The Phase Diagram of Three-Dimensional SU(3) + Adjoint Higgs Theory

We study the phase diagram of the three-dimensional SU(3)+adjoint Higgs theory with lattice Monte Carlo simulations. A critical line consisting of a first order line, a tricritical point and a second order line, divides the phase diagram into two parts distinguished by =0 and /=0. The location and the type of the critical line are determined by measuring the condensates and , and the masses of scalar and vector excitations. Although in principle there can be different types of broken phases, corresponding perturbatively to unbroken SU(2)xU(1) or U(1)xU(1) symmetries, we find that dynamically only the broken phase with SU(2)xU(1)-like properties is realized. The relation of the phase diagram to 4d finite temperature QCD is discussed.Comment: 21 pages, 8 figure

Ratios of Fluctuation Observables in the Search for the QCD Critical Point

The QCD critical point can be found in heavy ion collision experiments via the non-monotonic behavior of many fluctuation observables as a function of the collision energy. The event-by-event fluctuations of various particle multiplicities are enhanced in those collisions that freeze out near the critical point. Higher, non-Gaussian, moments of the event-by-event distributions of such observables are particularly sensitive to critical fluctuations, since their magnitude depends on the critical correlation length to a high power. We present quantitative estimates of the contribution of critical fluctuations to the third and fourth moments of the pion and proton, as well as estimates of various measures of pion-proton correlations, all as a function of the same five non-universal parameters. We show how to use nontrivial but parameter independent ratios among these more than a dozen fluctuation observables to discover the critical point. We also construct ratios that, if the critical point is found, can be used to overconstrain the values of the non-universal parameters.Comment: 5 pages, 1 figure - Talk given by C. Athanasiou at Hot Quarks 201

Bidirectional redox cycling of phenazine-1-carboxylic acid by Citrobacter portucalensis MBL drives increased nitrate reduction

Phenazines are secreted metabolites that microbes use in diverse ways, from quorum sensing to antimicrobial warfare to energy conservation. Phenazines are able to contribute to these activities due to their redox activity. The physiological consequences of cellular phenazine reduction have been extensively studied, but the counterpart phenazine oxidation has been largely overlooked. Phenazine-1-carboxylic acid (PCA) is common in the environment and readily reduced by its producers. Here, we describe its anaerobic oxidation by Citrobacter portucalensis strain MBL, which was isolated from topsoil in Falmouth, MA, and which does not produce phenazines itself. This activity depends on the availability of a suitable terminal electron acceptor, specifically nitrate or fumarate. When C. portucalensis MBL is provided reduced PCA and either nitrate or fumarate, it continuously oxidizes the PCA. We compared this terminal electron acceptor-dependent PCA-oxidizing activity of C. portucalensis MBL to that of several other γ-proteobacteria with varying capacities to respire nitrate and/or fumarate. We found that PCA oxidation by these strains in a fumarate-or nitrate-dependent manner is decoupled from growth and correlated with their possession of the fumarate or periplasmic nitrate reductases, respectively. We infer that bacterial PCA oxidation is widespread and genetically determined. Notably, reduced PCA enhances the rate of nitrate reduction to nitrite by C. portucalensis MBL beyond the stoichiometric prediction, which we attribute to C. portucalensis MBL’s ability to also reduce oxidized PCA, thereby catalyzing a complete PCA redox cycle. This bidirectionality highlights the versatility of PCA as a biological redox agent

The Ising model universality of the electroweak theory

Lattice simulations have shown that the first order electroweak phase transition turns into a regular cross-over at a critical Higgs mass m_{H,c}. We have developed a method which enables us to make a detailed investigation of the critical properties of the electroweak theory at m_{H,c}. We find that the transition falls into the 3d Ising universality class. The continuum limit extrapolation of the critical Higgs mass is m_{H,c} = 72(2) GeV, which implies that there is no electroweak phase transition in the Standard Model.Comment: 3 pages, contribution to LATTICE98(electroweak

Limit on the electric charge-nonconserving μ+→invisible\mu^+ \to invisible decay

The first limit on the branching ratio of the electric charge-nonconserving invisible muon decay $Br(\mu^+ \to invisible) < 5.2 \times 10^{-3}$ is obtained from the recently reported results on new determination of the Fermi constant from muon decays. The results of a feasibility study of a new proposed experiment for a sensitive search for this decay mode at the level of a few parts in 10^{11} are presented. Constrains on the $\tau \to invisible$ decay rate are discussed. These leptonic charge-nonconserving processes may hold in four-dimensional world in models with infinite extra dimensions, thus making their searches complementary to collider experiments probing new physics.Comment: 5 pages, 2 Figure, to appear in PR

Three-dimensional Ising model in the fixed-magnetization ensemble: a Monte Carlo study

We study the three-dimensional Ising model at the critical point in the fixed-magnetization ensemble, by means of the recently developed geometric cluster Monte Carlo algorithm. We define a magnetic-field-like quantity in terms of microscopic spin-up and spin-down probabilities in a given configuration of neighbors. In the thermodynamic limit, the relation between this field and the magnetization reduces to the canonical relation M(h). However, for finite systems, the relation is different. We establish a close connection between this relation and the probability distribution of the magnetization of a finite-size system in the canonical ensemble.Comment: 8 pages, 2 Postscript figures, uses RevTe

The Discovery and Biological Mechanisms of a Widespread Phenazine's Oxidation

During the 2017 Microbial Diversity course at the Marine Biological Laboratory in Woods Hole, MA, Scott Saunders and Yinon Bar-On started enrichment cultures in hopes of dis-covering biological oxidation of phenazine-1-carboxylic acid (PCA). I took these enrich-ment cultures and described their PCA oxidation activity. From one of the mixed cultures, I isolated a bacterial strain that recapitulated the behavior of the enrichment. I identified it as a strain of Citrobacter portucalensis via a whole-genome analysis and called the strain "MBL" in reference to the Marine Biological Laboratory. Using a combination of analytical chemistry, quantitative fluorescence measurements, and genetic engineering, I showed that C. portucalensis MBL couples PCA oxidation to each mode of anaerobic respiration it employs with nitrate, fumarate, dimethyl sulfoxide (DMSO), and trimethylamine-N-oxide (TMAO) as terminal electron acceptors (TEAs). I further found that most of the PCA oxidation activi-ty depends on electron flux through the quinone/quinol pool but can be driven by certain terminal reductase complexes when no quinones are available, particularly in the case of ni-trate reductases. Every bacterial strain I tested catalyzed PCA oxidation when provided the appropriate TEA. My described mechanism for bacterial PCA oxidation is generalizable and implies that this previously undocumented phenomenon should occur wherever PCA is produced in rhizosphere environments.</p