Bubble formation in ϕ6\phi^6 potential

Scalar field theory with an asymmetric potential is studied at zero temperature and high-temperature for $\phi^6$ potential. The equations of motion are solved numerically to obtain O(4) spherical symmetric and O(3) cylindrical symmetric bounce solutions. These solutions control the rates for tunneling from the false vacuum to the true vacuum by bubble formation. The range of validity of the thin-wall approximation (TWA) is investigated. An analytical solution for the bounce is presented, which reproduces the action in the thin-wall as well as the thick-wall limits.Comment: 22 pag

Durability assessment of external thermal insulation composite systems in urban and maritime environments

External Thermal Insulation Composite Systems (ETICS) are multilayer solutions which provide an enhanced thermal performance to the building envelope. However, significant anomalies can be detected on ETICS facades, in some cases shortly after the application of these systems. This study intends to evaluate and compare the durability of six commercially available ETICS after two years of outdoor exposure at both urban and maritime conditions in Portugal. The systems were characterized by means of non-destructive testing (i.e., visual and microscopic assessment, water transport properties, thermal conductivity, surface roughness), thus allowing to evaluate the performance loss throughout natural aging. The bio-susceptibility and aesthetic properties (color and gloss) were also investigated. Results showed that the performance and durability of the complete system is significantly affected by the rendering system formulation. The lime-based specimens obtained the highest rate of mold development after one year of aging in a maritime environment, becoming considerably darker and with lower surface gloss. Fungal analysis of this darkish stained area indicated the presence of mold species of the genera Alternaria, Didymella, Cladosporium and Epicoccum, and yeasts of the genera Vishniacozyma and Cystobasidium. An increase of both capillary water absorption and water vapor permeability was also registered for the aged lime-based specimens. Acrylic-based systems obtained lower capillary water absorption after aging and greater dirt deposition on their surfaces, especially in urban conditions. These systems had also higher color variation and surface gloss decrease and slightly higher mold growth, when compared with those aged in a maritime environment. Finally, no mold growth was detected on the silicate-based specimens after two years of aging. However, these specimens obtained higher capillary water absorption and lower vapor permeability after aging, possibly leading to moisture accumulation within the system. Results contribute towards the development of ETICS with enhanced performance and durability.info:eu-repo/semantics/publishedVersio

A Step Beyond the Bounce: Bubble Dynamics in Quantum Phase Transitions

We study the dynamical evolution of a phase interface or bubble in the context of a \lambda \phi^4 + g \phi^6 scalar quantum field theory. We use a self-consistent mean-field approximation derived from a 2PI effective action to construct an initial value problem for the expectation value of the quantum field and two-point function. We solve the equations of motion numerically in (1+1)-dimensions and compare the results to the purely classical evolution. We find that the quantum fluctuations dress the classical profile, affecting both the early time expansion of the bubble and the behavior upon collision with a neighboring interface.Comment: 12 pages, multiple figure

Solar Wakes of Dark Matter Flows

We analyze the effect of the Sun's gravitational field on a flow of cold dark matter (CDM) through the solar system in the limit where the velocity dispersion of the flow vanishes. The exact density and velocity distributions are derived in the case where the Sun is a point mass. The results are extended to the more realistic case where the Sun has a finite size spherically symmetric mass distribution. We find that regions of infinite density, called caustics, appear. One such region is a line caustic on the axis of symmetry, downstream from the Sun, where the flow trajectories cross. Another is a cone-shaped caustic surface near the trajectories of maximum scattering angle. The trajectories forming the conical caustic pass through the Sun's interior and probe the solar mass distribution, raising the possibility that the solar mass distribution may some day be measured by a dark matter detector on Earth. We generalize our results to the case of flows with continuous velocity distributions, such as that predicted by the isothermal model of the Milky Way halo.Comment: 30 pages, 8 figure

The Dipion Mass Spectrum In e+e- Annihilation and tau Decay: A Dynamical (rho0, omega, phi) Mixing Approach

