Renormalization of Scalar and Yukawa Field Theories with Lorentz Violation

We consider a theory of scalar and spinor fields, interacting through Yukawa and phi^4 interactions, with Lorentz-violating operators included in the Lagrangian. We compute the leading quantum corrections in this theory. The renormalizability of the theory is explicitly shown up to one-loop order. In the pure scalar sector, the calculations can be generalized to higher orders and to include finite terms, because the theory can be solved in terms of its Lorentz-invariant version.Comment: 30 page

Radiatively Induced Lorentz and Gauge Symmetry Violation in Electrodynamics with Varying alpha

A time-varying fine structure constant alpha(t) could give rise to Lorentz- and CPT-violating changes to the vacuum polarization, which would affect photon propagation. Such changes to the effective action can violate gauge invariance, but they are otherwise permitted. However, in the minimal theory of varying alpha, no such terms are generated at lowest order. At second order, vacuum polarization can generate an instability--a Lorentz-violating analogue of a negative photon mass squared -m^2 proportional to alpha [(d alpha/dt) / alpha]^2 log (Lambda^2), where Lambda is the cutoff for the low-energy effective theory.Comment: 14 page

Accuracy Improvement of Real-Time Load-Pull Measurements

This paper describes a new procedure aimed to improve the effectiveness of real-time load-pull calibration. Loadpull measurement accuracy is strongly affected by calibration residual uncertainty. The novel methodology reduces this uncertainty contribution by means of error terms optimization. The proposed method has been tested with simulations and applied to actual measurement data. Considerable improvements have been achieve

Interplane charge dynamics in a valence-bond dynamical mean-field theory of cuprate superconductors

We present calculations of the interplane charge dynamics in the normal state of cuprate superconductors within the valence-bond dynamical mean-field theory. We show that by varying the hole doping, the c-axis optical conductivity and resistivity dramatically change character, going from metallic-like at large doping to insulating-like at low-doping. We establish a clear connection between the behavior of the c-axis optical and transport properties and the destruction of coherent quasiparticles as the pseudogap opens in the antinodal region of the Brillouin zone at low doping. We show that our results are in good agreement with spectroscopic and optical experiments.Comment: 5 pages, 3 figure

A hybrid numerical flux for supersonic flows with application to rocket nozzles

The numerical simulation of shock waves in supersonic flows is challenging because of several instabilities which can affect the solution. Among them, the carbuncle phenomenon can introduce nonphysical perturbations in captured shock waves. In the present work, a hybrid numerical flux is proposed for the evaluation of the convective fluxes that avoids carbuncle and keeps high-accuracy on shocks and boundary layers. In particular, the proposed flux is a combination between an upwind approximate Riemann problem solver and the Local Lax-Friedrichs scheme. A simple strategy to mix the two fluxes is proposed and tested in the framework of a discontinuous Galerkin discretisation. The approach is investigated on the subsonic flow in a channel, on the supersonic flow around a cylinder, on the supersonic flow on a flat plate and on the flow in a overexpanded rocket nozzle