Self-duality and associated parallel or cocalibrated G2{\mathrm{G}}_2 structures

We find a remarkable family of $\mathrm{G}_2$ structures defined on certain principal $\mathrm{SO}(3)$-bundles $P_\pm\longrightarrow M$ associated with any given oriented Riemannian 4-manifold $M$. Such structures are always cocalibrated. The study starts with a recast of the Singer-Thorpe equations of 4-dimensional geometry. These are applied to the Bryant-Salamon cons\-truction of complete $\mathrm{G}_2$-holonomy metrics on the vector bundle of self- or anti-self-dual 2-forms on $M$. We then discover new examples of that special holonomy on disk bundles over ${\cal H}^4$ and ${\cal H}^2_{\mathbb{C}}$, respectively, the real and complex hyperbolic space. Only in the end we present the new $\mathrm{G}_2$ structures on principal bundles.Comment: 20 pages; final version, to appear in Annales Academi{\ae} Scientiarum Fennic{\ae

Production and spectroscopy of hadrons containing a b quark at ATLAS

We present studies of the production and spectroscopy of some members of the B-hadron family. We reconstruct B ground states in their hadronic decay modes with a J/{\psi} or {\Upsilon} in the final state. These studies are based on the 2011 7 TeV dataset collected by the ATLAS detector.Comment: Presentation at the DPF 2013 Meeting of the American Physical Society Division of Particles and Fields, Santa Cruz, California, August 13-17, 2013. 11 pages, 12 figure

On the Stability of Randall-Sundrum Braneworlds with Conformal Bulk Fields

In the Randall-Sundrum scenario we consider exact 5-dimensional solutions with localized gravity which are associated with a well defined class of conformal bulk fields. We analyze their behaviour under radion field perturbations. We show that if the Randall-Sundrum exponential warp is the localizing metric function and the equation of state of the conformal fields is not changed by the radion perturbation then the 5-dimensional solutions are unstable. We present new stable solutions which describe on the brane the dynamics of inhomogeneous dust, generalized dark radiation and homogeneous polytopic matter.Comment: 10 pages, latex, no figures. Contribution to the special issue of Vestnik of Tomsk State Pedagogical University in the field QFT/Cosmology/Gravity/Strings, edited by Sergei D. Odintso

Improving Demand Modeling in California\u27s Rail Transit System

This paper analyzes urban rail-fare elasticity and compares the results across four California transit systems. A method of Internet search is adopted to collect monthly transit-fare records from 2002 to 2013. This paper contributes towards improving demand modeling for public transit using more precise and monthly data and applies econometric techniques involving autoregressive integrated moving average (ARIMA) and panel data models. Results show that demand for public transit in California is very inelastic. Any ridership promotion policy may have a heterogeneous impact across transit systems