33,543 research outputs found
Loop Equations as a Generalized Virasoro Constraints
The loop equations in the lattice gauge theory are represented in the
form of constraints imposed on a generating functional for the Wilson loop
correlators. These constraints form a closed algebra with respect to
commutation. This algebra generalizes the Virasoro one, which is known to
appear in one-matrix models in the same way. The realization of this algebra in
terms of the infinitesimal changes of generators of the loop space is given.
The representations on the tensor fields on the loop space, generalizing the
integer spin conformal fields, are constructed. The structure constants of the
algebra under consideration being independent of the coupling constants, almost
all the results are valid in the continuum.Comment: 7 pages, LaTex (3 LaTex figures), SMI-94-
Approximate formula for the macroscopic polarization including quantum fluctuations
The many-body Berry phase formula for the macroscopic polarization is
approximated by a sum of natural orbital geometric phases with fractional
occupation numbers accounting for the dominant correlation effects. This
reduced formula accurately reproduces the exact polarization in the
Rice-Mele-Hubbard model across the band insulator-Mott insulator transition. A
similar formula based on a one-body reduced Berry curvature accurately predicts
the interaction-induced quenching of Thouless topological charge pumping
Model Hamiltonian for strongly-correlated systems: Systematic, self-consistent, and unique construction
An interacting lattice model describing the subspace spanned by a set of
strongly-correlated bands is rigorously coupled to density functional theory to
enable ab initio calculations of geometric and topological material properties.
The strongly-correlated subspace is identified from the occupation number band
structure as opposed to a mean-field energy band structure. The self-consistent
solution of the many-body model Hamiltonian and a generalized Kohn-Sham
equation exactly incorporates momentum-dependent and crystal-symmetric
correlations into electronic structure calculations in a way that does not rely
on a separation of energy scales. Calculations for a multiorbital Hubbard model
demonstrate that the theory accurately reproduces the many-body polarization.Comment: 19 pages, 11 figure
Optimal Control of charge transfer
In this work, we investigate how and to which extent a quantum system can be
driven along a prescribed path in space by a suitably tailored laser pulse. The
laser field is calculated with the help of quantum optimal control theory
employing a time-dependent formulation for the control target. Within a
two-dimensional (2D) model system we have successfully optimized laser fields
for two distinct charge transfer processes. The resulting laser fields can be
understood as a complicated interplay of different excitation and de-excitation
processes in the quantum system
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