=Paper= {{Paper |id=Vol-2748/Paper10 |storemode=property |title=Existence of Mild Solution For Stochastic Differential Equations With Fractional Derivative Driven by Multiplicative Noise |pdfUrl=https://ceur-ws.org/Vol-2748/IAM2020_paper_10.pdf |volume=Vol-2748 |authors=Habib Djourdem,Noureddine Boutera }} ==Existence of Mild Solution For Stochastic Differential Equations With Fractional Derivative Driven by Multiplicative Noise== https://ceur-ws.org/Vol-2748/IAM2020_paper_10.pdf
Existence of mild solution for stochastic differential
equations with fractional derivative driven by
multiplicative noise
Habib Djourdema , Noureddine Bouterab
a
    University Center Ahmed-Zabana, Relizane, Algeria
d
    Oran Higher School of Economics, Oran, Algeria


                                         Abstract
                                         This paper focuses on the study of the existence of a mild solution to time and space-fractional stochas-
                                         tic equation perturbed by multiplicative white noise. The required results are obtained by means of
                                         Krasnoselskii’s fixed point theorem.

                                         Keywords
                                         stochastic equation, mild solution, Expectation, Krasnoselskii’ s fixed point theorem.




1. Introduction
In this paper, we are interested in the existence of solutions for nonlinear fractional difference
equations
                 𝑐 𝛼
                  𝐷0+ [𝑒 βˆ’ β„Ž (𝑒)] = Δ𝑒 (𝑑) + 𝑒 β‹… βˆ‡π‘’ + 𝑔 (𝑒) π‘Š (𝑑) , π‘₯ ∈ 𝐷, 𝑑 > 0,               (1)
subject to the initial condition
                                                                                 𝑒 (π‘₯, 0) = 𝑒0 (π‘₯) , π‘₯ ∈ 𝐷, 𝑑 = 0,                            (2)
and the Dirichlet boundary conditions
                                                                                          𝑒 (π‘₯, 𝑑) = 0, π‘₯ ∈ πœ•π·,                               (3)
where 𝐷 βŠ‚ ℝ𝑑 , 𝑒 (π‘₯, 𝑑) represents the velocity field of the fluid, the state 𝑒 (β‹…) takes values in a
separable real Hilbert space 𝐻 with inner product βŸ¨β‹…, β‹…βŸ©, the term 𝑔 (𝑒) π‘Š (𝑑) = 𝑑𝑑𝑑 π‘Š (𝑑) describes
a state dependent random noise, where π‘Š (𝑑)π‘‘βˆˆ[0,𝑇 ] is a 𝐹𝑑 βˆ’adapted Wiener process defined
in completed probability space (Ξ©, 𝐹 , 𝑃) with expectaction 𝐸 and associate with the normal
filtration 𝐹𝑑 = 𝜎 {π‘Š (𝑠) ∢ 0 ≀ 𝑠 ≀ 𝑑}. The operator Ξ” is the Laplacian. Here, 𝑐 𝐷𝑑𝛼 denotes the
Caputo type derivative of order 𝛼 (0 < 𝛼 < 1) for the function 𝑒 (π‘₯, 𝑑)with respect time 𝑑 which
is defined by          {
                          𝑐 𝐷𝛼 𝑒            1     𝑑 πœ•π‘’(π‘₯,𝑠) 𝑑𝑠
                              𝑑 (π‘₯, 𝑑) = Ξ“(1βˆ’π›Ό) ∫0    πœ•π‘  (π‘‘βˆ’π‘ )𝛼 , 0 < 𝛼 < 1,
                            πœ•π‘’(π‘₯,𝑑)                                                               (4)
                              πœ•π‘‘ ,                                   𝛼 = 1,
IAM’20: Third conference on informatics and applied mathematics, 21–22 October 2020,Guelma, ALGERIA
" djourdem.habib7@gmail.com (H. Djourdem); bouteraa-27@hotmail.fr (N. Boutera)
 0000-0002-7992-581X (H. Djourdem); 0000-0002-8772-1315 (N. Boutera)
                                       Β© 2020 Copyright for this paper by its authors.
                                       Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
    CEUR
    Workshop
    Proceedings
                  http://ceur-ws.org
                  ISSN 1613-0073       CEUR Workshop Proceedings (CEUR-WS.org)
where Ξ“ (β‹…) stands for the Gamma function.

   The existence and non-existence of solutions for the Navier-Stokes equations (NSEs) have
been discussed in [13]. Chemin et al. [5] studied the global regularity for the large solutions
to the NSEs. Miura [19] focused on the uniqueness of mild solutions to the NSEs. Germain
[9] presented the uniqueness criteria for the solutions of the Cauchy problem associated to the
NSEs. However, The existence and uniqueness of solutions for the stochastic Navier-Stokes
equations (SNSEs) with multiplicative Gaussian noise were proved in [8], [20]. The large de-
viation principle for SNSEs with multiplicative noise had been established in [23], [27], [31],
[32]. Just mention a few, the study of time-fractional Navier-Stokes equations has become a
hot topic of research due to its significant role in simulating the anomalous diffusion in fractal
media [12], [16], [33].

   There has been a widespread interest during the last decade in constructing a stochastic
integration theory with respect to fractional Brownian motion (FBM) and solving stochastic
differential equations driven by FBM. On the other hand, time-fractional differential equations
are found to be quite effective in modelling anomalous diffusion processes as its can charac-
terize the long memory processes [22], [25], [28], [29], [30]. Hence, Burgers equation with
time-fractional can be adapted to describe the memory effect of the wall friction through the
boundary layer [35]. Furthermore, the analytical solutions of the time- and space-fractional
Burgers equations have been investigated by variational iteration method [11] and Adomian
decomposition method [21].

   The existence of solution for partial neutral integro-differential equation with infinite delay
in infinite dimensional spaces has been extensively studied by many authors. Ezzinbi and al.
[7] investigated the existence and regularity of solutions for some partial functional integro-
differential equations in Banach spaces. Cui and Yan [4] investigated the existence of mild
solutions for a class of fractional neutral stochastic integro-differential equations with infinite
delay in Hilbert spaces by means of Sadovskii’s fixed point theorem and in another paper [1],
Balasubramaniam et al. discussed the existence of mild and strong solutions of semilinear neu-
tral functional differential evolution equations with nonlocal conditions by using fractional
power of operators and Krasnoselskii fixed point theorem, Djourdem and Bouteraa [6] studied
the existence of a mild solution to time and space-fractional stochastic equation perturbed by
multiplicative with noise via Sadovskii’s fixed point theorem. In particular, the stability theory
of stochastic differential equations has been popularly applied in variety fields of science and
technology. Several authors have established the stability results of mild solutions for these
equations by using various techniques, we refer the reader to [2], [10], [17], [26].

   The main contribution of this paper is to establish the existence of mild solution for the prob-
lem (1)-(3). Using mainly the Krasnoselskii’s fixed point theorem. The rest f paper organised as
follows, In Section 2, we will introduce some notations and preliminaries, which play a crucial
role in our theorem analysis. In Section 3, the existence results on a mild solutions are derived.
2. Preliminaries
In this section, we give some notions and certain important preliminaries, which will be used
in the subsequent discussions. Let (Ξ©, 𝐹 , 𝑃, {𝐹 }𝑑β‰₯0 ) be a filtered probability space with a normal
filtration, where 𝑃 is a probability measure on (Ξ©, 𝐹 ) and 𝐹 is the Borel πœŽβˆ’algebra . Let {𝐹 }𝑑β‰₯0
satisfying that 𝐹0 contains all 𝑃-null sets. Theoperator 𝐴 is the infinitesimal generator of a
strongly continuous semigroup on a separable real Hilbert space 𝐻 .
Denote the basic functional space 𝐿𝑝 (𝐷) , 1 ≀ 𝑝 < ∞ and 𝐻 𝑠 (𝐷) by the usual Lebesgue and
Sobolev space, respectively. We assume that 𝐴 is the negative Laplacian βˆ’Ξ” in a bounded
domain with zero Dirichlet boundary conditions in Hilbert space 𝐻 = 𝐿2 (𝐷), which are given
by
                                𝐴 = βˆ’β–³, 𝐷 (𝐴) = 𝐻01 (𝐷) ∩ 𝐻 2 (𝐷) ,
since the operator 𝐴 is self-adjoint, i.e., there exist the eigenvectors π‘’π‘˜ corresponding to eigen-
values πœ†π‘˜ such that
                                            √
                       π΄π‘’π‘˜ = πœ†π‘˜ π‘’π‘˜ , π‘’π‘˜ = 2𝑠𝑖𝑛 (π‘˜πœ‹) , πœ†π‘˜ = πœ‹ 2 π‘˜ 2 , π‘˜ ∈ β„•+ .
                                                                                             𝜎
  For any 𝜎 > 0, let 𝐻 𝜎 be the domain of the fractional power 𝐴 2 = (βˆ’Ξ”) 2 , which can be
                                                                            𝜎


