96 research outputs found
Multibaryons with heavy flavors in the Skyrme model
We investigate the possible existence of multibaryons with heavy flavor
quantum numbers using the bound state approach to the topological soliton model
and the recently proposed approximation for multiskyrmion fields based on
rational maps. We use an effective interaction lagrangian which consistently
incorporates both chiral symmetry and the heavy quark symmetry including the
corrections up to order 1/m_Q. The model predicts some narrow heavy flavored
multibaryon states with baryon number four and seven.Comment: 8 pages, no figures, RevTe
T-duality and closed string non-commutative (doubled) geometry
We provide some evidence that closed string coordinates will become
non-commutative turning on H-field flux background in closed string
compactifications. This is in analogy to open string non-commutativity on the
world volume of D-branes with B- and F-field background. The class of
3-dimensional backgrounds we are studying are twisted tori (fibrations of a
2-torus over a circle) and the their T-dual H-field, 3-form flux backgrounds
(T-folds). The spatial non-commutativity arises due to the non-trivial
monodromies of the toroidal Kahler resp. complex structure moduli fields, when
going around the closed string along the circle direction. In addition we study
closed string non-commutativity in the context of doubled geometry, where we
argue that in general a non-commutative closed string background is T-dual to a
commutative closed string background and vice versa. Finally, in analogy to
open string boundary conditions, we also argue that closed string momentum and
winding modes define in some sense D-branes in closed string doubled geometry.Comment: 31 pages, references added, extended version contains new sections
3.3., 3.4 and
Baryons as non-topological chiral solitons
The present review gives a survey of recent developments and applications of
the Nambu--Jona-Lasinio model with and quark flavors for the
structure of baryons. The model is an effective chiral quark theory which
incorporates the SU(N)SU(N)U(1) approximate
symmetry of Quantum chromodynamics. The approach describes the spontaneous
chiral symmetry breaking and dynamical quark mass generation. Mesons appear as
quark-antiquark excitations and baryons arise as non-topological solitons with
three valence quarks and a polarized Dirac sea. For the evaluation of the
baryon properties the present review concentrates on the non-linear
Nambu--Jona-Lasinio model with quark and Goldstone degrees of freedom which is
identical to the Chiral quark soliton model obtained from the instanton liquid
model of the QCD vacuum. In this non-linear model, a wide variety of
observables of baryons of the octet and decuplet is considered. These include,
in particular, electromagnetic, axial, pseudoscalar and pion nucleon form
factors and the related static properties like magnetic moments, radii and
coupling constants of the nucleon as well as the mass splittings and
electromagnetic form factors of hyperons. Predictions are given for the strange
form factors, the scalar form factor and the tensor charge of the nucleon.Comment: 104 pages, 27 figures as uuencoded and compressed postscript files ,
hardcopy available upon request; Prog.Part.Nucl.Phys. 37 (1996) (in print
Physics and Applications of Laser Diode Chaos
An overview of chaos in laser diodes is provided which surveys experimental
achievements in the area and explains the theory behind the phenomenon. The
fundamental physics underpinning this behaviour and also the opportunities for
harnessing laser diode chaos for potential applications are discussed. The
availability and ease of operation of laser diodes, in a wide range of
configurations, make them a convenient test-bed for exploring basic aspects of
nonlinear and chaotic dynamics. It also makes them attractive for practical
tasks, such as chaos-based secure communications and random number generation.
Avenues for future research and development of chaotic laser diodes are also
identified.Comment: Published in Nature Photonic
Why education in public schools should include religious ideals
This article aims to open a new line of debate about religion in public schools by focusing on religious ideals. The article begins with an elucidation of the concept ‘religious ideals’ and an explanation of the notion of reasonable pluralism, in order to be able to explore the dangers and positive contributions of religious ideals and their pursuit on a liberal democratic society. We draw our examples of religious ideals from Christianity and Islam, because these religions have most adherents in Western liberal democracies that are the focus of this article. The fifth and most important section "Reasonable pluralism and the inclusion of religious ideals in public secondary schools" provides three arguments for our claim that public schools should include religious ideals, namely that they are important to religious people, that they are conducive for the development of pupils into citizens of a liberal democracy, and that the flourishing of pupils as adults is advanced by encountering religious ideals. We also offer a more practical reason: religious ideals can more easily be included within public education than religious dogmas and rules
Rapid Change in Articulatory Lip Movement Induced by Preceding Auditory Feedback during Production of Bilabial Plosives
BACKGROUND: There has been plentiful evidence of kinesthetically induced rapid compensation for unanticipated perturbation in speech articulatory movements. However, the role of auditory information in stabilizing articulation has been little studied except for the control of voice fundamental frequency, voice amplitude and vowel formant frequencies. Although the influence of auditory information on the articulatory control process is evident in unintended speech errors caused by delayed auditory feedback, the direct and immediate effect of auditory alteration on the movements of articulators has not been clarified. METHODOLOGY/PRINCIPAL FINDINGS: This work examined whether temporal changes in the auditory feedback of bilabial plosives immediately affects the subsequent lip movement. We conducted experiments with an auditory feedback alteration system that enabled us to replace or block speech sounds in real time. Participants were asked to produce the syllable /pa/ repeatedly at a constant rate. During the repetition, normal auditory feedback was interrupted, and one of three pre-recorded syllables /pa/, /Φa/, or /pi/, spoken by the same participant, was presented once at a different timing from the anticipated production onset, while no feedback was presented for subsequent repetitions. Comparisons of the labial distance trajectories under altered and normal feedback conditions indicated that the movement quickened during the short period immediately after the alteration onset, when /pa/ was presented 50 ms before the expected timing. Such change was not significant under other feedback conditions we tested. CONCLUSIONS/SIGNIFICANCE: The earlier articulation rapidly induced by the progressive auditory input suggests that a compensatory mechanism helps to maintain a constant speech rate by detecting errors between the internally predicted and actually provided auditory information associated with self movement. The timing- and context-dependent effects of feedback alteration suggest that the sensory error detection works in a temporally asymmetric window where acoustic features of the syllable to be produced may be coded
Light-Front View of The Axial Anomaly
Motivated by an apparent puzzle of the light-front vacua incompatible with
the axial anomaly, we have considered the two-dimensional massless Schwinger
model for an arbitrary interpolating angle of the quantization surface. By
examining spectral deformation of the Dirac sea under an external electric
field semiclassically, we have found that the axial anomaly is quantization
angle independent. This indicates an intricate nontrivial vacuum structure
present even in the light-front limit.Comment: 12 pages, REVTEX, one figure postscript file encode
Kaon properties in (proto)neutron stars
The modification on kaon and antikaon properties of in the interior of
(proto-)neutron stars is investigated using a chiral SU(3) model. The
parameters of the model are fitted to nuclear matter saturation properties,
baryon octet vacuum masses, hyperon optical potentials and low energy a
kaon-nucleon scattering lengths. We study the kaon/antikaon medium modification
and explore the possibility of antikaon condensation in (proto-)neutron star
matter at zero as well as finite temperature/entropy and neutrino content. The
effect of hyperons on kaon and antikaon optical potentials is also investigated
at different stages of the neutron star evolution.Comment: 17 pages including 4 figure
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