Aspects of the Electroweak Phase Transition

Presented at the 1992 Meeting of the DPF, Fermilab. The electroweak phase transition is reviewed in light of some recent developments. Emphasis is on the issue whether the transition is first or second order and its possible role in the generation of the baryon asymmetry of the universe.Comment: 5 page

Aspects of SU(N_c) Gauge Theories in the Limit of Small Number of Colors

We investigate properties of the color space of $SU(N_c)$ gauge theories in the limit of small number of colors $(N_c \to 0)$ and large number of flavors. More generally, we introduce a rescaling of $\alpha_s$ and $n_f$ which assigns a finite limit to colored quantities as $N_c \to 0$, which reproduces their known large-$N_c$ limit, and which expresses them as an analytic function of $N_c^2$ for arbitrary value of $N_c$. The vanishing-$N_c$ limit has an Abelian character and is also the small-$N_c$ limit of $[U(1)]^{N_c-1}$. This limit does not have an obvious quantum field theory interpretation; however, it provides practical consistency checks on QCD perturbative quantities by comparing them to their QED counterparts. Our analysis also describes the two-dimensional topological structure involved in the interpretation of the small $N_c$-limit in color space.Comment: Contract number added, LaTex, 16 page

Long Range Physics in a Hot Non-Abelian Plasma

We derive a set of equations describing the real time dynamics of modes with spatial momentum of order g^2 T in a high temperature gauge theory, where g is the coupling constant and T is the temperature. This dynamics is stochastic in nature. Important implications for baryon number violation at high temperature and for the physics at the electroweak phase transition, are discussed.Comment: 14 pages, uses LaTeX; Typographical errors corrected and references adde

Overlap formulation of Majorana--Weyl fermions

An overlap method for regularizing Majorana--Weyl fermions interacting with gauge fields is presented. A mod(2) index is introduced in relation to the anomalous violation of a discrete global chiral symmetry. Most of the paper is restricted to 2 dimensions but generalizations to 2+8k dimensions should be straightforward.Comment: 8 pages, Plain Te

Electroweak Baryogenesis and Standard Model CP Violation

We analyze the mechanism of electroweak baryogenesis proposed by Farrar and Shaposhnikov in which the phase of the CKM mixing matrix is the only source of $CP$ violation. This mechanism is based on a phase separation of baryons via the scattering of quasiparticles by the wall of an expanding bubble produced at the electroweak phase transition. In agreement with the recent work of Gavela, Hern\'andez, Orloff and P\`ene, we conclude that QCD damping effects reduce the asymmetry produced to a negligible amount. We interpret the damping as quantum decoherence. We compute the asymmetry analytically. Our analysis reflects the observation that only a thin, outer layer of the bubble contributes to the coherent scattering of the quasiparticles. The generality of our arguments rules out any mechanism of electroweak baryogenesis that does not make use of a new source of $CP$ violation.Comment: 36 pages, in LaTeX, one LaTeX figure included, 5 others available upon request, SLAC-PUB-647

Comments on the Electroweak Phase Transition

We report on an investigation of various problems related to the theory of the electroweak phase transition. This includes a determination of the nature of the phase transition, a discussion of the possible role of higher order radiative corrections and the theory of the formation and evolution of the bubbles of the new phase. We find in particular that no dangerous linear terms appear in the effective potential. However, the strength of the first order phase transition is 2/3 times less than what follows from the one-loop approximation. This rules out baryogenesis in the minimal version of the electroweak theory.Comment: 14 pages, 2 figures (not included

Development and validation of a rapid multiplex ELISA for pyrrolizidine alkaloids and their N-oxides in honey and feed

Pyrrolizidine alkaloids (PAs) are a group of plant secondary metabolites with carcinogenic and hepatotoxic properties. When PA-producing plants contaminate crops, toxins can be transferred through the food chain and cause illness in humans and animals, most notably hepatic venoocclusive disease. Honey has been identified as a direct risk of human exposure. The European Food Safety Authority has recently identified four groups of PAs that are of particular importance for food and feed: senecionine-type, lycopsaminetype, heliotrine-type and monocrotaline-type. Liquid or gas chromatography methods are currently used to detect PAs but there are no rapid screening assays available commercially. Therefore, the aim of this study was to develop a rapid multiplex ELISA test for the representatives of three groups of alkaloids (senecionine, lycopsamine and heliotrine types) that would be used as a risk-management tool for the screening of these toxic compounds in food and feed. The method was validated for honey and feed matrices and was demonstrated to have a detection capability less than 25 μg/kg for jacobine, lycopsamine, heliotrine and senecionine. The zinc reduction step introduced to the extraction procedure allows for the additional detection of the presence of N-oxides of PAs. This first multiplex immunoassay for PA detection with N-oxide reduction can be used for the simultaneous screening of 21 samples for >12 PA analytes. Honey samples (n =146) from various origins were analysed for PA determination. Six samples were determined to contain measurable PAs >25 μg/kg by ELISAwhich correlated to >10 μg/kg by LC-MS/MS.JRC.D.5-Standards for Food Bioscienc