Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum phase transitions and collapse of the Mott gap in the
  $d=1+\epsilon$ dimensional half-filled Hubbard model   We study the low-energy asymptotics of the half-filled Hubbard model with a
circular Fermi surface in $d=1+\epsilon$ continuous dimensions, based on the
one-loop renormalization-group (RG) method. Peculiarity of the $d=1+\epsilon$
dimensions is incorporated through the mathematica structure of the elementary
particle-partcile (PP) and particle-hole (PH) loops: infrared logarithmic
singularity of the PH loop is smeared for $\epsilon>0$. The RG flows indicate
that a quantum phase transition (QPT) from a metallic phase to the Mott
insulator phase occurs at a finite on-site Coulomb repulsion $U$ for
$\epsilon>0$. We also discuss effects of randomness.

28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin