2  Some Properties of the Kernel Functions

The results given in this section are extracted mainly from references [8], [9], and [14]. In the following r = p - q and r = |r|, Gk = Gk(p,q), G0 = G0(p,q).

2.1  Derivatives of G0 with respect to r

In two dimensions we have

G0
r
= - 1
2 p
1
r
  ,
(12)

2 G0
r2
= 1
2 p
1
r2
  .
(13)
In three dimensions we have

G0
r
= - 1
4 p
1
r2
  ,
(14)

2 G0
r2
= 1
2 p
1
r3
  .
(15)

2.2  Derivatives of Gk (k ¹ 0) with respect to r

In two dimensions we have

Gk
r
= - i
4
k H1(1)  ,
(16)
where H1(1) is the spherical Hankel function of the first kind and of order one and

2 Gk
r2
= i
4
k2 ( H1(1)
kr
-H0(1) )   .
(17)

In three dimensions we have

Gk
r
= eikr
4 pr2
( ikr - 1 ) ,
(18)

2 Gk
r2
= eikr
4 pr3
( 2 -2ikr -k2 r2 ) .
(19)

2.3  Expressions for the normal derivatives of Gk

The following expressions hold in both two and three dimensions and for all k:

Gk
nq
= Gk
r
  r
nq
 ,
(20)

Gk
vp
= Gk
r
  r
vp
 ,
(21)

2 Gk
vp nq
= Gk
r
  2 r
vp nq
+ 2 Gk
r2
  r
vp
r
nq
 .
(22)

2.4  Expressions for the normal derivative of r

The derivatives of r with respect to vp and nq may be written as follows:

r
nq
= - r.nq
r
  ,
(23)

r
vp
= r.vp
r
  ,
(24)

2 r
vp nq
= - 1
r
( vp.nq + r
vp
r
nq
)  .
(25)

2.5  Expressions for 2 G0/ vp nq

The following results can be derived from the substitution of (25) and (12),(13) or (14),(15) into (22) with k = 0:

2 G0
vp nq
= 1
2 pr2
( vp.nq + 2 r
vp
r
nq
)  in two dimensions,
(26)

G0
vp nq
= 1
4 pr3
( vp.nq + 3 r
vp
r
nq
)  in three dimensions.
(27)

2.6  Asymptotic Properties

In the following results, p, q Î G where G is a surface and G is smooth at p:


lim
q ® p 
( Gk(p,q) -G0(p,q) ) = O(r0) ,
(28)


lim
q ® p 
Gk
vp
(p,q) = O(r0) ,
(29)


lim
q ® p 
Gk
nq
(p,q) = O(r0) ,
(30)


lim
q ® p 
( 2 Gk
vp nq
(p,q) - 2 G0
vp nq
(p,q) + 1
2
k2 Gk(p,q) ) = O(r0) .
(31)