128 research outputs found
Domain wall Skyrmions
Skyrmions of different dimensions are related by domain walls. We obtain
explicit full numerical solutions of various Skyrmion configurations trapped
inside a domain wall. We find for the quadratic mass-term that multi-Skyrmions
are ring-shaped, and conjecture for the linear mass-term, that the
lowest-energy state of multi-Skyrmions will consist of charge-2 rings
accommodated in a lattice.Comment: LaTeX: 18 pages, 14 figures; V2: typos correcte
Higher-order Skyrme hair of black holes
Higher-order derivative terms are considered as replacement for the Skyrme
term in an Einstein-Skyrme-like model in order to pinpoint which properties are
necessary for a black hole to possess stable static scalar hair. We find two
new models able to support stable black hole hair in the limit of the Skyrme
term being turned off. They contain 8 and 12 derivatives, respectively, and are
roughly the Skyrme-term squared and the so-called BPS-Skyrme-term squared. In
the twelfth-order model we find that the lower branches, which are normally
unstable, become stable in the limit where the Skyrme term is turned off. We
check this claim with a linear stability analysis. Finally, we find for a
certain range of the gravitational coupling and horizon radius, that the
twelfth-order model contains 4 solutions as opposed to 2. More surprisingly,
the lowest part of the would-be unstable branch turns out to be the stable one
of the 4 solutions.Comment: LaTeX: 51 pages, 21 figures; V2: references added and typos correcte
Knotted domain strings
We construct meta-stable knotted domain strings on the surface of a soliton
of the shape of a torus in 3+1 dimensions. We consider the simplest case of Z2
Wess-Zumino-type domain walls for which we can cover the torus with a domain
string accompanied with an anti-domain string. In this theory, all (p,q)-torus
knots can be realized as a linked pair of a(n) (un)knotted domain string and an
anti-domain string.Comment: 6 pages, 8 figures; V2: extended version with more details about the
host model, the numerics and the stability of the solution
A higher-order Skyrme model
We propose a higher-order Skyrme model with derivative terms of eighth, tenth
and twelfth order. Our construction yields simple and easy-to-interpret
higher-order Lagrangians. We first show that a Skyrmion with higher-order terms
proposed by Marleau has an instability in the form of a baby-Skyrmion string,
while the static energies of our construction are positive definite, implying
stability against time-independent perturbations. However, we also find that
the Hamiltonians of our construction possess two kinds of dynamical
instabilities, which may indicate the instability with respect to
time-dependent perturbations. Different from the well-known Ostrogradsky
instability, the instabilities that we find are intrinsically of nonlinear
nature and also due to the fact that even powers of the inverse metric gives a
ghost-like higher-order kinetic-like term. The vacuum state is, however,
stable. Finally, we show that at sufficiently low energies, our Hamiltonians in
the simplest cases, are stable against time-dependent perturbations.Comment: LaTeX: 42 pages, 3 figures; V2: simplifications implemented in Secs.
5 and 6, and references adde
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