Dirac Born Infeld (DBI) Cosmic Strings

Motivated by brane physics, we consider the non-linear Dirac-Born-Infeld (DBI) extension of the Abelian-Higgs model and study the corresponding cosmic string configurations. The model is defined by a potential term, assumed to be of the mexican hat form, and a DBI action for the kinetic terms. We show that it is a continuous deformation of the Abelian-Higgs model, with a single deformation parameter depending on a dimensionless combination of the scalar coupling constant, the vacuum expectation value of the scalar field at infinity, and the brane tension. By means of numerical calculations, we investigate the profiles of the corresponding DBI-cosmic strings and prove that they have a core which is narrower than that of Abelian-Higgs strings. We also show that the corresponding action is smaller than in the standard case suggesting that their formation could be favoured in brane models. Moreover we show that the DBI-cosmic string solutions are non-pathological everywhere in parameter space. Finally, in the limit in which the DBI model reduces to the Bogomolnyi-Prasad-Sommerfield (BPS) Abelian-Higgs model, we find that DBI cosmic strings are no longer BPS: rather they have positive binding energy. We thus argue that, when they meet, two DBI strings will not bind with the corresponding formation of a junction, and hence that a network of DBI strings is likely to behave as a network of standard cosmic strings.Comment: 25 pages, 12 figure

Looking at the smoking epidemic through the lens of population pyramids: Sociodemographic patterns of smoking in Italy, 1983 to 2005

Background: Surveillance systems often present data by means of summary measures, like age-standardised rates. In this study, we aimed at comparing information derived from commonly used measures of smoking with that presented in modified population pyramids (PPs), using the example of the diffusion of smoking in Italy over the past two decades.Methods: Data were derived from four National Health Interview Surveys carried out in 1983, 1990 to 1991, 1999 to 2000, and 2004 to 2005. After computing both age-specific and age-standardised rates of current, former, and never smoking, we constructed modified PPs by stratifying the male and female populations according to smoking status and educational level.Results: Modified PPs showed several features of the smoking epidemic in Italy that were not apparent from conventional surveillance techniques. First, they showed that the population of smokers is aging, with most current smokers in 2005 being males aged 25 to 39 and females aged 40 to 49, whereas in 1983 most smokers belonged to the youngest age groups. Second, they showed that in 2005 most smokers were found among subjects with middle and higher education, whereas two decades earlier most smokers were (male) subjects with the lowest education.Conclusions: Modified PPs were able to show how absolute numbers of smokers were distributed by age and sex, how these numbers varied between population subgroups, and how they changed over time. PPs may help provide information on past and future trends in the absolute number of smokers and in their sociodemographic characteristics, which may be missed using only traditional surveillance methods

Modelling carbonaceous aerosol from residential solid fuel burning with different assumptions for emissions

Evidence is accumulating that emissions of primary particulate matter (PM) from residential wood and coal combustion in the UK may be underestimated and/or spatially misclassified. In this study, different assumptions for the spatial distribution and total emission of PM from solid fuel (wood and coal) burning in the UK were tested using an atmospheric chemical transport model. Modelled concentrations of the PM components were compared with measurements from aerosol mass spectrometers at four sites in central and Greater London (ClearfLo campaign, 2012), as well as with measurements from the UK black carbon network. The two main alternative emission scenarios modelled were Base4x and combRedist. For Base4x, officially reported PM2.5 from the residential and other non-industrial combustion source sector were increased by a factor of four. For the combRedist experiment, half of the baseline emissions from this same source were redistributed by residential population density to simulate the effect of allocating some emissions to the smoke control areas (that are assumed in the national inventory to have no emissions from this source). The Base4x scenario yielded better daily and hourly correlations with measurements than the combRedist scenario for year-long comparisons of the solid fuel organic aerosol (SFOA) component at the two London sites. However, the latter scenario better captured mean measured concentrations across all four sites. A third experiment, Redist – all emissions redistributed linearly to population density, is also presented as an indicator of the maximum concentrations an assumption like this could yield. The modelled elemental carbon (EC) concentrations derived from the combRedist experiments also compared well with seasonal average concentrations of black carbon observed across the network of UK sites. Together, the two model scenario simulations of SFOA and EC suggest both that residential solid fuel emissions may be higher than inventory estimates and that the spatial distribution of residential solid fuel burning emissions, particularly in smoke control areas, needs re-evaluation. The model results also suggest the assumed temporal profiles for residential emissions may require review to place greater emphasis on evening (including “discretionary”) solid fuel burning

Level structure of 30S: Implications for the astrophysical 29P(p,γ)30S reaction rate in ONe novae and x-ray bursts

