27,231 research outputs found
Canonical Quantization of SU(3) Skyrme Model in a General Representation
A complete canonical quantization of the SU(3) Skyrme model performed in the
collective coordinate formalism in general irreducible representations. In the
case of SU(3) the model differs qualitatively in different representations. The
Wess-Zumino-Witten term vanishes in all self-adjoint representations in the
collective coordinate method for separation of space and time variables. The
canonical quantization generates representation dependent quantum mass
corrections, which can stabilize the soliton solution. The standard symmetry
breaking mass term, which in general leads to representation mixing,
degenerates to the SU(2) form in all self-adjoint representations.Comment: 24 RevTex4 pages, no figure
Isospin Effects on Astrophysical S-Factors
We estimate the ratios of bare astrophysical S-factors at zero incident
energy for proton and deuteron induced reactions in a model which assumes a
compound nucleus formation probability plus a statistical decay. The obtained
ratios agree well with available experimental values, as far as the reactions
which have dominant s-wave entrance channel components are investigated. Due to
its simplicity the model could be used as a guidance for predictions on
reactions which have not been investigated yet.Comment: 12 pages, 1 figure
Influence of QED Corrections on the Orientation of Chiral Symmetry Breaking in the NJL model
We study QED corrections to chiral symmetry breaking in the
Nambu--Jona-Lasinio (NJL) model with two flavors of quarks. In this model, the
isospin symmetry is broken by the differences between the current quark masses
and the electromagnetic charges of the up and down quarks. To leading order in
the 1/N expansion, we calculate the effective potential of the model with
one-loop QED corrections at finite temperature.
Evaluating the effective potential, we study the influence of the isospin
symmetry breaking on the orientation of chiral symmetry breaking.
The current quark mass plays an essential role in maintaining the orientation
of the chiral symmetry breaking.
If the average of the up and down quark masses is small enough, we find a
phase in which the pion field has non-vanishing expectation value and dynamical
CP violation takes place.Comment: 22 pages, 13 figures; added discussion about pion mass differenc
Regularization dependence on phase diagram in Nambu-Jona-Lasinio model
We study the regularization dependence on meson properties and the phase
diagram of quark matter by using the two flavor Nambu-Jona-Lasinio model. We
find that the meson properties and the phase structure do not show drastically
difference depending the regularization procedures. We also find that the
location or the existence of the critical end point highly depends on the
regularization methods and the model parameters. Then we think that
regularization and parameters are carefully considered when one investigates
the QCD critical end point in the effective model studies.Comment: 28 page
Anisotropic Electronic Structure of the Kondo Semiconductor CeFe2Al10 Studied by Optical Conductivity
We report temperature-dependent polarized optical conductivity
[] spectra of CeFeAl, which is a reference material
for CeRuAl and CeOsAl with an anomalous magnetic
transition at 28 K. The spectrum along the b-axis differs
greatly from that in the -plane, indicating that this material has an
anisotropic electronic structure. At low temperatures, in all axes, a shoulder
structure due to the optical transition across the hybridization gap between
the conduction band and the localized states, namely -
hybridization, appears at 55 meV. However, the gap opening temperature and the
temperature of appearance of the quasiparticle Drude weight are strongly
anisotropic indicating the anisotropic Kondo temperature. The strong
anisotropic nature in both electronic structure and Kondo temperature is
considered to be relevant the anomalous magnetic phase transition in
CeRuAl and CeOsAl.Comment: 5 pages, 4 figure
Nonet meson properties in Nambu--Jona-Lasinio model with dimensional versus cutoff regularization
Nambu--Jona-Lasinio (NJL) model with Kobayashi-Maskawa-'t Hooft (KMT) term is
one of low energy effective theory of QCD which includes the anomaly.
We investigate nonet meson properties in this model with three flavors of
quarks. We employ two type of regularizations the dimensional and sharp cutoff
ones. The model parameters are fixed phenomenologically for each
regularization. Evaluating the kaon decay constant, the meson mass and
the topological susceptibility, we show the regularization dependence of the
results and discuss the applicability of the NJL model.Comment: 11 pages, 9 figure
Phonon engineering with superlattices: generalized nanomechanical potentials
Earlier implementations to simulate coherent wave propagation in
one-dimensional potentials using acoustic phonons with gigahertz-terahertz
frequencies were based on coupled nanoacoustic resonators. Here, we generalize
the concept of adiabatic tuning of periodic superlattices for the
implementation of effective one-dimensional potentials giving access to cases
that cannot be realized by previously reported phonon engineering approaches,
in particular the acoustic simulation of electrons and holes in a quantum well
or a double well potential. In addition, the resulting structures are much more
compact and hence experimentally feasible. We demonstrate that potential
landscapes can be tailored with great versatility in these multilayered
devices, apply this general method to the cases of parabolic, Morse and
double-well potentials and study the resulting stationary phonon modes. The
phonon cavities and potentials presented in this work could be probed by
all-optical techniques like pump-probe coherent phonon generation and Brillouin
scattering
Fermi Surface Nesting and Nanoscale Fluctuating Charge/Orbital Ordering in Colossal Magnetoresistive Oxides
We used high resolution angle-resolved photoemission spectroscopy to reveal
the Fermi surface and key transport parameters of the metallic state of the
layered Colossal Magnetoresistive (CMR) oxide La1.2Sr1.8Mn2O7. With these
parameters the calculated in-plane conductivity is nearly one order of
magnitude larger than the measured DC conductivity. This discrepancy can be
accounted for by including the pseudogap which removes at least 90% of the
spectral weight at the Fermi energy. Key to the pseudogap and many other
properties are the parallel straight Fermi surface sections which are highly
susceptible to nesting instabilities. These nesting instabilities produce
nanoscale fluctuating charge/orbital modulations which cooperate with
Jahn-Teller distortions and compete with the electron itinerancy favored by
double exchange
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