) If 𝑝≀1<π‘ž, for any given 𝛼, we can take 𝐢=π‘˜1/(π‘βˆ’π‘ž) such that (3.1) holds.  If π‘žβ‰€1 and thus 𝑝≀1, we can choose 𝐢 and 𝛼 satisfying πΆπ‘βˆ’1=𝛼, which make (3.1) validity.
Next, we show all global solutions are uniformly bounded when 𝑝<π‘ž or 𝑝=π‘ž and π‘˜β‰₯1. In fact, (1.1) has constant supersolution 𝑒=𝐴 whenever 𝑝<π‘ž or 𝑝=π‘ž and π‘˜β‰₯1. To see this, we choose 𝐴 large enough such that π‘˜π΄π‘žβ‰₯𝐴𝑝‖‖𝑒,𝐴β‰₯0β€–β€–βˆž,(3.2) which imply that 𝑒 is a supersolution of (1.1).
At last we show there exist global unbounded solutions when 𝑝=π‘ž and π‘˜<1. Indeed, let ξ‚»ξ€·(𝑓(𝑑)=1βˆ’π‘˜)(1βˆ’π‘)𝑑+𝑓1βˆ’π‘(ξ€Έ0)1/(1βˆ’π‘)𝑒,𝑝=π‘ž<1,((1βˆ’π‘˜)/2)𝑑,𝑝=π‘ž=1.(3.3) It is easy to see that if 𝑓(0)≀maxΩ𝑒0(π‘₯), 𝑓(𝑑) is a subsolution of (1.1). It is obvious that when 𝑝<1, 𝑓(𝑑) is unbounded.
(ii) We first show that if the initial data 𝑒0(π‘₯) is large enough, solutions of (1.1) blow up in finite time.
In the case of 𝑝>π‘ž>1. Integrating (1.1)1 in Ξ© and applying Fubini's theorem, we get π‘‘ξ€œπ‘‘π‘‘Ξ©ξ€œπ‘’(π‘₯,𝑑)𝑑π‘₯=Ω𝑒𝑝(ξ€œπ‘₯,𝑑)𝑑π‘₯βˆ’π‘˜Ξ©π‘’π‘ž(π‘₯,𝑑)𝑑π‘₯.(3.4) Using HΓΆlder's inequality, we could get π‘‘ξ€œπ‘‘π‘‘Ξ©ξ€œπ‘’(π‘₯,𝑑)𝑑π‘₯β‰₯Ω𝑒𝑝||Ξ©||(π‘₯,𝑑)𝑑π‘₯βˆ’π‘˜(π‘βˆ’π‘ž)/π‘ξ‚΅ξ€œΞ©π‘’π‘ξ‚Ά(π‘₯,𝑑)𝑑π‘₯π‘ž/𝑝=ξ‚΅ξ€œΞ©π‘’π‘ξ‚Ά(π‘₯,𝑑)𝑑π‘₯π‘ž/π‘ξƒ¬ξ‚΅ξ€œΞ©π‘’π‘ξ‚Ά(π‘₯,𝑑)𝑑π‘₯(π‘βˆ’π‘ž)/𝑝||Ξ©||βˆ’π‘˜(π‘βˆ’π‘ž)/𝑝,(3.5) where |Ξ©| is assumed to be the measure of Ξ©. Given positive constant π‘š>π‘˜1/(π‘βˆ’π‘ž) and 𝑒0β‰₯π‘š, we have by the comparison principle that the solution 𝑒(π‘₯,𝑑) of problem (1.1) satisfies 𝑒(π‘₯,𝑑)β‰₯π‘š. Thus π‘‘ξ€œπ‘‘π‘‘Ξ©ξ‚΅ξ€œπ‘’(π‘₯,𝑑)𝑑π‘₯β‰₯Ω𝑒𝑝(π‘₯,𝑑)𝑑π‘₯π‘ž/π‘ξ‚€π‘šπ‘βˆ’π‘ž||Ξ©||(π‘βˆ’π‘ž)/𝑝||Ξ©||βˆ’π‘˜(π‘βˆ’π‘ž)/𝑝.(3.6) Then we use Jensen's inequality to obtain π‘‘ξ€œπ‘‘π‘‘Ξ©ξ‚΅ξ€œπ‘’(π‘₯,𝑑)𝑑π‘₯>𝐢Ω𝑒(π‘₯,𝑑)𝑑π‘₯π‘ž,(3.7) where 𝐢 is a positive constant independent of the solution 𝑒. From this inequality, we could easily obtain that 𝑒(π‘₯,𝑑) blow up in finite time.
