Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An introduction to effective low-energy Hamiltonians in condensed matter
  physics and chemistry   These lecture notes introduce some simple effective Hamiltonians (also known
as semi-empirical models) that have widespread applications to solid state and
molecular systems. They are aimed as an introduction to a beginning graduate
student. I also hope that it may help to break down the divide between the
physics and chemistry literatures. After a brief introduction to second
quantisation notation, which is used extensively, I focus of the "four H's":
the Huckel (or tight binding), Hubbard, Heisenberg and Holstein models. Some
other related models, such as the Pariser-Parr-Pople model, the extended
Hubbard model, multi-orbital models and the ionic Hubbard model, are also
discussed. Finally, I discuss the epistemological basis of effective
Hamiltonians and compare and contrast this with that of ab initio methods as
well as discussing the problem of parametrising effective Hamiltonians.

13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int