Discrete Dynamics in Nature and Society
Volume 2017 (2017), Article ID 1364532, 12 pages
https://doi.org/10.1155/2017/1364532

Research Article

Periodic Solutions and -Asymptotically Periodic Solutions to Fractional Evolution Equations

Jia Mu,1,2 Yong Zhou,1,3 and Li Peng¹

¹Faculty of Mathematics and Computational Science, Xiangtan University, Hunan 411105, China
²School of Mathematics and Computer Science, Northwest University for Nationalities, Lanzhou, Gansu 730000, China
³Nonlinear Analysis and Applied Mathematics Research Group, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia

Correspondence should be addressed to Yong Zhou; yzhou@xtu.edu.cn

Received 1 January 2017; Accepted 15 March 2017; Published 3 April 2017

Academic Editor: Can Li

Copyright © 2017 Jia Mu 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.

This paper deals with the existence and uniqueness of periodic solutions, -asymptotically periodic solutions, and other types of bounded solutions for some fractional evolution equations with the Weyl-Liouville fractional derivative defined for periodic functions. Applying Fourier transform we give reasonable definitions of mild solutions. Then we accurately estimate the spectral radius of resolvent operator and obtain some existence and uniqueness results.

1. Introduction

It is well known that fractional order differential equations provide an excellent setting for capturing in a model framework real-world problems in many disciplines, such as chemistry, physics, engineering, and biology [1–4]. In recent years, there has been a significant development in ordinary and partial differential equations involving fractional derivatives; see the monographs of Podlubny [2], Kilbas et al. [1], Zhou [4], and the recent papers [5–8] and the references therein.

As a matter of fact, periodic motion is a very important and special phenomenon not only in natural science but also in social science such as climate, food supplement, insecticide population, and sustainable development.

In our previous paper [9], we discussed a class periodic boundary value problem to fractional evolution equations and obtained the existence and uniqueness results for positive mild solutions. However, since the fractional derivatives provide the description of memory property, the solution of periodic boundary value problems cannot be periodically extended to the time .

On the other hand, several authors have showed that for some fractional order systems the solutions do not show any periodic behavior if the lower terminal of the derivative is finite; see [10–14]. Let and . If is a nonconstant -periodic function of class , [10, 11] tell us that cannot be -periodic function, where is understood as one of the fractional derivatives (Caputo, Riemann-Liouville or Grunwald-Letnikov) with the lower terminal finite. Nevertheless, the authors also point out in [11] that fractional order derivative of other form, such as Weyl-Liouville fractional derivatives defined for periodic function [15], perhaps preserves periodicity. As indicated in [2, 15], the Weyl-Liouville derivative coincides with the Caputo, Riemann-Liouville or Grunwald-Letnikov derivative with lower limit , which is denoted by . There is essential difference between finity and infinity. As in, for instance, [2, 11], for , while for , where is the Caputo fractional derivative with order and the lower terminal , and denotes the two parameters Mittag-Leffler functions. It is obvious that the Weyl-Liouville fractional derivative is suitable for the study of periodic solutions to differential equations.

In real life, many phenomena are not strictly periodic; therefore many other generalized periodic cases need to be studied, such as almost periodic, asymptotically almost periodic, -asymptotically periodic, asymptotically periodic, pseudoperiodic, and pseudo-almost periodic. As the advantages of fractional derivatives, such as the memorability and heredity, many papers concern these types of solutions for fractional differential equations. Since -asymptotically periodic functions in Banach space were first studied by Henríquez et al. [16], there are some papers about -asymptotically periodic solutions for fractional equations; one can refer to [17–19]. For almost periodic solutions, asymptotically almost periodic and other types of bounded solutions to fractional differential equations, one can refer to [13, 17, 20–22]. Ponce [22] studied the existence and uniqueness of bounded solutions for semilinear fractional integrodifferential equation

where is a closed linear operator defined on a Banach space , is Weyl fractional derivative of order with the lower limit , is a scalar-valued kernel, and satisfies some Lipschitz type conditions. Assume that is the generator of an -resolvent family which is uniformly integrable. The mild solutions of (1) was given by

By Banach contraction principle, existence and uniqueness results of almost periodic, asymptotically almost periodic and other types of bounded solutions are established. In addition, Lizama and Poblete [21] gave some sufficient conditions ensuring the existence and uniqueness of bounded solutions to a fractional semilinear equation of order .

In this paper, we study the fractional evolution equations in an ordered Banach space

where is the Weyl-Liouville fractional derivative of order which is defined in Section 2 and is the infinitesimal generator of a -semigroup . Applying Fourier transform, we give reasonable definitions of mild solutions of (3). Then the existence and uniqueness results for the corresponding linear fractional evolution equations are established, and the spectral radius of resolvent operator is accurately estimated. Finally, some sufficient conditions are established for the existence and uniqueness of periodic solutions, -asymptotically periodic solutions, and other types of bounded solutions when satisfies some ordered or Lipschitz conditions.

Compared with the earlier related existence results which appeared in [21–23], there are at least four essence differences: (i) the order of the fractional derivative is ; (ii) in many papers concerning bounded solutions for differential equations, such as [21, 23], the solution is defined by the limit of the solution for the limit equation, without strict proofs of the solution for the given equation possessing that form, but, in this paper, we apply the Fourier transform to (3) itself and obtain the expression of the solution; naturally, we may define expression as a mild solution under suitable conditions; besides, the mild solution in this paper is expressed by the semigroups generated by , which are more convenient than some resolvent families applied in [22]; (iii) the spectral radius of resolvent operator is accurately estimated; (iv) the conditions on contain some ordered relations, and the associated method is monotone iterative technique.

The paper is organized as follows. Section 2 provides the definitions and preliminary results to be used in the article. In Section 3, the existence and uniqueness results for the linear equations are obtained. In Section 4, we consider the existence and uniqueness of the mild solutions for (3). In Section 5, we also give two examples to apply the abstract results.

2. Preliminaries

This section is devoted to some preliminary facts needed in the sequel. Let be an ordered Banach space with norm and partial order , whose positive cone ( is the zero element of ) is normal with normal constant . Denote by the space of all linear bounded operator on Banach space , with the norm . The notation stands for the Banach space of all bounded continuous functions from into equipped with the sup norm ; that is,

For , if for all . stands for the subspace of consisting of all -valued continuous -periodic functions. Set

These functions in are called -asymptotically -periodic (see [16]). We note that and are Banach spaces (see [16]), and .

A function , if for any there is a real number and in arbitrary interval of length such that for all is said to be almost periodic (in the sense of Bohr). We denote by the set of all these functions. The space of almost automorphic functions (resp., compact almost automorphic functions) will be written as (resp., ). The bounded continuous function (resp., ) for every sequence there is a subsequence such that and for each (resp., uniformly on compact subsets of ). Clearly the compact almost automorphic function above is continuous on .

For convenience, we set . We regard the direct sum of and as the space of asymptotically periodic functions , the direct sum of and as the space of asymptotically almost periodic functions , the direct sum of and as the space of asymptotically compact almost automorphic functions, and the direct sum of and as the space of asymptotically almost automorphic functions.

Then we set

and regard the direct sum of and as the space of pseudoperiodic functions, the direct sum of and as the space of pseudo-almost periodic functions, the direct sum of and as the space of pseudocompact almost automorphic functions, and the direct sum of and as the space of pseudo-almost automorphic functions.

The relationship of the above different classes of subspaces is presented in [21, p. 805]:

Denote by or simply the following function spaces:

and the space of all functions satisfying uniformly for each in any bounded subset of . For fixed , then for and , the following conditions could ensure that :

() is uniformly continuous with respect to on for each bounded subset of . More precisely, given and , there exists such that and imply that ;()for all bounded subset , is bounded;()if , where and , is uniformly continuous with respect to on for each bounded subset of .

Then the results shown in Table 1 hold; see [21, Remark3.4 and p. 810].

Table 1

Corollary 1 (see [21, Corollary  3.9]). Let and be given and fixed. Assume that there exists a constant such that

for all and . Let ; then .

Now we recall the definitions of some fractional derivatives and integrals which are used in this paper (see [15]).

Definition 2. Let be periodic with period and such that its integral over a period vanishes. The Weyl fractional integral of order is defined as

where

for .

The above Weyl definition is accordant with the Riemann-Liouville definition [1]

for periodic functions whose integral over a periodic vanishes.

The Weyl-Liouville fractional derivative is defined as

for .

