Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fixed-charge transportation problems on trees   We consider a class of fixed-charge transportation problems over graphs. We
show that this problem is strongly NP-hard, but solvable in pseudo-polynomial
time over trees using dynamic programming. We also show that the LP formulation
associated to the dynamic program can be obtained from extended formulations of
single-node flow polytopes. Given these results, we present a unary
expansion-based formulation for general graphs that is computationally
advantageous when compared to a standard formulation, even if its LP relaxation
is not stronger.

19
The categories of this paper are: eess
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con