Functionals (i.e., functions of functions) are widely used in quantum field theory and solid-state physics. In this paper, functionals are given a rigorous mathematical framework and their main properties are described. The choice of the proper space of test functions (smooth functions) and of the relevant concept of differential (Bastiani differential) are discussed. The relation between the multiple derivatives of a functional and the corresponding distributions is described in detail. It is proved that, in a neighborhood of every test function, the support of a smooth functional is uniformly compactly supported and the order of the corresponding distribution is uniformly bounded. Relying on a recent work by Dabrowski, several spaces of functionals are furnished with a complete and nuclear topology. In view of physical applications, it is shown that most formal manipulations can be given a rigorous meaning. A new concept of local functionals is proposed and two characterizations of them are given: the first one uses the additivity (or Hammerstein) property, the second one is a variant of Peetre’s theorem. Finally, the first step of a cohomological approach to quantum field theory is carried out by proving a global Poincaré lemma and defining multi-vector fields and graded functionals within our framework.

1.
J.
Schwinger
,
Proc. Natl. Acad. Sci. U. S. A.
37
,
452
(
1951
).
2.
J.
Schwinger
,
Proc. Natl. Acad. Sci. U. S. A.
37
,
455
(
1951
).
3.
W.
Kohn
and
L. J.
Sham
,
Phys. Rev.
140
,
A1133
(
1965
).
4.
E.
Engel
and
R. M.
Dreizler
,
Density Functional Theory: An Advanced Course
(
Springer
,
Heidelberg
,
2011
).
5.
K.
Rejzner
,
Perturbative Algebraic Quantum Field Theory: An Introduction for Mathematicians
(
Springer
,
Cham
,
2016
).
6.
M.
Dütsch
and
K.
Fredenhagen
, in
Rigorous Quantum Field Theory: A Festschrift for Jacques Bros
, Volume 251 of Progress in Mathematics, edited by
A. B.
de Monvel
,
D.
Buchholz
,
D.
Iagolnitzer
, and
U.
Moschella
(
Birkhäuser
,
Basel
,
2006
), pp.
113
124
.
7.
R.
Brunetti
,
K.
Fredenhagen
, and
K.
Rejzner
,
Commun. Math. Phys.
345
,
741
(
2016
).
8.
D.
Bahns
and
K.
Rejzner
, “
The quantum sine-Gordon model of perturbative AQFT
,”
Commun. Math. Phys.
(published online).
9.
L.
Lempert
and
N.
Zhang
,
Acta Math.
193
,
241
(
2004
).
10.
L.
Dickey
,
Soliton Equations and Hamiltonian Systems
(
World Scientific
,
2003
), Vol. 26.
11.
J.
Lee
and
R. M.
Wald
,
J. Math. Phys.
31
,
725
(
1990
).
12.
R. M.
Wald
,
General Relativity
(
The University of Chicago Press
,
Chicago
,
1984
).
13.
J. D.
Stasheff
,
Contemp. Math.
219
,
195
(
1998
).
14.
G.
Barnich
,
F.
Brandt
, and
M.
Henneaux
,
Phys. Rep.
338
,
439
(
2000
).
15.
I.
Khavkine
,
Classical Quantum Gravity
32
,
185019
(
2015
).
16.
K.
Fredenhagen
and
K.
Rejzner
,
Commun. Math. Phys.
314
,
93
(
2012
).
17.
R.
Brunetti
,
M.
Dütsch
, and
K.
Fredenhagen
,
Adv. Theor. Math. Phys.
13
,
1541
(
2009
).
18.
R.
Brunetti
and
K.
Fredenhagen
, in
Quantum Field Theory on Curved Spacetimes: Concepts and Mathematical Foundations
, Volume 786 of Lecture Notes in Physics, edited by
C.
Bär
and
K.
Fredenhagen
(
Springer
,
Berlin
,
2009
), pp.
129
155
.
19.

In this article, all manifolds shall be assumed to be paracompact.

