Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The phantom menaced: constraints on low-energy effective ghosts   It has been suggested that a scalar field with negative kinetic energy, or
``ghost,'' could be the source of the observed late-time cosmological
acceleration. Naively, such theories should be ruled out by the catastrophic
quantum instability of the vacuum. We derive phenomenological bounds on the
Lorentz-violating ultraviolet cutoff Lambda which must apply to low-energy
effective theories of ghosts, in order to keep the instability at unobservable
levels. Assuming only that ghosts interact at least gravitationally, we show
that Lambda < 3 MeV for consistency with the cosmic gamma ray background. We
also show that theories of ghosts with a Lorentz-conserving cutoff are
completely excluded.

23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
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The categories of this paper are: eess
34
The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga
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The categories of this paper are: math-ph
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn