Mareike Haberichter

Isospinning baby Skyrmion solutions

We perform full two-dimensional (2D) numerical relaxations of isospinning soliton solutions in the baby Skyrme model in which the global O(3) symmetry is broken by the 2D analogue of the pion mass term in the Skyrme model. In our calculations we explicitly allow the isospinning solitons to deform and to break the symmetries of the static configurations. We find that stable isospinning baby Skyrme solutions can be constructed numerically for all angular frequencies omega <= min (mu, 1), where mu is the mass parameter of the model. Stable, rotationally symmetric baby Skyrmion solutions for higher angular velocities are simply an artefact of the hedgehog approximation. Isospinning multisoliton solutions of topological charge B turn out to be unstable to break up into their B charge-1 constituents at some critical breakup frequency value. Furthermore, we find that for mu sufficiently large the rotational symmetry of charge-2 baby Skyrmions becomes broken at a critical angular frequency omega.

Radial vibrations of BPS skyrmions

We study radial vibrations of spherically symmetric Skyrmions in the Bogomol’nyi-Prasad-Sommerfield Skyrme model. Concretely, we numerically solve the linearized field equations for small fluctuations in a Skyrmion background, both for linearly stable oscillations and for (unstable) resonances. This is complemented by numerical solutions of the full nonlinear system, which confirm all the results of the linear analysis. In all cases, the resulting fundamental excitation provides a rather accurate value for the Roper resonance, supporting the hypothesis that the Bogomol’nyi-Prasad-Sommerfield Skyrme model already gives a reasonable approximate description of this resonance. Furthermore, for many potentials additional higher resonances appear, again in agreement with known experimental results.

Electromagnetic Transition Strengths for Light Nuclei in the Skyrme model

This work was partly undertaken on the COSMOS Shared Memory system at DAMTP, University of Cambridge operated on behalf of the STFC DiRAC HPC Facility. This equipment is funded by BIS National E-infrastructure capital grant no. ST/J005673/1 and STFC grants no. ST/J001341/1, ST/H008586/1, ST/K00333X/1. M.H. has been partially funded by the UK Science and Technology Facilities Council under grant no. ST/J000434/1. M.H. thanks Andrzej Wereszczynski and the Jagiellonian University, Krakow for hospitality. P.H.C.L. thanks Ling-Yan Hung and Fudan University in Shanghai for hospitality. P.H.C.L. acknowledges support as an International Research Fellow of the Japan Society for the Promotion of Science (JSPS).

Skyrme models and nuclear matter equation of state

We investigate the role of pressure in a class of generalised Skyrme models. We introduce pressure as the trace of the spatial part of the energy-momentum tensor and show that it obeys the usual thermodynamical relation. Then, we compute analytically the mean-field equation of state in the high and medium pressure regimes by applying topological bounds on compact domains. The equation of state is further investigated numerically for the charge one skyrmions. We identify which term in a generalised Skyrme model is responsible for which part in the equation of state. Further, we compare our findings with the corresponding results in the Walecka model.

Classically isospinning Hopf solitons

We perform full 3-dimensional numerical relaxations of isospinning Hopf solitons with Hopf charge up to 8 in the Skyrme-Faddeev model with mass terms included. We explicitly allow the soliton solution to deform and to break the symmetries of the static configuration. It turns out that the model with its rich spectrum of soliton solutions, often of similiar energy, allows for transmutations, formation of new solution types and the rearrangement of the spectrum of minimal-energy solitons in a given topological sector when isospin is added. We observe that the shape of isospinning Hopf solitons can differ qualitatively from that of the static solution. In particular the solution type of the lowest energy soliton can change. Our numerical results are of relevance for the quantization of the classical soliton solutions.

Classically isospinning Skyrmion solutions

We investigate how isospin affects the geometrical shape and energy of classical soliton solutions of topological charges

Head butting sheep: Kink Collisions in the Presence of False Vacua

B=1-4,8

Baby Skyrme models without a potential term

in the Skyrme model. The novel appoach in our work is that we study classically isospinning Skyrmions beyond the rigid body approximation, that is, we explicitly allow the soliton solutions to deform and to break the symmetries of the static configurations. Our fully three-dimensional relaxation calculations reveal that the symmetries of isospinning Skyrme solitons can differ significantly from the ones of the static configurations. In particular, isospinning Skyrmion solutions can break up into lower charge Skyrmions, can deform into new solution types that do not exist at vanishing angular frequency

The volume of a soliton

\omega

Classically spinning and isospinning solitons

or energy degeneracy can be removed. These types of deformations have been largely ignored in previous work on modelling nuclei by quantized Skyrmion solutions.