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Register a new userSmall deformations of kinks and walls
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J.R. Morris
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A Rayleigh-Schrodinger type of perturbation scheme is employed to study weak self-interacting scalar potential perturbations occurring in scalar field models describing 1D domain kinks and 3D domain walls. The solutions for the unperturbed defects are modified by the perturbing potentials. An illustration is provided by adding a cubic potential to the familiar quartic kink potential and solving for the first order correction to the kink solution, using a slab approximation. A result is the appearance of an asymmetric scalar potential with different, nondegenerate, vacuum values and the subsequent formation of vacuum bubbles.
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A Rayleigh-Schr{o}dinger type of perturbation scheme is employed to study weakly interacting kinks and domain walls formed from two different real scalar fields $chi$ and $varphi$. An interaction potential $% V_{1}(chi,varphi)$ is chosen which vanishes in a vacuum state of either field. Approximate first order corrections for the fields are found, which are associated with scalar field condensates inhabiting the zeroth order topological solitons. The model considered here presents several new and interesting features. These include (1) a condensate of textit{each} kink field inhabits the textit{other} kink, (2) the condensates contribute an associated mass to the system which vanishes when the kinks overlap, (3) a resulting mass defect of the system for small interkink distances allows the existence of a loosely bound state when the interkink force is repulsive. An identification of the interaction potential energy and forces allows a qualitative description of the classical motion of the system, with bound states, along with scattering states, possible when the interkink force is attractive. (4) Finally, the interaction potential introduces a mixing and oscillation of the perturbative $chi$ and $varphi$ meson flavor states, which has effects upon meson-kink interactions.
We present a more detailed numerical investigation of the head-on collision of a two-kink/two-antikink system. We identified the escape of oscillon-like configurations as a pair of kinks of the standard $phi^4$ model moving apart from each other. New pieces of evidence support that the lump-like defects can emerge from the two-kinks interaction to form metastable configurations. Moreover, these configurations signalize the windows of escape that have a fractal structure similar to the $n$-bounce sequence when the kinks of $phi^4$ interact. As the last piece of the numerical experiment, we show that by perturbing conveniently a lump-like defect it is possible to recover another lump-like configuration as a metastable configuration.
We discuss some hitherto puzzling features of the small-scale structure of cosmic strings. We argue that kinks play a key role, and that an important quantity to study is their sharpness distribution. In particular we suggest that for very small scales the two-point correlation function of the string tangent vector varies linearly with the separation and not as a fractional power, as proposed by Polchinski and Rocha [Phys. Rev. D 74, 083504 (2006)]. However, our results are consistent with theirs, because the range of scales to which this linearity applies shrinks as evolution proceeds.
We study the creation of solitons from particles, using the $lambda phi^4$ model as a prototype. We consider the scattering of small, identical, wave pulses, that are equivalent to a sequence of particles, and find that kink-antikink pairs are created for a large region in parameter space. We also find that scattering at {it low} velocities is favorable for creating solitons that have large energy compared to the mass of a particle.
We present and study new mechanism of interaction between the solitons based on the exchange interaction mediated by the localized fermion states. As particular examples, we consider solutions of simple 1+1 dimensional scalar field theories with self-interaction potentials, including sine-Gordon model and the polynomial $phi^4$, $phi^6$ models, coupled to the Dirac fermions with back-reaction. We discover that there is an additional fermion exchange interaction between the solitons, it leads to the formation of static multi-soliton bound states. Further, we argue that similar mechanisms of formation of stable coupled multi-soliton configurations can be observed for a wide class of physical systems.
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