It is shown that the Weyl-Liouville derivative

coincides with the Caputo, Riemann-Liouville, or Grunwald-Letnikov derivative with lower limit [2]. It is known that for any , where denotes the identity operator and holds with ; see [3]. For example, for the function,

Denote by the Fourier transform of ; that is,

for and . Thus ; see [1, Remark2.11].

Let us recall the definitions and properties of operator semigroups; for details see [24]. Assume that is the infinitesimal generator of a -semigroup . If there are and such that , then

A -semigroup is called exponentially stable if there exist constants and such that

The growth bound of the semigroup is defined as

Furthermore, could also be expressed by

For -semigroup , if there exists a constant such that

then it is called uniformly bounded. A -semigroup is called compact if is compact for . The positive -semigroup is -semigroup satisfying for all and . For the positive operators semigroup, one can refer to [25].

In the following part, we shall recall the definitions and properties of Mittag-Leffler functions (see [1]). Note

These functions have the following properties for and .

Lemma 3.

(1)[26, Lemma2.2] , .(2)[27, p. 2004] .(3)([28, Lemma2.2], [29, Eq. ( 14)]) .

Considering the probability density function

the following results hold.

Remark 4.

(1)[30, p. 212] for , for .(2)[31, p. 90, p. 112, p. 168] for .(3)[30, p. 212] for .(4)[30, p. 212] for .

Let

where is a -semigroup. We have the following results.

Lemma 5.

(1)Assume that is a uniformly bounded semigroup and satisfies (21). Then, for any fixed , is a linear and bounded operator; that is, for any , we get

(2)If is a semigroup, then is strongly continuous.(3)If is a positive -semigroup, then is positive for .(4)If is exponentially stable and satisfies (18), then

Proof. For the proof of (1)-(2), we can see [32, Lemma2.9]. By Remark 4, we obtain . In view of Remark 4, we have

Then (4) holds.

Next, we consider the following linear abstract fractional evolution equation:

where generates a -semigroup of operators on Banach space and is continuous.

For convenience, we assume the following condition:

(), , for , and satisfies (28), where

Lemma 6. Assume that generates an exponentially stable -semigroup . If is a function satisfying equation (28) and assumption , then satisfies the following integral equation:

where is defined by (24).

Proof. Applying Fourier transform to (28), we get for . In view of (17) and Remark 4, we have

where . By the uniqueness of Fourier transform, we deduce that the assertion of lemma holds. This completes the proof.

Definition 7. A function is said to be a mild solution of problem (28) if

where is given by (24).

3. Results for Linear Equations

Theorem 8. If is exponentially stable and satisfies (18), belongs to one of , and

where is defined by (24); then and belong to the same space.

Proof. : If , then

Therefore, .
: by the hypotheses, for any , we can find a real number for any interval of length and there exists a number in this interval such that for all . From Lemmas 3, 5(4), and , we have

and and are all almost periodic.
: since , there is and such that and as , uniformly on compact subsets of .

therefore by Lebesgue dominated convergence theorem, when , we get for all .
Furthermore, for a compact set and , by Lemmas 3 and 5, we choose and such that

where . For , by Lemmas 3 and 5, we estimate

which implies that that the convergence is irrelevant to . Similarly, we can prove that if uniformly for on compact subsets of . The case of the space is similar too.
: set . For all sequence , there is of such that

Since

by (36) and Lemmas 3 and 5, for any , we get as . For any Lebesgue dominated convergence theorem implies that as . It is similar that

: assume that . For any , there exists such that for . Then, by Lemmas 3 and 5, we get

for . It follows that as . Thus, .
We next consider the asymptotic property of the solutions. For and , we have for some and . Then Lemmas 3 and 5 imply that

which implies that as . Naturally, we can also get the results for the spaces , , , and .
Set . For we get

We can find that the set is translation-invariant and get

by Lebesgue dominated convergence theorem. Then , , , and have the maximal regularity property under the convolution defined by (33).

Theorem 9. Assume that ; generates an exponentially stable -semigroup and satisfies (18). Then linear fractional evolution equation (28) possesses a unique mild solution , and

Proof. In view of Definition 7 and Theorem 8, is a mild solution of (28) and . By Lemmas 3 and 5, we have

where is defined by (24). Then we obtain

Remark 10. Equation (46) is an optimal estimation. In fact, for , the periodic solution of equation is .

Corollary 11. Let . Assume that generates a uniformly bounded -semigroup and satisfies (21). If , then linear fractional evolution equation

has a unique mild solution , and

Proof. generates a -semigroup , and . Then , so is exponentially stable for . The conclusion follows by Theorem 9.

Theorem 12. Let . Assume that generates an exponentially stable -semigroup , that is, the growth bound

Then linear fractional evolution equation (28) has a unique mild solution , is bounded linear, and spectral radius .

Proof. By Theorem 9 and Lemma 5, we obtain that (28) has a unique mild solution , and is bounded linear.
For all , there exists such that

Define a new norm in as

Since , then is equivalent to . The norm of in is denoted by . Then, for , we have

This implies that . Remark 4 implies that

where is defined by (24). Since , we have . By (55) and Lemma 3, we have

which implies that . Then , and spectral radius . Since is any number in , we obtain .

Remark 13. Similarly to [9], if is a compact and positive analytic semigroup and is a regeneration cone, then , where is the first eigenvalue of .

Corollary 14. Assume that and positive cone is a regeneration cone, compact and positive -semigroup is generated by , whose first eigenvalue

Then (28) possesses a unique mild solution , is positive and bounded linear, and the corresponding spectral radius .

Proof. The proof is similar to that in [9].

4. Results for Nonlinear Equations

Theorem 15. Let be an ordered Banach space, whose positive cone is normal with normal constant . Assume that generates a positive -semigroup , , and satisfies the results shown in Table 1, for , and the following assumptions hold:

()for , there is such that

 where , , , ;()there exists , such that

 where , .

Then (3) has a unique positive mild solution .

Proof. Let ; then , . Next we consider linear equation

We know that a positive -semigroup could be generated by , whose growth bound is . From Theorem 12, linear equation (60) has a unique positive mild solution .
If and is the constant in , without loss of generality, we may assume that . In the following part, we consider linear equation

is the generator of a positive -semigroup with growth bound . From Theorem 12, for , linear equation (61) has a unique mild solution , and is a positive bounded linear operator, and spectral radius .
Set ; then by Lemma 5, Corollary 1, and Theorem 8, it follows that and is continuous. By , is incremental on . Set ; we can construct the sequences

By (61), we have that is another mild solution of (60). Since the mild solution of (60) is unique, we have

Let , in ; then

By (63) and (64) and the definition and the positivity of , we obtain

Since is an increasing operator on , in view of (62) we can show that

Therefore,

By induction,

Since the cone is normal, then we get

Moreover, for some , so it follows that . By the Gelfand formula, . Then there exists such that for . Equation (69) implies that

Combining (66) and (70), by the nested interval method, there is a unique such that

Since operator is continuous, by (62) we have

It follows from the definition of and (66) that is a positive mild solution of (61) for . Hence, is a positive mild solution of (3).
Finally, we prove the uniqueness. If , are the positive mild solutions of (3), substitute and for , respectively; then (). Equation (70) implies that

Thus, ; (3) has a unique positive mild solution .

From Theorem 15 and Remark 13, we obtain the following results.

Corollary 16. Let be an ordered Banach space, whose positive cone is a regeneration cone. Assume that generates a compact and positive -semigroup , , , and satisfies the results shown in Table 1, for , and the following conditions are satisfied:

there exists (where is the first eigenvalue of ) such that

 for any , .

Then (3) has a unique positive mild solution .

Theorem 17. Assume that generates an exponentially stable -semigroup and satisfies (18), , , and satisfies the results shown in Table 1. If the following condition is satisfied:

is Lipschitz continuous with respect to ; that is, there exists a constant such that

 for all and ;

then (3) has a unique mild solution for .

Proof. We define operator by

Form Lemma 5, Corollary 1, and Theorem 8, it follows that is continuous.
By and Lemmas 3 and 5, for all , , , we get

Thus,

When , is a contraction in . Using Banach fixed point theorem we have that has a unique fixed point in . This completes the proof.

Corollary 18. Assume that generates a uniformly bounded -semigroup and satisfies (21), , , and satisfies the results shown in Table 1. If satisfies , then (3) has a unique mild solution for .

Proof. Similar to the proof in Corollary 11, we know that generates an exponentially stable -semigroup . By Theorem 17, (3) possesses a unique mild solution for .

Theorem 19. Assume that generates an exponentially stable -semigroup and satisfies (18), , , and satisfies the results shown in Table 1. Assume that the following conditions are satisfied:

is local Lipschitz continuous in : for all , there exists such that

 for , , .

