Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Imaginary-Scaling versus Indefinite-Metric Quantization of the
  Pais-Uhlenbeck Oscillator   Using the Pais-Uhlenbeck Oscillator as a toy model, we outline a consistent
alternative to the indefinite-metric quantization scheme that does not violate
unitarity. We describe the basic mathematical structure of this method by
giving an explicit construction of the Hilbert space of state vectors and the
corresponding creation and annihilation operators. The latter satisfy the usual
bosonic commutation relation and differ from those of the indefinite-metric
theories by a sign in the definition of the creation operator. This change of
sign achieves a definitization of the indefinite-metric that gives life to the
ghost states without changing their contribution to the energy spectrum.

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The categories of this paper are: chem-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: funct-an
16
The categories of this paper are: stat
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
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The categories of this paper are: atom-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
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The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
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The categories of this paper are: supr-con