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Abstract and Applied Analysis

Volume 2012 (2012), Article ID 450984, 21 pages

http://dx.doi.org/10.1155/2012/450984

## Long-Time Behaviour of Solutions for Autonomous Evolution Hemivariational Inequality with Multidimensional “Reaction-Displacement” Law

^{1}Institute for Applied System Analysis NAS of Ukraine, Peremogy Avenue 37, Building 35, Kyiv 03056, Ukraine^{2}Department of Mathematics and Applications “R. Caccioppoli”, University of Naples “Federico II”, Via Claudio 21, 80125 Naples, Italy

Received 2 December 2011; Accepted 27 January 2012

Academic Editor: Muhammad Aslam Noor

Copyright © 2012 Pavlo O. Kasyanov et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

We consider autonomous evolution inclusions and hemivariational inequalities with nonsmooth dependence between determinative parameters of a problem. The dynamics of all weak solutions defined on the positive semiaxis of time is studied. We prove the existence of trajectory and global attractors and investigate their structure. New properties of complete trajectories are justified. We study classes of mathematical models for geophysical processes and fields containing the multidimensional “reaction-displacement” law as one of possible application. The pointwise behavior of such problem solutions on attractor is described.

#### 1. Introduction

Let a viscoelastic body occupies a bounded domain in applications, and it is acted upon by volume forces and surface tractions (this section is based on results of [1] and references therein). The boundary of is supposed to be Lipschitz continuous, and it is partitioned into two disjoint measurable parts and such that means . We consider the process of evolution of the mechanical state on the interval . The body is clamped on and thus the displacement vanishes there. The forces field of density act in , the surface tractions of density are applied on . We denote by the displacement vector, by the stress tensor and by the linearized (small) strain tensor , where .

The mechanical problem consists in finding the displacement field such that where and are given linear constitutive functions and being the outward unit normal vector to .

In the above model, the dynamic equation (1.1) is considered with the viscoelastic constitutive relationship of the Kelvin-Voigt type (1.2) while (1.3) and (1.4) represent the displacement and traction boundary conditions, respectively. The functions and are the initial displacement and the initial velocity, respectively. In order to formulate the skin effects, we suppose (following [2, 3]) that the body forces of density consists of two parts: which is prescribed external loading and which is the reaction of constrains introducing the skin effects, that is, . Here, is a possibly multivalued function of the displacement . We consider the reaction-displacement law of the form: where is locally Lipschitz function in , and represents the Clarke subdifferential with respect to . Let be the space of second-order symmetric tensors on .

We consider the following problem: examine the long-time (as ) behavior of all (weak, generalized) solutions for (1.1)–(1.5) and (1.6).

We remark that existence solutions theorems for evolution equations and inclusions where considered in [1–40] (see works and references therein).

In [1] for finite time interval, it was presented the hemivariational formulation of problems similar to (1.1)–(1.6) and an existence theorem for evolution inclusions with pseudomonotone operators. We give now variational formulation of the above problem. To this aim let , , , and be the closed subspace of defined by

On we consider the inner product and the corresponding norm given by

From the Korn inequality for with , it follows that and are the equivalent norms on . Identifying with its dual, we have an evolution triple (see, e.g., [8]) with dense and compact embeddings. We denote by the duality of and its dual , by the norm in . We have for all and .

We admit the following hypotheses. the linear symmetric viscosity operator satisfies the Carathéodory condition (i.e., is measurable on for all , and is continuous on for a.e. ) and the elasticity operator is of the form (Hooke's law) with a symmetric elasticity tensor , that is, with . Moreover, is a function such that(i) is measurable for all and ;(ii) is locally Lipschitz and regular [5] for all ;(iii) for all with ;(iv) for all , with , where is the directional derivative of at the point in the direction . and .

Next we need the spaces , and , where the time derivative involved in the definition of is understood in the sense of vector-valued distributions, . Endowed with the norm , the space becomes a separable reflexive Banach space. We also have . The duality for the pair is denoted by . It is well known (cf. [8]) that the embedding and are continuous. Next we define by Taking into account the condition (1.6), we obtain the following variational formulation of our problem: We define the operators and by Obviously, the bilinear forms (1.13) are symmetric, continuous and coercive.