Denote , then for (3) has only one mild solution in .

Proof. Let , we know that the mild solution of (3) is the fixed point of in .
For any , by (46) and , we have

where . By Lemma 5, Corollary 1, and Theorem 8, we obtain that is continuous. On the other hand, for , by , we get

For , we have . Thus is a contraction in .
Banach fixed point theorem implies that there is only one such that . Therefore (3) has only one mild solution in .

Corollary 20. Assume that generates a uniformly bounded -semigroup and satisfies (21), , , and satisfies the results shown in Table 1 and . Set ; then (3) has only one mild solution in for .

Proof. Similar to the proof in Corollary 11, we know that generates an exponentially stable -semigroup . By Theorem 19, equation (3) has only one mild solution in for .

5. Examples

Example 1. Let ; we discuss briefly the existence of mild solutions of the following fractional parabolic partial differential equation:

where is Liouville fractional partial derivative of order with the lower limit , is bounded and boundary is sufficiently smooth, and is the Laplace operator.

Theorem 21. Let , and . Assume that has continuous partial derivatives for in arbitrary bounded domain, and the supremum of is smaller than , where is the first eigenvalue of Laplace operator with . Then (82) possesses only one positive mild solution .

Proof. Let ; then is a positive cone in . Define operator in as follows:

In view of [24], generates a compact and analytic semigroup . Thus, (82) can be formulated as the abstract fractional partial differential equation (3), where . By the maximum principle of parabolic equations, is a positive -semigroup. It is easy to see that satisfies and . By Corollary 16, (82) has only one positive mild solution .

Example 2. Consider the problem

where is Liouville fractional partial derivative of order with the lower limit , .

Proof. Set , , and

For for , , it follows that for any , with

for . In consequence, (84) has only one mild solution (by Theorem 17).

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

Research was supported by National Natural Science Foundation of China (11326100, 11671339) and Natural Science Foundation of Gansu Province (1506RJYA272).

References

A. A. Kilbas, H. M. Srivastava, and J. J. Trujillo, Theory and Applications of Fractional Differential Equations, Elsevier, Amsterdam, The Netherlands, 2006.

I. Podlubny, Fractional Differential Equations, vol. 198 of Mathematics in Science and Engineering, Academic Press, San Diego, Calif, USA, 1999.

K. S. Miller and B. Ross, An Introduction to the Fractional Calculus and Fractional Differential Equations, A Wiley-Interscience Publication, John Wiley & Sons, New York, NY, USA, 1993.

Y. Zhou, Basic Theory of Fractional Differential Equations, World Scientific, Singapore, 2014.

Y. Zhou and L. Peng, “On the time-fractional Navier—Stokes equations,” Computers & Mathematics with Applications, vol. 73, no. 6, pp. 874–891, 2017.

Y. Zhou and L. Peng, “Weak solutions of the time-fractional Navier—Stokes equations and optimal control,” Computers & Mathematics with Applications, vol. 73, no. 6, pp. 1016–1027, 2017.

Y. Zhou and L. Zhang, “Existence and multiplicity results of homoclinic solutions for fractional Hamiltonian systems,” Computers & Mathematics with Applications, vol. 73, no. 6, pp. 1325–1345, 2017.

Y. Zhou, V. Vijayakumar, and R. Murugesu, “Controllability for fractional evolution inclusions without compactness,” Evolution Equations and Control Theory, vol. 4, no. 4, pp. 507–524, 2015.

J. Mu and H. Fan, “Positive mild solutions of periodic boundary value problems for fractional evolution equations,” Journal of Applied Mathematics, vol. 2012, Article ID 691651, 13 pages, 2012.

I. Area, J. Losada, and J. J. Nieto, “On fractional derivatives and primitives of periodic functions,” Abstract and Applied Analysis, vol. 2014, Article ID 392598, 8 pages, 2014.

E. Kaslik and S. Sivasundaram, “Non-existence of periodic solutions in fractional-order dynamical systems and a remarkable difference between integer and fractional-order derivatives of periodic functions,” Nonlinear Analysis. Real World Applications, vol. 13, no. 3, pp. 1489–1497, 2012.

M. S. Tavazoei and M. Haeri, “A proof for non existence of periodic solutions in time invariant fractional order systems,” Automatica, vol. 45, no. 8, pp. 1886–1890, 2009.

