2,213 research outputs found
Symmetries of hadrons after unbreaking the chiral symmetry
We study hadron correlators upon artificial restoration of the spontaneously
broken chiral symmetry. In a dynamical lattice simulation we remove the lowest
lying eigenmodes of the Dirac operator from the valence quark propagators and
study evolution of the hadron masses obtained. All mesons and baryons in our
study, except for a pion, survive unbreaking the chiral symmetry and their
exponential decay signals become essentially better. From the analysis of the
observed spectroscopic patterns we conclude that confinement still persists
while the chiral symmetry is restored. All hadrons fall into different chiral
multiplets. The broken U(1)_A symmetry does not get restored upon unbreaking
the chiral symmetry. We also observe signals of some higher symmetry that
includes chiral symmetry as a subgroup. Finally, from comparison of the \Delta
- N splitting before and after unbreaking of the chiral symmetry we conclude
that both the color-magnetic and the flavor-spin quark-quark interactions are
of equal importance.Comment: 12 pages, 14 figures; final versio
Covariant baryon charge radii and magnetic moments in a chiral constituent quark model
The charge radii and magnetic moments of all the light and strange baryons
are investigated within the framework of a constituent quark model based on
Goldstone-boson-exchange dynamics. Following the point-form approach to
relativistic quantum mechanics, the calculations are performed in a manifestly
covariant manner. Relativistic (boost) effects have a sizeable influence on the
results. The direct predictions of the constituent quark model are found to
fall remarkably close to the available experimental data.Comment: 6 pages, 4 table
A High Precision Study of the QQ(bar) Potential from Wilson Loops in the Regime of String Breaking
For lattice QCD with two sea quark flavours we compute the static quark
antiquark potential V(R) in the regime where string breaking is expected. In
order to increase statistics, we make full use of the lattice information by
including all lattice vectors R to any possible lattice separation in the
infrared regime. The corresponding paths between the lattice points are
constructed by means of a generalized Bresenham algorithm as known from
computer graphics. As a results we achieve a determination of the unquenched
potential in the range .8 to 1.5 fm with hitherto unknown precision.
Furthermore, we demonstrate some error reducing methods for the evaluation of
the transition matrix element between two- and four-quark states.Comment: 6 pages, 7 figure
Interacting scalar and spinor fields in Bianchi type I universe filled with magneto-fluid
Self-consistent system of spinor, scalar and BI gravitational fields in
presence of magneto-fluid and -term is considered. Assuming that the
expansion of the BI universe is proportional to the component of
the shear tensor, exact solutions for the metric functions, as well as for
scalar and spinor fields are obtained. For a non-positive the
initially anisotropic space-time becomes isotropic one in the process of
expansion, whereas, for an oscillatory mode of expansion of the
BI model occurs.Comment: RevTex4, 8 pages, no figure
and resonances on the lattice at nearly physical quark masses and
Working with a pion mass MeV, we study and
scattering using two flavours of non-perturbatively improved Wilson
fermions at a lattice spacing fm. Employing two lattice
volumes with linear spatial extents of and points and moving
frames, we extract the phase shifts for p-wave and scattering
near the and resonances.Comparing our results to those of previous
lattice studies, that used pion masses ranging from about 200 MeV up to 470
MeV, we find that the coupling appears to be remarkably
constant as a function of .Comment: 16 pages, 8 figures, v2: "and " added to the title, references
updated, some figures replaced, including improved summary plots, alternative
parametrizations are considered and analytical continations are performed to
determine pole positions on the second Riemann shee
Weed control in soybean (Glycine max L.) through resource management strategies and its influence on yield and nutrient uptake
A field experiment was conducted during kharif season of 2011 at Research Farm, Sher-e-Kashmir University of Agricultural Sciences and Technology, Chatha, Jammu to evaluate the effect of weed management prac-tices on yield and nutrient uptake of soybean utilizing different resource management strategies. The lowest weed density and dry matter of weeds was recorded with hand weeding at 15 and 35 days after sowing (DAS) which was equally effective as imazethapyr @ 75 g ha -1 (PoE) fb hoeing at 35 DAS and quizalofop-ethyl @ 40 g ha-1 (PoE) fb hoeing at 35 DAS. All weed control treatments had significant effect on yield and nutrient up-take of soybean. Among the different weed control treatments, lowest N, P and K uptake by weeds were recorded in hand-weeding (15 and 35 DAS) which was statistically at par with imazethapyr @ 75 g ha -1 fb hoeing at 35 DAS. The maximum uptake by seed and straw were recorded in weed free which was statistically at par with twice hand weeding at 15 and 35 DAS, imazethapyr @ 75 g ha-1 fb hoeing at 35 DAS and quizalofop-ethyl @ 40 g ha-1 fb hoeing at 35 DAS. The highest seed and straw yield of soybean was harvested with hand-weeding (15 and 35 DAS) followed by imazethapyr @ 75 g ha -1 fb hoeing at 35 DAS. For the first time, soybean crop has been introduced in Jammu region for research purpose. Weed management varies with agro-climatic conditions. The study would be helpful to understand weed menace in this particular climatic condition of Jammu and to manage them combinedly and efficiently
Bianchi Type I Massive String Magnetized Barotropic Perfect Fluid Cosmological Model in General Relativity
Bianchi type I massive string cosmological model with magnetic field of
barotropic perfect fluid distribution through the techniques used by Latelier
and Stachel, is investigated. To get the deterministic model of the universe,
it is assumed that the universe is filled with barotropic perfect fluid
distribution. The magnetic field is due to electric current produced along
x-axis with infinite electrical conductivity. The behaviour of the model in
presence and absence of magnetic field together with other physical aspects is
further discussed.Comment: 10 pages, no figure. Chin. Phys. Lett., Vol. 24, No. 8 (2007), to
appea
Unbreaking chiral symmetry
In Quantum Chromodynamics (QCD) the eigenmodes of the Dirac operator with
small absolute eigenvalues have a close relationship to the dynamical breaking
of the chiral symmetry. In a simulation with two dynamical quarks, we study the
behavior of meson propagators when removing increasingly more of those modes in
the valence sector, thus partially removing effects of chiral symmetry
breaking. We find that some of the symmetry aspects are restored (e.g., the
masses of and approach each other) while confining properties
persist.Comment: 5 pages, 5 figures (figure added, references updated
Bianchi Type III String Cosmological Models with Time Dependent Bulk Viscosity
Bianchi type III string cosmological models with bulk viscous fluid for
massive string are investigated. To get the determinate model of the universe,
we have assumed that the coefficient of bulk viscosity () is inversely
proportional to the expansion () in the model and expansion ()
in the model is proportional to the shear (). This leads to , and are constants. The behaviour of the model in presence
and absence of bulk viscosity, is discussed. The physical implications of the
models are also discussed in detail.Comment: 11 pages, no figur
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