Let us introduce the functional defined by From [5, Chapter II] under Assumptions , the functional defined by (1.14) satisfies is a functional such that:(i) is well defined, locally Lipschitz (in fact, Lipschitz on bounded subsets of ) and regular;(ii) implies for with ;(iii) for with , where denotes the directional derivative of at a point in the direction .

We can now formulate the second-order evolution inclusions associated with the variational form of our problem. In this paper, we study a general autonomous evolution inclusion which includes (1.15).

#### 2. Setting of the Problem

Let and be real separable Hilbert spaces such that with compact and dense embedding. Let be the dual space of . We identify with (dual space of ). For the linear operators , , and locally Lipschitz functional we consider a problem of investigation of dynamics for all weak solutions defined for of nonlinear second order autonomous differential-operator inclusion: We need the following hypotheses is a linear symmetric such that there exists for all ; is linear, symmetric, and there exists for all (we remark that operators and are continuous on [8, Chapter III]); is a function such that(i) is locally Lipschitz and regular [5, Chapter II], that is, (a)for any , the usual one-sided directional derivative exists,(b)for all , , where ;(ii)there exists : for all ;(iii)there exists : where for all denotes the Clarke subdifferential of at a point (see [5] for details), , : for all .

We note that in (1.15) we can consider . Indeed, let , then . If is a weak solution of (1.15), then is a weak solution of where satisfies with respective parameters. Thus, to simplify our conclusions, without loss of generality, further we will consider problem (2.1).

The phase space for Problem (2.1) is the Hilbert space: where with . Let .

*Definition 2.1. *The function with is called a *weak solution* for (2.1) on , if there exists , for a.e. , such that for all , for all :

Evidently, if is a weak solution of (2.1) on , then and .

We consider the class of functions . Further , and we recall parameters of Problem (2.1). The main purpose of this work is to investigate the long-time behavior (as ) of all weak solutions for the problem (2.1) on .

#### 3. Preliminaries

To simplify our conclusions, since condition , we suppose that Lebourg mean value theorem [5, Chapter 2] provides the existence of constants and :

Lemma 3.1. *Let be a locally Lipschitz and regular functional, . Then for , there exists for all . Moreover, .*

*Proof. *Since , then is strictly differentiable at the point for any . Hence, taking into account the regularity of and [5, Theorem 2.3.10], we obtain that the functional is regular one at and . On the other hand, since is locally Lipschitz then is globally Lipschitz, and therefore it is absolutely continuous. Hence for a.e. there exists , and for all . At that taking into account the regularity of , note that for a.e. , and all . This implies that for .

At the inclusion (2.1) on we associate the conditions where and . From [37, Theorem 1] we get the following lemma.

Lemma 3.2. *For any the Cauchy problem (2.1), (3.3) has a weak solution . Moreover, each weak solution of the Cauchy problem (2.1), (3.3) on the interval belongs to the space and .*

#### 4. Properties of Solutions

Let us consider the next denotations: for all we set is a weak solution of (2.1) on . From Lemma 3.2, it follows that .

Let us check that translation and concatenation of weak solutions are weak solutions too.

Lemma 4.1. *If , then for all . If and , then
**
belongs to .*

* Proof. *The first part of the statement of this lemma follows from the autonomy of the inclusion (2.1). The proof of the second part follows from the definition of the solution of (2.1) and from that fact that as soon as , and , where

Let and

Lemma 4.2. *Let . Then is absolutely continuous and for , where depends only on parameters of Problem (2.1) (we remark that is equivalent norm on , generated by inner product ).*

*Proof. *Let be an arbitrary weak solution of (2.1) on . From [8, Chapter IV] we get that the function is absolutely continuous and for :
where for and depends only on parameters of Problem (2.1), in virtue of is equivalent norm on . As and is regular and locally Lipschitz, according to Lemma 3.1 we obtain that for a.e. there exists . Moreover, and for a.e. and all we have . In particular, for a.e. . Taking into account (4.4), we finally obtain the necessary statement.

The lemma is proved.

