Mathematical Analysis

116 Pages·1971·4.537 MB·English

by  V. P. Palamodov (auth.), R. V. Gamkrelidze (eds.)

10
Vol.
Editor
R.V. Gamkrelidze
Progress in
Mathematics
PROGRESS IN
MATHEMATICS
Valurne 10
Mathematical Analysis
PROGRESS IN MATHEMATICS
Translations of Itogi Nauki-Seriya Matematika
1968: Volume 1-Mathematical Analysis
Volume 2 - Mathematical Analysis
1969: Volume 3-Probability Theory, Mathematical
Statistics, and Theoretical
Cybernetics
Volume 4 - Mathematical Analysis
Volume 5 - Algebra
1970: Volume 6-Topology and Geometry
Volume 7-Probability Theory, Mathematical
Statistics, and Theoretical
Cybernetics
Volume 8-Mathematical Analysis
1971: Volume 9 - Algebra and Geometry
Volume 10-Mathematical Analysis
Volume 11-Probability Theory, Mathematical
Statistics, and Theoretical
Cybernetics
In preparation:
Volume 12-Algebra and Geometry
Volume 13-Probability Theory, Mathematical
Statistics, and Theoretical
Cybernetics
Volume 14 - Algebra, Geometry, and Topology
PROGRESS IN
MATHEMATICS
Volume 10
Mathematical Analysis
Edited by
R. V. Gamkrelidze
V. A. Steklov Mathematics Institute
Academy of Seiences of the USSR, Moscow
Translated from Russian by J. S. W ood
<.:f?
SPRINGER SCIENCE+BUSINESS MEDIA LLC 1971
The original Russian text was published for the All-Union Institute of
Scientific and Technical Information in Moscow in 1969 as a volume of
Itogi Nauki- Seriya Maternatika
EDITORIAL BOARD
R. V. Gamkrelidze, Editor-in-Chief
N. M. Ostianu, Secretary
P. S. Aleksandrov V. N. Latyshev
N. G. Chudakov Yu. V. Linnik
M. K. Kerimov M. A. Naimark
A. N. Kolmogorov S. M. Nikol'skii
L. D. Kudryavtsev N. Kh. Rozov
G. F. Laptev V. K. Saul'ev
Library of Congress Catalog Card Nurober 67-27902
ISBN 978-1-4757-1591-0 ISBN 978-1-4757-1589-7( eBook)
DOI 10.1007/978-1-4757-1589-7
The present translation is published under an agreement with
Mezhdunarodnaya Kniga, the Soviet book export agency
© 1971 Springer Science+Business Media New York
Originally published by Plenum Press, New York in 1971
All rights reserved
No part of this publication may be reproduced in any form
without written permission from the publisher
Preface
The present book contains three articles: "Systems of Linear
Differential Equations," by V. P. Palamodov; "Fredholm Operators
and Their Generalizations," by S. N. Krachkovskii and A. S. Di
kanskii; and "Representations of Groups and Algebras in Spaces
with an Indefinite Metric" by M. A. Naimark and R. S. Ismagilov.
In the fi.rst article the accent is on those characteristics of
systems of differential equations which distinguish the systems
from the scalar case. Considerable space is devoted in particular
to "nonquadratic systems," a topic that has very recently stimulated
interest.
The second article is devoted to the algebraic aspects of the
theory of operators (determinant theory in particular) in Banach
and linear topological spaces.
The third article reflects the present state of the art in the
given area of the theory of representations, which has been re
ceiving considerable attention in connection with its applications
in physics (particularly in quantum field theory) and in the theory
of differential equations.
V
Contents
SYSTEMS OF LINEAR DIFFERENTIAL EQUA TIONS
V. P. Palamodov . . . . . . . . . . . . . 1
1. Quadratic Systems of Equations . . . . . . . . . . . . 1
2. Systems with Constant Coefficients . . . . . . . . . 5
3. Sperrcer Constructions and the Local Solvability
of Systems with Variable Coefficients . . . . . . . 14
4. The Global Solvability Problem and the Generalized
Neumann Problem . . . . . . . . . . . . . 21
Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
FREDHOLM OPERATORSAND THEIR GENERALIZATIONS
S. N. Krachkovskii and A. S. Dikanskii . . . . . . . . . . . . . . . 37
1 . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2. The <I>-Operators and Their Generalizations in Banach
Spaces .................................. 42
3. The <I>-Operators and Their Generalizations
in Topological Vector Spaces. . . . . . . . . . . . . 53
4. Abstract Development of the Determinant Theory
of Fredholm . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Literature Cited . . . . . . . . . . 62
Supplement to Literature Cited ............. . 72
REPRESENTATIONS OF GROUPS AND ALGEBRAS
IN SPACES WITH INDEFINITE METRIC
M. A. Naimark and R. S. Ismagilov. . . . 73
Introduction . . . . . . . . . . . . . . . . . . . 73
1. Theorems on Invariant Subspaces . . . . . . . . 75