defined by
                                      𝜎        𝜎
                             𝜎 > 0, 𝐴 2 π‘’π‘˜ = π›Ύπ‘˜2 π‘’π‘˜ , π‘˜ = 1, 2, …
and                                  {                                           }
                                                                       ∞ 𝜎
                               𝜎
                     𝜎                       2
                    𝐻 = 𝐷 (𝐴 ) = 𝑣 ∈ 𝐿
                               2                 (𝐷) , 𝑠.𝑑. ‖𝑣‖2𝐻 𝜎 = βˆ‘π›Ύπ‘˜2 π‘£π‘˜2 < ∞       ,
                                                                      π‘˜=1
                                                                                    β€– 𝜎 β€–
where π‘£π‘˜ = βŸ¨π‘£, π‘’π‘˜ ⟩ with the inner product βŸ¨β‹…, β‹…βŸ© in 𝐿2 (𝐷), the norm ‖𝐻 𝜎 𝑣‖ = ‖𝐴 2 𝑣 β€–, the bilinear
                                                                                    β€–   β€–
operator 𝐡 (𝑒, 𝑣) = 𝑒 β‹… βˆ‡π‘£ and  (𝐡) = 𝐻01 (𝐷) with the slight abuse of notation 𝐡 (𝑒) = 𝐡 (𝑒, 𝑒).
Then we can rewrite the equation (1)-(3) as follows in the abstract form
              {
                 𝑐 𝐷𝛼                                                     π‘Š (𝑑)
                    𝑑 [𝑒 (𝑑) βˆ’ β„Ž (𝑒 (𝑑))] = 𝐴𝑒 (𝑑) + 𝐡 (𝑒 (𝑑)) + 𝑔 (𝑒 (𝑑)) 𝑑𝑑 , 𝑑 > 0,
                                                                                                   (5)
                        𝑒 (0) = 𝑒0 ,
where {π‘Š (𝑑) , 𝑑 β‰₯ 0} is a 𝑄-Wiener process with linear bounded covarience operator 𝑄 such
                                                       ∞
that a trace class operator 𝑄 denote 𝑇 π‘Ÿ (𝑄) = βˆ‘ πœ†π‘˜ < ∞, which satisfies that π‘„π‘’π‘˜ = πœ†π‘˜ π‘’π‘˜ , π‘˜ =
                                                    π‘˜=1
1, 2, …, then the Wiener process is given by
                                              ∞ √
                                      π‘Š (𝑑) = βˆ‘ πœ†π‘˜ π›½π‘˜ (𝑑) π‘’π‘˜ ,
                                                 π‘˜=1

where {π›½π‘˜ }∞
           π‘˜=1 is a sequence of real-valued standard Brownian motions.


Let 𝐿20 = 𝐿2 (𝑄 2 (𝐻 ) , 𝐻 ) be a Hilbert-Schmidt space of operators from 𝑄 2 (𝐻 ) to 𝐻 with the
                1                                                                    1


norm                                                            1
                                                           ∞          2
                                         β€– 1β€–             1
                                β€–πœ™β€–πΏ20 = β€–πœ™π‘„ 2 β€– 𝜎 = βˆ‘πœ™π‘„ 2 𝑒𝑛   ,
                                         β€–     ‖𝐻   ( 𝑛=1     )
i.e.,                                  {                          }
                                                             β€– ∞ β€–
                                                               2     1       1
                            𝐿20 = πœ™ ∈ 𝐿 (𝐻 ) ∢ βˆ‘ β€–β€–πœ†π‘› πœ™π‘„ 𝑒𝑛 β€–β€– < ∞ , 2       2

                                               𝑛=1 β€–         β€–
where 𝐿 (𝐻 ) is the space of bounded linear operators from 𝐻 to 𝐻 .
For an arbitrary Banach space 𝐡, we denote
                                                1
                                            𝑝
                   ‖𝑣‖𝐿𝑝 (Ξ©,𝐡) = (𝐸 ‖𝑣‖𝐡 ) 𝑝 , βˆ€π‘£ ∈ 𝐿𝑝 (Ξ©, 𝐹 , 𝑃, 𝐡) , 𝑓 π‘œπ‘Ÿ π‘Žπ‘›π‘¦ 𝑝 β‰₯ 2.

   We shall also need the following result with respect to the operator 𝐴 (see [28]).
   For any 𝜈 > 0, an analytic semigroup 𝑇 (𝑑) = 𝑒 βˆ’π‘‘π΄ , 𝑑 β‰₯ 0 is generated by the operator 𝐴 on
𝐿𝑝 , there exists a constant 𝐢𝜈 dependent on 𝜈 such that

                                           ‖𝐴𝑇 (𝑑)‖𝐿(𝐿𝑝 ) ≀ 𝐢𝜈 𝑑 βˆ’πœˆ , 𝑑 > 0,

in which 𝐿 (𝐡) denotes the Banach space of all bounded operators from 𝐡 to itself.
   Next we will introduce the following lemma to estimate the stochastic integrals, which con-
tains the Burkhoder-Davis-Gundy’s inequality.
   [15] For any 0 ≀ 𝑑1 < 𝑑2 ≀ 𝑇 and 𝑝 β‰₯ 2 and for any predictable stochastic process 𝑣 ∢
[0, 𝑇 ] Γ— Ξ© β†’ 𝐿20 which satisfies
                                                                         𝑝
                                             βŽ‘βŽ› 𝑇              ⎞ 2 ⎀βŽ₯
                                             ⎒⎜
                                           𝐸 ⎒ ∫ ‖𝑣 (𝑠)β€–2𝐿2 𝑑𝑠 ⎟ βŽ₯ < ∞,
                                             ⎒⎜⎝ 0             ⎟ βŽ₯
                                                          0

                                             ⎣                 ⎠ ⎦

then, we have
                                                                                 𝑝
                         βŽ‘β€– 𝑑2           ‖𝑝 ⎀          βŽ‘βŽ› 𝑑2            ⎞ 2 ⎀βŽ₯
                          β€–
                         βŽ’β€–              β€– βŽ₯           ⎒⎜
                                         β€–                        2
                       𝐸 βŽ’β€–βˆ« 𝑣 (𝑠) π‘‘π‘Š (𝑠)β€– βŽ₯ < 𝐢 (𝑝) 𝐸 ⎒ ∫ ‖𝑣 (𝑠)‖𝐿2 𝑑𝑠 ⎟ βŽ₯ .
                          β€–              β€–
                                                       βŽ’βŽœβŽπ‘‘1            ⎟ βŽ₯
                                                                    0
                         βŽ’β€–π‘‘1            β€– βŽ₯                            ⎠ ⎦
                         βŽ£β€–              β€–  ⎦          ⎣
  Ispired by the definition of the mild solution to the time-fractional differential equations (see
[24], [34]), we give the following definition of mild solution for our time-fractional stochastic
equation.
  An 𝐹𝑑 -adapted stochastic process (𝑒 (𝑑) , 𝑑 ∈ [0, 𝑇 ]) is called a mild solution to (5) if the fol-
lowing integral equation is satisfied
                                                           𝑑

                 𝑒 (𝑑) = 𝐸𝛼 (𝑑) 𝑒0 + β„Ž (𝑒 (𝑑)) + ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) 𝐡 (𝑒 (𝑠)) 𝑑𝑠
                                                       0

                                   𝑑

                             + ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) 𝑔 (𝑒 (𝑠)) π‘‘π‘Š (𝑠) ,                        (6)
                               0
where the generalized Mittag-Leffler operators 𝐸𝛼 (𝑑) and 𝐸𝛼,𝛼 (𝑑) are defined, respectively, by
                                                                 ∞

                                           𝐸𝛼 (𝑑) = ∫ πœπ›Ό (πœƒ) 𝑇 (𝑑 𝛼 πœƒ) π‘‘πœƒ,
                                                             0

and
                                                                 ∞

                                      𝐸𝛼,𝛼 (𝑑) = ∫ π›Όπœƒπœπ›Ό (πœƒ) 𝑇 (𝑑 𝛼 πœƒ) π‘‘πœƒ,
                                                             0

where 𝑇 (𝑑)         𝑑 β‰₯ 0 is an analytic semi group generated by the operator βˆ’π΄ and the
             = 𝑒 βˆ’π‘‘π΄ ,
Mainardi’s Wright-type function with 𝛼 ∈ (0, 1) is given by
                                                             ∞
                                                                      (βˆ’1)π‘˜ πœƒ π‘˜
                                       πœπ›Ό (πœƒ) = βˆ‘                                    .
                                                             π‘˜=0
                                                                 π‘˜!Ξ“ (1 βˆ’ 𝛼 (1 + π‘˜))

[3] For any 𝛼 ∈ (0, 1) and βˆ’1 < 𝜈 < ∞, it is not difficult to verity that
                                                                 ∞
                                                                                         Ξ“ (1 + 𝜈)
                              πœπ›Ό (πœƒ) β‰₯ 0 π‘Žπ‘›π‘‘ ∫                        πœƒ 𝜈 πœπ›Ό (πœƒ) π‘‘πœƒ =              ,          (7)
                                                             0                          Ξ“ (1 + π›Όπœˆ)
for all πœƒ β‰₯ 0.
  The operators and {𝐸𝛼 (𝑑)}𝑑β‰₯0 and {𝐸𝛼,𝛼 (𝑑)}𝑑β‰₯0 in (7) have the following properties.
  For any 𝐸𝛼 (𝑑) and 𝐸𝛼,𝛼 (𝑑) are linear and bounded operators. Moreover, for 0 < 𝛼 < 1 and
0 ≀ 𝜈 < 2, there exists a constant 𝐢 > 0 such that 𝐸𝛼 (𝑑) and 𝐸𝛼,𝛼 (𝑑) are defined, respectively, by

                                                                                                              (8)
                                                        π›Όπœˆ
                          ‖𝐸𝛼 (𝑑) πœ’ ‖𝐻 𝜈 ≀ 𝐢𝑑 βˆ’ 2 β€–πœ’ β€– ,                  ‖𝐸𝛼,𝛼 (𝑑) πœ’ β€– 𝜈 ≀ 𝐢𝑑 βˆ’ π›Όπœˆ2 β€–πœ’ β€– .
                                                                          β€–           ‖𝐻
 For 𝑇 > 0 and 0 ≀ 𝜈 < 2, by means of Lemma 2 and Lemma 2, we have
                                                ∞

                         ‖𝐸𝛼 (𝑑) πœ’ ‖𝐻 𝜈 ≀ ∫ πœπ›Ό (πœƒ) β€–π΄πœˆ 𝑇 (𝑑 𝛼 πœƒ) πœ’ β€– π‘‘πœƒ
                                            0

                                                    ∞
                                                                     π›Όπœˆ
                                           ≀ ∫ 𝐢𝜈 𝑑 βˆ’ 2 πœƒ βˆ’πœˆ πœπ›Ό (πœƒ) β€–πœ’ β€– π‘‘πœƒ
                                                0