Lemma 4.3. *Let . If is a weak solution of (2.1) on , then there exists its extension on which is weak solution of (2.1) on , that is, with for all and there exists for a.e. , such that for all , for all :
*

*Proof. *The statement of this lemma follows from Lemmas 3.2–4.2, Conditions (3.1), (3.2) and from the next estimates: for all , for all , for all for all .

The lemma is proved.

For an arbitrary , let be the set of all weak solutions (defined on ) of problem (2.1) with initial data . We remark that from the proof of Lemma 4.3 we obtain the next corollary.

Corollary 4.4. *For any and the next inequality is fulfilled:
*

From Corollary 4.4 and Conditions , , in a standard way we obtain such proposition.

Theorem 4.5. *Let be an arbitrary sequence of weak solutions of (2.1) on such that weakly in . Then there exist and such that weakly in uniformly on , that is, weakly in for any with .*

Theorem 4.6. *Let be an arbitrary sequence of weak solutions of (2.1) on such that strongly in . Then there exists such that up to a subsequence in .*

*Proof. *Let be an arbitrary sequence of weak solutions of (2.1) on such that

Let and as in Theorem 4.5. It is important to remark that in the proof of Theorem 4.5, by using the inequality (Lemma 4.2, Corollary 4.4, (3.2)):
we establish that

Let us prove that
By contradiction suppose the existence of and subsequence such that for all for all . Without loss of generality we suppose that . Therefore, by virtue of the continuity of , we have

On the other hand, we prove that

Firstly, we remark that (Theorem 4.5)
Secondly, let us prove that

Since is sequentially weakly continuous on is sequentially weakly lower semicontinuous on . Hence, we obtain
and hence
We remark that the last inequality in (4.15) follows from weak convergence of to in and because of the functional is sequentially weakly lower semi-continuous on .

Since the energy equation and (4.7) both sides of (4.16) are equal to (see Lemma 4.2), it follows that , and then (4.14). Convergence (4.12) directly follows from (4.13) and (4.14). Finally, we remark that (4.12) contradicts (4.11). Therefore, (4.10) is true.

The theorem is proved.

We define the -semiflow as . Denote the set of all nonempty (nonempty bounded) subsets of by ). We remark that the multivalued map is *strict **-semiflow*, that is, (see Lemma 4.1) (the identity map), for all . Further, will mean that for some .

*Definition 4.7 (see [41, page 35]). *The -semiflow is called *asymptotically compact*, if for any sequence with bounded, and for any sequence , the sequence has a convergent subsequence.

Theorem 4.8. *The -semiflow is asymptotically compact.*

*Proof. *Let . Let us check the precompactness of in . In order to do that without loss of the generality it is sufficiently to extract a convergent in subsequence from . From Corollary 4.4 we obtain that there exist and such that weakly in , , . We show that . Let us fix an arbitrary . Then for rather big . Hence , where and
(see Corollary 4.4). From Theorem 4.5 for some , we obtain
From the definition of we set for all , , , , where , , , ,

Now we fix an arbitrary . Let for each , :
Then, in virtue of [8, Chapter IV],
where
Thus, for any and

From (4.6), (4.18) and Lemma 4.2 we have
where is a constant. Moreover,
Therefore,
The last inequality holds because of the functional is sequentially weakly lower semicontinuous on . Furthermore,
from which, by Corollary 4.4, we have
Thus,
and, due to (4.25), for any and
Hence, for all we have
Thus, .

The theorem is proved.

Let us consider the family of all weak solutions of the inclusion (2.1), defined on . Note that is *translation invariant one*, that is, for all and all we have , where , . On , we set the *translation semigroup *, , , . In view of the translation invariance of , we conclude that as .

On , we consider the topology induced from the Fréchet space . Note that where is the restriction operator to the interval [42, page 179]. We denote the restriction operator to by .

Let us consider the autonomous inclusion (2.1) on the entire time axis. Similarly to the space , the space is endowed with the topology of local uniform convergence on each interval (cf. [42, page 180]). A function is said to be *a complete trajectory* of the inclusion (2.1), if for all [42, page 180]. Let be a family of *all complete trajectories* of the inclusion (2.1). Note that for all , for all . We say that the complete trajectory is *stationary* if for all for some (rest point). Following [43, page 486], we denote the set of rest points of by . We remark that .

