PHYSICS/BK21 SEMINAR [6.7]

Entanglement perturbation theory for the long-range correlations in Heisenberg antiferromagnets

* Speaker : Prof. Sung G. Chung (Western Michigan University)
* Place : Physics Seminar Room (Science Bldg, 3-201)
* Date & Time : June  7 (Mon)  4:00  ~  5:00 pm

 * Abstract:

 Progress in the understanding of strongly correlated materials
depends crucially on powerful many-body methods. The major
methods currently available are various mean field theories,
Monte Carlo and numerical renormalization group. Over the
recent years, we have been developing a novel many-body
method, entanglement perturbation theory (EPT), for calculating
partition functions, ground states and elementary excitations.
The idea of EPT is divide and conquer: no Hilbert space truncation,
no finite-size problem, no fermion sign problem, just SVD
from operators to eigenstates, leading to tensor product
representations, and reducing the problem to a key concept,
iterative solution of the generalized eigenvalue problems. Physically,
it pursues a conviction that the systematic inclusion of correlations ~
entanglements, will be the only perturbation theory which converges.
Also important conviction is, the fermion sign problem arising from
the infinite-range anticommutation algebra, is inherently incompatible
with any methods which include as a core step an update of the
wave function based on the application of local operators, not the
entire Hamiltonian, a well-known example being the real-space
renormalization group.  In this talk, I will give an overview of this
new theoretical endeavor as well as a recent result for the long-range
correlation functions, long enough to be comparable with field theories.

Contact Person : Prof. Byung Il Min (054-279-2074,  bimin@postech.ac.kr)