Phase transitions in the early universe

Phase transitions are a generic prediction of models in particle physics. In the Standard Model, for example, there are two phase transitions: the QCD confinement transition and the electroweak phase transition, both occurring in the very early stages of the universe. Many extensions to the Standard Model predict new phase transitions, all occurring at very high temperatures. Depending on how these transitions proceed they may lead to signatures which can be detected today, offering a way to probe the early stages of the universe. This thesis is on phase transitions and their impacts on early universe cosmology. Chapter 1 is an overview of the physics of phase transitions, both in the Standard Model and extensions of it. The different phases of gauge theories are described before discussing the phase transitions in the Standard Model and general features of phase transitions in theories beyond the Standard Model. The cosmological implications of these transitions is then summarised, with a focus on the production of topological defects, the gravitational wave signal and constraints from supercooling. Chapter 2 focuses on the confining transition in Randall-Sundrum models. The transition places severe cosmological constraints on the model, meaning the model is only marginally under parametric control as an effective field theory. In this chapter a mechanism is presented which circumvents the problematic phase transition by making the confined phase metastable at high temperatures. The phenomenological features of the model, in particular dark matter production, are also presented in this chapter. Everyday phase transitions are often catalysed by the presence of defects or impurities in the material, leading to an enhanced transition rate. In cosmology, however, phase transitions are typically considered to proceed from a homogeneous initial state. In chapter 3 the possibility that magnetic monopoles could act as catalysts for cosmological phase transitions is considered, and an algorithm developed to solve the field equations describing the transition. A similar idea is pursued in chapter 4 for the case of domain walls catalysing the electroweak phase transition

Description and molecular diagnosis of a new species of Brunfelsia (Solanaceae) from the Bolivian and Argentinean Andes

Brunfelsia plowmaniana N.Filipowicz & M.Nee sp. nov., a species from humid and cloud forests of the Bolivian and Argentinean Andes, is described and provided with a molecular diagnosis, using provisions available in the recently approved International Code of Nomenclature for algae, fungi and plants. Specimens belonging to the new species were previously placed in the polymorphic B. uniflora (Pohl) D.Don, which a molecular phylogeny revealed as polyphyletic. Revision of numerous collections revealed clear morphological differences between the new species and B. uniflora, the type locality of which is in the state of São Paulo, Brazil

The Boring Monopole

We study false vacuum decays catalysed by magnetic monopoles which act as tunnelling sites with exponentially enhanced decay rates. The field profiles describing the decay do not have the typically assumed $O(3)/O(4)$ symmetry, thus requiring an extension of the usual decay rate calculation. To numerically determine the saddle point solutions which describe the tunnelling process we use a new algorithm based on the mountain pass theorem. This method can be applied more widely to phase transitions with reduced symmetry, such as decays away from the zero and infinite temperature limits. Our results show that monopole-catalysed tunnelling can dominate over the homogeneous false vacuum decay for a wide range of parameters, significantly modify the gravitational wave signal or trigger phase transitions which would otherwise never complete. A single boring monopole in our Hubble patch may determine the lifetime of the Standard Model vacuum.Comment: 19 pages, 6 figures, Journal versio

15N NMR study of a mixture of uniformly labeled tRNAs

15N NMR spectra were taken of 15N-enriched tRNA extracted from bakers yeast; ammonium sulfate was used as a nitrogen source. The increase in the degree of denaturation of tRNA, which occurs with increase in temperature from 30 degrees C to 70 degrees C, resulted in no large changes in 15N chemical shifts at acidic and neutral pH but quite pronounced changes in proton-15N nuclear Overhauser effects

New species of Solanum and Capsicum (Solanaceae) from Bolivia, with clarification of nomenclature in some Bolivian Solanum

Journal ArticleBolivian floristic diversity is high, reflecting its great topographic and habitat diversity. Habitats in Bolivia range from seasonally flooded savannas to arid Chaco and high elevation deserts to hyper-humid montane and lowland rainforests

Methods of quantifying specialized knowledge and network rewiring

Technological innovations are a major driver of economic development that depend on the exchange of knowledge and ideas among those with unique but complementary specialized knowledge and knowhow. However, measurement of specialized knowledge embedded in technologists, scientists and entrepreneurs in the knowledge economy presents an empirical challenge as both the exchange of knowledge and knowledge itself remain difficult to observe. We develop novel measures of specialized knowledge using a unique dataset of longitudinal records of participation at technology-focused meetup events in two regional knowledge economics. Our measures of specialized knowledge can be further used to quantify the extend of knowledge spillover and network rewiring and uncover underlying social mechanisms that contribute to the development of increasingly complex and differentiated networks in maturing knowledge economies. We apply these methods in the context of the rapid morphogenesis of emerging regional technology economies in New York City and Los Angeles.Comment: 21 pages, 6 figure

Electroweak phase transition with a double well done doubly well

We revisit the electroweak phase transition in the scalar singlet extension of the standard model with a ℤ2 symmetry. In significant parts of the parameter space the phase transition occurs in two steps — including canonical benchmarks used in experimental projections for gravitational waves. Domain walls produced in the first step of the transition seed the final step to the electroweak vacuum, an effect which is typically neglected but leads to an exponentially enhanced tunnelling rate. We improve previous results obtained for the seeded transition, which made use of the thin-wall or high temperature approximations, by using the mountain pass algorithm that was recently proposed as a useful tool for seeded processes. We then determine the predictions of the seeded transition for the latent heat, bubble size and characteristic time scale of the transition. Differences compared to homogeneous transitions are most pronounced when there are relatively few domain walls per hubble patch, potentially leading to an enhanced gravitational wave signal. We also provide a derivation of the percolation criteria for a generic seeded transition, which applies to the domain wall seeds we consider as well as to strings and monopoles

Solanaceae—A Model for Linking Genomics With Biodiversity

Recent progress in understanding the phylogeny of the economically important plant family Solanaceae makes this an ideal time to develop models for linking the new data on plant genomics with the huge diversity of naturally occurring species in the family. Phylogenetics provides the framework with which to investigate these linkages but, critically, good species-level descriptive resources for the Solanaceae community are currently missing. Phylogeny in the family as a whole is briefly reviewed, and the new NSF Planetary Biodiversity Inventories project ‘PBI: Solanum—a worldwide treatment’ is described. The aims of this project are to provide species-level information across the global scope of the genus Solanum and to make this available over the Internet. The project is in its infancy, but will make available nomenclatural information, descriptions, keys and illustrative material for all of the approximately 1500 species of Solanum. With this project, the opportunity of linking valid, up-to-date taxonomic information about wild species of Solanum with the genomic information being generated about the economically important species of the genus (potato, tomato and eggplant) can be realized. The phylogenetic framework in which the PBI project is set is also of enormous potential benefit to other workers on Solanum. The community of biologists working with Solanaceae has a unique opportunity to effectively link genomics and taxonomy for better understanding of this important family, taking plant biology to a new level for the next century

I. Reactions of Bicyclo[3.3.0]octenyl Tosylates II. Nitrogen-15 Nuclear Magnetic Resonance Investigations of Organic Reactions

PART I A. Elimination Reactions of 6-Bicyclo[3.2.0]-2-heptenyl Tosylates The 6- and 7-bicyclo[3.3.0]-2-octenyl tosylates with 2,4,6-trimethylpyridine have been reported to yield mixtures of bicyclo[3.3.0]octa-2,6-diene and bicyclo[3.3.0]octa-2,7-diene. Under the same conditions, the stereoisomeric 6-bicyclo[3.2.0]-2-heptenyl tosylate gives ring-opened products, 1,3,5-cycloheptatriene and 5-ethylidene-1,3-cyclopentadiene. B. Acetolysis of Some Bicyclo[3.3.0]-2-octenyl Tosylates The products of the acetolysis of the stereoisomeric 6-,7-, and 8-bicyclo[3.3.0]-2-octenyl tosylates are reported. These tosylates were themselves stable to skeletal rearrangements, but were found to undergo 1,2-hydride shifts and elimination solvolysis. PART II Assignment of the Nitrogen-15 Nuclear Magnetic Resonances of Biotin and Unequivocal Synthesis of (+)-[1-15N]Biotin The 15N NMR spectra of biotin, desthiobiotin, and 2-imidazolidinone were measured. Assignment of the resonances of biotin and desthiobiotin was achieved by off-resonance decoupling. The biotin assignment was confirmed by measurement of biotin specifically labeled with 15N at N1. PART III A 15N Nuclear Magnetic Resonance Study of the Base-Catalyzed -NH2 Exchange Reactions of Acetamide and Thioacetamide The base-catalyzed -NH2 exchange reactions of acetamide and thioacetamide were studied by 15N nuclear magnetic resonance spectroscopy by use of line-shape analysis. The 15N NMR spectra of these primary amides at intermediate exchange rates were broad doublets, which indicated that the two amide protons were exchanging at different rates. The line-shape analysis indicated that the ratio of exchange rates was 6 ± 1 for acetamide and 3 ± 1 for thioacetamide. PART IV Determination of the Binding Interactions of cis-[Pt(NH3)2Cl2] with Nucleosides by 15N Nuclear Magnetic Resonance Spectroscopy The 15N NMR chemical shifts and 15N-195Pt coupling constants of several platinum(II)-ammine complexes were measured. The magnitude of the coupling constants were dependent on the trans ligand. A similar dependence on the trans ligand was found for the 15N chemical shifts of the coordinated ammonia ligands. The magnitude of the 15N platinum coordination shift was proportional to the 15N protonation shift of the ligand. Cis-[Pt(NH3)2Cl2] was found to bind to guanosine through N7 and another nitrogen site. The drug also binds to N3 of cytidine and to all four of the nitrogen sites of adenosine. No evidence was found to support chelate binding of nucleosides by cis-[Pt(NH3)2Cl2].</p