1
ISSN 1064–5624, Doklady Mathematics, 2009, Vol. 79, No. 3, pp. 1–5. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © L.N. Lyakhov, E.L. Shishkina, 2009, published in Doklady Akademii Nauk, 2009, Vol. 426, No. 4, pp. 443–447.
An application of hypersingular integrals to study
classical spaces of Riesz potentials was suggested by
Samko [1] (see also [2]). Axially symmetric potentials
were studied by Weinstein (see book [3] and the refer-
ences therein). At present, the potentials introduced by
Weinstein are known as (Riesz) B-potentials, or (Riesz)
weight potentials. A distinguishing feature of these
potentials is that they involve generalized shift, which
arises in axially symmetric theory. In [4], the inversion
of B-potentials with constant characteristic was stud-
ied. This paper presents results on the inversion of more
general B-potentials (general B-potentials). The gener-
alization consists in that, first, B-potentials with non-
constant (homogeneous) characteristic and, secondly,
the so-called mixed B-potentials (in which generalized
shifts act on a part of variables, while on the remaining
variables ordinary shifts act) are allowed. The theory
uses general B-hypersingular integrals introduced in [5]
and [6] and results of [7] on inversion of similar opera-
tors with density from the test function space S
ev
or Φ
γ
.
Let denote the part of Euclidean space
N
con-
sisting of points x = ( x ', x ''), where x ' = ( x
1
, x
2
, …, x
n
)
and x '' = ( x
n + 1
, x
n + 2
, …, x
N
) , for which x
1
> 0, x
2
> 0,
…, x
n
> 0. By (
N
) we denote the set of infinitely
differentiable functions even with respect to each of the
variables x
1
, x
2
, …, x
n
, where 0 ≤ n ≤ N . The test func-
tion space S
ev
consists of all functions from ( )
belonging to the space of Schwarz test functions. By
we denote the class of distributions generated by
the weight linear form ( f , g )
γ
= ( x ) g ( x )( x ')
γ
dx ,
N
+
C
ev
∞
C
ev
∞
N
+
S
ev
'
f
N
+
∫
where x')
γ
= and γ = (γ
1
, γ
2
, …, γ
n
) is a multi-
index consisting of fixed positive numbers.
The generalized shift acting on a variable x
i
with i =
1, 2, …, n is defined by
where x
1, i
= (x
1
, x
2
, …, x
i – 1
) and x
i, n
= (x
i + 1
, x
i + 2
, …, x
n
).
The mixed generalized shift is defined by
(1)
Shift (1) generates a generalized convolution of
functions [3] of the form
In this paper, we use a special integral transform
which acts as the Hankel transform
1
on each of the first
variables x
i
with i = 1, 2, …, n and as the Fourier trans-
form on the remaining variables x '' . Such a mixed Fou-
rier–Bessel transform (see [1]) has the form
1
This transform is also known as the Bessel transform or the one-
dimensional Fourier–Bessel transform. The latter term is used in [1];
however, it is shown in [1] that this transform is an identical mod-
ification of the Hankel transform.
x
i
γ
i
i 1 =
n
∏
T
x
i
y
i
fx ()
Γ
γ
i
1 +
2
------------
Γ
γ
i
2
---
π
---------------------- fx
1 i ,
, (
0
π
∫
=
x
i
2
2 x
i
y
i
β
i
y
i
2
+ cos – x
in ,
x'' ) β
i
β
i
, d sin
γ
i
1 –
, ,
T
y
f ( ) x () T
x'
y'
fx' x'' y'' – , ( ) =
= T
x
1
y
1
…T
x
n
y
n
fx' x'' y'' – , ( ) .
f
*
g ( )
γ
fy () T
y
g ( ) x () y' ( )
γ
y . d
N
+
∫
=
F
B
f [ ]ξ () f
ˆ
ξ () j
γ
x' ξ' , ( ) e
i x'' ξ'' , 〈 〉 –
fx () x' ( )
γ
x . d
N
+
∫
= =
MATHEMATICS
Inversion of General Riesz B-Potentials with Homogeneous
Characteristic in Weight Classes of Functions
L. N. Lyakhov
a
and E. L. Shishkina
b
Presented by Academician E.I. Moiseev November 20, 2008
Received January 26, 2009
DOI: 10.1134/S106456240903@@@@
a
Voronezh State Technological Academy, pr. Revolyutsii 19,
Voronezh, 394017 Russia; e-mail: ilina_dico@mail.ru
b
Voronezh State University, Universitetskaya pl. 1,
Voronezh, 394006 Russia; e-mail: lyakhov@box.vsi.ru