From Conditions and and [39, Chapter 2], the following follows.

Lemma 4.9. *The set is nonempty and bounded in .*

From Lemma 4.2, the existence of Lyapunov function (see [43, page 486]) for follows.

Lemma 4.10. *The functional , defined by (4.3), is a Lyapunov function for .*

#### 5. Existence of the Global Attractor

First we consider constructions presented in [43, 44]. We recall that the set is said to be a *global attractor* for , if(1) is negatively semi-invariant (i.e., for all );(2) is attracting set, that is,
where is the Hausdorff semidistance;(3)for any closed set , satisfying (5.1), we have (minimality).

The global attractor is said to be *invariant*, if for all .

Note that from the definition of the global attractor it follows that it is unique.

We prove the existence of the invariant compact global attractor.

Theorem 5.1. *The -semiflow has the invariant compact in the phase space global attractor . For each the limit sets:
**
are connected subsets of on which is constant. If is totally disconnected (in particular, if is countable) the limits:
**
exist; and are rest points; furthermore, tends to a rest point as for every .*

*Proof. *The existence of the global attractor with required properties directly follows from Lemmas 3.2, 4.1, 4.9, and 4.10, Theorems 4.5–4.8 and [41, Theorem 2.7].

#### 6. Properties of Complete Trajectories

We remark in advance (Section 4):

Lemma 6.1. *The set is nonempty, and
**
where is the global attractor from Theorem 5.1.*

*Proof. *Let us show that . Note that in virtue of Lemma 4.9, the set is nonempty and bounded in . Let . We set for all . Then .

Let us prove (6.2). For any there exists : for all . We set . Note that for all for all . From Theorem 5.1 and from (5.1), it follows that for all there exists : for all . Hence taking into account the compactness of in , it follows that for any .

Lemma 6.2. *The set is compact in and bounded in .*

* Proof. *The boundedness of in follows from (6.2) and from the boundedness of in .

Let us check the compactness of in . In order to do that it is sufficient to check the precompactness and completeness.*Step 1. *Let us check the precompactness of in . If it is not true then in view of (6.1), there exists : is not precompact set in . Hence there exists a sequence , that has not a convergent subsequence in . On the other hand , where , , . Since is compact set in (see Theorem 5.1), then in view of Theorem 4.6, there exists , there exists , there exists : in , in , . We obtained a contradiction.*Step 2. *Let us check the completeness of in . Let , : in , . From the boundedness of in , it follows that . From Theorem 4.6 we have that for all the restriction to the interval belongs to . Therefore, is a complete trajectory of the inclusion (2.1). Thus, .

Lemma 6.3. *Let be the global attractor from Theorem 5.1. Then
*

*Proof. *Let , . From Theorem 5.1 for all . Therefore,
For any , we set
Note that , for all (hence ) and in view of Lemma 4.1, . Moreover .

#### 7. Existence of the Trajectory Attractor

We shall construct the attractor of the translation semigroup , acting on . We recall that the set is said to be *an attracting one* for the trajectory space of the inclusion (2.1) in the topology of , if for any bounded (in ) set and an arbitrary number the next relation:
holds.

A set is said to be *trajectory attractor* in the trajectory space with respect to the topology of (cf. [42], Definition 1.2, page 179), if(i) is a compact set in and bounded in ;(ii) is strictly invariant with respect to , that is, for all ;(iii) is an attracting set in the trajectory space in the topology .

Note that from the definition of the trajectory attractor it follows that it is unique.

The existence of the trajectory attractor and its structure properties follow from such theorem.

Theorem 7.1. *Let be the global attractor from Theorem 5.1. Then there exists the trajectory attractor in the space , and we have
*

*Proof. *The proof intersects with proofs of corresponding statements from [14, 45] (see papers and references therein), and it is based on previous sections results.

From Lemmas 6.1 and 6.2 and the continuity of the operator it follows that the set is nonempty, compact in and bounded in . Moreover, the second equality in (7.2) holds (Lemma 6.1 and the proof of Lemma 6.3). The strict invariance of follows from the autonomy of the inclusion (2.1).

Let us prove that