                                                    𝐢𝜈 Ξ“ (1 βˆ’ 𝜈) βˆ’ π›Όπœˆ
                                            =                   𝑑 2 β€–πœ’ β€– ,              πœ’ ∈ 𝐿2 (𝐷) ,
                                                    Ξ“ (1 βˆ’ π›Όπœˆ)
and
                                           ∞
                  ‖𝐸𝛼,𝛼 (𝑑) πœ’ β€– 𝜈 ≀                    𝛼
                  β€–           ‖𝐻    ∫ π›Όπœƒπœπ›Ό (πœƒ) β€–π΄πœˆ 𝑇 (𝑑 πœƒ) πœ’ β€– π‘‘πœƒ
                                       0
                                                ∞
                                                                     π›Όπœˆ
                                        ≀ ∫ 𝐢𝜈 𝛼𝑑 βˆ’ 2 πœƒ 1βˆ’πœˆ πœπ›Ό (πœƒ) β€–πœ’ β€– π‘‘πœƒ
                                            0
                                                     𝐢𝜈 𝛼Γ (2 βˆ’ 𝜈) βˆ’ π›Όπœˆ
                                            =                     𝑑 2 β€–πœ’ β€– ,        πœ’ ∈ 𝐿2 (𝐷) ,
                                                      Ξ“ (1 βˆ’ π›Όπœˆ)
so, 𝐸𝛼 (𝑑) and 𝐸𝛼,𝛼 (𝑑) are linear and bounded operators. The proof is completed.
   For any 𝑑 > 0, the operators 𝐸𝛼 (𝑑) and 𝐸𝛼,𝛼 (𝑑) are strongly continuous. Moreover, for 0 <
𝛼 < 1 and 0 ≀ 𝜈 < 2 and 0 ≀ 𝑑1 < 𝑑2 ≀ 𝑇 , there exists a constant 𝐢 > 0 such that
                                                                                         π›Όπœˆ
                                 β€–(𝐸𝛼 (𝑑2 ) βˆ’ 𝐸𝛼 (𝑑1 )) πœ’ ‖𝐻 𝜈 ≀ 𝐢 (𝑑2 βˆ’ 𝑑1 ) 2 β€–πœ’ β€– ,                         (9)

and
                          β€–(𝐸𝛼,𝛼 (𝑑2 ) βˆ’ 𝐸𝛼,𝛼 (𝑑1 )) πœ’ β€– 𝜈 ≀ 𝐢 (𝑑2 βˆ’ 𝑑1 ) π›Όπœˆ2 β€–πœ’ β€– .                          (10)
                          β€–                            ‖𝐻
  For any 0 < 𝑇0 ≀ 𝑑1 < 𝑑2 ≀ 𝑇 , it iseasy to deduce that
                     𝑑2
                  𝑑𝑇 (𝑑 𝛼 πœƒ)
                ∫            𝑑𝑑 = 𝑇 (𝑑2𝛼 πœƒ) βˆ’ 𝑇 (𝑑1πœƒ )
                    𝑑𝑑
                𝑑1

                                            𝑑2

                                     = ∫ 𝛼𝑑 π›Όβˆ’1 πœƒπ΄π‘‡ (𝑑 𝛼 πœƒ) 𝑑𝑑,
                                       𝑑1

and by (7) and Lemma 2, we have

   β€–(𝐸𝛼 (𝑑2 ) βˆ’ 𝐸𝛼 (𝑑1 )) πœ’ ‖𝐻 𝜈 = β€–π΄πœˆ (𝐸𝛼 (𝑑2 ) βˆ’ 𝐸𝛼 (𝑑1 )) πœ’ β€–
                                          β€– ∞                                     β€–
                                          β€–                 𝛼          πœƒ
                                                                                  β€–
                                        = β€–βˆ« πœπ›Ό (πœƒ) 𝐴𝜈 (𝑇 (𝑑2 πœƒ) βˆ’ 𝑇 (𝑑1 )) πœ’ π‘‘πœƒ β€–β€–
                                          β€–
                                          β€–                                       β€–
                                          β€–0                                      β€–
                                                     ∞                𝑑2

                                        ≀ ∫ π›Όπœƒπœπ›Ό (πœƒ) ∫ 𝑑 π›Όβˆ’1 ‖𝐴2+𝜈 𝑇 (𝑑 𝛼 πœƒ) πœ’ ‖𝐿2 π‘‘π‘‘π‘‘πœƒ
                                                 0               𝑑1
                                                         ∞
                                                                            βŽ› 𝑑2 π›Όπœˆ        ⎞
                                                              βˆ’ 𝜈2
                                            ≀ ∫ 𝐢𝜈 π›Όπœƒ                πœπ›Ό (πœƒ) ⎜∫ 𝑑 βˆ’ 2 βˆ’1 𝑑𝑑 ⎟ β€–πœ’ β€– π‘‘πœƒ
                                                                            ⎜              ⎟
                                                     0                      βŽπ‘‘1            ⎠
                                                 2𝐢𝜈 Ξ“ (1 βˆ’ 𝜈2 )          2βˆ’ π›Όπœˆ2  βˆ’ π›Όπœˆ
                                         =
                                                     πœˆΞ“ (1 βˆ’ π›Όπœˆ        (𝑑1 βˆ’ 𝑑2 ) β€–πœ’ β€–
                                                              2 )

                                                      2𝐢𝜈 Ξ“ (1 βˆ’ 𝜈2 )               π›Όπœˆ
                                            ≀                              (𝑑2 βˆ’ 𝑑1 ) 2 β€–πœ’ β€– , πœ’ ∈ 𝐿2 (𝐷) .
                                                     πœˆπ‘‡0π›Όπœˆ Ξ“ (1 βˆ’ π›Όπœˆ
                                                                   2 )
Also
        β€–(𝐸𝛼,𝛼 (𝑑2 ) βˆ’ 𝐸𝛼,𝛼 (𝑑1 )) πœ’ β€– 𝜈 = β€–π΄πœˆ (𝐸𝛼,𝛼 (𝑑2 ) βˆ’ 𝐸𝛼,𝛼 (𝑑1 )) πœ’ β€–
        β€–                            ‖𝐻    β€–                               β€–
                                               β€– ∞                                         β€–
                                               β€–                                           β€–
                                            = β€–β€–βˆ« π›Όπœƒπœπ›Ό (πœƒ) 𝐴𝜈 (𝑇 (𝑑2𝛼 πœƒ) βˆ’ 𝑇 (𝑑1πœƒ )) πœ’ π‘‘πœƒ β€–β€–
                                               β€–                                           β€–
                                               β€–0                                          β€–
                                                     ∞                    𝑑2

                                         ≀ ∫ 𝛼 πœƒ πœπ›Ό (πœƒ) ∫ 𝑑 π›Όβˆ’1 ‖𝐴2+𝜈 𝑇 (𝑑 𝛼 πœƒ) πœ’ ‖𝐿2 π‘‘π‘‘π‘‘πœƒ
                                                         2 2

                                                 0                   𝑑1
                                                     ∞
                                                                            βŽ› 𝑑2 π›Όπœˆ        ⎞
                                                           2 1βˆ’ 𝜈2
                                             ≀ ∫ 𝐢𝜈 𝛼 πœƒ              πœπ›Ό (πœƒ) ⎜∫ 𝑑 βˆ’ 2 βˆ’1 𝑑𝑑 ⎟ β€–πœ’ β€– π‘‘πœƒ
                                                                            ⎜              ⎟
                                                 0                          βŽπ‘‘1            ⎠
                                                     2π›ΌπΆπœˆ Ξ“ (2 βˆ’ 𝜈2 )   βˆ’ π›Όπœˆ   βˆ’ π›Όπœˆ
                                         =                      𝜈    ( 𝑑1 2 βˆ’ 𝑑2 2 ) β€–πœ’ β€–
                                                 πœˆΞ“ (1 + 𝛼 (1 βˆ’ 2 ))
                                                     2𝐢𝜈 Ξ“ (2 βˆ’ 𝜈2 )                          π›Όπœˆ
                                     ≀                                               (𝑑2 βˆ’ 𝑑1 ) 2 β€–πœ’ β€– , πœ’ ∈ 𝐿2 (𝐷) .
                                         πœˆπ‘‡0π›Όπœˆ Ξ“ (1 + 𝛼 (1 βˆ’ 𝜈2 ))
It is obviously to see that the term

                                     β€–(𝐸𝛼 (𝑑2 ) βˆ’ 𝐸𝛼 (𝑑1 )) πœ’ ‖𝐻 𝜈 β†’ 0,

and
                                    β€–(𝐸𝛼,𝛼 (𝑑2 ) βˆ’ 𝐸𝛼,𝛼 (𝑑1 )) πœ’ β€– 𝜈 β†’ 0,
                                    β€–                            ‖𝐻
as 𝑑1 β†’ 𝑑2 which mean that the operators 𝐸𝛼 (𝑑) and 𝐸𝛼,𝛼 (𝑑) are strongly continuous.


3. Existence results
In this section, we present our main results on the existence of mild solutions of problem (5)
and we define the following space
                             {                                      }
                          𝐾 = 𝑒 ∢ 𝑒 ∈ 𝐢 ([0, 𝑇 ] , 𝐻 𝜈 ) , sup ‖𝑒‖ < ∞ .
                                                                               π‘‘βˆˆ[0,𝑇 ]

To do this, we make the following hypotheses:
(𝐻1 ) 𝐴 is the infinitesimal generator of a strongly continuous semigroup {𝑇 (𝑑) , 𝑑 β‰₯ 0} on 𝐻 .
We will also suppose that the operator 𝐸𝛼 (𝑑) , 𝑑 > 0 is compact.
(𝐻2 ) The function 𝑔 ∢ Ω×𝐻 β†’ 𝐿20 satisfies the following global Lipshitz and growth conditions:

                          ‖𝑔 (𝑣)‖𝐿20 ≀ 𝐢 ‖𝑒‖ , ‖𝑔 (𝑒) βˆ’ 𝑔 (𝑣)‖𝐿20 ≀ 𝐢 ‖𝑒 βˆ’ 𝑣‖ ,

for any 𝑒 ∈ 𝐻 , 𝑣 ∈ 𝐻 .