20.
R.
Brunetti
,
K.
Fredenhagen
, and
P. L.
Ribeiro
, e-print arXiv:1209.2148 (
2012
).
21.
Y.
Dabrowski
, e-print arXiv:1411.3012 (
2014
).
22.
Y.
Dabrowski
, e-print arXiv:1412.1749 (
2014
).
23.
H.
Epstein
and
V.
Glaser
,
Ann. Inst. Henri Poincaré, Ser. A
19
,
211
(
1973
), available at http://www.numdam.org/item?id=AIHPA_1973__19_3_211_0.
24.
A. S.
Wightman
,
Fortschr. Phys.
44
,
143
(
1996
).
25.
M.
Martellini
,
Il Nuovo Cimento A
67
,
305
(
1982
).
26.
M.
Dütsch
and
K.
Fredenhagen
,
Commun. Math. Phys.
219
,
5
(
2001
).
27.
L.
Schwartz
,
Théorie des Distributions
, 2nd ed. (
Hermann
,
Paris
,
1966
).
28.
A.
Kriegl
and
P. W.
Michor
,
The Convenient Setting of Global Analysis
(
American Mathematical Society
,
Providence
,
1997
).
29.
E. C. G.
Stueckelberg
,
Phys. Rev.
81
,
130
(
1951
).
30.
J.
Horváth
,
Topological Vector Spaces and Distributions
(
Addison-Wesley
,
Reading
,
1966
).
31.
F.
Trèves
,
Topological Vector Spaces, Distributions and Kernels
(
Dover
,
New York
,
2007
).
32.
L.
Hörmander
,
The Analysis of Linear Partial Differential Operators I: Distribution Theory and Fourier Analysis
, 2nd ed. (
Springer Verlag
,
Berlin
,
1990
).
33.

Since an open set is absorbing (Ref. 30, p. 80), for every xU and every vE there is an ϵ > 0 such that x + tvU if |t| < ϵ. Thus, f(x + tv) is well defined for every t such that |t| < ϵ.

34.
A.
Shapiro
,
J. Optim. Theory Appl.
66
,
477
(
1990
).
35.
G. A.
Ladas
and
V.
Laskhmikantham
,
Differential Equations in Abstract Spaces
(
Academic Press
,
New York
,
1972
).
36.
A. J.
Kurdila
and
M.
Zabarankin
,
Convex Functional Analysis
(
Birkhäuser
,
Basel
,
2005
).
37.
H.
Sagan
,
Introduction to the Calculus of Variations
(
Dover
,
New York
,
1992
).
38.
S.
Yamamuro
,
Differential Calculus in Topological Linear Spaces
, Volume 374 of Lecture Notes in Mathematics (
Springer
,
Berlin
,
1974
).
39.
A.
Bastiani
,
J. Anal. Math.
13
,
1
(
1964
).
40.
R. S.
Hamilton
,
Bull. Am. Math. Soc.
7
,
65
(
1982
).
41.
A.
Bastiani
, “
Differentiabilité dans les espaces localement convexes. Distructures
,” Ph.D. thesis,
Université de Paris
,
1962
.
42.
K.-H.
Neeb
, in
Infinite Dimensional Kähler Manifolds
, edited by
A.
Huckleberry
and
T.
Wurzbacher
(
Birkhäuser
,
Basel
,
2001
), pp.
131
178
.
43.
44.
H. H.
Keller
,
Differential Calculus in Locally Convex Spaces
, Volume 417 of Lecture Notes in Mathematics (
Springer
,
Berlin
,
1974
).
45.
V. I.
Averbukh
and
O. G.
Smolyanov
,
Russ. Math. Surv.
23
,
67
(
1968
).
46.
W.
Gähler
,
Grundstrukturen der Analysis
(
Birkhäuser
,
Basel
,
1978
), Vol. 2.
47.
P.
Ver Eecke
,
Fondements du Calcul Différentiel
(
Presses Universitaires de France
,
Paris
,
1983
).
48.
M. Z.
Nashed
, in
Nonlinear Functional Analysis and Applications
, edited by
L. B.
Rall
(
Academic Press
,
New York
,
1971
), pp.
103
359
.
49.
M. C.
Abbati
and
A.
Manià
,
J. Geom. Phys.
29
,
35
(
1999
).
50.
P. W.
Michor
,
Manifolds of Differentiable Mappings
(
Shiva Publishing Ltd
,
Orpington
,
1980
).
51.
J.
Milnor
, in
Relativity, Groups, and Topology II
, Volume 40 of Les Houches, edited by
B. S.
DeWitt
and
R.
Stora
(
North Holland
,
Amsterdam
,
1983
), pp.
1007
1057
.
52.
B.
Khesin
and
R.
Wendt
,
The Geometry of Infinite-Dimensional Groups
(
Springer
,
Berlin
,
2009
).
53.
W.
Bertram
,
Differential Geometry, Lie Groups and Symmetric Spaces Over General Base Fields and Rings
, Memoirs of the American Mathematical Society (
American Mathematical Society
,
Providence
,
2008
), Vol. 192.
54.
J.
Szilasi
and
R. L.
Lovas
, in
Handbook of Global Analysis
, edited by
D.
Krupka
and
D.
Saunders
(
Oxford University Press
,
Oxford
,
2008
), pp.
1069
1114
.
55.
56.
A. D.
Michal
,
Proc. Natl. Acad. Sci. U. S. A.
24
,
340
(
1938
).
57.
H.
Massam
and
S.
Zlobec
,
Math. Program.
7
,
144
(
1974
).
58.
A.
Ehresmann
,
Category Theory Yesterday, Today (and Tomorrow?): A Colloquium in Honour of Jean Benabou
(
ENS
,
Paris
,
2011
).
59.
J. L.
Kelley
,
General Topology
, Volume 27 of Graduate Texts in Mathematics, Revised 3rd ed. (
Springer-Verlag
,
New York
,
1955
).
60.
N.
Bourbaki
,
Elements of Mathematics: General Topology. Part 2
(
Addison-Wesley
,
Reading
,
1966
).
61.
N.
Bourbaki
,
Elements of Mathematics: Topological Vector Spaces
(
Springer
,
Berlin
,
2003
).
62.
M.
Reed
and
B.
Simon
,
Methods of Modern Mathematical Physics: I. Functional Analysis
, 2nd ed. (
Academic Press
,
New York
,
1980
).
63.
K.-H.
Neeb
,
Ann. Inst. Fourier
61
,
1839
(
2011
).
64.
N.
Bourbaki
,
Eléments de Mathématique: Intégration
, 2nd ed. (
Hermann
,
Paris
,
1965
), Chaps. 1 and 4.
65.
N.
Bourbaki
, “
Intégration vectorielle
,” in
Eléments de Mathématique: Intégration
(
Hermann
,
Paris
,
1959
), Chap. 6.
66.
H.
Glöckner
,
Orlicz Centenary Volume
, Volume 55 of Banach Center Publications (
Polish Academy of Sciences
,
Warsaw
,
2002
), pp.
43
59
.
67.
K.-H.
Neeb
,
Monastir Summer School: Infinite-Dimensional Lie Groups
, Preprint 2433 (
TU Darmstadt
,
Darmstadt
,
2006
).
68.
H.
Glöckner
,
Infinite-Dimensional Lie Groups
, Lecture Notes (
TU Darmstadt
,
Darmstadt
,
2005
).
69.
E.
Shult
and
D.
Surowski
,
Algebra: A Teaching and Source Book
(
Springer
,
Berlin
,
2015
).
70.
N.
Bourbaki
,
Elements of Mathematics: Algebra I
(
Springer
,
Berlin
,
1989
), Chaps 1–3.
71.
R. A.
Ryan
,
Applications of Topological Tensor Products to Infinite Dimensional Topology
