Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Canonical Complex Structure and the Bosonic Signature Operator for
  Scalar Fields in Globally Hyperbolic Spacetimes   The bosonic signature operator is defined for Klein-Gordon fields and
massless scalar fields on globally hyperbolic Lorentzian manifolds of infinite
lifetime. The construction is based on an analysis of families of solutions of
the Klein-Gordon equation with a varying mass parameter. It makes use of the
so-called bosonic mass oscillation property which states that integrating over
the mass parameter generates decay of the field at infinity. We derive a
canonical decomposition of the solution space of the Klein-Gordon equation into
two subspaces, independent of observers or the choice of coordinates. This
decomposition endows the solution space with a canonical complex structure. It
also gives rise to a distinguished quasi-free state. Taking a suitable limit
where the mass tends to zero, we obtain corresponding results for massless
fields. Our constructions and results are illustrated in the examples of
Minkowski space and ultrastatic spacetimes.

1
The categories of this paper are: cs
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex