Асимптотические оценки. Мицик М.Ф. - 12 стр.

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
γ
. 

( )
λ
F

+∞
λ
.
, 

, .
, 
γγ≠
, 
1.
( ) ( )
( )
( )
( )
;dzezfdzezfF
zSzS λ
γ
λ
γ
λ
==
2. 
,
0
∈γz

)(Re zS

( )
;0
0
zf
3.
constzS
)(Im

∈γz

0
z
.

0
γ

γ
, 
0
z
. 

0
>
, 
δ< )(Re)(Re
0
zSzS

0
\ γγz
. 
( ) ( ) ( )
10
, ttttiytxtzz
+
=
=

γ
, 
( )
=
00
];[:,0 γβαzzz
.
, 
( ) ( )
( )
( )( ) ( )
( )( )
=
==
dtetztzfdzezfF
tzS
t
t
zS λλ
γ
λ
1
0
( )
( )
( )
( )( )
,1
0
Im
+=
λ
λ
β
α
λ
Odtetfe
tSzSi
(18)

(
)
(
)
(
)
(
)
(
)
(
)
(
)
tzStStztzftf Re,
=
=
.

(
)
tS
,

.
,  1, 2, 3 
.
1. .

( ) ( )
ziVzUzS +=)(

(
)
(
)
(
)
tiytxtzz
+
=
=

( )
( )
0
tz

γ
, 
( )
0
0 zz
=
. 
=
0t


(
)
(
)
tzSRe
, 
                                               γ.
                   F (λ )                   λ → +∞ .
                                                                              ,

                                   ,                                                                             .
                                           ,                                                  γ∗ ≠γ           ,


          1. F (λ ) =                  ∫ f (z ) e                           ∫ f (z ) e
                                                        λ S (z )                         λ S (z )
                                                                   dz =                             dz ;
                                       γ                                    γ∗

          2.                                                                            z0 ∈ γ ∗ ,                              Re S ( z )
                                                               f (z 0 ) ≠ 0;
          3. Im S ( z ) ≡ const                                    z ∈γ ∗                                    z0 .
                         γ 0∗ −                                                   γ∗,                                z0 .
                        δ >0                        ,              Re S ( z ) < Re S ( z0 ) − δ              z ∈ γ ∗ \ γ 0∗ .
z = z (t ) = x(t ) + iy (t ), t 0 ≤ t ≤ t1 –                                                                                     γ∗
      ,                z (0) = z0 , z : [α ; β ] → γ 0∗ .
                                                                                   ,
                                                                       t1

          F (λ ) =            ∫        f (z ) e   λ S (z )
                                                             dz = ∫ f ( z (t ))z ′(t ) e λ S ( z (t ))dt =
                              γ∗                                       t0

                                       β
          =e       iλ Im S ( z0 )
                                       ∫ f (t ) e
                                           ∗
                                                        λ S∗ (t )
                                                                       (
                                                                    dt 1 + O λ−∞ ,( ))                                           (18)
                                       α

     f ∗ (t ) = f ( z (t ))z ′(t ), S∗ (t ) = Re S ( z (t )) .
                                                             S∗ (t )                                                                     ,

               .
                          ,                                                                 1, 2, 3
                   .
          1.                                                                                                 .
           S ( z ) = U ( z ) + iV ( z )                            z = z (t ) = x(t ) + iy (t )
( z′(t ) ≠ 0)                              γ∗                  ,            z (0) = z 0 .                  t =0−
                                               Re S ( z (t )) ,