61 research outputs found
Pion correlation from Skyrmion-AntiSkyrmion annihilation
We study two pion correlations from Skyrmion and antiSkyrmion collision,
using the product ansatz and an approximate random grooming method for nucleon
projection. The spatial-isospin coupling inherent in the Skyrme model, along
with empirical averages, leads to correlations not only among pions of like
charges but also among unlike charge types.Comment: uuencoded files of REVTeX and postscript, 18 pages including 2
figures, submitted to Phys.Rev.
Coherent Pion Radiation From Nucleon Antinucleon Annihilation
A unified picture of nucleon antinucleon annihilation into pions emerges from
a classical description of the pion wave produced in annihilation and the
subsequent quantization of that wave as a coherent state. When the constraints
of energy-momentum and iso-spin conservation are imposed on the coherent state,
the pion number distribution and charge ratios are found to be in excellent
agreement with experiment.Comment: LaTex, 8 text pages, 1 PostScript figure, PSI-PR-93-2
Symmetry conserving non-perturbative s-wave renormalization of the pion in hot and baryon dense medium
A non-perturbative s-wave renormalization of the pion in a hot and baryon
rich medium is presented. This approach proceeds via a mapping of the canonical
pion into the axial Noether's charge. The mapping was made dynamical in the
Hartree-Fock-Bogoliubov random phase approximation (HFB-RPA). It is shown that
this approach, while order mixing, is still symmetry conserving both in the
baryon free and baryon rich sectors, at zero as well as finite temperature. The
systematic character of this approach is emphasized and it is particularly
argued that it may constitute an interesting alternative for the
non-perturbative assessment of the nuclear matter saturation properties.Comment: Latex, 22 pages, 3 figure
Coherent state formulation of pion radiation from nucleon antinucleon annihilation
We assume that nucleon antinucleon annihilation is a fast process leading to
a classical coherent pion pulse. We develop the quantum description of such
pion waves based on the method of coherent states. We study the consequences of
such a description for averages of charge types and moments of distributions of
pion momenta with iso-spin and four-momentum conservation taken into account.
We briefly discuss the applicability of our method to annihilation at rest,
where we find agreement with experiment, and suggest other avenues for its use.Comment: 24 pages, 3 figures, 1 table, PSI-preprin
Symmetry Decomposition of Potentials with Channels
We discuss the symmetry decomposition of the average density of states for
the two dimensional potential and its three dimensional
generalisation . In both problems, the energetically
accessible phase space is non-compact due to the existence of infinite channels
along the axes. It is known that in two dimensions the phase space volume is
infinite in these channels thus yielding non-standard forms for the average
density of states. Here we show that the channels also result in the symmetry
decomposition having a much stronger effect than in potentials without
channels, leading to terms which are essentially leading order. We verify these
results numerically and also observe a peculiar numerical effect which we
associate with the channels. In three dimensions, the volume of phase space is
finite and the symmetry decomposition follows more closely that for generic
potentials --- however there are still non-generic effects related to some of
the group elements
Two Skyrmion Dynamics with Omega Mesons
We present our first results of numerical simulations of two skyrmion
dynamics using an -meson stabilized effective Lagrangian. We consider
skyrmion-skyrmion scattering with a fixed initial velocity of , for
various impact parameters and groomings. The physical picture that emerges is
surprisingly rich, while consistent with previous results and general
conservation laws. We find meson radiation, skyrmion scattering out of the
scattering plane, orbiting and capture to bound states.Comment: 19 pages, 22 figure
Hartree Fock Calculations in the Density Matrix Expansion Approach
The density matrix expansion is used to derive a local energy density
functional for finite range interactions with a realistic meson exchange
structure. Exchange contributions are treated in a local momentum
approximation. A generalized Slater approximation is used for the density
matrix where an effective local Fermi momentum is chosen such that the next to
leading order off-diagonal term is canceled. Hartree-Fock equations are derived
incorporating the momentum structure of the underlying finite range
interaction. For applications a density dependent effective interaction is
determined from a G-matrix which is renormalized such that the saturation
properties of symmetric nuclear matter are reproduced. Intending applications
to systems far off stability special attention is paid to the low density
regime and asymmetric nuclear matter. Results are compared to predictions
obtained from Skyrme interactions. The ground state properties of stable nuclei
are well reproduced without further adjustments of parameters. The potential of
the approach is further exemplified in calculations for A=100...140 tin
isotopes. Rather extended neutron skins are found beyond 130Sn corresponding to
solid layers of neutron matter surrounding a core of normal composition.Comment: Revtex, 29 pages including 14 eps figures, using epsfig.st
Collision-Induced Decay of Metastable Baby Skyrmions
Many extensions of the standard model predict heavy metastable particles
which may be modeled as solitons (skyrmions of the Higgs field), relating their
particle number to a winding number. Previous work has shown that the
electroweak interactions admit processes in which these solitons decay,
violating standard model baryon number. We motivate the hypothesis that
baryon-number-violating decay is a generic outcome of collisions between these
heavy particles. We do so by exploring a 2+1 dimensional theory which also
possesses metastable skyrmions. We use relaxation techniques to determine the
size, shape and energy of static solitons in their ground state. These solitons
could decay by quantum mechanical tunneling. Classically, they are metastable:
only a finite excitation energy is required to induce their decay. We attempt
to induce soliton decay in a classical simulation by colliding pairs of
solitons. We analyze the collision of solitons with varying inherent
stabilities and varying incident velocities and orientations. Our results
suggest that winding-number violating decay is a generic outcome of collisions.
All that is required is sufficient (not necessarily very large) incident
velocity; no fine-tuning of initial conditions is required.Comment: 24 pages, 7 figures, latex. Very small changes onl
Semiclassical Trace Formulas for Noninteracting Identical Particles
We extend the Gutzwiller trace formula to systems of noninteracting identical
particles. The standard relation for isolated orbits does not apply since the
energy of each particle is separately conserved causing the periodic orbits to
occur in continuous families. The identical nature of the particles also
introduces discrete permutational symmetries. We exploit the formalism of
Creagh and Littlejohn [Phys. Rev. A 44, 836 (1991)], who have studied
semiclassical dynamics in the presence of continuous symmetries, to derive
many-body trace formulas for the full and symmetry-reduced densities of states.
Numerical studies of the three-particle cardioid billiard are used to
explicitly illustrate and test the results of the theory.Comment: 29 pages, 11 figures, submitted to PR
- âŠ