The Matsubara-Fradkin Thermodynamical Quantization of Podolsky Electrodynamics

In this work we apply the Matsubara-Fradkin formalism and the Nakanishi's auxiliary field method to the quantization of the Podolsky electrodynamics in thermodynamic equilibrium. This approach allows us to write consistently the path integral representation for the partition function of gauge theories in a simple manner. Furthermore, we find the Dyson-Schwinger-Fradkin equations and the Ward-Fradkin-Takahashi identities for the Podolsky theory. We also write the most general form for the polarization tensor in thermodynamic equilibrium.Comment: Submitted to Physical Review

Fluctuations and vortex pattern ordering in fully frustrated XY model with honeycomb lattice

The accidental degeneracy of various ground states in a fully frustrated XY model with a honeycomb lattice is shown to survive even when the free energy of the harmonic fluctuations is taken into account. The reason for that consists in the existence of a hidden gauge symmetry between the Hamiltonians describing the harmonic fluctuations in all these ground states. A particular vortex pattern is selected only when anharmonic fluctuations are taken into account. However, the observation of vortex ordering requires relatively large system size L>>100000.Comment: 4 pages, 2 figures, RevTeX4, a different method is used to find which state is selected by anharmonic fluctuations, the last third of the text is completly rewritte

A cluster algorithm for resistively shunted Josephson junctions

We present a cluster algorithm for resistively shunted Josephson junctions and similar physical systems, which dramatically improves sampling efficiency. The algorithm combines local updates in Fourier space with rejection-free cluster updates which exploit the symmetries of the Josephson coupling energy. As an application, we consider the localization transition of a single junction at intermediate Josephson coupling and determine the temperature dependence of the zero bias resistance as a function of dissipation strength.Comment: 4 page

Galactic longitude dependent Galactic model parameters

We present the Galactic model parameters for thin disc estimated by Sloan Digital Sky Survey (SDSS) data of 14 940 stars with apparent magnitudes $16<g_{o}\leq21$ in six intermediate latitude fields in the first Galactic quadrant. Star/galaxy separation was performed by using the $SDSS$ photometric pipeline and the isodensity contours in the $(g-r)_{0}-(r-i)_{0}$ two colour diagram. The separation of thin disc stars is carried out by the bimodal distribution of stars in the $(g-r)_{o}$ histogram, and the absolute magnitudes were evaluated by a procedure presented in the literature Bilir et al. (2005). Exponential density law fits better to the derived density functions for the absolute magnitude intervals $8<M(g)\leq9$ and $11<M(g)\leq12$, whereas sech/sech$^{2}$ laws are more appropriate for absolute magnitude intervals $9<M(g)\leq10$ and $10<M(g)\leq11$. We showed that the scaleheight and scalelength are Galactic longitude dependent. The average values and ranges of the scaleheight and the scalelength are $=220$ pc ($196\leq H \leq 234$ pc) and $=1900$ pc ($1561\leq h \leq 2280$ pc) respectively. This result would be useful to explain different numerical values claimed for those parameters obtained by different authors for the fields in different directions of the Galaxy.Comment: 28 pages, including 12 figures and 7 tables, accepted for publication in New Astronom

Measurement of charm production in deep inelastic scattering with the ZEUS detector

We present measurements of charm production in DIS using the ZEUS detector. Data with an integrated luminosity of 83 pb$^{-1}$ have been analysed. For the channel $D^{*+} \to D^{0}\pi_{s}^{+} \to K^{-}\pi^{+}\pi_{s}^{+} (+ c.c.)$ a cross section has been extracted, differential in the kinematical variables $Q^{2}$ and Bjorken $x$. In addition the decay $\overline{c}q \to e^-\overline{\nu}_e X$ has been studied in a data sample of an integrated luminosity of 34 pb$^{-1}$. This results in a cross section, differential in $Q^2$,$x$ and $W$ of the event and in $p_{T}$ and $\eta$ of the decay electron. The structure function f2-charm has also been determined for this channel. All measured cross sections show good agreement with NLO pQCD predictions from HVQDIS.Comment: 4 pages, 4 figures. As presented at DIS01 Bologna, Ital