In the case of 𝑝>1β‰₯π‘ž, it follows from π‘’π‘žβ‰€π‘’+1 and Jensen's inequality that ξ€œΞ©π‘’π‘(ξ€œπ‘₯,𝑑)𝑑π‘₯βˆ’π‘˜Ξ©π‘’π‘ž(ξ€œπ‘₯,𝑑)𝑑π‘₯β‰₯Ω𝑒𝑝(ξ€œπ‘₯,𝑑)𝑑π‘₯βˆ’π‘˜Ξ©||Ξ©||β‰₯||Ξ©||𝑒(π‘₯,𝑑)𝑑π‘₯βˆ’π‘˜1βˆ’π‘ξ‚΅ξ€œΞ©π‘’ξ‚Ά(π‘₯,𝑑)𝑑π‘₯π‘ξ€œβˆ’π‘˜Ξ©π‘’||Ξ©||.(π‘₯,𝑑)𝑑π‘₯βˆ’π‘˜(3.8) Substituting this inequality into (3.4), we obtain π‘‘ξ€œπ‘‘π‘‘Ξ©||Ξ©||𝑒(π‘₯,𝑑)𝑑π‘₯β‰₯1βˆ’π‘ξ‚΅ξ€œΞ©ξ‚Άπ‘’(π‘₯,𝑑)𝑑π‘₯π‘ξ€œβˆ’π‘˜Ξ©||Ξ©||.𝑒(π‘₯,𝑑)𝑑π‘₯βˆ’π‘˜(3.9)
Therefore, if we take the initial data 𝑒0 large enough such that |Ξ©|1βˆ’π‘(βˆ«Ξ©π‘’0(π‘₯)𝑑π‘₯)π‘βˆ«βˆ’π‘˜Ξ©π‘’0(π‘₯)𝑑π‘₯βˆ’π‘˜|Ξ©|>0, then βˆ«Ξ©π‘’(π‘₯,𝑑)𝑑π‘₯ blows up in finite time. So does 𝑒(π‘₯,𝑑).
Next we show when the initial data 𝑒0(π‘₯) is small, solutions of (1.1) exist globally. Consider constant 𝐡. Let 0<π΅β‰€π‘˜1/(π‘βˆ’π‘ž). Then 𝐡𝑑β‰₯π΅π‘βˆ’π‘˜π΅π‘ž. Henceforth, if 𝑒0(π‘₯)≀𝐡, 𝐡 is a supersolution of (1.1). From the comparison principle, we know solutions of (1.1) are global in this case.

4. Blowup Rate Estimate

In this section, we study the blowup rate and prove Theorem 1.2.

Proof of Theorem 1.2. Let π‘ˆ(𝑑)=𝑒(π‘₯(𝑑),𝑑)=maxπ‘₯βˆˆΞ©π‘’(π‘₯,𝑑). It is easy to see that π‘ˆ(𝑑) is Lipschitz continuous and thus it is differential almost everywhere [23]. From the first equality of (1.1) we have ξ€œπ‘ˆβ€²(𝑑)≀Ω𝐽(π‘₯βˆ’π‘¦)(𝑒(𝑦,𝑑)βˆ’π‘’(π‘₯(𝑑),𝑑))𝑑𝑦+𝑒𝑝(π‘₯(𝑑),𝑑)βˆ’π‘˜π‘’π‘ž(π‘₯(𝑑),𝑑)≀𝑒𝑝(π‘₯(𝑑),𝑑)(4.1) at any point of differentiability of π‘ˆ(𝑑). Here we used βˆ‡π‘’(π‘₯(𝑑),𝑑)=0. Noticing that 𝑝>1 and integrating (4.1) from 𝑑 to 𝑇, we obtain maxπ‘₯βˆˆΞ©π‘’(π‘₯,𝑑)β‰₯(π‘βˆ’1)βˆ’1/(π‘βˆ’1)(π‘‡βˆ’π‘‘)βˆ’1/(π‘βˆ’1).(4.2)
Next we will establish the upper estimate. For any (π‘₯,𝑑)βˆˆΞ©Γ—[0,𝑇), we have 𝑒𝑑(π‘₯,𝑑)β‰₯βˆ’π‘’(π‘₯,𝑑)+𝑒𝑝(π‘₯,𝑑)βˆ’π‘˜π‘’π‘ž(π‘₯,𝑑)=𝑒𝑝(π‘₯,𝑑)1βˆ’π‘’βˆ’(π‘βˆ’1)(π‘₯,𝑑)βˆ’π‘˜π‘’βˆ’(π‘βˆ’π‘ž)ξ€Έ.(π‘₯,𝑑)(4.3) In particular, π‘ˆξ…ž(𝑑)β‰₯π‘ˆπ‘ξ€·(𝑑)1βˆ’π‘ˆ(𝑑)βˆ’(π‘βˆ’1)βˆ’π‘˜π‘ˆ(𝑑)βˆ’(π‘βˆ’π‘ž)ξ€Έ.(4.4)
From the lower estimate (4.2) we get π‘ˆξ…ž(𝑑)β‰₯π‘ˆπ‘ξ€·(𝑑)1βˆ’(π‘βˆ’1)(π‘‡βˆ’π‘‘)βˆ’π‘˜(π‘βˆ’1)(π‘βˆ’π‘ž)/(π‘βˆ’1)(π‘‡βˆ’π‘‘)(π‘βˆ’π‘ž)/(π‘βˆ’1)ξ€Έ.(4.5)
Integrating in (𝑑,𝑇), we get maxπ‘₯βˆˆΞ©β‰€ξ‚΅π‘’(π‘₯,𝑑)(π‘βˆ’1)(π‘‡βˆ’π‘‘)βˆ’(π‘βˆ’1)22(π‘‡βˆ’π‘‘)2βˆ’π‘˜(π‘βˆ’1)(3π‘βˆ’π‘žβˆ’2)/(π‘βˆ’1)2π‘βˆ’π‘žβˆ’1(π‘‡βˆ’π‘‘)(2π‘βˆ’π‘žβˆ’1)/(π‘βˆ’1)ξ‚Άβˆ’1/(π‘βˆ’1),(4.6) combining with (4.2), the conclusion of Theorem 1.2 is proved if one takes the limit as 𝑑→𝑇.

5. Blowup Set

Next we will concern the blowup set for the solution to problem (1.1). We will first localize the blowup set near any point in Ξ© just by taking an initial condition being very large near that point and not so large in the rest of the domain.

Proof of Theorem 1.4. Given π‘₯0∈Ω and πœ€>0, we could construct an initial condition 𝑒0 such that 𝐡(𝑒)βŠ‚π΅πœ€ξ€·π‘₯0ξ€Έ=π‘₯βˆˆβ€–β€–Ξ©βˆΆπ‘₯βˆ’π‘₯0‖‖<πœ€.(5.1)
In fact, we will consider 𝑒0 concentrated near π‘₯0 and small away from π‘₯0.
Let πœ‘ be a nonnegative smooth function such that supp(πœ‘)βŠ‚π΅πœ€/2(π‘₯0) and πœ‘(π‘₯)>0 for π‘₯βˆˆπ΅πœ€/2(π‘₯0).
Next, let 𝑒0(π‘₯)=π‘€πœ‘(π‘₯)+𝛿.(5.2) We want to choose 𝑀 large and 𝛿 small such that (5.1) holds.
First we can assume that 𝑇 is as small as we need by taking 𝑀 large enough. Indeed, we have 𝑇≀𝐢(Ξ©,𝑝,πœ‘)π‘€π‘žβˆ’1or𝑇≀𝐢(Ξ©,𝑝,πœ‘)π‘€π‘βˆ’1(5.3) from the proof of Theorem 1.1.
Now, from the proof of blowup rate, we havemaxπ‘₯βˆˆΞ©β‰€ξ‚΅π‘’(π‘₯,𝑑)(π‘βˆ’1)(π‘‡βˆ’π‘‘)βˆ’(π‘βˆ’1)22(π‘‡βˆ’π‘‘)2βˆ’π‘˜(π‘βˆ’1)(3π‘βˆ’π‘žβˆ’2)/(π‘βˆ’1)2π‘βˆ’π‘žβˆ’1(π‘‡βˆ’π‘‘)(2π‘βˆ’π‘žβˆ’1)/(π‘βˆ’1)ξ‚Άβˆ’1/(π‘βˆ’1)≀𝐢(π‘‡βˆ’π‘‘)βˆ’1/(π‘βˆ’1).(5.4) Henceforth, for any π‘₯∈Ω, 𝑒𝑑=ξ€œπ‘₯,𝑑Ω𝐽(π‘₯,𝑦)𝑒(𝑦,𝑑)βˆ’π‘’π‘₯,𝑑𝑑𝑦+𝑒𝑝π‘₯,π‘‘βˆ’π‘˜π‘’π‘žξ€·ξ€Έβ‰€ξ€œπ‘₯,𝑑Ω𝐽π‘₯,𝑦𝑒(𝑦,𝑑)𝑑𝑦+𝑒𝑝π‘₯,𝑑≀𝐢(π‘‡βˆ’π‘‘)βˆ’1/(π‘βˆ’1)+𝑒𝑝.π‘₯,𝑑(5.5) Therefore, if π‘₯βˆˆΞ©β§΅π΅πœ–(π‘₯0), then 𝑒(π‘₯,𝑑) is a subsolution to 𝑀𝑑=𝐢(π‘‡βˆ’π‘‘)βˆ’1/(π‘βˆ’1)+𝑀𝑝𝑀(𝑑),(0)=𝛿,(5.6) which shows 𝑒π‘₯,𝑑≀𝑀(𝑑).(5.7)
Next, we only need to prove that a solution 𝑀 to (5.6) remains bounded up to 𝑑=𝑇, provided that 𝛿 and 𝑇 are small enough.
