A Linear Sigma Model with Three Flavors and Vector and Axial-Vector Mesons

We outline the extension of the globally chirally invariant Nf = 2 linear sigma model with vector and axial-vector degrees of freedom to Nf=3. We present preliminary results concerning the scalar meson masses.Comment: Prepared for the Proceedings of the 11th International Workshop on Meson Production, Properties and Interaction (MESON 2010), in Krakow, Poland, 10-15 June 2010. Three page

Center Vortex Model for the Infrared Sector of SU(3) Yang-Mills Theory - Vortex Free Energy

The vortex free energy is studied in the random vortex world-surface model of the infrared sector of SU(3) Yang-Mills theory. The free energy of a center vortex extending into two spatial directions, which is introduced into Yang-Mills configurations when acting with the 't Hooft loop operator, is verified to furnish an order parameter for the deconfinement phase transition. It is shown to exhibit a weak discontinuity at the critical temperature, corresponding to the weak first order character of the transition.Comment: 13 pages, 2 figures containing 3 eps file

Scalar mesons in a linear sigma model with (axial-)vector mesons

The structure of the scalar mesons has been a subject of debate for many decades. In this work we look for $\bar{q}q$ states among the physical resonances using an extended Linear Sigma Model that contains scalar, pseudoscalar, vector, and axial-vector mesons both in the non-strange and strange sectors. We perform global fits of meson masses, decay widths and amplitudes in order to ascertain whether the scalar $\bar{q}q$ states are below or above 1 GeV. We find the scalar states above 1 GeV to be preferred as $\bar{q}q$ states.Comment: 6 pages, 1 figure, To appear in the proceedings of the XII. Hadron Physics Conference, Bento Goncalves, Brasil, April, 22 - 27, 201

Principal Component Analysis of RR Lyrae light curves

In this paper, we analyze the structure of RRab star light curves using Principal Component Analysis. We find this is a very efficient way to describe many aspects of RRab light curve structure: in many cases, a Principal Component fit with 9 parameters can describe a RRab light curve including bumps whereas a 17 parameter Fourier fit is needed. As a consequence we show statistically why the amplitude is also a good summary of the structure of a RR Lyrae light curve. We also use our analysis to derive an empirical relation relating absolute magnitude to light curve structure. In comparing this formula to those derived from exactly the same dataset but using Fourier parameters, we find that the Principal Component Analysis approach has disticnt advantages. These advantages are, firstly, that the errors on the coefficients in such formulae are smaller, and secondly, that the correlation between Principal Components is significantly smaller than the correlation between Fourier amplitudes. These two factors lead to reduced formal errors, in some cases estimated to be a factor of 2, on the eventual fitted value of the absolute magnitude. This technique will prove very useful in the analysis of data from existing large scale survey projects concerning variable stars.Comment: 8 pages, 10 figures, revised version, accepted for publication to MNRA