(𝐻3 ) The initial value 𝑒0 ∢ Ξ© β†’ 𝐻 𝜈 is a 𝐹0 βˆ’ measurable random variable, it hold that

                              ‖𝑒0 ‖𝐿𝑝 (Ξ©,𝐻 𝜈 ) < ∞, 𝑓 π‘œπ‘Ÿ π‘Žπ‘›π‘¦ 0 ≀ 𝜈 < 𝛼 < 2.

(𝐻4 ) The function β„Ž ∢ 𝐿20 β†’ 𝐿20 is continuous and there exists πΏβ„Ž > 0 such that
                                         𝑝                                       𝑝
            𝐸 β€–β„Ž (𝑒1 (𝑑)) βˆ’ β„Ž (𝑒2 (𝑑))‖𝐿2 ≀ πΏβ„Ž ‖𝑒1 (𝑑) βˆ’ 𝑒2 (𝑑)‖𝐿2 , 𝑑 ∈ [0, 𝑇 ] , 𝑒1 , 𝑒2 ∈ 𝐿20 ,
                                             0                                       0
and
                                                   𝑝                             𝑝
                          𝐸 β€–β„Ž (𝑒 (𝑑))‖𝐿2 ≀ πΏβ„Ž 𝐸 ‖𝑒 (𝑑)‖𝐿2 , 𝑑 ∈ [0, 𝑇 ] , 𝑒 ∈ 𝐿20 .
                                                       0                             0

(𝐻5 ) Let 𝐢 > 0 be a real number, then the bounded bilinear operator 𝐡 ∢ 𝐿2 (𝐷) β†’ 𝐻 βˆ’1 (𝐷)
satisfies the following properties

                                                           ‖𝐡 (𝑒)‖𝐻 βˆ’1 ≀ 𝐢 ‖𝑒‖2 ,

and
                              ‖𝐡 (𝑒) βˆ’ 𝐡 (𝑣)‖𝐻 βˆ’1 ≀ 𝐢 (‖𝑒‖ + ‖𝑣‖) ‖𝑒 βˆ’ 𝑣‖ ,
for any 𝑒, 𝑣 ∈ 𝐿2 (𝐷).
Our main results is based on the following Krasnoselskii fixed points theorem [14]. [14] Let
𝑋 be a Banach space, 𝐢 a closed, bounded, convex and nonemty subset of 𝑋 . Consider the
operators 𝐹1 and 𝐹2 such that
(𝑖) 𝐹1 𝑒 + 𝐹2 𝑣 ∈ 𝐢 whenever 𝑒, 𝑣 ∈ 𝐢,
(𝑖𝑖𝑖) 𝐹1 is a contraction mapping.
(𝑖𝑖) 𝐹2 is compact and continuous.
Then there exists 𝑧 ∈ 𝐢 such that 𝑧 = 𝐹1 𝑧 + 𝐹2 𝑧.
   In the proof of main result, we need the following Lemmas. Assume that conditions (𝐻1 ) and
(𝐻2 ) hold. Let Ξ¦1 and Ξ¦2 be two operators defined respectively for each 𝑒 ∈ 𝐾 by
                                                       𝑑

                            Ξ¦1 (𝑒) = ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) 𝐡 (𝑒 (𝑠)) 𝑑𝑠,
                                                                                                                                           (11)
                                                   0
                                                       𝑑

                            Ξ¦2 (𝑒) = ∫ 𝑆𝛼 (𝑑 βˆ’ 𝑠) 𝑓 (𝑒 (𝑠)) π‘‘π‘Š (𝑠) .
                                                   0

Then Φ1 and Φ2 are continuous and map 𝐾 into itself.
It is obvious that Ξ¦1 is continuous. Next we show that Ξ¦1 (𝐾 ) βŠ‚ 𝐾 . By (𝐻1 ) and (𝐻2 ), from the
equation (11) and by applying Holder inequality, we have
                                      β€–    𝑑                                                          ‖𝑝
                        𝑝        β€–                           π›Όβˆ’1
                                                                                                      β€–
          𝐸 β€–(Ξ¦1 𝑒) (𝑑)‖𝐻 𝜈 = 𝐸 β€–β€–βˆ«            (𝑑 βˆ’ 𝑠)             𝐴1 𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) π΄πœˆβˆ’1 𝐡 (𝑒 (𝑠)) 𝑑𝑠 β€–β€–
                                      β€–                                                               β€–
                                      β€–0                                                              ‖𝐻 𝜈
                                                       𝑑                                   π‘βˆ’1
                                               βŽ›                     𝑝 π›Όβˆ’1
                                                                     (   2   )      ⎞                      𝑑
                                  ≀ 𝐢𝛼𝑝 ⎜∫                 (𝑑 βˆ’ 𝑠)     π‘βˆ’1       𝑑𝑠 ⎟              ∫           𝐸 [β€–π΄πœˆβˆ’1 𝐡 (𝑒 (𝑠))‖𝑝 ] 𝑑𝑠
                                               ⎜                                    ⎟                  0
                                               ⎝0                                   ⎠
                                                                     π‘βˆ’1                           𝑑
                                   2 (𝑝 βˆ’ 1)
                                   𝑝
                                                                                         π‘βˆ’2                          𝑝
                           ≀ 𝐢 𝐢𝛼
                                  [ π‘βˆ’2 ]
                                                                             (𝑇 )         2
                                                                                               ∫ 𝐸 [‖𝑒 (𝑑)‖𝐻 𝜈 ]
                                                                                               0
                                  𝑑

                                                                                                                                           (12)
                                                            𝑝
                        = 𝛾1 ∫ 𝐸 [‖𝑒 (𝑠)‖𝐻 𝜈 ] 𝑑𝑠                                                                            ,
                              0
                                π‘βˆ’1            π‘βˆ’2
where 𝛾1 = 𝐢 𝑝 𝐢𝛼 [ 2(π‘βˆ’1)
                     π‘βˆ’2 ]            (𝑇 ) 2 . This complete the proof.

By using also the Holder inequality and Lemma 2, we obtain

                                      β€–    𝑑                                                     ‖𝑝
                       𝑝        β€–                            π›Όβˆ’1
                                                                                                 β€–
         𝐸 β€–(Ξ¦2 𝑒) (𝑑)‖𝐻 𝜈 = 𝐸 β€–β€–βˆ«             (𝑑 βˆ’ 𝑠)             𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) 𝑔 (𝑒 (𝑠)) π‘‘π‘Š (𝑠)β€–β€–
                                      β€–                                                          β€–
                                      β€–0                                                         ‖𝐻 𝜈
                                                                                                         𝑝
                                  βŽ‘βŽ› 𝑑                                       ⎞ 2 ⎀βŽ₯
                                  ⎒⎜ β€–        π›Όβˆ’1          β€–2          2
                        ≀ 𝐢 (𝑝) 𝐸 ⎒ ∫ β€–(𝑑 βˆ’ 𝑠) 𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠)β€– β€–π΄πœˆ 𝑔 (𝑒)‖𝐿2 𝑑𝑠 ⎟ βŽ₯
                                        β€–                  β€–
                                  ⎒⎜⎝ 0                                      ⎟ βŽ₯
                                                                         0

                                  ⎣                                          ⎠ ⎦
                                                                       π‘βˆ’2
                             βŽ› 𝑑       2𝑝(π›Όβˆ’1)
                                               ⎞ 2 𝑑
                            π‘βŽœ                              𝑝
                   ≀ 𝐢 (𝑝) 𝐢𝛼 ∫ (𝑑 βˆ’ 𝑠) π‘βˆ’2 ⎟ ∫ 𝐸 β€–π΄πœˆ 𝑔 (𝑒)‖𝐿2 𝑑𝑠
                             ⎜                 ⎟              0
                             ⎝0                ⎠ 0
                                                                        π‘βˆ’2       𝑑
                                                           2
                                               π‘βˆ’2                        𝑝
                  ≀ 𝐢 (𝑝) 𝐢𝛼𝑝                                 𝐸 β€–π΄πœˆ 𝑔 (𝑒)‖𝐿2 𝑑𝑠
                              (            𝑝 (2𝛼 βˆ’ 1) βˆ’ 2 ) ∫               0
                                                                              0
                            𝑑

                                                                                                             (13)
                                               𝑝
                 = 𝛾2 ∫ 𝐸 [‖𝑒 (𝑠)‖𝐻 𝜈 ] 𝑑𝑠,
                        0
                                                   π‘βˆ’2

where 𝛾2 = 𝐢 (𝑝) 𝐢𝛼 𝐢 𝑝 [ 𝑝(2π›Όβˆ’1)βˆ’2 ] .
                    𝑝        π‘βˆ’2                    2


That is Ξ¦2 (𝐾 ) βŠ‚ 𝐾 .
  Assume that conditions (𝐻1 ) and (𝐻4 ) hold. Let Ξ¦3 be the operator defined by for each 𝑒 ∈ 𝐾

                                               (Ξ¦3 𝑒) (𝑑) = 𝐸𝛼 (𝑑) 𝑒0 + β„Ž (𝑒 (𝑑)) .
  Then Φ3 is continuous and maps 𝐾 into 𝐾 . The continuity of Φ3 follows from (𝐻4 ).
Next, we show that Ξ¦3 (π‘Œ ) βŠ‚ π‘Œ . By (𝐻1 ), (𝐻5 ) and from (13), we have
                                                         𝑝                            𝑝          𝑝
                                𝐸 β€–(Ξ¦3 𝑒) (𝑑)‖𝐿2 ≀ 𝐸 β€–β„Ž (𝑒 (𝑑))‖𝐿2 ≀ πΏβ„Ž 𝐸 ‖𝑒 (𝑑)‖𝐿2 .
                                                             0                            0          0


So, we conclude Ξ¦3 (𝐾 ) βŠ‚ 𝐾 .
  Assume that conditions (𝐻1 ) and (𝐻2 ) hold. Then

                                                𝐸 [‖𝐸𝛼 (𝑑) 𝑒0 ‖𝐻 𝜈 ] ≀ 𝐸 [‖𝑒0 ‖𝐻 𝜈 ] .


  By Lemma 2, we have

                                 ⎑ ∞                              1    ⎀
        𝐸 [‖𝐸𝛼 (𝑑) 𝑒0 ‖𝐻 𝜈 ] ≀ 𝐸 ⎒∫ πœπ›Ό (πœƒ) (β€–π΄πœˆ 𝑇 (𝑑 𝛼 πœƒ) 𝑒0 β€–2 ) 2 π‘‘πœƒ βŽ₯
                                 ⎒                                     βŽ₯
                                 ⎣0                                    ⎦
                                                                                      1
                                    ⎑ ∞         ∞                          2    ⎀
                                                      βˆ’π‘‘ 𝛼 πœƒπ΄          2
                                    ⎒
                                 ≀ 𝐸 ∫ πœπ›Ό (πœƒ) βˆ‘ ⟨𝐴𝜈 𝑒         𝑒0 , 𝑒𝑛 ⟩      π‘‘πœƒ βŽ₯
                                    ⎒        ( 𝑛=1                       )      βŽ₯
                                    ⎣0                                          ⎦
                                                                                          1
                                    ⎑ ∞         ∞
                                                            𝛼
                                                               𝜈
                                                                2
                                                                       2 2    ⎀
                                ≀ 𝐸 ⎒∫ πœπ›Ό (πœƒ) βˆ‘ 𝐴𝜈 𝑒0 , 𝑒 βˆ’π‘‘ πœƒπœ†π‘› , 𝑒𝑛      π‘‘πœƒ βŽ₯
                                    ⎒        ( 𝑛=1 ⟨                  ⟩)      βŽ₯
                                    ⎣0                                        ⎦
                                     ⎑ ∞                   ⎀
                                 ≀ 𝐸 ⎒∫ πœπ›Ό (πœƒ) ‖𝑒0 ‖𝐻 𝜈 π‘‘πœƒ βŽ₯ = 𝐸 [‖𝑒0 ‖𝐻 𝜈 ] .
                                     ⎒                     βŽ₯
                                     ⎣0                    ⎦
  First, we define a map 𝐹 ∢ 𝐾 β†’ 𝐢 ([0, 𝑇 ] , 𝐻 𝜈 ) in the following manner: for any 𝑒 ∈ 𝐾 ,
                      𝑑                                                 𝑑

      (𝐹 𝑒) (𝑑) = ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) 𝐡 (𝑒 (𝑠)) 𝑑𝑠 + ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) 𝑓 (𝑒 (𝑠)) π‘‘π‘Š (𝑠)
                  0                                                 0

                                              +𝐸𝛼 (𝑑) 𝑒0 (𝑠) + β„Ž (𝑒 (𝑑)) .
  Now, we set 𝐹 = 𝐹1 + 𝐹2 , where

                                         (𝐹1 𝑒) (𝑑) = 𝐸𝛼 (𝑑) 𝑒0 (𝑠) + β„Ž (𝑒 (𝑑)) ,

and
                      𝑑                                                 𝑑
                               π›Όβˆ’1
      (𝐹2 𝑒) (𝑑) = ∫ (𝑑 βˆ’ 𝑠)         𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) 𝐡 (𝑒 (𝑠)) 𝑑𝑠 + ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) 𝑓 (𝑒 (𝑠)) π‘‘π‘Š (𝑠) ,
                  0                                                 0

for 𝑑 ∈ [0, 𝑇 ].
   Assume (𝐻2 ) , (𝐻4 ), (𝐻5 ) hold and 0 < 𝜈 < 𝛼 ≀ 2, 𝑝 β‰₯ 2, Then
                                                       𝑝                       π›Όπœˆ
                                                             𝑝
                               𝐸 ‖𝐸𝛼 (𝑑2 ) βˆ’ 𝐸𝛼 (𝑑1 )‖𝐻 𝜈 ≀ 𝐢𝛼,𝜈 (𝑑2 βˆ’ 𝑑1 ) 2 𝐸 ‖𝑒0 ‖𝑝 .


We set
                                  𝐼1 = 𝐹1 (𝑑2 ) βˆ’ 𝐹1 (𝑑1 ) = 𝐸𝛼 (𝑑2 ) 𝑒0 βˆ’ 𝐸𝛼 (𝑑2 ) 𝑒0
For any 𝑝 β‰₯ 2, by vertue of Lemma 2, it follows that
                                        𝑝
                               𝐸 [‖𝐼1 ‖𝐻 𝜈 ] = 𝐸 [𝐴 ‖𝐸𝛼 (𝑑2 ) 𝑒0 βˆ’ 𝐸𝛼 (𝑑2 ) 𝑒0 ‖𝑝 ]
                                                               π›Όπœˆ
                                                 𝑝
                                              ≀ 𝐢𝛼,𝜈 (𝑑2 βˆ’ 𝑑1 ) 2 𝐸 ‖𝑒0 ‖𝑝 .
It is obviously to see that the term β€–(𝐹1 (𝑑2 ) βˆ’ 𝐹1 (𝑑1 ))β€–π‘Œ β†’ 0 as 𝑑1 β†’ 𝑑2 which mean that the
operators 𝐹1 is strongly continuous.
   Assume (𝐻2 ) , (𝐻4 ), (𝐻5 ) hold and 0 < 𝜈 < 𝛼 ≀ 2, 𝑝 β‰₯ 2, then the operator 𝐹2 is uniformly
bounded.
  From Lemma 11, using the estimate (12) and by means of extension of Gronwall’s lemma,
we have
                                                  𝑝
                               𝑠𝑒𝑝 𝐸 [‖𝐹2 (𝑒 (𝑑))‖𝐻 𝜈 ] ≀ ∞,
                                                         π‘‘βˆˆ[0,𝑇 ]

that is the operator 𝐹2 is uniformly bounded.
  Assume (𝐻2 ) , (𝐻4 ), (𝐻5 ) hold and 0 < 𝜈 < 𝛼 ≀ 2, 𝑝 β‰₯ 2. Then the operator 𝐹2 is equicontinu-
ous.
  For any 0 ≀ 𝑑1 < 𝑑2 ≀ 𝑇 , from
                                                             𝑑2

            (𝐹2 𝑒) (𝑑2 ) βˆ’ (𝐹2 𝑒) (𝑑1 ) = ∫ (𝑑2 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) 𝐡 (𝑒 (𝑠)) 𝑑𝑠
                                                         0

                𝑑1                                                            𝑑2
                              π›Όβˆ’1
          βˆ’ ∫ (𝑑1 βˆ’ 𝑠)              𝐸𝛼,𝛼 (𝑑1 βˆ’ 𝑠) 𝐡 (𝑒 (𝑠)) 𝑑𝑠 + ∫ (𝑑2 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) 𝑔 (𝑒) π‘‘π‘Š (𝑠) .
            0                                                             0
                                                 𝑑1

                                    βˆ’ ∫ (𝑑1 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑1 βˆ’ 𝑠) 𝑔 (𝑒) π‘‘π‘Š (𝑠) = 𝐼2 + 𝐼3 ,                              (14)
                                             0
where
                         𝑑2                                                            𝑑1
                                    π›Όβˆ’1
          𝐼2 = ∫ (𝑑2 βˆ’ 𝑠)                        𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) 𝐡 (𝑒 (𝑠)) 𝑑𝑠 βˆ’ ∫ (𝑑1 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑1 βˆ’ 𝑠) 𝐡 (𝑒) 𝑑 (𝑠)
                     0                                                             0

                         𝑑1

            = ∫ (𝑑1 βˆ’ 𝑠)π›Όβˆ’1 [𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) βˆ’ 𝐸𝛼,𝛼 (𝑑1 βˆ’ 𝑠)] 𝐡 (𝑒 (𝑠)) 𝑑𝑠
                     0
                                        𝑑1

                               + ∫ [(𝑑2 βˆ’ 𝑠)π›Όβˆ’1 βˆ’ (𝑑1 βˆ’ 𝑠)π›Όβˆ’1 ] 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) 𝐡 (𝑒 (𝑠)) 𝑑𝑠
                                    0
                                        𝑑2

                               + ∫ (𝑑2 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) 𝐡 (𝑒 (𝑠)) 𝑑𝑠
                                𝑑1

                 = 𝐼21 + 𝐼22 + 𝐼23 ,                                                                                    (15)
and
                 𝑑2                                                                    𝑑1
                              π›Όβˆ’1
        𝐼3 = ∫ (𝑑2 βˆ’ 𝑠)                 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) 𝑓 (𝑒 (𝑠)) π‘‘π‘Šπ‘  βˆ’ ∫ (𝑑1 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑1 βˆ’ 𝑠) 𝑓 (𝑒) π‘‘π‘Š (𝑠)
            0                                                                      0

                         𝑑1

            = ∫ (𝑑1 βˆ’ 𝑠)π›Όβˆ’1 [𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) βˆ’ 𝐸𝛼,𝛼 (𝑑1 βˆ’ 𝑠)] 𝑓 (𝑒 (𝑠)) π‘‘π‘Š (𝑠)
                     0
                            𝑑1

                     + ∫ [(𝑑2 βˆ’ 𝑠)π›Όβˆ’1 βˆ’ (𝑑1 βˆ’ 𝑠)π›Όβˆ’1 ] 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) 𝑓 (𝑒 (𝑠)) π‘‘π‘Š (𝑠)
                        0
                            𝑑2

                     + ∫ (𝑑2 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) 𝑓 (𝑒 (𝑠)) π‘‘π‘Š (𝑠)
                       𝑑1

          = 𝐼31 + 𝐼32 + 𝐼33 .                                                                                           (16)
For the first term 𝐼21 in (15), applying the assumptions (𝐻5 ) and Lemma 2 and Holder inequality,
we have

                                 βŽ‘β€– 𝑑1                                                    ‖𝑝 ⎀
                 𝑝           β€–                    π›Όβˆ’1
                                                                                          β€–
        𝐸 [‖𝐼21 ‖𝐻 𝜈 ] = 𝐸 βŽ’β€–β€–βˆ« (𝑑1 βˆ’ 𝑠) [𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) βˆ’ 𝐸𝛼,𝛼 (𝑑1 βˆ’ 𝑠)] 𝐡 (𝑒 (𝑠)) 𝑑𝑠 β€–β€– βŽ₯
                           βŽ’β€–                                                             β€– βŽ₯
                          βŽ£β€– 0                                                            β€– ⎦
                                                                       π‘βˆ’1
                                               βŽ› 𝑑1                   ⎞    𝑑
                          𝑝
                      ≀ πΆπ›Όπœˆ (𝑑2 βˆ’ 𝑑1 )
                                       𝑝𝛼(𝜈+1)
                                          2    ⎜    (𝑑 βˆ’ 𝑠)
                                                            𝑝(π›Όβˆ’1)
                                                             π‘βˆ’1   𝑑𝑠 ⎟                         𝑝
                                                                             𝐸 [β€–π΄βˆ’1 𝐡 (𝑒 (𝑠))‖𝐻 1 ] 𝑑𝑠                 (17)
                                               ⎜∫ 1                   ⎟ ∫
                                               ⎝0                     ⎠ 0
                                                     π‘βˆ’1
                                          π‘βˆ’1                              2𝑝              𝑝𝛼(𝜈+1)
                      ≀ 𝐢 𝑝 πΆπ›Όπœˆ
                              𝑝
                                𝑇 𝑝𝛼                       𝑠𝑒𝑝 𝐸 [‖𝑒 (𝑠)‖𝐻 1 ] (𝑑2 βˆ’ 𝑑1 ) 2 .
                                     ( 𝑝𝛼 βˆ’ 1 ) (π‘‘βˆˆ[0,𝑇 ]                      )

Using the assumptions (𝐻5 ) and Lemma 2 and Holder inequality, we have

                           βŽ‘β€–β€– 𝑑1                                                             ‖𝑝 ⎀
                 𝑝                                                                            β€–
        𝐸 [‖𝐼22 ‖𝐻 𝜈 ] = 𝐸 βŽ’β€–β€–βˆ« [(𝑑2 βˆ’ 𝑠)π›Όβˆ’1 βˆ’ (𝑑1 βˆ’ 𝑠)π›Όβˆ’1 ] [𝐴𝜈 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠)] 𝐡 (𝑒 (𝑠)) 𝑑𝑠 β€–β€– βŽ₯
                           βŽ’β€–                                                                 β€– βŽ₯
                           βŽ£β€– 0                                                               β€– ⎦
                                                                                                   π‘βˆ’1
                          βŽ› 𝑑1 {                                    βˆ’π›Ό(𝜈+1)
                                                                            } π‘βˆ’1
                                                                               𝑝     ⎞
                      ≀ 𝐢𝛼 ∫ [(𝑑2 βˆ’ 𝑠)π›Όβˆ’1 βˆ’ (𝑑1 βˆ’ 𝑠)π›Όβˆ’1 ] Γ— (𝑑2 βˆ’ 𝑠) 2
                         π‘βŽœ
                                                                                  𝑑𝑠 ⎟
                          ⎜                                                          ⎟
                          ⎝0                                                         ⎠
                                     𝑑                                                                                  (18)
                                                           𝑝
                            Γ—βˆ«           𝐸 [β€–π΄βˆ’1 𝐡 (𝑒 (𝑠))‖𝐻 1 ] 𝑑𝑠
                                 0
                                                               π‘βˆ’1
                               βŽ›               ⎞
                         𝑝 𝑝 ⎜       π‘βˆ’1       ⎟                                       2𝑝               𝑝𝛼(1βˆ’πœˆ)βˆ’2
                      ≀ 𝐢 𝐢𝛼 𝑇 ⎜               ⎟                        𝑠𝑒𝑝 𝐸 ‖𝑒 (𝑠)‖𝐻 1 ] (𝑑2 βˆ’ 𝑑1 )       2       ,
                               ⎜ 𝑝 (𝛼 βˆ’ 𝛼(𝜈+1)                        (π‘‘βˆˆ[0,𝑇 ] [         )
                                          2 )⎟
                               ⎝               ⎠
and
                            βŽ‘β€– 𝑑2                                          ‖𝑝 ⎀
                            βŽ’β€–                                             β€– βŽ₯
                  𝑝          β€–                                             β€–
         𝐸 [‖𝐼23 ‖𝐻 𝜈 ] = 𝐸 βŽ’β€–βˆ« (𝑑2 βˆ’ 𝑠)π›Όβˆ’1 𝐴𝜈 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) 𝐡 (𝑒 (𝑠)) 𝑑𝑠 β€– βŽ₯
                             β€–                                             β€–
                            βŽ’β€–π‘‘1                                           β€– βŽ₯
                            βŽ£β€–                                             β€– ⎦
                                                        π‘βˆ’1
                              βŽ› 𝑑2                     ⎞      𝑑2
                                        π›Όβˆ’1βˆ’ 𝛼(𝜈+1)
                                                                                                                     (19)
                            π‘βŽœ                         ⎟                           𝑝
                        ≀ 𝐢𝛼 ∫ (𝑑2 βˆ’ 𝑠)        2    𝑑𝑠      ∫    𝐸 [β€–π΄βˆ’1 𝐡 (𝑒 (𝑠))‖𝐻 1 ] 𝑑𝑠
                              ⎜                        ⎟
                              βŽπ‘‘1                      ⎠ 𝑑1
                                                            π‘βˆ’1
                             βŽ›                ⎞
                         𝑝 π‘βŽœ        π‘βˆ’1      ⎟                                     2𝑝                 𝑝𝛼(1βˆ’πœˆ)
                      ≀ 𝐢 𝐢𝛼 ⎜                ⎟                     𝑠𝑒𝑝 𝐸 ‖𝑒 (𝑠)‖𝐻 1 ] (𝑑2 βˆ’ 𝑑1 )         2      .
                                      𝛼(𝜈+1)
                             ⎜ 𝑝 (𝛼 βˆ’ 2 ) βˆ’ 1 ⎟                   (π‘‘βˆˆ[0,𝑇 ] [         )
                             ⎝                ⎠
Next, by following similar arguments as in the proof of (17)-(19) and using Lemma 2 there
holds,

                                βŽ‘β€– 𝑑1                                                               ‖𝑝 ⎀
                     𝑝           β€–             π›Όβˆ’1
                                                                                                    β€–
            𝐸 [‖𝐼31 ‖𝐻 𝜈 ] = 𝐸 βŽ’β€–β€–βˆ«     (𝑑1 βˆ’ 𝑠)     [𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) βˆ’ 𝐸𝛼,𝛼 (𝑑1 βˆ’ 𝑠)] 𝑓 (𝑒 (𝑠)) π‘‘π‘Šπ‘  β€–β€– βŽ₯
                               ⎒ β€–                                                                  β€– βŽ₯
                                βŽ£β€– 0                                                                β€– ⎦
                                                                                                         𝑝
                     βŽ‘βŽ› 𝑑1                                                              ⎞ 2 ⎀βŽ₯
                     ⎒⎜ β€–         π›Όβˆ’1                                β€–2           2
           ≀ 𝐢 (𝑝) 𝐸 ⎒ ∫ β€–(𝑑1 βˆ’ 𝑠) 𝐴𝜈 [𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) βˆ’ 𝐸𝛼,𝛼 (𝑑1 βˆ’ 𝑠)]β€– ‖𝑓 (𝑒 (𝑠))‖𝐿2 𝑑𝑠 ⎟ βŽ₯
                           β€–                                         β€–
                     ⎒⎜⎝ 0                                                              ⎟ βŽ₯
                                                                                    0

                     ⎣                                                                  ⎠ ⎦
                                                            π‘βˆ’2

                               π‘π›Όπœˆ
                                     βŽ› 𝑑1      2𝑝(π›Όβˆ’1)
                                                       ⎞ 2 𝑑1
               𝑝                     ⎜ (𝑑1 βˆ’ 𝑠) π‘βˆ’2 𝑑𝑠 ⎟                   𝑝
      ≀ 𝐢 (𝑝) πΆπ›Όπœˆ (𝑑2 βˆ’ 𝑑1 )    2                             𝐸 ‖𝑓 (𝑒 (𝑠))‖𝐿2 𝑑𝑠
                                     ⎜∫                ⎟ ∫                   0
                                     ⎝0                ⎠ 0
                                                          π‘βˆ’1
                             2π‘π›Όβˆ’π‘βˆ’1        π‘βˆ’1                                                  π‘π›Όπœˆ
               ≀ 𝐢 𝑝 πΆπ›Όπœˆ
                      𝑝
                         𝑇      2                                 𝑠𝑒𝑝 𝐸 [‖𝑒 (𝑠)‖𝑝 ] (𝑑2 βˆ’ 𝑑1 ) 2 ,                   (20)
                                       ( 2𝑝𝛼 βˆ’ 𝑝 βˆ’ 2 )          (π‘‘βˆˆ[0,𝑇 ]          )
and

                             βŽ‘β€–β€– 𝑑1                                                              ‖𝑝 ⎀
                   𝑝                                                                             β€–
          𝐸 [‖𝐼32 ‖𝐻 𝜈 ] = 𝐸 βŽ’β€–β€–βˆ« [(𝑑2 βˆ’ 𝑠)π›Όβˆ’1 βˆ’ (𝑑1 βˆ’ 𝑠)π›Όβˆ’1 ] [𝐴𝜈 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠)] 𝑓 (𝑒 (𝑠)) π‘‘π‘Šπ‘  β€–β€– βŽ₯
                             βŽ’β€–                                                                  β€– βŽ₯
                             βŽ£β€– 0                                                                β€– ⎦
                                                                                                         𝑝
                     βŽ‘βŽ› 𝑑1                                                            ⎞ 2 ⎀βŽ₯
                     ⎒⎜ β€–          π›Όβˆ’1        π›Όβˆ’1                  β€–2           2
           ≀ 𝐢 (𝑝) 𝐸 ⎒ ∫ β€–[(𝑑2 βˆ’ 𝑠) βˆ’ (𝑑1 βˆ’ 𝑠) ] [𝐴𝜈 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠)]β€– ‖𝑓 (𝑒 (𝑠))‖𝐿2 𝑑𝑠 ⎟ βŽ₯
                           β€–                                       β€–
                     ⎒⎜⎝ 0                                                            ⎟ βŽ₯
                                                                                  0

                     ⎣                                                                ⎠ ⎦
                                                                                               π‘βˆ’2
                           βŽ› 𝑑1 {                              βˆ’π›Όπœˆ
                                                                   } π‘βˆ’2
                                                                      2𝑝    ⎞ 2
                          π‘βŽœ           π›Όβˆ’1        π›Όβˆ’1
                 ≀ 𝐢 (𝑝) 𝐢𝛼 ∫ [(𝑑2 βˆ’ 𝑠) βˆ’ (𝑑1 βˆ’ 𝑠) ] Γ— (𝑑2 βˆ’ 𝑠) 2        𝑑𝑠 ⎟
                           ⎜                                                ⎟
                           ⎝0                                               ⎠
                                                 𝑑
                                                             𝑝
                                           Γ— ∫ 𝐸 [‖𝑓 (𝑒 (𝑠))‖𝐿2 ] 𝑑𝑠
                                                              0
                                             0
                                                             π‘βˆ’2
                                                            2
                                         2 (𝑝 βˆ’ 2)
           ≀ 𝐢 (𝑝) 𝐢 𝐢𝛼𝑝 𝑇
                      𝑝
                           (      2𝑝𝛼 (2 βˆ’ 𝜈) βˆ’ 2 (𝑝 + 2) )
                                                                   2𝑝𝛼(2βˆ’πœˆ)βˆ’2(𝑝+2)
                              Γ—     𝑠𝑒𝑝 𝐸 [‖𝑒 (𝑑)‖𝑝 ] (𝑑2 βˆ’ 𝑑1 )          4              ,        (21)
                                  (π‘‘βˆˆ[0,𝑇 ]          )
and

                           βŽ‘β€– 𝑑2                                         ‖𝑝 ⎀
                           ⎒ β€–                                           β€– βŽ₯
                 𝑝           β€–                                           β€–
        𝐸 [‖𝐼33 ‖𝐻 𝜈 ] = 𝐸 βŽ’β€–βˆ« (𝑑2 βˆ’ 𝑠)π›Όβˆ’1 𝐴𝜈 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠) 𝐡 (𝑒 (𝑠)) 𝑑𝑠 β€– βŽ₯
                             β€–                                           β€–
                           βŽ’β€–π‘‘1                                          β€– βŽ₯
                           βŽ£β€–                                            β€– ⎦
                                                                                     𝑝
                    βŽ‘βŽ› 𝑑1                                            ⎞ 2 ⎀βŽ₯
                    ⎒⎜ β€–         π›Όβˆ’1              β€–2           2
          ≀ 𝐢 (𝑝) 𝐸 ⎒ ∫ β€–(𝑑2 βˆ’ 𝑠) 𝐴𝜈 𝐸𝛼,𝛼 (𝑑2 βˆ’ 𝑠)β€– ‖𝑓 (𝑒 (𝑠))‖𝐿2 𝑑𝑠 ⎟ βŽ₯
                          β€–                       β€–
                    ⎒⎜⎝ 0                                            ⎟ βŽ₯
                                                                 0

                    ⎣                                                ⎠ ⎦
                                           π‘βˆ’2
                 βŽ› 𝑑2                ⎞ 2      𝑑2
                π‘βŽœ           π›Όβˆ’1βˆ’ π›Όπœˆ
                                   2 ⎟
                                                           𝑝
       ≀ 𝐢 (𝑝) 𝐢𝛼 ∫ (𝑑2 βˆ’ 𝑠)             Γ— ∫ 𝐸 [‖𝑓 (𝑒 (𝑠))‖𝐿2 ] 𝑑𝑠
                 ⎜                   ⎟                       0
                 βŽπ‘‘1                 ⎠     𝑑1
                                                     π‘βˆ’2
                                                  2
                               2 (𝑝 βˆ’ 2)                                          2𝑝𝛼(2βˆ’πœˆ)βˆ’2𝑝
      ≀ 𝐢 (𝑝) 𝐢 𝐢𝛼𝑝
                𝑝
                                                      𝑠𝑒𝑝 𝐸 [‖𝑒 (𝑑)‖𝑝 ] (𝑑2 βˆ’ 𝑑1 ) 4          .   (22)
                    (   2𝑝𝛼 (2 βˆ’ 𝜈) βˆ’ 2 (𝑝 + 2) )   (π‘‘βˆˆ[0,𝑇 ]          )
Taking expectation on the both side of (14) and in view of estimates (15) and (17) βˆ’ (22), we
conclude that
                             β€–(𝐹2 𝑒) (𝑑2 ) βˆ’ (𝐹2 𝑒) (𝑑1 )‖𝐿𝑝 (Ξ©,𝐻 𝜈 ) ≀ 𝐢 (𝑑2 βˆ’ 𝑑1 )𝛾 ,
                {                                    }
where 𝛾 = π‘šπ‘–π‘› π›Όπœˆ   2  , 𝛼𝑝(1βˆ’πœˆ)βˆ’2 2𝑝𝛼(2βˆ’πœˆ)βˆ’2(𝑝+2)
                           2𝑝     ,        4𝑝            when 0 < 𝑑2 βˆ’ 𝑑1 < 1.
                                                        {                                  }
Otherwise, if 𝑑2 βˆ’ 𝑑1 β‰₯ 1, then we set 𝛾 = π‘šπ‘Žπ‘₯ 𝛼(𝜈+1)         2    ,  𝛼(2βˆ’πœˆβˆ’1) 2𝑝𝛼(2βˆ’πœˆ)βˆ’2𝑝
                                                                         2    ,      4𝑝     .

  Assume the conditions (𝐻1 ) and (𝐻2 ) hold. Then 𝐹 maps 𝐾 into itself.
  Let the nonlinear operator 𝐹 defined by, for 𝑑 β‰₯ 0,
                                                         𝑑

               (𝐹 𝑒) (𝑑) = 𝐸𝛼 (𝑑) 𝑒0 + β„Ž (𝑒 (𝑑)) + ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) 𝐡 (𝑒 (𝑠)) 𝑑𝑠
                                                     0

                                       𝑑

                               + ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) 𝑔 (𝑒) π‘‘π‘Š (𝑠) .
                                   0
We prove that the operator 𝐹 has a fixed point, which is a mild solution of the problem (1)-(2).
We shall employ Theorem 3. For better readability, we divide the proof into two steps.

Step 1. 𝐹 ∢ π‘Œ β†’ 𝐢 ([0, 𝑇 ] , 𝐻 𝜎 ) is continuous. Let {𝑒𝑛 (𝑑)}𝑛β‰₯0 with 𝑒𝑛 β†’ 𝑒 (𝑛 β†’ ∞) in
π‘Œ . Then there is
               { a number π‘Ÿ > 0 such } that 𝐸 ‖𝑒𝑛 (𝑑)‖𝐻 𝜈 ≀ π‘Ÿ for all 𝑛 and π‘Ž.𝑒. 𝑑 ∈ [0, 𝑇 ], so
                                                      2


𝑒𝑛 ∈ π΅π‘Ÿ (0, π‘Œ ) = 𝑒 ∈ π‘Œ ∢ 𝑠𝑒𝑝 ‖𝑒‖𝐻 𝜎             and 𝑒 ∈ π΅π‘Ÿ (0, π‘Œ ). By the assumptions (𝐻2 ) and similar
                                 π‘‘βˆˆ[0,𝑇 ]
argument to obtain (12) and (13), we have
                                            𝑝
              𝐸 β€–(𝐹 𝑒𝑛 ) (𝑑) βˆ’ (𝐹 𝑒) (𝑑)‖𝐻 𝜈
                                                                                           𝑝
               ≀ 3π‘βˆ’1 β€–β„Ž (𝑒𝑛 (𝑑)) βˆ’ β„Ž (𝑒 (𝑑))‖𝑃𝐻 𝜈 + 3π‘βˆ’1 𝐸 β€–Ξ¦1 (𝑒𝑛 (𝑑) βˆ’ 𝑒 (𝑑))‖𝐻 𝜈
                                                       𝑝
                     + 3π‘βˆ’1 𝐸 β€–Ξ¦2 (𝑒𝑛 (𝑑) βˆ’ 𝑒 (𝑑))‖𝐻 𝜈
                                                                                  𝑑
                                                                             βŽ›                         ⎞
                   π‘βˆ’1                           𝑝                                              𝑝
               ≀3        β€–β„Ž (𝑒𝑛 (𝑑)) βˆ’ β„Ž (𝑒 (𝑑))‖𝐻 𝜈 + 3π‘βˆ’1 (𝐺𝛾1 + 𝐾 𝛾2 ) ⎜∫          𝐸 ‖𝑒𝑛 βˆ’ 𝑒‖𝐻 𝜈 𝑑𝑠 ⎟ .
                                                                          ⎜                            ⎟
                                                                             ⎝0                        ⎠
Then, we have for all 𝑑 ∈ [0, 𝑇 ] ,
                                                   𝑝
                                       ‖𝐹 𝑒𝑛 βˆ’ 𝐹 π‘’β€–π‘Œ ⟢ 0, π‘Žπ‘  𝑛 ⟢ ∞.

Therefore 𝐹 is continuous.

Step 2. We decompose 𝐹 as 𝐹 = 𝐹1 + 𝐹2 where 𝐹1 and 𝐹2 defined above.