2. Description of Commutative Symmetrie Algebras of
Operators in Spaces of Type IIk . . . . . . . . . . . . . . 77
vii
CONTENTS
viii
3. Group Representations Which Are Unitary in
Indefinite Metric ................. . 90
4. Dissipative Operators and the Extension of Dual
Subspaces .......... . 102
5. Some Unsolved Problems .. 105
Literature Cited ......... . 107
Systems of Linear Differential Equations
V. P. Palamodov
The present article is concerned with research in the last
five toten years on systems of linear partial differential equations.
The total number of published works in this area, of course, is too
great to cover each one in sufficient detail. While consciously
refraining from undertaking such a task, I have endeavered to focus
a proportierrate amount of attention on each facet of the topic in
sofar as it embodies the characteristics which distinguish the
theory of systems from the analogaus theory of one equation in one
unknown function. For example, considerable space is accorded
the 6-Neumann problem, which is endowed with a specialized char
acter and whose solution has contributed a great deal that is con
ceptually new to the general theory. On the other band, the highly
developed theory of boundary-value problems is scarcely touched
at all, as its methods pertain by and large to scalar theory.
§ 1. Quadratic Systems of Equations
We interpret the following as a quadratic system:
N
~ Pii (x, D) ui (x) = f; (x), i = 1 , ... , N, (1.1)
I
in which the number of equations N is equal to the number of un
known functions and the determinant of the characteristic matrix
p(x,. H = {pii (x, O} is not identically equal to zero. Of all the sys
tems of differential equations, the class of quadratic systems is
most nearly akin to scalar systems (N = 1) in its properties and
has been the most fully investigated. The study of quadratic sys
tems, for example the local properties of solutions and the solv-
1
2 V. P. PALAMODOV
ability of boundary-value problems, is approached, as in the scalar
case, on the basis of the delineation of elliptic, hyperbolic, and
other types. The type-discriminatioh process, in turn, is based on
the Separation of the principal part of the operator p = {pii}, but
this, as opposed to the scalar case, is a substantive problem.
The most general method for separating the principal part
of the operator p corresponding to a quadratic system has been
proposed by Douglis and Nirenberg [73]. Their method entails the
following: Let integers s1, ••• , sNand 11 •.•• , tN ~e chosensuch
that degpii ~ si + ti for any i and j. We denote by Pij_the sum of
terms of order si + ti in the operator Pii; the IE-atrix p = Wij} is
called the principal part of p. It is clear that p depends on the
choice of numbers si and tj, and the latter do not contain useful
information on the operator p for every choice. Douglis and Nire
berg have proved that if for a certain choice of si and ti the deter
minant of p (x, ~) is the elliptic operator symbol, then system (1.1)
is subject to the classical theorems on the regularity of elliptic
equations. Specifically, there is adequate correspondence between
the smoothness of the right-hand sides of fi with regard for their
weights si and the smootheness of the solutions ui with regard for
their weights ti. In [73] a suitable a priori estimate is also es
tablished. For the same class of systems Morrey and Nirenberg
[122] have proved the analyticity of the solutions on the assumption
of analyticity of the right-hand sides and coefficients of the opera
tors Pw
Volevich [8], in an analysis of the Douglis-Nirenberg concept
of the principal part of a system, has shown that the numbers si
and ti can always be chosen so that the determinant of the matrix
p
(x, ~ ) proves to be equal to the sum of the highest-erder terms
that occur under _the standard technique for computing the deter
minant of the matrix p (x, ~ ) . Consequently, under Volevich' s rule
p
for the selection of the weights the matrix (x, ~ ) is degenerate if
and only if the highest terms in the expression for detp (x, ~) can
cel one another. Related tothistype of degeneracy is the example
given by Volevich in [9] of a system with N = 2 and two independent
variables. In this example detp (x, 0 is the elliptic operator sym
bol, but the homogeneaus system pu = 0 has solutions of finite
smoothness.
In [11] Volevich delineates a class of hypoelliptic systems,
which includes systems of pseudodifferential equations as weil and