A calculus approach to hyperfunctions. II
A calculus approach to hyperfunctions. II
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超函数的微积分方法。
DOI:
10.1090/s0002-9947-1989-0997676-7
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发表时间:
1989
影响因子:
1.3
通讯作者:
T. Matsuzawa
中科院分区:
文献类型:
--
作者:
T. Matsuzawa
We consider any hyperfunctions with the compact support as initial values of the solutions of the heat equation. The main aim of this paper is to unify the theory of distributions and hyperfunctions as well as simplify proofs of some important results via heat kernel. INTRODUCTION In the previous paper [9], we have discussed the theory of the hyperfunctions by a calculus approach motivated by the analysis developed in [3, Chapter 9]. We have shown in [9] the idea of our approach. Namely, we have proposed to take hyperfunctions with the compact support as initial values of the solutions of the heat equation. The main aim of this paper is to reformulate the foundation of hyperfunction theory by a limiting process via heat kernel in the theory of Schwartz distributions. For this purpose, two fundamental tools will be used. One is the estimate for the heat kernel in (1.14) which is obtained as a special case of the result given in [1, Chapter 4]. The other is a series of structure theorems on ultradistributions given in [5, 6 and 7]. As was mentioned in [9], the advantage of our method is that it can unify the theory of distributions and hyperfunctions as well as simplify proofs of some important results. In ?1, we briefly recall the definitions of distributions and hyperfunctions with the compact support. Especially, the space of hyperfunctions (analytic functionals) A'[K] with the compact support in K c Rn (n > 1) is considered as the dual of the space A[K] of functions which are real analytic near K. We will prepare a useful estimate for the heat kernel in Proposition 1.1. In ?2, we will prove that we can take u E A'[K] as an initial value of a unique solution U of the heat equation (a/ot-A)U(x,t)=O inRn+l =R n x R+ U(-,O) = u. We shall see in Theorem 2.1 that Schwartz distributions and ultradistributions are also characterized by the asymptotic behavior of U(., t) as t -+ 0 at the Received by the editors June 8, 1987 and, in revised form, December 8, 1987. 1980 Mathematics Subject Classification (1985 Revision). Primary 46F15; Secondary 46F05, 46F10, 46F12, 35K05. ? 1989 American Mathematical Society 0002-9947/89 $1.00 + $.25 per page