J. Wang, M. Feckan, and Y. Zhou, “Nonexistence of periodic solutions and asymptotically periodic solutions for fractional differential equations,” Communications in Nonlinear Science and Numerical Simulation, vol. 18, no. 2, pp. 246–256, 2013.

M. Yazdani and H. Salarieh, “On the existence of periodic solutions in time-invariant fractional order systems,” Automatica, vol. 47, no. 8, pp. 1834–1837, 2011.

R. Hilfer, “Threefold introduction to fractional derivatives,” in Anomalous Transport: Foundations and Applications, R. Klages, G. Radons, and I. M. Sokolov, Eds., pp. 17–74, Wiley-VCH, New York, NY, USA, 2008.

H. R. Henríquez, M. Pierri, and P. Táboas, “On S-asymptotically ω-periodic functions on Banach spaces and applications,” Journal of Mathematical Analysis and Applications, vol. 343, no. 2, pp. 1119–1130, 2008.

X.-B. Shu, F. Xu, and Y. Shi, “S-asymptotically ω-positive periodic solutions for a class of neutral fractional differential equations,” Applied Mathematics and Computation, vol. 270, pp. 768–776, 2015.

C. Cuevas and J. Cesar de Souza, “Existence of S-asymptotically ω-periodic solutions for fractional order functional integro-differential equations with infinite delay,” Nonlinear Analysis. Theory, Methods & Applications, vol. 72, no. 3-4, pp. 1683–1689, 2010.

C. Cuevas and J. Souza, “S-asymptotically image-periodic solutions of semilinear fractional integro-differential equations,” Applied Mathematics Letters, vol. 22, pp. 865–870, 2009.

E. Alvarez-Pardo and C. Lizama, “Weighted pseudo almost automorphic mild solutions for two-term fractional order differential equations,” Applied Mathematics and Computation, vol. 271, pp. 154–167, 2015.

C. Lizama and F. Poblete, “Regularity of mild solutions for a class of fractional order differential equations,” Applied Mathematics and Computation, vol. 224, pp. 803–816, 2013.

R. Ponce, “Bounded mild solutions to fractional integro-differential equations in Banach spaces,” Semigroup Forum, vol. 87, no. 2, pp. 377–392, 2013.

C. Lizama and G. M. N'Guérékata, “Bounded mild solutions for semilinear integro differential equations in Banach spaces,” Integral Equations and Operator Theory, vol. 68, no. 2, pp. 207–227, 2010.

A. Pazy, Semigroups of Linear Operators and Applications to Partial Differential Equations, vol. 44 of Applied Mathematical Sciences, Springer, New York, NY, USA, 1983.

J. Banasiak and L. Arlotti, Perturbations of Positive Semigroups with Applications, Springer, New York, NY, USA, 2006.

Z. Wei, Q. Li, and J. Che, “Initial value problems for fractional differential equations involving Riemann-Liouville sequential fractional derivative,” Journal of Mathematical Analysis and Applications, vol. 367, no. 1, pp. 260–272, 2010.

X.-B. Shu, Y. Lai, and Y. Chen, “The existence of mild solutions for impulsive fractional partial differential equations,” Nonlinear Analysis. Theory, Methods & Applications, vol. 74, no. 5, pp. 2003–2011, 2011.

Z. Wei, W. Dong, and J. Che, “Periodic boundary value problems for fractional differential equations involving a Riemann-Liouville fractional derivative,” Nonlinear Analysis: Theory, Methods & Applications, vol. 73, no. 10, pp. 3232–3238, 2010.

A. M. Krägeloh, “Two families of functions related to the fractional powers of generators of strongly continuous contraction semigroups,” Journal of Mathematical Analysis and Applications, vol. 283, no. 2, pp. 459–467, 2003.

R.-N. Wang, D.-H. Chen, and T.-J. Xiao, “Abstract fractional Cauchy problems with almost sectorial operators,” Journal of Differential Equations, vol. 252, no. 1, pp. 202–235, 2012.

V. M. Zolotarev, One-Dimensional Stable Distributions, American Mathematical Society, Providence, RI, USA, 1986.

J. Wang and Y. Zhou, “A class of fractional evolution equations and optimal controls,” Nonlinear Analysis: Real World Applications, vol. 12, no. 1, pp. 262–272, 2011.