Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ground state energy of a non-integer number of particles with delta
  attractive interactions   We show how to define and calculate the ground state energy of a system of
quantum particles with delta attractive interactions when the number of
particles n$is non-integer. The question is relevant to obtain the probability
distribution of the free energy of a directed polymer in a random medium. When
one expands the ground state energy in powers of the interaction, all the
coefficients of the perturbation series are polynomials in n, allowing to
define the perturbation theory for non-integer n. We develop a procedure to
calculate all the cumulants of the free energy of the directed polymer and we
give explicit, although complicated, expressions of the first three cumulants.

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The categories of this paper are: math-ph
1
The categories of this paper are: cs
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
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The categories of this paper are: quant-ph