19,240 research outputs found
Canonical Quantization of the Self-Dual Model coupled to Fermions
This paper is dedicated to formulate the interaction picture dynamics of the
self-dual field minimally coupled to fermions. To make this possible, we start
by quantizing the free self-dual model by means of the Dirac bracket
quantization procedure. We obtain, as result, that the free self-dual model is
a relativistically invariant quantum field theory whose excitations are
identical to the physical (gauge invariant) excitations of the free
Maxwell-Chern-Simons theory. The model describing the interaction of the
self-dual field minimally coupled to fermions is also quantized through the
Dirac bracket quantization procedure. One of the self-dual field components is
found not to commute, at equal times, with the fermionic fields. Hence, the
formulation of the interaction picture dynamics is only possible after the
elimination of the just mentioned component. This procedure brings, in turns,
two new interaction terms, which are local in space and time while
non-renormalizable by power counting. Relativistic invariance is tested in
connection with the elastic fermion-fermion scattering amplitude. We prove that
all the non-covariant pieces in the interaction Hamiltonian are equivalent to
the covariant minimal interaction of the self-dual field with the fermions. The
high energy behavior of the self-dual field propagator corroborates that the
coupled theory is non-renormalizable. Certainly, the self-dual field minimally
coupled to fermions bears no resemblance with the renormalizable model defined
by the Maxwell-Chern-Simons field minimally coupled to fermions.Comment: 16 pages, no special macros, no corrections in the pape
Noncommuting Electric Fields and Algebraic Consistency in Noncommutative Gauge theories
We show that noncommuting electric fields occur naturally in
-expanded noncommutative gauge theories. Using this noncommutativity,
which is field dependent, and a hamiltonian generalisation of the
Seiberg-Witten Map, the algebraic consistency in the lagrangian and hamiltonian
formulations of these theories, is established. A comparison of results in
different descriptions shows that this generalised map acts as canonical
transformation in the physical subspace only. Finally, we apply the hamiltonian
formulation to derive the gauge symmetries of the action.Comment: 16 pages, LaTex, considerably expanded version with a new section on
`Gauge symmetries'; To appear in Phys. Rev.
Hierarchical spatial models for predicting tree species assemblages across large domains
Spatially explicit data layers of tree species assemblages, referred to as
forest types or forest type groups, are a key component in large-scale
assessments of forest sustainability, biodiversity, timber biomass, carbon
sinks and forest health monitoring. This paper explores the utility of coupling
georeferenced national forest inventory (NFI) data with readily available and
spatially complete environmental predictor variables through spatially-varying
multinomial logistic regression models to predict forest type groups across
large forested landscapes. These models exploit underlying spatial associations
within the NFI plot array and the spatially-varying impact of predictor
variables to improve the accuracy of forest type group predictions. The
richness of these models incurs onerous computational burdens and we discuss
dimension reducing spatial processes that retain the richness in modeling. We
illustrate using NFI data from Michigan, USA, where we provide a comprehensive
analysis of this large study area and demonstrate improved prediction with
associated measures of uncertainty.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS250 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Rotational spectroscopy of AlO: Low N transitions of astronomical interest in the X^2 Sigma^+ state
The detection of rotational transitions of the AlO radical at millimeter
wavelengths from an astronomical source has recently been reported. In view of
this, rotational transitions in the ground X^2 Sigma^+ state of AlO have been
reinvestigated. Comparisons between Fourier transform and microwave data
indicate a discrepancy regarding the derived value of gamma_D in the v = 0
level of the ground state. This discrepancy is discussed in the light of
comparisons between experimental data and synthesized rotational spectra in the
v = 0, 1 and 2 levels of X^2 Sigma^+. A list of calculated rotational lines in
v = 0, 1 and 2 of the ground state up to N' = 11 is presented which should aid
astronomers in analysis and interpretation of observed AlO data and also
facilitate future searches for this radical.Comment: To appear in Astronomy and Astrophysic
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