A γ-ray spectroscopy study of 30S is presented. Excitation energies have been determined with improved precision over previous studies and firm spin-parity assignments have been made for key 29P+p resonant states. An evaluation of the 29P(p,γ)30S reaction for T=0.08-2.5 GK shows that the 3+ and 2+ resonant states located at Er=289(3) and 410(3) keV, respectively, dominate the 29P(p,γ)30S reaction rate in ONe novae, while the 410-keV resonance is expected to govern the rate in x-ray burster environments. These new, precise resonance energy measurements and firm spin-parity assignments have significantly reduced uncertainties in the 29P(p,γ)30S reaction in ONe novae and x-ray bursts. In particular, the reaction rate is now specified precisely enough for calculations of isotopic abundances in ONe novae ejecta

M3 and E4 K-forbidden decays of the Kπ=23/2- isomer in 177Lu

Decay of the long-lived (T1/2=160.44 d) Kπ=23/2- isomer in 177Lu was investigated using a chemically purified source and the Gammasphere array. New, high-multipolarity M3 and E4 deexcitation branches to the known Iπ=17/2- and 15/2- members of the π9/2-[514] band were discovered. The reduced hindrance factors per degree of K forbiddenness deduced for these two transitions are found to be relatively large when compared to similar decays from the Kπ=37/2- (T1/2=51.4 min) and Kπ=16+ (T1/2=31 yr) isomers in 177Hf and 178Hf, respectively. This is attributed to significant configuration changes that occur in the decay of this 177Lu isomer

Properties of excited states in Ge77

The nucleus Ge77 was studied through the Ge76(C13,C12)Ge77 reaction at a sub-Coulomb energy. The angular distributions of γ rays depopulating excited states in Ge77 were measured in order to constrain spin and parity assignments. Some of these assignments are of use in connection with neutrinoless double beta decay, where the population of states near the Fermi surface of Ge76 was recently explored using transfer reactions

Precise electromagnetic tests of ab initio calculations of light nuclei: States in Be10

In order to test ab initio calculations of light nuclei, we have remeasured lifetimes in Be10 using the Doppler shift attenuation method (DSAM) following the Li7(Li7,α)Be10 reaction at 8 and 10 MeV. The new experiments significantly reduce systematic uncertainties in the DSAM technique. The Jπ=21+ state at 3.37 MeV has τ=205±(5)stat±(7)sysfs corresponding to a B(E2) of 9.2(3)e2fm4 in broad agreement with many calculations. The Jπ=22+ state at 5.96 MeV was found to have a B(E2) of 0.11(2)e2fm4 and provides a more discriminating test of nuclear models. New Green's function Monte Carlo calculations for these states and transitions with a number of Hamiltonians are also reported and compared to experiment

Xe 136 + Pb 208 reaction: A test of models of multinucleon transfer reactions

The yields of over 200 projectile-like fragments (PLFs) and target-like fragments (TLFs) from the interaction of (Ec.m.=450 MeV) Xe136 with a thick target of Pb208 were measured using Gammasphere and off-line γ-ray spectroscopy, giving a comprehensive picture of the production cross sections in this reaction. The measured yields were compared to predictions of the grazing model and the predictions of Zagrebaev and Greiner using a quantitative metric, the theory evaluation factor tef. The grazing model predictions are adequate for describing the yields of nuclei near the target or projectile but they grossly underestimate the yields of all other products. The predictions of Zagrebaev and Greiner correctly describe the magnitude and maxima of the observed TLF transfer cross sections for a wide range of transfers (ΔZ=-8 to ΔZ=+2). However, for ΔZ=+4, the observed position of the maximum in the distribution is four neutrons richer than the predicted maximum. The predicted yields of the neutron-rich N=126 nuclei exceed the measured values by two orders of magnitude. Correlations between TLF and PLF yields are discussed

High-spin transition quadrupole moments in neutron-rich Mo and Ru nuclei: Testing γ softness?

The transition quadrupole moments, Qt, of rotational bands in the neutron-rich, even-mass 102-108Mo and 108-112Ru nuclei were measured in the 8-16 ℏ spin range with the Doppler-shift attenuation method. The nuclei were populated as fission fragments from 252Cf fission. The detector setup consisted of the Gammasphere spectrometer and the HERCULES fast-plastic array. At moderate spin, the Qt moments are found to be reduced with respect to the values near the ground states. Attempts to describe the observations in mean-field-based models, specifically cranked relativistic Hartree-Bogoliubov theory, illustrate the challenge theory faces and the difficulty to infer information on γ softness and triaxiality from the data