18,986 research outputs found
Testing symmetries in effective models of higher derivative field theories
Higher derivative field theories with interactions raise serious doubts about
their validity due to severe energy instabilities. In many cases the
implementation of a direct perturbation treatment to excise the dangerous
negative-energies from a higher derivative field theory may lead to violations
of Lorentz and other symmetries. In this work we study a perturbative
formulation for higher derivative field theories that allows the construction
of a low-energy effective field theory being a genuine perturbations over the
ordinary-derivative theory and having a positive-defined Hamiltonian. We show
that some discrete symmetries are recovered in the low-energy effective theory
when the perturbative method to reduce the negative-energy degrees of freedom
from the higher derivative theory is applied. In particular, we focus on the
higher derivative Maxwell-Chern-Simons model which is a Lorentz invariant and
parity-odd theory in 2+1 dimensions. The parity violation arises in the
effective action of QED as a quantum correction from the massive fermionic
sector. We obtain the effective field theory which remains Lorentz invariant,
but parity invariant to the order considered in the perturbative expansion.Comment: 13 pages, Sec. III, additional references added, P symmetry revised,
accepted for publication in PR
Nongauge bright soliton of the nonlinear Schrodinger (NLS) equation and a family of generalized NLS equations
We present an approach to the bright soliton solution of the NLS equation
from the standpoint of introducing a constant potential term in the equation.
We discuss a `nongauge' bright soliton for which both the envelope and the
phase depend only on the traveling variable. We also construct a family of
generalized NLS equations with solitonic sech^p solutions in the traveling
variable and find an exact equivalence with other nonlinear equations, such as
the Korteveg-de Vries and Benjamin-Bona-Mahony equations when p=2Comment: ~4 pages, 3 figures, 16 references, published versio
- …