3,081 research outputs found

### Instabilities of noncommutative two dimensional BF model

The noncommutative extension of two dimensional BF model is considered. It is
shown that the realization of the noncommutative map via the Groenewold-Moyal
star product leads to instabilities of the action, hence to a non
renormalizable theory.Comment: 9 page

### FROM THE CONCEPT OF MULTIFUNCTIONAL AGRICULTURE TO THE MEASURE OF MULTIFUNCTIONAL FARMING

The objective of this paper is to deeply analyze some of the theoretical and methodological implications linked to the definition, the characterization, the evaluation and the estimation of the economic results of a multifunction agricultural farm. A deep study of these aspects seems essential for two reasons. On one hand, society is pressing farms to enlarge the existing set of goods and services; on the other hand, sector policies offer to farms new opportunities, which regard the allocation of services linked to the different functions that agriculture is able to carry out. In these conditions, in order to make the entrepreneur able to decide which services to set in motion, considering the economical input that their activation could bring to the farm, it is fundamental to identify an analytic method that is capable to estimate and evaluate the economic results of a multifunction farm.Multifunctionality, Economic indicators, Rural development, Agribusiness, Labor and Human Capital, Teaching/Communication/Extension/Profession,

### 3D Dynamics of 4D Topological BF Theory With Boundary

We consider the four dimensional abelian topological BF theory with a planar
boundary introduced following the Symanzik's method. We find the most general
boundary conditions compatible with the fields equations broken by the
boundary. The residual gauge invariance is described by means of two Ward
identities which generate an algebra of conserved currents. We interpret this
algebra as canonical commutation relations of fields, which we use to construct
a three dimensional Lagrangian. As a remarkable by-product, the (unique)
boundary condition which we found, can be read as a duality relation between 3D
dynamical variables.Comment: 22 pages, no figures, version to appear on New Journal of Physic

### Comment on the ``$\theta$-term renormalization in the (2+1)-dimensional $CP^{N-1}$ model with $\theta$ term''

It is found that the recently published first coefficient of nonzero
$\beta$-function for the Chern-Simons term in the $1/N$ expansion of the
$CP^{N-1}$ model is untrue numerically. The correct result is given. The main
conclusions of Park's paper are not changed.Comment: 3 pages, LATE

### Signatures of the transition from galactic to extragalactic cosmic rays

We discuss the signatures of the transition from galactic to extragalactic
cosmic rays in different scenarios, giving most attention to the dip scenario.
The dip is a feature in the diffuse spectrum of ultra-high energy (UHE) protons
in the energy range $1\times 10^{18} - 4\times 10^{19}$ eV, which is caused by
electron-positron pair production on the cosmic microwave background (CMB)
radiation. The dip scenario provides a simple physical description of the
transition from galactic to extragalactic cosmic rays. Here we summarize the
signatures of the pair production dip model for the transition, most notably
the spectrum, the anisotropy and the chemical composition. The main focus of
our work is however on the description of the features that arise in the
elongation rate and in the distribution of the depths of shower maximum $X_{\rm
max}$ in the dip scenario. We find that the curve for $X_{\max}(E)$ shows a
sharp increase with energy, which reflects a sharp transition from an iron
dominated flux at low energies to a proton dominated flux at $E\sim 10^{18}$
eV. We also discuss in detail the shape of the $X_{\max}$ distributions for
cosmic rays of given energy and demonstrate that this represents a powerful
tool to discriminate between the dip scenario and other possible models of the
transition.Comment: Version accepted for publication in Physical Review

### Vector Supersymmetry of 2D Yang-Mills Theory

The vector supersymmetry of the 2D topological BF model is extended to 2D
Yang-Mills. The consequences of the corresponding Ward identity on the
ultraviolet behavior of the theory are analyzed.Comment: Some references adde

### Secondary Cosmic Ray Nuclei from Supernova Remnants and Constraints to the Propagation Parameters

The secondary-to-primary B/C ratio is widely used to study the cosmic ray
(CR) propagation processes in the Galaxy. It is usually assumed that secondary
nuclei such as Li-Be-B are entirely generated by collisions of heavier CR
nuclei with the interstellar medium (ISM). We study the CR propagation under a
scenario where secondary nuclei can also be produced or accelerated from
galactic sources. We consider the processes of hadronic interactions inside
supernova remnants (SNRs) and re-acceleration of background CRs in strong
shocks. Thus, we investigate their impact in the propagation parameter
determination within present and future data. The spectra of Li-Be-B nuclei
emitted from SNRs are harder than those due to CR collisions with the ISM. The
secondary-to-primary ratios flatten significantly at ~TeV/n energies, both from
spallation and re-acceleration in the sources. The two mechanisms are
complementary to each other and depend on the properties of the local ISM
around the expanding remnants. The secondary production in SNRs is significant
for dense background media, n ~1 cm^-3, while the amount of re-accelerated CRs
is relevant for SNRs expanding into rarefied media, n ~0.1 cm-3. Due to these
effects, the the diffusion parameter 'delta' may be misunderstood by a factor
of ~5-15%. Our estimations indicate that an experiment of the AMS-02 caliber
can constrain the key propagation parameters while breaking the
source-transport degeneracy, for a wide class of B/C-consistent models. Given
the precision of the data expected from on-going experiments, the SNR
production/acceleration of secondary nuclei should be considered, if any, to
prevent a possible mis-determination of the CR transport parameters.Comment: 13 pages, 9 figures; matches the published versio

### N=2 SYM Action as a BRST Exact Term, Topological Yang Mills and Instantons

By constructing a nilpotent extended BRST operator \bs that involves the
N=2 global supersymmetry transformations of one chirality, we show that the
standard N=2 off-shell Super Yang Mills Action can be represented as an exact
BRST term \bs \Psi, if the gauge fermion $\Psi$ is allowed to depend on the
inverse powers of supersymmetry ghosts. By using this nonanalytical structure
of the gauge fermion (via inverse powers of supersymmetry ghosts), we give
field redefinitions in terms of composite fields of supersymmetry ghosts and
N=2 fields and we show that Witten's topological Yang Mills theory can be
obtained from the ordinary Euclidean N=2 Super Yang Mills theory directly by
using such field redefinitions. In other words, TYM theory is obtained as a
change of variables (without twisting). As a consequence it is found that
physical and topological interpretations of N=2 SYM are intertwined together
due to the requirement of analyticity of global SUSY ghosts. Moreover, when
after an instanton inspired truncation of the model is used, we show that the
given field redefinitions yield the Baulieu-Singer formulation of Topological
Yang Mills.Comment: Latex, 1+15 pages. Published versio

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