Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Exact dynamics in the inhomogeneous central-spin model   We study the dynamics of a single spin-1/2 coupled to a bath of spins-1/2 by
inhomogeneous Heisenberg couplings including a central magnetic field. This
central-spin model describes decoherence in quantum bit systems. An exact
formula for the dynamics of the central spin is presented, based on the Bethe
ansatz. This formula is evaluated explicitly for initial conditions such that
the bath spins are completely polarized at the beginning. For this case we
find, after an initial decay, a persistent oscillatory behaviour of the central
spin. For a large number of bath spins $N_b$, the oscillation frequency is
proportional to $N_b$, whereas the amplitude behaves like $1/N_b$, to leading
order. No asymptotic decay due to the non-uniform couplings is observed, in
contrast to some recent studies.

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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
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The categories of this paper are: eess
1
The categories of this paper are: cs
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The categories of this paper are: solv-int
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The categories of this paper are: chem-ph
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The categories of this paper are: physics
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The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: nlin
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The categories of this paper are: plasm-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: q-bio
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The categories of this paper are: adap-org