(1) 𝐹1 is a contraction on π‘Œ . Let 𝑒, 𝑣 ∈ π‘Œ . It follows from Lemma 3 that
                                            𝑝                       𝑝
                          𝐸 ‖𝐹1 𝑒 βˆ’ 𝐹1 𝑣‖𝐻 𝜈 ≀ πΏβ„Ž 𝐸 ‖𝑒 (𝑠) βˆ’ 𝑣 (𝑠)‖𝐻 𝜈
                                                                                       𝑝
                                                 ≀ πΏβ„Ž 𝑠𝑒𝑝 𝐸 ‖𝑒 (𝑠) βˆ’ 𝑣 (𝑠) 𝑑𝑠‖𝐻 𝜈
                                                       π‘ βˆˆ[0,𝑇 ]
                                                                         𝑝
                                                ≀ πΏβ„Ž ‖𝑒 (𝑠) βˆ’ 𝑣 (𝑠) π‘‘π‘ β€–π‘Œ
Taking supremum over 𝑑
                                                   𝑝                         𝑝
                                       ‖𝐹1 𝑒 βˆ’ 𝐹1 π‘£β€–π‘Œ ≀ 𝐿0 ‖𝑒 (𝑠) βˆ’ 𝑣 (𝑠)β€–π‘Œ ,
where 𝐿0 = πΏβ„Ž < 1.
Hence 𝐹1 is a contraction on π‘Œ .

(2) 𝐹2 is compact operator. Let 𝑒, 𝑣 ∈ π‘Œ . It follows from (𝐻2 ) , (𝐻5 ) and Lemma 3 that
                                β€– 𝑑                                                          β€–2
                                β€–                                                            β€–
  𝐸 ‖𝐹2 𝑒 βˆ’ 𝐹2 𝑣‖2𝐻 𝜈 ≀ 2π‘βˆ’1 𝐸 β€–β€–βˆ« (𝑑 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) 𝐴𝜈 [𝑔 (𝑒 (𝑠)) βˆ’ 𝑔 (𝑣 (𝑠))] π‘‘π‘Š (𝑠)β€–β€–
                                β€–                                                            β€–
                                β€–0                                                           ‖𝐻 𝜈
                                            β€– 𝑑                                                       ‖𝑝
                                            β€–                                                         β€–
                                   +2π‘βˆ’1 𝐸 β€–β€–βˆ« (𝑑 βˆ’ 𝑠)π›Όβˆ’1 𝐸𝛼,𝛼 (𝑑 βˆ’ 𝑠) 𝐴𝜈 [𝐡 (𝑒 (𝑠)) βˆ’ 𝐡 (𝑣 (𝑠))] 𝑑𝑠 β€–β€–
                                            β€–                                                         β€–
                                            β€–0                                                        ‖𝐻 𝜈
                                            βŽ› 𝑑               ⎞
                             ≀ (𝛾1 + 𝛾2 ) 𝐸 ⎜∫ ‖𝑒 βˆ’ 𝑣‖2𝐻 𝜈 𝑑𝑠 ⎟ ,
                                            ⎜                 ⎟
                                            ⎝0                ⎠
which implies
                        𝑠𝑒𝑝 𝐸 ‖𝐹2 𝑒 βˆ’ 𝐹2 𝑣‖2𝐻 𝜈 = (𝛾1 + 𝛾2 ) 𝑠𝑒𝑝 𝐸 ‖𝑒 βˆ’ 𝑣‖2𝐻 𝜈 .
                       π‘‘βˆˆ[0,𝑇 ]                              π‘‘βˆˆ[0,𝑇 ]

Since 0 < 𝐿 = 𝛾1 + 𝛾2 < 1, then 𝐹 is contraction maping on π‘Œ .

From Lemma 3 and Lemma 3, the operator 𝐹2 is relatively compact. together with Ascoli’s
theorem, we conclude that the operator 𝐹2 is compact.
In view of Theorem 3, we conclude that 𝐹 has at least one fixed point, which is a mild solution
of the problem (1)-(2).


References
[1] P. Balasubramaniama, J.Y. Park and A. V. A. Kumar, Existence of solutions for semilinear
    neutral stochastic functional differential equations with nonlocal conditions, Nonlinear
    Analysis, 71 (2009), 1049–1058
[2] T.Caraballo and K.Liu, Exponential stability of mild solutions of stochastic partial differen-
    tial equations with delays. Stoch. Anal. Appl. 17(1999), 743-763 .
[3] P. M. De Carvalho-Neto, P. Gabriela, Mild solutions to the time fractional Navier-Stokes
    equations in RN, J. Differential Equations. 259(2015), 2948-2980.
[4] J .Cui, L. Yan, Existence result for fractional neutral stochastic integro-differential equa-
    tions with infinite delay. J. Phys. A Math. Theor. 44, (2011), 335-201.
[5] J. Y. Chemin, I. Gallagher, M. Paicu, Global regularity for some classes of large solutions to
    the Navier-Stokes equations, Ann. of Math. (2), V.173, N.2, 2011, pp.983-1012.
[6] H. Djourdem and N. Bouteraa, Mild Solution for a Stochastic Partial Differential Equation
    with Noise, WSEAS Transactions on Systems, Volume 19, 2020, Art. 29, pp. 246-256
[7] K. Ezzinbi, S. Ghnimi Local Existence and global continuation for some partial functional
    integrodifferential equations, African Diaspora Journal of Mathematics, Special Volume in
    Honor of Profs. C. Corduneanu, A. Fink, and S. Zaidman Volume 12, Number 1(2011), 34-45.
[8] F. Flandoli, B. Maslowski, Ergodicity of the 2-D Navier-Stokes equation under random
    perturbations, Commun. Math. Phys. 172(1)(1995), 119-141.
[9] P. Germain, Multipliers, paramultipliers, and weak-strong uniqueness for the Navier-
    Stokes equations, J. Differential Equations, V.226, N.2 (2006), 373-428.
[10] T .E. Govindan, Stability of mild solutions of stochastic evolutions with variable decay,
    Stoch.Anal.Appl. 21(2003), 1059-1077.
[11] M. Inc, The approximate and exact solutions of the space- and time-fractional Burgers
    equations with initial conditions by variational iteration method, J. Math. Anal. Appl.
    345(1)(2008), 476-484.
[12] M. Hairer, J.C. Mattingly, Ergodicity of the 2D Navier-Stokes equations with degenerate
    stochastic forcing, Ann. Math. (2006), 993-1032.
[13] Y. Jiang, T. Wei, X. Zhou, Stochastic generalized Burgers equations driven by fractional
    noises, J. Differential Equations. 252(2)(2012), 1934-1961.
[14] M. A. Krasnoselskii, Topological Methods in the Theory of Nonlinear Integral Equations,
    Pergamon, Elmsford (1964).
[15] R. Kruse, Strong and weak approximation of semilinear stochastic evolution equations,
    Springer, 2014.
[16] P. G. Lemari’e-Rieusset, Recent developments in the Navier-Stokes problem, Chapman
    Hall/CRC Research Notes in Mathematics, 431. Chapman Hall/CRC, Boca Raton, FL, 2002,
    395 p.
[17] K. Liu, Stability of Infnite Dimensional Stochastic Differential Equations with Applica-
    tions, Chapman Hall, CRC, London, 2006.
[18] J. Luo, Fixed points and exponential stability of mild solutions of stochastic partial differ-
    ential equations with delays. J. Math. Anal. Appl. 342(2008), 753-760.
[19] H. Miura, Remark on uniqueness of mild solutions to the Navier-Stokes equations, J.
    Funct. Anal., V.218, N.1, (2005), 110-129.
[20] R. Mikulevicius, B.L. Rozovskii, Global 𝐿2 -solutions of stochastic Navier-Stokes equations,
    Ann. Probab. 33(1) (2005), 137-176.
[21] S. Momani, Non-perturbative analytical solutions of the space- and time-fractional Burg-
    ers equations, Chaos Soliton Fract. 28 (2006), 930-937.
[22] L. Pan, Existence of mild solution for impulsive stochastic differential equations with non-
    local conditions, Differential Equations and Applications, Volume 4, Number 3 (2012), 485-
    494.
[23] Z. Qiu and H. Wang, Large deviation principle for the 2D stochastic
    Cahn–Hilliard–Navier–Stokes equations. Z. Angew. Math. Phys. (2020), 71:88
[24] Y.V. Rogovchenko, Nonlinear impulse evolution systems and applications to population
    models, J. Math. Anal. Appl. 207(1997), 300-315.
[25] Y. Ren, D.D. Sun, Second-order neutral stochastic evolution equations with infinite delay
    under carathodory conditions,J. Optim. Theory Appl. 147 (2010), 569-582.
[26] Y. Ren, Q. Zhou, L. Chen, Existence, uniqueness and stability of mild solutions for time-
    dependent stochastic evolution equations with Poisson jumps and infinite delay, J. Optim.
    Theory Appl. 149 (2011) 315-331.
[27] S. S. Sritharan and P. Sundar, Large deviations for the two-dimensional Navier–Stokes
    equations with multiplicative noise. Stochastic Proceess. Appl. 116(11), 1636–1659 (2006)
[28] T. Taniguchi, The existence of energy solutions to 2-dimensional non-Lipschitz stochastic
    Navier-Stokes equations in unbounded domains, J. Differential Equations. 251(12) (2011),
    3329-3362.
[29] G. Wang, M. Zeng, B. Guo, Stochastic Burgers’ equation driven by fractional Brownian
    motion, J. Math. Anal. Appl. 371(1)(2010), 210-222.
[30] R. N. Wang, D. H. Chen, T. J. Xiao, Abstract fractional Cauchy problems with almost
    sectorial operators, J. Differential Equations. 252(1)(2012), 202-235.
[31] R. Wang, J. Zhai, T. Zhang, A moderate deviation principle for 2-D stochastic Navier-
    Stokes equations, J. Differential Equations. 258(10)(2015), 3363-3390.
[32] X. J. Yang, Advanced local fractional calculus and its applications, World Science, New
    York, 2012.
[33] X. J. Yang, H. M. Srivastava, J. A. Machado, A new fractional derivative without singular
    kernel: Application to the modelling of the steady heat flow, Therm. Sci. 20(2)(2016), 753-
    756.
[34] Y. Zhou, L. Peng, On the time-fractional Navier-Stokes equations, Comput. Math. Appl.
    73(6)(2017), 874-891.
[35] G. Zou, B. Wang, Stochastic Burgers equation with fractional derivative driven by multi-
    plicative noise, Comput. Math. Appl. (2017) http://dx.doi.org/10.1016/ j.camwa.2017.08.023.