Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Causality and Superluminal Fields   The expression of causality depends on an underlying choice of chronology.
Since a chronology is provided by any Lorentzian metric in relativistic
theories, there are as many expressions of causality as there are
non-conformally related metrics over spacetime. Although tempting, a definitive
choice of a preferred metric to which one may refer to is not satisfying. It
would indeed be in great conflict with the spirit of general covariance.
Moreover, a theory which appear to be non causal with respect to (hereafter,
w.r.t) this metric, may well be causal w.r.t another metric. In a theory
involving fields that propagate at different speeds (e.g. due to some
spontaneous breaking of Lorentz invariance), spacetime is endowed with such a
finite set of non-conformally related metrics. In that case one must look for a
new notion of causality, such that 1. no particular metric is favored and 2.
there is an unique answer to the question : ``is the theory causal?''. This new
causality is unique and defined w.r.t the metric drawing the wider cone in the
tangent space of a given point of the manifold. Moreover, which metric defines
the wider cone may depend on the location on spacetime. In that sense,
superluminal fields are generically causal, provided that some other basic
requirements are met.

11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
2
The categories of this paper are: math
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom