Effective Theories for Hot Non-Abelian Dynamics

The dynamics of soft ($|\vec{p}|\sim g^2 T$) non-Abelian gauge fields at finite temperature is non-perturbative. The effective theory for the soft fields can be obtained by first integrating out the momentum scale T, which yields the well known hard thermal loop effective theory. Then the latter is used to integrate out the scale gT. One obtains a Boltzmann equation, which can be solved in a leading logarithmic approximation. The resulting effective theory for the soft fields is described by a Langevin equation, and it is well suited for non-perturbative lattice simulations.Comment: 11 pages, 3 figures; plenary talk given at Conference on Strong and Electroweak Matter (SEWM 98), Copenhagen, Denmark, 2-5 Dec 199

Diagrammatic approach to soft non-Abelian dynamics at high temperature

The dynamics of soft ($|\vec{p}|\sim g^2 T$) non-Abelian gauge fields at finite temperature is non-perturbative. The effective theory for the soft scale is determined by diagrams with external momenta p_0\lsim g^2 T, $|\vec{p}|\sim g^2 T$ and loop momenta larger than $g^2 T$. We consider the polarization tensor beyond the hard thermal loop approximation, which accounts for loop momenta of order $T$. There are higher loop diagrams, involving also the scale $gT$, which are as important as the hard thermal loops. These higher loop contributions are characteristic for non-Abelian gauge theories and their calculation is simplified by using the hard thermal loop effective theory. Remarkably, the effective one-loop polarization tensor is found to be gauge fixing independent and transverse at leading order in $g$. The transversality indicates that this approach leads to a gauge invariant effective theory.Comment: 23 pages, latex, 4 figures, uses axodraw.sty; discussion of higher loop contributions and of their relation to the Boltzmann equation (Sect. 5) added, several references added, to appear in Nucl. Phys.

Plasmon properties in classical lattice gauge theory

In order to investigate the features of the classical approximation at high temperatures for real time correlation functions, the plasmon frequencies and damping rates were recently computed numerically in the SU(2)+Higgs model and in the pure SU(2) theory. We compare the lattice results with leading order hard thermal loop resummed perturbation theory. In the broken phase of the SU(2)+Higgs model, we show that the lattice results can be reproduced and that the lattices used are too coarse to observe some important plasmon effects. In the symmetric phase, the main qualitative features of the lattice results can also be understood. In the pure SU(2) theory, on the other hand, there are discrepancies which might point to larger Landau and plasmon damping effects than indicated by perturbation theory.Comment: 17 pages, 5 figures. A few points written more clearly (e.g., in the abstract). A note added concerning two recent papers. Conclusions unchanged. To appear in Phys.Lett.

Finite baryon density effects on gauge field dynamics

We discuss the effective action for QCD gauge fields at finite temperatures and densities, obtained after integrating out the hardest momentum scales from the system. We show that a non-vanishing baryon density induces a charge conjugation (C) odd operator to the gauge field action, proportional to the chemical potential. Even though it is parametrically smaller than the leading C even operator, it could have an important effect on C odd observables. The same operator appears to be produced by classical kinetic theory, allowing in principle for a non-perturbative study of such processes.Comment: 20 page

Equilibration of right-handed electrons

We study the equilibration of right-handed electrons in the symmetric phase of the Standard Model. Due to the smallness of the electron Yukawa coupling, it happens relatively late in the history of the Universe. We compute the equilibration rate at leading order in the Standard Model couplings, by including gauge interactions, the top Yukawa- and the Higgs self-interaction. The dominant contribution is due to $2 \to 2$ particle scattering, even though the rate of (inverse) Higgs decays is strongly enhanced by multiple soft scattering which is included by Landau-Pomeranchuk-Migdal (LPM) resummation. Our numerical result is substantially larger than approximations presented in previous literature.Comment: 31 pages, 5 figures. v2: Added appendix estimating the conversion of right-handed electron number into hypermagnetic fields through the chiral anomaly. References added, minor errors corrected, results and conclusions unchanged, published versio

An effective theory for hot non-Abelian dynamics

I try to explain some recent progress in understanding the non-perturbative dynamics of hot non-Abelian gauge theories. The non-perturbative physics is due to soft spatial momenta $|\vec{p}|\sim g^2 T$ where $g$ is the gauge coupling and $T$ is the temperature. An effective theory for the soft field modes is obtained by integrating out the field modes with momenta of order $T$ and of order $g T$ in a leading logarithmic approximation. In this effective theory the time evolution of the soft fields is determined by a local Langevin-type equation. This effective theory determines the parametric form of the rate for hot electroweak baryon number violation as $\Gamma = \kappa g^{10} \log(1/g) T^4$. The non-perturbative coefficient $\kappa$ is independent of the gauge coupling and it can be computed by solving the effective equations of motion on a lattice.Comment: 10 pages, revtex, Talk presented at the 5th International Workshop on Thermal Field Theories and their Applications, Regensburg, Germany, August 199

The Contribution of Patient Reported Outcome Measures to Shared Decision-Making in Radiation Oncology at a Midwestern Comprehensive Cancer Center

Background. Chronic diseases, such as lung cancer, require a provider-patient relationship developed over time. This relationship fosters shared decision-making (SDM), a collaborative, dynamic information exchange and analysis between provider and patient regarding treatment and desired outcomes. Established benefits to SDM include an improved quality of life and decreased anxiety and depression. Despite established benefits, recent research suggests radiation oncologists are not engaging in SDM. A decision-aid tool utilizing patient reported outcome measures may increase SDM between radiation oncologists and patients with lung cancer. Patient-reported outcome measures, wherein the patient provides direct assessment of their health and quality of life, can inform and initiate SDM. This study investigated the design and implementation of a collaborative decision-aid tool for patients with lung cancer at a Midwestern cancer center as informed by stakeholders, practice considerations, and the evidence base. Objectives. The primary objective was to develop a collaborative decision-aid tool, using patient-reported outcome measures, that can be implemented in an academic radiation oncology clinic. Secondary objectives then assessed the tool’s impact through surrogates of shared decision making (add-on oncology visits, concomitant medication prescriptions), medical management (adverse events, radiation therapy compliance, chemotherapy compliance) and emergent care and its costs (emergency room visits and estimated costs, inpatient admissions and estimated costs). The hypothesized result was a decision aid designed to increase collaborative communication between radiation oncologists and patients will result in improved shared decision making, yielding better medical management and patient outcomes and reducing emergent care costs. Lastly, an implementation roadmap provided information on experienced barriers, facilitators, and considerations for performance objectives. Materials and Methods. A sequential exploratory mixed methods design was employed. The qualitative strand explored how stakeholders, practice considerations, and the evidence base informed the design and installation of an ideal collaborative decision-aid tool. Semi-structured interviews were completed with both patients who completed radiation therapy for lung cancer and their radiation oncologist. Interviews were coded and evaluated for themes. Interviews were transcribed verbatim, coded using Atlas.ti software, and analyzed thematically and visually. The results of this analysis, combined with information from the literature base and implementation stakeholders, was used to inform design of the collaborative decision-aid tool that was installed employing the principles of clinical implementation using the plan-do-study-act (PDSA) implementation cycle model. Simple descriptive analysis was performed on objective measures. Mixed analysis included data display, comparison, and integration. Results. Six patients and six radiation oncologists participated in the semi-structured interviews. Interviews provided insights that patients did not know what to ask of their radiation oncologists, prioritized survival over reduced side effects, and minimized complaints to their radiation oncologists, often to their detriment. Interviews yielded feedback on commonly used patient reported outcome instruments, identifying context as important and the recall timeframe as difficult. Commonly patient-identified adverse events of concern were fatigue, dyspnea, vomiting, and dysphagia. Radiation oncologists identified a patient’s personality as critical to care and translating responses and symptoms to adverse events of treatment. For this reason, numeric scales were not endorsed as they were seen as ambiguous and lacking context. With this feedback, a collaborative decision-aid tool was designed that focused on adverse events of interest (nausea, vomiting, fatigue, dyspnea, chest pain, weight loss). Rather than numeric scales, responses provided granular context that clued physicians to medical needs (i.e., “I cannot walk to my appointment,” “It hurts when I eat,” “I am not vomiting but I’m not hungry”). This tool was implemented as a quality initiative project for pragmatic impact. Four patients were assigned the tool during the first PDSA implementation cycle. The first follow-up evaluation meeting identified four critical outcomes for the next implementation cycle: how to identify which consults require the decision-aid, how the need for the decision-aid on doctor visits is consistently provided to scheduling, how unplanned visits/special complaints are addressed with regard to the decision-aid, and what actions are necessary if the patient leaves prior to the decision-aid being reviewed. Mixed analysis provided direction for next steps in implementation, tool design, and quantitative data measures. The primary concern, increase in time expended per clinic visit, was not supported by the limited data available from the first implementation cycle. Conclusion. Implementation of collaborative decision-aid within the radiation oncology clinic is feasible without disruption of the on-treatment visit time. Radiation oncologists can use the tool as a guide for routine on-treatment visit review, so that it is harmonized with their routine practice. Care should be taken during implementation to ensure all stakeholders are included in the tool’s implementation and that desired outcomes are appropriately identified to truly capture what impact the tool has, if any, on clinical outcomes. Focusing on the patient with the goal of improving their experience will guide collaborative decision-aid tool adaptation, implementation, and uptake

Changes in the polar vortex: Effects on Antarctic total ozone observations at various stations

October mean total column ozone data from four Antarctic stations form the basis for understanding the evolution of the ozone hole since 1960. While these stations show similar emergence of the ozone hole from 1960 to 1980, the records are divergent in the last two decades. The effects of long-term changes in vortex shape and location are considered by gridding the measurements by equivalent latitude. A clear eastward shift of the mean position of the vortex in October with time is revealed, which changes the fraction of ozone measurements taken inside/outside the vortex for stations in the vortex collar region. After including only those measurements made inside the vortex, ozone behavior in the last two decades at the four stations is very similar. This suggests that dynamical influence must be considered when interpreting and intercomparing ozone measurements from Antarctic stations for detecting ozone recovery and ozone-related changes in Antarctic climate

QCD plasma instability and thermalisation at heavy ion collisions

Under suitable non-equilibrium conditions QCD plasma can develop plasma instabilities, where some modes of the plasma grow exponentially. It has been argued that these instabilities can play a significant role in the thermalisation of the plasma in heavy-ion collision experiments. We study the instability in SU(2) plasmas using the hard thermal loop effective lattice theory, which is suitable for studying real-time evolution of long wavelength modes in the plasma. We observe that under suitable conditions the plasma can indeed develop an instability which can grow to a very large magnitude, necessary for the rapid thermalisation in heavy-ion collisions.Comment: 7 pages, contribution to Lattice 2007, Regensburg, Germany, 30 July - 4 August 200

Can electroweak bubble walls run away?

In extensions of the Standard Model with SU(2) singlet scalar fields, there can be regions of parameter space for which the electroweak phase transition is first order already at the mean-field level of analysis. We show that in this case the phase interface (bubble wall) can become ultra-relativistic, with the relativistic gamma factor gamma = (1-v_{wall}^2)^{-1/2} growing linearly with the wall's propagation distance. We provide a simple criterion for determining whether the bubble wall "runs away" in this way or if gamma approaches a terminal value.Comment: references adde