(
Trinity College
,
Dublin
,
1980
).
72.
G.
Köthe
,
Topological Vector Spaces II
(
Springer Verlag
,
New York
,
1979
).
73.
A.
Grothendieck
,
Produits Tensoriels Topologiques et Espaces Nucléaires
, Volume 16 of Memoirs of the American Mathematical Society (
American Mathematical Society
,
Providence
,
1955
).
74.
N. N.
Tarkhanov
,
The Analysis of Solutions of Elliptic Equations
(
Kluwer Academic Publishers
,
Dordrecht
,
1997
).
75.
M.
Grosser
,
Novi Sad J. Math.
38
,
121
(
2008
), avilable at http://www.dmi.uns.ac.rs/nsjom/Papers/38_3/NSJOM_38_3_121_128.pdf.
76.
H.
Glöckner
,
J. Funct. Anal.
194
,
347
(
2002
).
77.
C.
Wockel
,
Central Extensions of Gauge Groups
(
Diplomarbeit, Technische Universität Darmstadt
,
2003
).
78.
C.
Wockel
, “
Infinite-dimensional Lie theory for gauge groups
,” Ph.D. thesis,
Technische Universität Darmstadt
,
2006
.
79.
C.
Brouder
,
N. V.
Dang
, and
F.
Hélein
,
J. Phys. A: Math. Theor.
47
,
443001
(
2014
).
80.
J.-F.
Colombeau
and
R.
Meise
,
Functional Analysis, Holomorphy, and Approximation Theory
, Volume 843 of Lecture Notes in Mathematics (
Springer
,
Berlin
,
1981
), pp.
195
216
.
81.
K.
Fredenhagen
and
K.
Rejzner
,
Commun. Math. Phys.
317
,
697
(
2013
).
82.
K.
Fredenhagen
and
K.
Rejzner
, “
Perturbative algebraic quantum field theory
,” in
Mathematical Aspects of Quantum Field Theories
, edited by
D.
Calaque
and
T.
Strobl
(
Springer
,
2015
), pp.
17
55
.
83.
C.
Bär
and
R. T.
Wafo
,
Math. Phys. Anal. Geom.
18
,
7
(
2015
).
84.
T.
Hirai
,
H.
Shimomura
,
N.
Tatsuuma
, and
E.
Hirai
,
J. Math. Kyoto Univ.
41
,
475
(
2001
).
85.
Y.
Dabrowski
and
C.
Brouder
,
Commun. Math. Phys.
332
,
1345
(
2014
).
86.
S.
Hollands
and
R. M.
Wald
,
Commun. Math. Phys.
223
,
289
(
2001
).
87.
K.
Rejzner
, “
Batalin-Vilkovisky formalism in locally covariant field theory
,” Ph.D. thesis,
University of Hamburg
,
2011
.
88.
M. M.
Rao
, in
Measure Theory Oberwolfach 1979
, Volume 794 of Lecture Notes in Mathematics (
Springer
,
Berlin
,
1980
), pp.
484
496
.
89.
A. G.
Pinsker
,
C. R. (Dokl.) Acad. Sci. URSS
18
,
399
(
1938
).
90.
I. M.
Gel’fand
and
N. Y.
Vilenkin
,
Generalized Functions: Applications of Harmonic Analysis
(
Academic Press
,
New York
,
1964
), Vol. IV.
91.
M.
Dütsch
and
K.
Fredenhagen
,
Rev. Math. Phys.
16
,
1291
(
2004
).
92.
K. J.
Keller
,
J. Math. Phys.
50
,
103503
(
2009
).
93.
R. V.
Chacon
and
N.
Friedman
,
Arch. Ration. Mech. Anal.
18
,
230
(
1965
).
95.
S. H.
Fesmire
, in
Functional Analysis and Its Applications
, Volume 399 of Lecture Notes in Mathematics (
Springer
,
Berlin
,
1974
), pp.
129
148
.
96.
A.
de Korvin
and
C. E.
Roberts
, Jr.
,
Pac. J. Math.
92
,
329
(
1981
).
97.
98.
Z.
Ercan
,
Czech. Math. J.
49
,
187
(
1999
).
99.
H. G. R.
Millington
, e-print arXiv:0706.4281 (
2007
).
100.
J. A.
Navarro
,
Math. Proc. Cambridge Philos. Soc.
117
,
371
(
1995
).
101.
R.
Moosa
, preprint arXiv:math/0405563 (
2004
).
102.
J.
Kantor
,
Mém. Soc. Math. Fr.
53
,
5
(
1977
).
103.

Since all manifolds in this article are assumed to be paracompact, for every property T on the set of all open subsets on M, provided that (i) open subsets of subsets satisfying T satisfy T and (ii) every point of M admits a neighborhood that satisfies property T, there exists an open cover (Ui)iI made of subsets satisfying the property T that admits a partition of unity (χi)iI relative to it.

104.

That is, txkJxk(f)=f.

105.
N. V.
Dang
,
Ann. Henri Poincaré
17
,
819
(
2016
).
106.
C.
Brouder
,
N. V.
Dang
, and
F.
Hélein
,
Stud. Math.
232
,
201
(
2016
); e-print arXiv:1409.7662.
107.
J. M.
Lee
,
Introduction to Smooth Manifolds
(
Springer
,
New York
,
2003
).
108.
J.
Navarro
and
J. B.
Sancho
, e-print arXiv:1411.7499 (
2014
).
109.
J.-P.
Brasselet
and
M. J.
Pflaum
,
Ann. Math.
167
,
1
(
2008
).
110.
J.
Slovák
,
Ann. Global Anal. Geom.
6
,
273
(
1988
).
111.
K.
Rejzner
,
Rev. Math. Phys.
23
,
1009
(
2011
).
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