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Controllability of Single-valued Chapter | 7  209


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             abstract space C h . The functions f :J 3 C h -H and σ:J 3 C h -L ðK; HÞ are
                                                                   2
                                         0
             the appropriate functions, where L ðK; HÞ denotes the space of all Q-Hilbert-
                                         2
             Schmidt operators from K into H.
             7.3.1  Preliminaries
             The abstract phase space C h is defined by
                                                     1
                 (
                                                      2
                                                   2

             C h 5 ψ:ð2N; 0Š-H:for any a . 0; EjψðθÞj  is bounded and measurable
                                                             1      )
                                                              2
                                        Ð  0  ^            2
                  function on½ 2 a; 0Š with  hðsÞ sup  EjψðθÞj  ds , N :
                                        2N
                                               s # θ # 0
                If C h is endowed with the norm
                              ð 0                    1
                                  ^
                            5     hðsÞ sup        2 2
                      OψO C h               EjψðθÞj  ds; for all ψAC h
                               2N    s # θ # 0
                         Þ is a Banach space [Li and Liu (2007)].
             then ðC h ; OUO C h
                Let Cðð2N; bŠ; HÞ be the space of all continuous H-valued stochastic
             process fξðtÞ; tAð2N; bŠg. Let C b 5 fx:xACðð2N; bŠ; HÞ; x 0 5 φAC h g. Set
             OUO b to be a seminorm defined by
                                                       1

                                                    2 2
                                       1 sup EjxðsÞj   ; xAC b :
                            OxO b 5 Ox 0 O C h
                                          sA½0;bŠ
             Lemma 7.4: (Li and Liu, 2007) Assume that xAC b , then for all tAJ; x t AC h .
             Moreover,
                                  1                      1

                               2 2                     2 2
                         l EjxðtÞj  # Ox t O C h  # l sup EjxðsÞj  1 Ox 0 O C h
                                            sA½0;tŠ
                      Ð 0  ^
             where l 5   hðsÞds , N.
                      2N
                Consider the following fractional stochastic integro-differential equation
                                                       ð t
                    c  α                    12α
                     D xðtÞ 5 AxðtÞ 1 BðtÞuðtÞ 1 J  fðt; x t Þ 1  σðs; x s ÞdWðsÞ
                      t                     t
                                                        2N
             the above equation is equivalent to the following integral equation
                              1  ð t                1  ð t
                 xðtÞ 5 φð0Þ 1     ðt2sÞ α21 AxðsÞds 1   ðt2sÞ α21 BðsÞuðsÞds
                            ΓðαÞ  0               ΓðαÞ  0

                        Ð t          1  ð t   α21   ð s
                      1   fðs; x s Þds 1  ðt2sÞ        σðτ; x τ ÞdWðτÞ ds
                         0
                                    ΓðαÞ  0         2N
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