310,956 research outputs found
Comment on "Remark on the external-field method in QCD sum rules"
It is proved, that suggested by Jin modified formalism in the external-field
method in QCD sum rules exactly coincides with the formalism used before.
Therefore, unlike the claims of ref.1, this formalism cannot improve the
predictability and reliability of external-field sum rule calculations in
comparison with those, done by the standard approach.
PACS number(s): 12.38.Lg, 11.55.HxComment: 5 pages, RevTe
Background field method, Batalin-Vilkovisky formalism and parametric completeness of renormalization
We investigate the background field method with the Batalin-Vilkovisky
formalism, to generalize known results, study parametric completeness and
achieve a better understanding of several properties. In particular, we study
renormalization and gauge dependence to all orders. Switching between the
background field approach and the usual approach by means of canonical
transformations, we prove parametric completeness without making use of
cohomological theorems, namely show that if the starting classical action is
sufficiently general all divergences can be subtracted by means of parameter
redefinitions and canonical transformations. Our approach applies to
renormalizable and non-renormalizable theories that are manifestly free of
gauge anomalies and satisfy the following assumptions: the gauge algebra is
irreducible and closes off shell, the gauge transformations are linear
functions of the fields, and closure is field-independent. Yang-Mills theories
and quantum gravity in arbitrary dimensions are included, as well as effective
and higher-derivative versions of them, but several other theories, such as
supergravity, are left out.Comment: 40 pages; v2: minor changes, PRD versio
LDA+Gutzwiller Method for Correlated Electron Systems: Formalism and Its Applications
We introduce in detail our newly developed \textit{ab initio} LDA+Gutzwiller
method, in which the Gutzwiller variational approach is naturally incorporated
with the density functional theory (DFT) through the "Gutzwiller density
functional theory (GDFT)" (which is a generalization of original Kohn-Sham
formalism). This method can be used for ground state determination of electron
systems ranging from weakly correlated metal to strongly correlated insulators
with long-range ordering. We will show that its quality for ground state is as
high as that by dynamic mean field theory (DMFT), and yet it is computationally
much cheaper. In additions, the method is fully variational, the charge-density
self-consistency can be naturally achieved, and the quantities, such as total
energy, linear response, can be accurately obtained similar to LDA-type
calculations. Applications on several typical systems are presented, and the
characteristic aspects of this new method are clarified. The obtained results
using LDA+Gutzwiller are in better agreement with existing experiments,
suggesting significant improvements over LDA or LDA+U.Comment: 20 pages, 11 figure
Spin dependent electron transport through a magnetic resonant tunneling diode
Electron transport properties in nanostructures can be modeled, for example,
by using the semiclassical Wigner formalism or the quantum mechanical Green's
functions formalism. We compare the performance and the results of these
methods in the case of magnetic resonant-tunneling diodes. We have implemented
the two methods within the self-consistent spin-density-functional theory. Our
numerical implementation of the Wigner formalism is based on the
finite-difference scheme whereas for the Green's function formalism the
finite-element method is used. As a specific application, we consider the
device studied by Slobodskyy et all. [Phys. Rev. Lett. 90, 246601 (2003)] and
analyze their experimental results. The Wigner and Green's functions formalisms
give similar electron densities and potentials but, surprisingly, the former
method requires much more computer resources in order to obtain numerically
accurate results for currents. Both of the formalisms can successfully be used
to model magnetic resonant tunneling diode structures.Comment: 13 pages and 12 figure
Hamiltonian construction of W-gravity actions
We show that all W-gravity actions can be easilly constructed and understood
from the point of view of the Hamiltonian formalism for the constrained
systems. This formalism also gives a method of constructing gauge invariant
actions for arbitrary conformally extended algebras.Comment: 9 page
How to Solve Quantum Nonlinear Abelian Gauge Theory in Two Dimension in the Heisenberg Picture
The new method based on the operator formalism proposed by Abe and Nakanishi
is applied to the quantum nonlinear abelian gauge theory in two dimension. The
soluble models in this method are extended to wider class of quantum field
theories. We obtain the exact solution in the canonical-quantization operator
formalism in the Heisenberg picture. So this analysis might shed some light on
the analysis of gravitational theory and non-polynomial field theories.Comment: LaTeX, 12 pages, to be published in IJMP
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