3,293 research outputs found
The parity-violating pion-nucleon coupling constant from a realistic three flavor Skyrme model
We study the parity-violating pion-nucleon coupling in the framework
of a realistic three flavor Skryme model. We find a sizeable enhancement of
compared to previous calculations in
two-flavor models with vector mesons. This strangeness enhancement stems from
induced kaon fields of the chiral soliton and the non-monotoneous dependence on
symmetry breaking of the nucleon matrix element of the flavor singlet piece of
the operator associated with these induced fields. Both features are sensitive
to four quark operators including an pair.Comment: 10 pp, LaTeX, uses epsf, 2 figs, small corrections plus additional
explanations, value of Gpi somewhat smalle
Energies of Quantum QED Flux Tubes
In this talk I present recent studies on vacuum polarization energies and
energy densities induced by QED flux tubes. I focus on comparing three and four
dimensional scenarios and the discussion of various approximation schemes in
view of the exact treatment.Comment: 9 pages latex, Talk presented at the QFEXT 05 workshop in Barcelona,
Sept. 2005. To appear in the proceeding
Soliton Models for the Nucleon and Predictions for the Nucleon Spin Structure
In these lectures the three flavor soliton approach for baryons is reviewed.
Effects of flavor symmetry breaking in the baryon wave--functions on axial
current matrix elements are discussed. A bosonized chiral quark model is
considered to outline the computation of spin dependent nucleon structure
functions in the soliton picture.Comment: 12 pages, Lectures presented at the Advanced Study Institute Symmetry
and Spin, Prague, 2001, to appear in the proceedings. References correcte
Chiral Quark Model
In this talk I review studies of hadron properties in bosonized chiral quark
models for the quark flavor dynamics. Mesons are constructed from
Bethe--Salpeter equations and baryons emerge as chiral solitons. Such models
require regularization and I show that the two--fold Pauli--Villars
regularization scheme not only fully regularizes the effective action but also
leads the scaling laws for structure functions. For the nucleon structure
functions the present approach serves to determine the regularization
prescription for structure functions whose leading moments are not given by
matrix elements of local operators. Some numerical results are presented for
the spin structure functions.Comment: Talk presented at the workshop QCD 2002, IIT Kanpur, Nov. 2002, 10
pages, proceedings style files include
Cosmic Strings Stabilized by Fermion Fluctuations
We provide a thorough exposition of recent results on the quantum
stabilization of cosmic strings. Stabilization occurs through the coupling to a
heavy fermion doublet in a reduced version of the standard model. The study
combines the vacuum polarization energy of fermion zero-point fluctuations and
the binding energy of occupied energy levels, which are of the same order in a
semi-classical expansion. Populating these bound states assigns a charge to the
string. Strings carrying fermion charge become stable if the Higgs and gauge
fields are coupled to a fermion that is less than twice as heavy as the top
quark. The vacuum remains stable in the model, because neutral strings are not
energetically favored. These findings suggest that extraordinarily large
fermion masses or unrealistic couplings are not required to bind a cosmic
string in the standard model.Comment: Based on talk by HW at QFEXT 11 (Benasque, Spain), 15p, uses
ws-ijmpcs.cls (incl
CP-violating asymmetry in in the Skyrme model
We study the CP-violating asymmetry in nonleptonic decay .
By employing the Skyrme model to calculate this decay amplitude contributed by
the gluonic diploe operator, we find a possible large CP-violating asymmetry
could be expected, which is consistent with the previous study.Comment: LaTeX file, To appear in J Phys G: Nucl Phys and Part Phy
Instability of the hedgehog shape for the octet baryon in the chiral quark soliton model
In this paper the stability of the hedgehog shape of the chiral soliton is
studied for the octet baryon with the SU(3) chiral quark soliton model. The
strangeness degrees of freedom are treated by a simplified bound-state
approach, which omits the locality of the kaon wave function. The mean field
approximation for the flavor rotation is applied to the model. The classical
soliton changes shape according to the strangeness. The baryon appears as a
rotational band of the combined system of the deformed soliton and the kaon.Comment: 24 pages, LaTeX, 8 eps file
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