Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Many-Body Density Matrices for Free Fermions   Building upon an analytical technique introduced by Chung and Peschel [M.
Chung and I. Peschel, Phys. Rev. B 64, art. 064412 (2001)], we calculated the
density matrix rho_B of a finite block of B sites within an infinite system of
free spinless fermions. In terms of the block Green function matrix G (whose
elements are G_ij = < c_i^+ c_j>, where c_i^+ and c_j are fermion creation and
annihilation operators acting on sites i and j within the block respectively),
the density matrix can be written as rho_B = det(1 - G) exp[ sum_ij (log G(1 -
G^{-1})_ij c_i^+ c_j]. Implications of such a result to Hilbert space
truncation for real-space renormalization schemes is discussed.

24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc