Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Modelling a Particle Detector in Field Theory   Particle detector models allow to give an operational definition to the
particle content of a given quantum state of a field theory. The commonly
adopted Unruh-DeWitt type of detector is known to undergo temporary transitions
to excited states even when at rest and in the Minkowski vacuum. We argue that
real detectors do not feature this property, as the configuration "detector in
its ground state + vacuum of the field" is generally a stable bound state of
the underlying fundamental theory (e.g. the ground state-hydrogen atom in a
suitable QED with electrons and protons) in the non-accelerated case. As a
concrete example, we study a local relativistic field theory where a stable
particle can capture a light quantum and form a quasi-stable state. As
expected, to such a stable particle correspond energy eigenstates of the full
theory, as is shown explicitly by using a dressed particle formalism at first
order in perturbation theory. We derive an effective model of detector (at
rest) where the stable particle and the quasi-stable configurations correspond
to the two internal levels, "ground" and "excited", of the detector.

19
The categories of this paper are: eess
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
37
The categories of this paper are: supr-con