12 research outputs found
Electrodynamic Limit in a Model for Charged Solitons
We consider a model of topological solitons where charged particles have
finite mass and the electric charge is quantised already at the classical
level. In the electrodynamic limit, which physically corresponds to
electrodynamics of solitons of zero size, the Lagrangian of this model has two
degrees of freedom only and reduces to the Lagrangian of the Maxwell field in
dual representation. We derive the equations of motion and discuss their
relations with Maxwell's equations. It is shown that Coulomb and Lorentz forces
are a consequence of topology. Further, we relate the U(1) gauge invariance of
electrodynamics to the geometry of the soliton field, give a general relation
for the derivation of the soliton field from the field strength tensor in
electrodynamics and use this relation to express homogeneous electric fields in
terms of the soliton field.Comment: 13 pages, 4 figures, Introduction and Section II (Model Lagrangian)
rewritten, new chapters concerning electrodynamic limit and discussion of
causality inserte
Low Temperature Static and Dynamic Behavior of the Two-Dimensional Easy-Axis Heisenberg Model
We apply the self-consistent harmonic approximation (SCHA) to study static
and dynamic properties of the two-dimensional classical Heisenberg model with
easy-axis anisotropy. The static properties obtained are magnetization and spin
wave energy as functions of temperature, and the critical temperature as a
function of the easy-axis anisotropy. We also calculate the dynamic correlation
functions using the SCHA renormalized spin wave energy. Our analytical results,
for both static properties and dynamic correlation functions, are compared to
numerical simulation data combining cluster-Monte Carlo algorithms and Spin
Dynamics. The comparison allows us to conclude that far below the transition
temperature, where the SCHA is valid, spin waves are responsible for all
relevant features observed in the numerical simulation data; topological
excitations do not seem to contribute appreciably. For temperatures closer to
the transition temperature, there are differences between the dynamic
correlation functions from SCHA theory and Spin Dynamics; these may be due to
the presence of domain walls and solitons.Comment: 12 pages, 14 figure
Localized D-dimensional global k-defects
We explicitly demonstrate the existence of static global defect solutions of
arbitrary dimensionality whose energy does not diverge at spatial infinity, by
considering maximally symmetric solutions described by an action with
non-standard kinetic terms in a D+1 dimensional Minkowski space-time. We
analytically determine the defect profile both at small and large distances
from the defect centre. We verify the stability of such solutions and discuss
possible implications of our findings, in particular for dark matter and charge
fractionalization in graphene.Comment: 6 pages, published versio
Gendered representations in Hawaiâiâs anti-GMO activism
The aim of this article is to analyse some of the representations of intersectional gender that materialise in activism against genetically modified organisms (GMOs). It uses the case of Hawaiâi as a key node in global transgenic seed production and hotspot for food, land and farming controversies. Based on ethnographic work conducted since 2012, the article suggests some of the ways that gender is represented within movements against GMOs by analysing activist media representations. The article shows how gender, understood intersectionally, informs possibilities for movement-identification, exploring how themes of motherhood, warrior masculinities and sexualised femininities are represented within these movements. The article suggests that some activist representations of gender invoke what could be considered as normative framings of gender similar to those seen in other environmental, food and anti-GMO movements. It is suggested that these gendered representations may influence and limit how different subjects engage with Hawai'i anti-GMO movements. At the same time, contextual, intersectional readings demonstrate the complex histories behind what appear to be gender normative activist representations. Taken together, this emphasis on relative norms of femininities and masculinities may provide anti-GMO organising with familiar social frames that counterbalance otherwise threatening campaigns against (agri)business in the settler state. Understood within these histories, the work that gender does within anti-GMO organising may offer generative examples for thinking through the relationships between gendered representations and situated, indigenous-centred, food and land-based resistances