We readdress the problem of finding a simultaneous description of the pion form factor data in e+e- annihilations and in tau decays. For this purpose, we work in the framework of the Hidden Local Symmetry (HLS) Lagrangian and modify the vector meson mass term by including the pion and kaon loop contributions. This leads us to define the physical rho, omega and phi fields as linear combinations of their ideal partners, with coefficients being meromorphic functions of s, the square of the 4--momentum flowing into the vector meson lines. This allows us to define a dynamical, i.e. s-dependent, vector meson mixing scheme. The model is overconstrained by extending the framework in order to include the description of all meson radiative (V P gamma and P gamma gamma couplings) and leptonic (Ve+e- couplings) decays and also the isospin breaking (omega/ phi --> pi+ pi-) decay modes. The model provides a simultaneous, consistent and good description of the e+e- and tau dipion spectra. The expression for pion form factor in the latter case is derived from those in the former case by switching off the isospin breaking effects specific to e+e- and switching on those for tau decays. Besides, the model also provides a good account of all decay modes of the form V P gamma, Pgamma gamma as well as the isospin breaking decay modes. It leads us to propose new reference values for the rho^0 --> e+ e- and omega --> pi+ pi- partial widths which are part of our description of the pion form factor. Other topics (phi --> K anti K, the rho meson mass and width parameters) are briefly discussed. Therefore, we confirm the 3.3 sigma discrepancy between the theoretical estimate of a_mu based on e+e- and its direct BNL measurement.Comment: 71 pages, 8 figures. Accepted by EPJ C. Version 3: correct minor typos, minor changes spread out into the text. Extension of Sections 12.2 and 12.3.5 and introduction of the new Appendix

Effects of long-term diet supplementation with Gliricidia sepium foliage mixed with Enterolobium cyclocarpum pods on enteric methane, apparent digestibility, and rumen microbial population in crossbred heifers

In the last decades, strategies have been evaluated to reduce rumen methane (CH4) production by supplementing tropical forages rich in secondary compounds; however, most of these beneficial effects need to be validated in terms of their persistence over time. The aim of this study was to assess CH4 emissions over time in heifers fed with and without Gliricidia sepium foliage (G) mixed with ground pods of Enterolobium cyclocarpum(E). Two groups of four crossbred (Bos taurus x Bos indicus) heifers (284 ±17 kg initial weight) were fed with two diets (0 and 15% of a mixture of the pods and foliage [E+G:0 and E+G:15, respectively] over 80 days, plus two weeks before the experiment, in which every animal was fed a legume and pod-free diet. Every 14 days, CH4 production, apparent digestibility, volatile fatty acids (VFA), and microbial population were quantified for each animal. The experiment was conducted with a repeated measurements design over time. Diets fed differed in terms of their crude protein (CP), condensed tannins (CT) and saponins content supplied by E. cyclocarpum and G. sepium. For most of the experiment, dry matter intake (DMI) and digestible dry-matter intake (DDMI) were 6.3 kg DMI/d and 512 g DDMI/kg, respectively for both diets (Diet: P>0.05). Apparent digestible crude protein (DCP) was reduced by 21 g DCP/kg DM when the diet was supplemented with E+G:15 (P=0.040). Molar proportions of VFA’s in the rumen did not differ between diets or in time (P>0.05). Daily methane production, expressed in relation to DMI was 23.95 vs 23.32 g CH4/kg DMI for the diet E+G:0 and E+G:15 respectively (Diet: P=0.016; Time: P>0.05). Percent gross energy loss as CH4 (Ym) with grassonly diets was above 8.1%, whereas when feeding heifers with the alternate supplementation, Ym values of 7.59% (P=0.016) were observed. The relative abundance of total bacterial, protozoa, and methanogenic archaeal replicates was not affected by time nor by the incorporation of legume and pods into the diet (P>0.05). Results suggest that addition of G. sepium mixed with E. cyclocarpum pods can reduce CH4 production in heifers and this response remains over time, without effect on microbial population and VFA concentration and a slight reduction in crude protein digestibility

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results