Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Impossible Measurements on Quantum Fields   It is shown that the attempt to extend the notion of ideal measurement to
quantum field theory leads to a conflict with locality, because (for most
observables) the state vector reduction associated with an ideal measurement
acts to transmit information faster than light. Two examples of such
information-transfer are given, first in the quantum mechanics of a pair of
coupled subsystems, and then for the free scalar field in flat spacetime. It is
argued that this problem leaves the Hilbert space formulation of quantum field
theory with no definite measurement theory, removing whatever advantages it may
have seemed to possess vis a vis the sum-over-histories approach, and
reinforcing the view that a sum-over-histories framework is the most promising
one for quantum gravity.

3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex