3,081 research outputs found

    Instabilities of noncommutative two dimensional BF model

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    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


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    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

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    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 ``őł\theta-term renormalization in the (2+1)-dimensional CPN‚ąí1CP^{N-1} model with őł\theta term''

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    It is found that the recently published first coefficient of nonzero ő≤\beta-function for the Chern-Simons term in the 1/N1/N expansion of the CPN‚ąí1CP^{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

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    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√ó1018‚ąí4√ó10191\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 XmaxX_{\rm max} in the dip scenario. We find that the curve for Xmax‚Ā°(E)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‚ąľ1018E\sim 10^{18} eV. We also discuss in detail the shape of the Xmax‚Ā°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

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    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

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    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

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    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 ő®\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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