Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Coulomb interaction and semimetal-insulator transition in graphene   The strong Coulomb interaction between massless Dirac fermions can drive a
semimetal-insulator transition in single-layer graphene by dynamically
generating an excitonic fermion gap. There is a critical interaction strength
$\lambda_c$ that separates the semimetal phase from the insulator phase. We
calculate the specific heat and susceptibility of the system and show that they
exhibit distinct behaviors in the semimetal and insulator phases.

7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex