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∂
( ∆u−u) −u=
f.
∂t
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u(
r,
t)
=
1
2πir
σ + i∞
∫
σ −i∞
1
e
p
pt −
p+
1
r
p
dp.
u(
r,
t)
+∞
t
−
1 µ
2
iµ
r µ + 1
= ∫ e e dµ
.
2
πir
−∞µ
+ 1
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ijb\_^_ldnhjfme_
∞ n
1 −r
t −r
n
k −1
−r
u(
r,
t)
= e − e + ( ∑t
∑ aknr
) e ,
r 2 n=
2 k = 0
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−r(1−δ
)
An
e
B(
δ ) t
u( r,
t)
≤ ,
1+
n 0. 5n−e
u(
r,
t)
≤ A(
δ ) e ,
r t
r
Bgl_j_kgucj_amevlZlihemqZ_lkyijbjZkkfhlj_gbbk_q_gbcr/t=CK≠0A^_kv
ijbf_gy_lkyf_lh^i_j_\ZeZdhlhjuc^Z_l
−at
1 −3 2
u(
r,
t)
= e ( d cosbt
+ g sin bt)
⋅ ( + O(
t )),
t