685 research outputs found
The Momentum--Space Bosonization of the Nambu--Jona-Lasinio Model with Vector and Axial-Vector Mesons
The momentum-space bosonization method is extended to the case of a
Nambu--Jona-Lasinio type model with vector and axial-vector mesons. The method
presented gives the possibility of deriving any meson vertex function to all
orders in momenta and to the leading order in . Two-point functions,
which describe one-particle transitions to the hadronic vacuum, and meson
self-energies are considered. We find new relations which generalize the
well-known KSFR relation and both the first and the second Weinberg sum rules.
These result from a consistent treatment of higher order terms in the momentum
expansion.Comment: 11pp, TeX, CRN 93-5
The Rho-Meson as a Collective Excitation
A model of the rho-meson as a collective excitation of pairs in a
system that obeys the modified Nambu--Jona-Lasinio Lagrangian is proposed. The
rho emerges as a dormant Goldstone boson. The origin of the rho-meson mass is
understood as a result of spontaneous chiral symmetry breaking. The low-energy
dynamics of rho, pi, omega and gamma is consistently described in this new
framework. The model accounts for the origin of the celebrated
Kawarabayashi--Suzuki--Riazuddin--Fayyazuddin relation.Comment: 8 pages, plain LaTe
Light Quark Masses in Multi-Quark Interactions
We suggest and discuss in detail a multi-quark three flavor Lagrangian of the
Nambu -- Jona-Lasinio type, which includes a set of effective interactions
proportional to the current quark masses. It is shown that within the dynamical
chiral symmetry breaking regime, the masses of the pseudo Goldstone bosons and
their chiral partners, members of the low lying scalar nonet, are in perfect
agreement with current phenomenological expectations. The role of the new
interactions is analyzed.Comment: 8 pages, published versio
Representations of affine Lie algebras, elliptic r-matrix systems, and special functions
There were some errors in paper hep-th/9303018 in formulas 6.1, 6.6, 6.8,
6.11. These errors have been corrected in the present version of this paper.
There are also some minor changes in the introduction.Comment: 33 pages, no figure
Aspects of U_A(1) breaking in the Nambu and Jona-Lasinio model
The six-quark instanton induced 't Hooft interaction, which breaks the
unwanted U_A (1) symmetry of QCD, is a source of perturbative corrections to
the leading order result formed by the four-quark forces with the U_L(3)X
U_R(3) chiral symmetry. A detailed quantitative calculation is carried out to
bosonize the model by the functional integral method. We concentrate our
efforts on finding ways to integrate out the auxiliary bosonic variables. The
functional integral over these variables cannot be evaluated exactly. We show
that the modified stationary phase approach leads to a resummation within the
perturbative series and calculate the integral in the ``two-loop''
approximation. The result is a correction to the effective mesonic Lagrangian
which may be important for the low-energy spectrum and dynamics of the scalar
and pseudoscalar nonets.Comment: 42 pages, 3 figures; concluding section and references adde
Low-energy dynamics of the reaction
We calculate the one-quark-loop amplitude for the low energy
collision in the context of the Nambu and Jona-Lasinio
model with scalar and pseudoscalar four quark couplings to all orders in the
external momenta. We show that the NJL predictions for the
reaction are not far from the Born amplitude, which
is close to the data, and is compatible with the chiral perturbation theory
estimations. We determine the corrections given by the NJL model in leading
order of to the chiral loop amplitude for .
Numerical results for the cross sections and
for pion polarizabilities are given.Comment: 20 pages in LaTex, 3 figures in 1 Postscript fil
Analysis of the Threshold Effect of Government Expenditure and Commercial Bank Credit on Agricultural Output in Nigeria
This study empirically investigated the threshold effect of government expenditure and commercial bank credit on agricultural performance in Nigeria spanning 1986 to 2021. The study used the Threshold Autoregression (TAR) analysis to carry out the analysis. The result of the TAR regression established a threshold value of N390.01 billion for government agricultural expenditure. The TAR regression established a linear relationship between government expenditure and agricultural performance in Nigeria, thus, a positive threshold effect of 2% and 22% below and above the threshold value respectively was established by the TAR regression. Similarly, an asymmetric inverted U-shaped relationship exists between commercial bank credit to the agricultural sector and the performance of the agricultural sector in Nigeria. It found a threshold value of commercial bank credit to the agricultural sector at N610.15 billion; stating that below this threshold, commercial bank credit to the agricultural sector has a positive and significant effect of 51% on the performance of the agricultural sector in Nigeria. However, above this threshold, commercial bank credit adversely affect the performance of the agricultural sector, reducing the sector’s performance by 6%. Based on these findings, this study recommends that commercial bank credit to the agricultural sector should be kept within the established threshold level. Furthermore, to maximize the performance of the agricultural sector, the study recommends the allocation of additional funds to the agricultural sector by the government. Keywords: Government Expenditure, Commercial Banks Credits, Agricultural Output, Threshold Regression. Jel Codes: H50,G21,Q10,C14 DOI: 10.7176/JESD/13-18-06 Publication date:September 30th 202
Nucleon Structure from Lattice QCD
Recent advances in lattice field theory, in computer technology and in chiral
perturbation theory have enabled lattice QCD to emerge as a powerful
quantitative tool in understanding hadron structure. I describe recent progress
in the computation of the nucleon form factors and moments of parton
distribution functions, before proceeding to describe lattice studies of the
Generalized Parton Distributions (GPDs). In particular, I show how lattice
studies of GPDs contribute to building a three-dimensional picture of the
proton. I conclude by describing the prospects for studying the structure of
resonances from lattice QCD.Comment: 6 pages, invited plenary talk at NSTAR 2007, 5-8 September 2007,
Bonn, German
Lowering the critical temperature with eight-quark interactions
It is shown that eight-quark interactions, which are needed to stabilize the
ground state of the combined three flavor Nambu -- Jona-Lasinio and 't Hooft
Lagrangians, play also an important role in determining the critical
temperature at which transitions occur from the dynamically broken chiral phase
to the symmetric phase.Comment: 4 pages, 2 figure
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