Методы математической физики - 76 стр.

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t = 0 t = t
0
G(x, ξ, t t
0
) =
1
2
p
πa
2
(t t
0
)
exp
µ
(x ξ)
2
4a
2
(t t
0
)
.
ϕ
ε
(x) 6= 0 (ξ ε, ξ + ε)
G(x, ξ, t t
0
) x
t t = t
0
x = ξ Q
c ρ
−∞ < x <
c ρ
Z
−∞
G(x, ξ, t t
0
) dx =
=
c ρ
2
p
πa
2
(t t
0
)
Z
−∞
exp
µ
(x ξ)
2
4a
2
(t t
0
)
dx = c ρ ,
G(x, ξ, t t
0
) x
t
G(x, ξ, t t
0
) t
x x = ξ x 6= ξ
lim
tt
0
G(x 6= ξ) = 0 , lim
tt
0
G(x = ξ) .
u
t
= a
2
u
xx
+ f(x, t)