Let 𝑧(𝑠)=(π‘‡βˆ’π‘‘)1/(π‘βˆ’1)𝑀(𝑑),𝑠=βˆ’ln(π‘‡βˆ’π‘‘).(5.8) Then 𝑧(𝑠) satisfies π‘§ξ…ž(𝑠)=πΆπ‘’βˆ’π‘ βˆ’1π‘βˆ’1𝑧(𝑠)+𝑧𝑝(𝑠),𝑧(βˆ’ln𝑇)=𝛿𝑇1/(π‘βˆ’1),(5.9) which show that for 𝑇 and 𝛿 small (𝑇 is small if 𝑀 is large), we have 1πΆπ‘‡βˆ’π‘βˆ’1𝛿𝑇1/(π‘βˆ’1)+𝛿𝑝𝑇𝑝/(π‘βˆ’1)<0.(5.10) So 𝑧′(𝑠)<0 for all 𝑠>βˆ’ln𝑇. From this and Lemma 4.2 of [24], we know 𝑧(𝑠)⟢0,π‘ βŸΆβˆž.(5.11) Combining the equation verified by 𝑧 we obtain that, for given positive constant 𝛾(<1/𝑝(π‘βˆ’1)), there exists 𝑠0>0 such that π‘§ξ…ž(𝑠)β‰€πΆπ‘’βˆ’π‘ βˆ’ξ‚΅1ξ‚Άπ‘βˆ’1βˆ’π›Ύπ‘§(𝑠)(5.12) for 𝑠>𝑠0.
Let 𝑣(𝑠) be a solution of π‘£ξ…ž(𝑠)=πΆπ‘’βˆ’π‘ βˆ’ξ‚΅1ξ‚Άπ‘βˆ’1βˆ’π›Ύπ‘£(𝑠)(5.13) with 𝑣(𝑠0)β‰₯𝑧(𝑠0). Integrating this equation we get 𝑣(𝑠)=𝐢1π‘’βˆ’π‘ +𝐢2π‘’βˆ’(1/(π‘βˆ’1)βˆ’π›Ύ)𝑠.(5.14) By a comparison argument we could get that for every 𝑠>𝑠0, 𝑧(𝑠)≀𝑣(𝑠)=𝐢1π‘’βˆ’π‘ +𝐢2π‘’βˆ’(1/(π‘βˆ’1)βˆ’π›Ύ)𝑠.(5.15) Now we go back to 𝑧′(𝑠)=πΆπ‘’βˆ’π‘ βˆ’(1/(π‘βˆ’1))𝑧(𝑠)+𝑧𝑝(𝑠). We have π‘§ξ…ž(𝑠)+(1/(π‘βˆ’1))𝑧(𝑠)=πΆπ‘’βˆ’π‘ +𝑧𝑝(𝑠),(5.16) then 𝑒(1/(π‘βˆ’1))𝑠𝑧(𝑠)ξ…ž=𝑒(1/(π‘βˆ’1))𝑠(πΆπ‘’βˆ’π‘ +𝑧𝑝).(5.17) Integrating form 𝑠0 to 𝑠, one could get 𝑧(𝑠)=π‘’βˆ’(1/(π‘βˆ’1))𝑠𝐢1+ξ€œπ‘ π‘ 0𝑒(1/(π‘βˆ’1))𝜎(πΆπ‘’βˆ’πœŽ+𝑧𝑝(𝑠))π‘‘πœŽ=π‘’βˆ’(1/(π‘βˆ’1))𝑠𝐢1+ξ€œπ‘ π‘ 0π‘’βˆ’((π‘βˆ’2)/(π‘βˆ’1))𝜎(𝐢+π‘’πœŽπ‘§π‘ξ‚Ά.(𝑠))π‘‘πœŽ(5.18) Using (5.15) and 𝛾<1/𝑝(π‘βˆ’1), we have 𝑒𝑠𝑧𝑝≀𝐢𝑝1π‘’βˆ’(π‘βˆ’1)𝑠+𝐢𝑝2π‘’βˆ’(𝑝/(π‘βˆ’1)βˆ’π‘π›Ύβˆ’1)π‘ βŸΆ0(5.19) as 𝑠→+∞.
And thus from (5.18), we get 𝑧(𝑠)β‰€π‘’βˆ’(1/(π‘βˆ’1))𝑠𝐢1+𝐢3ξ€œπ‘ π‘ 0π‘’βˆ’((π‘βˆ’2)/(π‘βˆ’1))πœŽξ‚Άπ‘‘πœŽβ‰€πΆ1π‘’βˆ’(1/(π‘βˆ’1))𝑠+𝐢4π‘’βˆ’π‘ .(5.20)
As 𝑝>2, we have 𝑧(𝑠)β‰€πΆπ‘’βˆ’(1/(π‘βˆ’1))𝑠.(5.21) This implies that 𝑀(𝑑)≀𝐢, for 0≀𝑑<𝑇. From the boundedness of 𝑀 and (5.7) we get 𝑒(π‘₯,𝑑)≀𝑀(𝑑)≀𝐢 for every π‘₯βˆˆΞ©β§΅π΅πœ–(π‘₯0), as we wished.

Next, we will consider the radial symmetric case, that is, the proof of Theorem 1.5. For the convenience of writing, we only deal with the one dimensional case, Ξ©=(βˆ’π‘™,𝑙). The radial case is analogous; we leave the details to the reader.

Proof of Theorem 1.5. Under the hypothesis on the initial condition imposed in Theorem 1.5 we have that the solution is symmetric and 𝑒π‘₯<0 in (0,𝑙]Γ—(0,𝑇) from the stand parabolic theorem and Lemma 4.1 of [10]. Therefore the solution has a unique maximum at the origin for every π‘‘βˆˆ(0,𝑇).
Let us perform the following change of variables 𝑧(π‘₯,𝑠)=(π‘‡βˆ’π‘‘)1/(π‘βˆ’1)𝑒(π‘₯,𝑑),𝑠=βˆ’ln(π‘‡βˆ’π‘‘).(5.22) Our remainder proof consist of two steps.
Step 1. We first prove the only blowup point that verifies the blowup estimate (1.7) is π‘₯=0. And this shows that for π‘₯β‰ 0, 𝑧(π‘₯,𝑠) does not converge to 𝐢𝑝=(π‘βˆ’1)βˆ’1/(π‘βˆ’1) as 𝑠→+∞.
We conclude by contradiction. Assume that (π‘‡βˆ’π‘‘)1/(π‘βˆ’1)𝑒(π‘₯0,𝑑)→𝐢𝑝 for a π‘₯0>0.
Let 𝑣(𝑑)=𝑒(0,𝑑)βˆ’π‘’(π‘₯0,𝑑). Then π‘£ξ…žξ€œ(𝑑)=π‘™βˆ’π‘™ξ€œπ½(βˆ’π‘¦)(𝑒(𝑦,𝑑)βˆ’π‘’(0,𝑑))π‘‘π‘¦βˆ’π‘™βˆ’π‘™π½ξ€·π‘₯0ξ€·π‘₯βˆ’π‘¦ξ€Έξ€·π‘’(𝑦,𝑑)βˆ’π‘’0,𝑑𝑑𝑦+π‘πœ‰π‘βˆ’1(𝑑)𝑣(𝑑)βˆ’π‘˜π‘žπœ‚π‘žβˆ’1(𝑑)𝑣(𝑑),(5.23) where πœ‰(𝑑) and πœ‚(𝑑) are between 𝑒(0,𝑑) and 𝑒(π‘₯0,𝑑). Hence π‘£ξ…žξ€œ(𝑑)β‰₯π‘™βˆ’π‘™ξ€·ξ€·π‘₯𝐽(βˆ’π‘¦)βˆ’π½0+ξ€œβˆ’π‘¦ξ€Έξ€Έπ‘’(𝑦,𝑑)π‘‘π‘¦π‘™βˆ’π‘™ξ€·π½ξ€·π‘¦βˆ’π‘₯0ξ€Έξ€Έβˆ’π½(𝑦)𝑒(0,𝑑)π‘‘π‘¦βˆ’π‘£(𝑑)+π‘πœ‰π‘βˆ’1(𝑑)𝑣(𝑑)βˆ’π‘˜π‘žπœ‚π‘žβˆ’1(=ξ€œπ‘‘)𝑣(𝑑)π‘™βˆ’π‘™ξ€·π½ξ€·π‘¦βˆ’π‘₯0ξ€Έξ€Έβˆ’π½(𝑦)(𝑒(0,𝑑)βˆ’π‘’(𝑦,𝑑))π‘‘π‘¦βˆ’π‘£(𝑑)+π‘πœ‰π‘βˆ’1(𝑑)𝑣(𝑑)βˆ’π‘˜π‘žπœ‚π‘žβˆ’1β‰₯ξ€·(𝑑)𝑣(𝑑)βˆ’πΆ1+π‘πœ‰π‘βˆ’1(𝑑)βˆ’π‘˜π‘žπœ‚π‘žβˆ’1ξ€Έ(𝑑)𝑣(𝑑),(5.24) for some positive constant.
Integrating the above inequality, we obtain 𝑑ln(𝑣)(𝑑)βˆ’ln(𝑣)0ξ€Έβ‰₯ξ€œπ‘‘π‘‘0ξ€·βˆ’πΆ1+π‘πœ‰π‘βˆ’1(𝑠)βˆ’π‘˜π‘žπœ‚π‘žβˆ’1(𝑠)𝑑𝑠.(5.25) Remember that (π‘‡βˆ’π‘‘)1/(π‘βˆ’1)𝑒(π‘₯0,𝑑)→𝐢𝑝, (π‘‡βˆ’π‘‘)1/(π‘βˆ’1)𝑒(0,𝑑)→𝐢𝑝, we have limπ‘‘β†’π‘‡πœ‰(𝑑)(π‘‡βˆ’π‘‘)1/(π‘βˆ’1)=limπ‘‘β†’π‘‡πœ‚(𝑑)(π‘‡βˆ’π‘‘)1/(π‘βˆ’1)=𝐢𝑝.(5.26) And this implies that ξ€œπ‘‘π‘‘0ξ€·βˆ’πΆ1+π‘πœ‰π‘βˆ’1(𝑠)βˆ’π‘˜π‘žπœ‚π‘žβˆ’1ξ€Έξ€œ(𝑠)𝑑𝑠β‰₯𝑝𝑑𝑑0πΆπ‘π‘βˆ’1βˆ’π›Ώ1ξ€œπ‘‡βˆ’π‘ π‘‘π‘ βˆ’π‘˜π‘žπ‘‘π‘‘0ξ‚€πΆπ‘π‘žβˆ’1+𝛿2(π‘‡βˆ’π‘ )βˆ’(π‘žβˆ’1)/(π‘βˆ’1)π‘‘π‘ βˆ’πΆ2.(5.27)𝑝>π‘ž implies that (π‘‡βˆ’π‘ )βˆ’(π‘žβˆ’1)/(π‘βˆ’1)≀𝛿3(π‘‡βˆ’π‘ )βˆ’1 as 𝑠→𝑇 for given 𝛿3>0. Hence ξ€œπ‘‘π‘‘0ξ€·βˆ’πΆ1+π‘πœ‰π‘βˆ’1(𝑠)βˆ’π‘˜π‘žπœ‚π‘žβˆ’1ξ€Έξ€œ(𝑠)𝑑𝑠β‰₯𝑝𝑑𝑑0πΆπ‘π‘βˆ’1βˆ’π›Ώπ‘‡βˆ’π‘ π‘‘π‘ βˆ’πΆ2𝐢=βˆ’π‘π‘π‘βˆ’1ξ‚βˆ’π›Ώln(π‘‡βˆ’π‘‘)βˆ’πΆ2(5.28) for some 𝛿>0.
Hence 𝑣(𝑑)β‰₯𝐢(π‘‡βˆ’π‘‘)βˆ’π‘(πΆπ‘π‘βˆ’1βˆ’π›Ώ)=𝐢(π‘‡βˆ’π‘‘)π‘π›Ώβˆ’π‘/(π‘βˆ’1).(5.29) Using this fact, we have 0=lim𝑑→𝑇(π‘‡βˆ’π‘‘)1/(π‘βˆ’1)𝑣(𝑑)β‰₯𝐢lim𝑑→𝑇(π‘‡βˆ’π‘‘)1/(π‘βˆ’1)βˆ’π‘/(π‘βˆ’1)+𝑝𝛿=+∞.(5.30) This contradiction proves our claim.
Step 2. We will show the only possible blowup point is π‘₯=0.
Remembering the transform (5.22), 𝑧(π‘₯,𝑠) satisfies 𝑧𝑠=π‘’βˆ’π‘ ξ€œπ‘™βˆ’π‘™1𝐽(π‘₯βˆ’π‘¦)(𝑧(𝑦,𝑠)βˆ’π‘§(π‘₯,𝑠))π‘‘π‘¦βˆ’π‘βˆ’1𝑧+π‘§π‘βˆ’π‘˜π‘’((π‘žβˆ’π‘)/(π‘βˆ’1))π‘ π‘§π‘ž.(5.31) Note that the blowup rate of 𝑒 implies that 𝑧(π‘₯,𝑠)≀𝐢 for every (π‘₯,𝑠)∈[βˆ’π‘™,𝑙]Γ—(βˆ’ln𝑇,∞). Therefore, 𝑧𝑠(π‘₯,𝑠)β‰€πΆπ‘’βˆ’π‘ βˆ’1π‘βˆ’1𝑧(π‘₯,𝑠)+𝑧𝑝(π‘₯,𝑠).(5.32) From this we know that if there exists 𝑠0 such that 𝑧𝑝(π‘₯,𝑠0)βˆ’(1/(π‘βˆ’1))𝑧(π‘₯,𝑠0)<βˆ’πΆπ‘’βˆ’π‘ 0, then 𝑧(π‘₯,𝑠)β†’0 as π‘ β†’βˆž (see Lemma 4.2 in [24]).
Moreover, if there exists 𝑠0 such that 𝑧𝑝(π‘₯,𝑠0)βˆ’(1/(π‘βˆ’1))𝑧(π‘₯,𝑠0)>πΆπ‘’βˆ’π‘ 0 then 𝑧(π‘₯,𝑠) blows up in finite time 𝑠. This follows from Lemma 4.3 of [24] using that 𝑧𝑠(π‘₯,𝑠)β‰₯βˆ’πΆπ‘’βˆ’π‘ βˆ’1π‘βˆ’1𝑧(π‘₯,𝑠)+𝑧𝑝(π‘₯,𝑠).(5.33)
Thus if 𝑧(π‘₯,𝑠) does not converge to zero and does not blow up in finite time, then 𝑧(π‘₯,𝑠) satisfies πΆπ‘’βˆ’π‘ β‰₯𝑧𝑝1(π‘₯,𝑠)βˆ’π‘βˆ’1𝑧(π‘₯,𝑠)β‰₯βˆ’πΆπ‘’βˆ’π‘ .(5.34) Henceforth, 𝑧𝑝1(π‘₯,𝑠)βˆ’π‘βˆ’1𝑧(π‘₯,𝑠)⟢0(π‘ βŸΆ+∞).(5.35) As 𝑧(π‘₯,𝑠) is continuous, bounded and does not go to zero, we conclude that 𝑧(π‘₯,𝑠)→𝐢𝑝.
Now we could conclude that 𝑧(π‘₯,𝑠) verifies 𝑧(π‘₯,𝑠)β†’0(𝑠→+∞), or 𝑧(π‘₯,𝑠)→𝐢𝑝(𝑠→+∞), or 𝑧(π‘₯,𝑠) blows up in finite time.
From Step 1 we know for π‘₯β‰ 0, 𝑧(π‘₯,𝑠) is bounded and does not converge to 𝐢𝑝, so 𝑧(π‘₯,𝑠)β†’0 as 𝑠→+∞. Combined with inequality (5.32), we could get 𝑧𝑠(π‘₯,𝑠)β‰€πΆπ‘’βˆ’π‘ βˆ’ξ‚΅1ξ‚Άπ‘βˆ’1βˆ’πœƒπ‘§(π‘₯,𝑠)(5.36) for any πœƒ>0.
By a comparison argument as in the proof of Theorem 1.4, it follows that 𝑧(π‘₯,𝑠)≀𝐢1π‘’βˆ’π‘ +𝐢2π‘’βˆ’(1/(π‘βˆ’1)βˆ’πœƒ)𝑠.(5.37) Going back to the equation verified by 𝑧(π‘₯,𝑑) we obtain 𝑒(1/(π‘βˆ’1))𝑠𝑧(π‘₯,𝑠)𝑠=𝑒(1/(π‘βˆ’1))π‘ ξ‚΅π‘’βˆ’π‘ ξ€œπ‘™βˆ’π‘™π½(π‘₯βˆ’π‘¦)(𝑧(𝑦,𝑠)βˆ’π‘§(π‘₯,𝑠))𝑑𝑦+𝑧𝑝(π‘₯,𝑠)βˆ’π‘˜π‘’((π‘žβˆ’π‘)/(π‘βˆ’1))𝑠.𝑧(π‘₯,𝑠)(5.38) Integrating we get 𝑧(π‘₯,𝑠)=π‘’βˆ’(1/(π‘βˆ’1))𝑠𝐢1+ξ€œπ‘ π‘ 0π‘’βˆ’((π‘βˆ’2)/(π‘βˆ’1))πœŽξ‚΅ξ€œπ‘™βˆ’π‘™π½(π‘₯βˆ’π‘¦)(𝑧(𝑦,𝑠)βˆ’π‘§(π‘₯,𝑠))𝑑𝑦+π‘’πœŽπ‘§π‘(π‘₯,𝑠)βˆ’π‘˜π‘’((π‘žβˆ’1)/(π‘βˆ’1))𝜎.𝑧(π‘₯,𝑠)π‘‘πœŽξ‚Άξ‚Ά(5.39) On the other hand, (5.37) implies that 𝑒𝑠𝑧𝑝(π‘₯,𝑠)β†’0 as π‘ β†’βˆž. Henceforth, 𝑧(π‘₯,𝑠)β‰€π‘’βˆ’(1/(π‘βˆ’1))𝑠𝐢1+𝐢2ξ€œπ‘ π‘ 0π‘’βˆ’((π‘βˆ’2)/(π‘βˆ’1))πœŽξ‚Ά.π‘‘πœŽ(5.40) Using that 𝑝>2, one could have 𝑧(π‘₯,𝑠)≀𝐢3π‘’βˆ’(1/(π‘βˆ’1))𝑠.(5.41) Remembering the transform (5.22), we have 𝑒(π‘₯,𝑑)=𝑒(1/(π‘βˆ’1))𝑠𝑧(π‘₯,𝑠)≀𝑐3.(5.42) And so our proof is complete.

6. Numerical Experiments

At the end of this paper, we will use several numerical examples to demonstrate our results about the location of blowup points. For this purpose, we discretize the problem in the spacial variable to obtain an ODE system. Taking Ξ©=[βˆ’4,4] and βˆ’4=π‘₯βˆ’π‘<β‹―<π‘₯𝑁=4,𝑁=100, we consider the following system: π‘’ξ…žπ‘–(𝑑)=𝑁𝑗=βˆ’π‘π½ξ€·π‘₯π‘–βˆ’π‘₯𝑗𝑒𝑗(𝑑)βˆ’π‘’π‘–ξ€Έ+𝑒(𝑑)𝑖𝑝𝑒(𝑑)βˆ’π‘˜π‘–ξ€Έπ‘žπ‘’(𝑑),𝑖(0)=𝑒0ξ€·π‘₯𝑖.(6.1) Next we choose 𝑝=3, π‘ž=1, π‘˜=1 and ⎧βŽͺ⎨βŽͺ⎩1𝐽(𝑧)=1,|𝑧|≀,1100,|𝑧|>.10(6.2)

In Figure 1 we choose a nonsymmetric initial condition very large near the point π‘₯0=1,  𝑒0(π‘₯)=1/4+100(1βˆ’|π‘₯βˆ’1|)+. We observe that the blowup set is localized in a neighborhood of π‘₯0=1.

Next we choose a symmetric initial condition with a unique maximum at the origin, 𝑒0(π‘₯)=16βˆ’π‘₯20. We observe that the solution blows up only at the origin, Figure 2.


Y. Wang is supported by the Key Scientific Research Foundation of Xihua University (no.  Z0912611), the Scientific Research Found of Sichuan Provincial Education Department (no. 09ZB081) and the Research Fund of Key Disciplinary of Application Mathematics of Xihua University (no. XZD0910-09-1). Z. Xiang is supported by NNSF of China (11101068), the Sichuan Youth Science & Technology Foundation (2011JQ0003), the Fundamental Research Funds for the Central Universities (ZYGX2009X019) and the SRF for ROCS, SEM. J. Hu is supported by the Scientific Research Found of Sichuan Provincial Education Department (no. 11ZB009).


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