425 research outputs found

### Pion-delta sigma-term

We use a configuration space chiral model in order to evaluate nucleon and
delta sigma-terms. Analytic expressions are consistent with chiral counting
rules and give rise to expected non-analytic terms in the chiral limit. We
obtain the results $\sigma_N=46$ MeV and $\sigma_{\Delta}=32$ MeV, which are
very close to values extracted from experiment and produced by other groups.Comment: 18 pages, 4 figure

### Collective Quantisation of a Gravitating Skyrmion

Collective quantisation of a B=1 gravitating skyrmion is described. The
rotational and isorotational modes are quantised in the same manner as the
skyrmion without gravity. It is shown in this paper how the static properties
of nucleons such as masses, charge densities, magnetic moments are modified by
the gravitational interaction.Comment: 10 pages, 9 figures, minor corrections, published versio

### Chiral symmetry breaking and vacuum polarization in a bag

We study the effects of a finite quark mass in the hedgehog configuration in
the two phase chiral bag model. We discuss the chiral properties, such as the
fractional baryon number and the chiral Casimir energy, by using the Debye
expansion for the analytical calculation and the Strutinsky's smearing method
for the numerical computation. It is shown that the fractional baryon number
carried by massive quarks in the vacuum is canceled by that in the meson
sector. A finite term of the chiral Casimir energy is obtained with subtraction
of the logarithmic divergence term

### Topology in Physics - A Perspective

This article, written in honor of Fritz Rohrlich, briefly surveys the role of
topology in physics.Comment: 16pp, 2 figures included (encapsulated postscript

### Topological Objects in Two-component Bose-Einstein Condensates

We study the topological objects in two-component Bose-Einstein condensates.
We compare two competing theories of two-component Bose-Einstein condensate,
the popular Gross-Pitaevskii theory and the recently proposed gauge theory of
two-component Bose-Einstein condensate which has an induced vorticity
interaction. We show that two theories produce very similar topological
objects, in spite of the obvious differences in dynamics. Furthermore we show
that the gauge theory of two-component Bose-Einstein condensate, with the U(1)
gauge symmetry, is remarkably similar to the Skyrme theory. Just like the
Skyrme theory the theory admits the non-Abelian vortex, the helical vortex, and
the vorticity knot. We construct the lightest knot solution in two-component
Bose-Einstein condensate numerically, and discuss how the knot can be
constructed in the spin-1/2 condensate of $^{87}{\rm Rb}$ atoms.Comment: 18 pages, 15 figures, Phys. Rev. A in pres

### The nucleus as a fluid of skyrmions: Energy levels and nucleon properties in the medium

A model of a fluid of skyrmions coupled to a scalar and to the \o meson
mean fields is developed. The central and spin-orbit potentials of a skyrmion
generated by the fields predict correct energy levels in selected closed shell
nuclei. The effect of the meson fields on the properties of skyrmions in nuclei
is investigated.Comment: Latex format, 6 figures, Journal of Physics G, to be publishe

### ppK- bound states from Skyrmions

The bound kaon approach to the strangeness in the Skyrme model is applied to
investigating the possibility of deeply bound $ppK^-$ states. We describe the
$ppK^-$ system as two-Skyrmion around which a kaon field fluctuates. Each
Skyrmion is rotated in the space of SU(2) collective coordinate. The rotational
motions are quantized to be projected onto the spin-singlet proton-proton
state. We derive the equation of motion for the kaon in the background field of
two Skyrmions at fixed positions. From the numerical solution of the equation
of motion, it is found that the energy of $K^-$ can be considerably small, and
that the distribution of $K^-$ shows molecular nature of the $ppK^-$ system.
For this deep binding, the Wess-Zumino-Witten term plays an important role. The
total energy of the $ppK^-$ system is estimated in the Born-Oppenheimer
approximation. The binding energy of the $ppK^-$ state is $B.E.\simeq 126$ MeV.
The mean square radius of the $pp$ subsystem is $\sqrt{}\simeq 1.6$
fm.Comment: Oct 2007, 15 pages, 8 figures; added references, corrected typo

### On the electromagnetic form factors of the proton from generalized Skyrme models

We compare the prediction of Skyrme-like effective Lagrangians with data for
electromagnetic form factors of proton and consider the possibility of fixing
the parameters of these higher-order Lagrangians. Our results indicate that one
or two-parameter models can lead to better agreement with the data but more
accurate determination of the effective Lagragian faces theoretical
uncertainties.Comment: 8 pages, 2 figures, revte

### High-density Skyrmion matter and Neutron Stars

We examine neutron star properties based on a model of dense matter composed
of B=1 skyrmions immersed in a mesonic mean field background. The model
realizes spontaneous chiral symmetry breaking non-linearly and incorporates
scale-breaking of QCD through a dilaton VEV that also affects the mean fields.
Quartic self-interactions among the vector mesons are introduced on grounds of
naturalness in the corresponding effective field theory. Within a plausible
range of the quartic couplings, the model generates neutron star masses and
radii that are consistent with a preponderance of observational constraints,
including recent ones that point to the existence of relatively massive neutron
stars with mass M 1.7 Msun and radius R (12-14) km. If the existence of neutron
stars with such dimensions is confirmed, matter at supra-nuclear density is
stiffer than extrapolations of most microscopic models suggest.Comment: 27 pages, 5 figures, AASTeX style; to be published in The
Astrophysical Journa

### Spin textures in slowly rotating Bose-Einstein Condensates

Slowly rotating spin-1 Bose-Einstein condensates are studied through a
variational approach based upon lowest Landau level calculus. The author finds
that in a gas with ferromagnetic interactions, such as $^{87}$Rb, angular
momentum is predominantly carried by clusters of two different types of
skyrmion textures in the spin-vector order parameter. Conversely, in a gas with
antiferromagnetic interactions, such as $^{23}$Na, angular momentum is carried
by $\pi$-disclinations in the nematic order parameter which arises from spin
fluctuations. For experimentally relevant parameters, the cores of these
$\pi$-disclinations are ferromagnetic, and can be imaged with polarized light.Comment: 14 pages, 12 low resolution bitmapped figures, RevTeX4. High
resolution figures available from author. Suplementary movies available from
autho

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