An application of the renormalization group to the calculation of the vacuum decay rate in flat and curved space-time

I show that an application of renormalization group arguments may lead to significant corrections to the vacuum decay rate for phase transitions in flat and curved space-time. It can also give some information regarding its dependence on the parameters of the theory, including the cosmological constant in the case of decay in curved space-time.Comment: 10 pages, LaTeX, various comments and references adde

Derivative expansion and gauge independence of the false vacuum decay rate in various gauges

In theories with radiative symmetry breaking, the calculation of the false vacuum decay rate requires the inclusion of higher-order terms in the derivative expansion of the effective action. I show here that, in the case of covariant gauges, the presence of infrared singularities forbids the consistent calculation by keeping the lowest-order terms. The situation is remedied, however, in the case of $R_{\xi}$ gauges. Using the Nielsen identities I show that the final result is gauge independent for generic values of the gauge parameter $v$ that are not anomalously small.Comment: Some comments and references adde

Symmetry breaking and restoration in Lifshitz type theories

We consider the one-loop effective potential at zero and finite temperature in scalar field theories with anisotropic space-time scaling. For $z=2$, there is a symmetry breaking term induced at one-loop at zero temperature and we find symmetry restoration through a first-order phase transition at high temperature. For $z=3$, we considered at first the case with a positive mass term at tree level and found no symmetry breaking effects induced at one-loop, and then we study the case with a negative mass term at tree level where we cannot conclude about symmetry restoration effects at high temperature because of the imaginary parts that appear in the effective potential for small values of the scalar field.Comment: 11 pages, 2 figures, version accepted in Physics Letters

Symmetry breaking and restoration for interacting scalar and gauge fields in Lifshitz type theories

We consider the one-loop effective potential at zero and finite temperature in field theories with anisotropic space-time scaling, with critical exponent $z=2$, including both scalar and gauge fields. Depending on the relative strength of the coupling constants for the gauge and scalar interactions, we find that there is a symmetry breaking term induced at one-loop at zero temperature and we find symmetry restoration through a first-order phase transition at high temperature.Comment: 12 pages, 2 figures, final version accepted in Phys. Let

Hard thermal loops with a background plasma velocity

I consider the calculation of the two and three-point functions for QED at finite temperature in the presence of a background plasma velocity. The final expressions are consistent with Lorentz invariance, gauge invariance and current conservation, pointing to a straightforward generalization of the hard thermal loop formalism to this physical situation. I also give the resulting expression for the effective action and identify the various terms.Comment: 11 pages, no figure

Plasmon interactions in the quark-gluon plasma

Yang-Mills theory at finite temperature is rewritten as a theory of plasmons which provides a Hamiltonian framework for perturbation theory with resummation of hard thermal loops.Comment: 12 pages, LaTeX, minor typos corrected, discussion adde

A Finite Element Model of the Breast for Predicting Mechanical Deformations during Biopsy Procedures

Currently, High Field (1.5T) Superconducting MR image-guided needle breast procedures allow the physician only to calculate approximately the location and extent of a cancerous tumor in the compressed patient breast before inserting the needle. It can then become relatively uncertain that the tissue specimen removed during the biopsy actually belongs to the lesion of interest. A new method for guiding clinical breast biopsy is presented, based on a deformable finite element model of the breast. The geometry of the model is constructed from MR data, and its mechanical properties are modeled using a non-linear material model. This method allows imaging the breast without compression before the procedure, then compressing the breast and using the finite element model to predict the tumor’s position during the procedure