Why Does Inflation Start at the Top of the Hill?

We show why the universe started in an unstable de Sitter state. The quantum origin of our universe implies one must take a `top down' approach to the problem of initial conditions in cosmology, in which the histories that contribute to the path integral, depend on the observable being measured. Using the no boundary proposal to specify the class of histories, we study the quantum cosmological origin of an inflationary universe in theories like trace anomaly driven inflation in which the effective potential has a local maximum. We find that an expanding universe is most likely to emerge in an unstable de Sitter state, by semiclassical tunneling via a Hawking-Moss instanton. Since the top down view is forced upon us by the quantum nature of the universe, we argue that the approach developed here should still apply when the framework of quantum cosmology will be based on M-Theory.Comment: 21 pages, 1 figur

First direct measurement of 12C (12C,n) 23Mg at stellar energies

© 2016 Owned by the authors, published by EDP Sciences. Neutrons produced by the carbon fusion reaction12C(12C,n)23Mg play an important role in stellar nucleosynthesis. Past studies have shown large discrepancies between experimental data and theory, leading to an uncertain cross section extrapolation at astrophysical energies. We present the first direct measurement which extends deep into the astrophysical energy range along with a new and improved extrapolation technique based on experimental data from the mirror reaction12C(12C,p)23Na. The new reaction rate has been determined with a well-defined uncertainty which exceeds the precision required by astrophysics models. Using our constrained rate, we find that12C(12C,n)23Mg is crucial to the production of Na and Al in Pop-III Pair Instability Supernovae

Constraining the 12C+12C fusion cross section for astrophysics

The 12 C+ 12 C reaction is one of the single most important nuclear reactions in astrophysics. It strongly influences late evolution of massive stars as well as the dynamics of type Ia supernovae and x-ray superbursts. An accurate estimation of the cross section at relevant astrophysical energies is extremely important for modeling these systems. However, the situation is complicated by the unpredictable resonance structure observed at higher energies. Two recent studies at Notre Dame have produced results which help reduce the uncertainty associated with this reaction. The first uses correlations with the isotope fusion systems, 12 C+ 13 C and 13 C+ 13 C, to establish an upper limit on the resonance strengths in 12 C+ 12 C. The other focuses on the specific channel 12 C+ 12 C→ 23 Mg+n and its low-energy measurement and extrapolation which is relevant to s-process nucleosynthesis. The results from each provide important constraints for astrophysical models

Improved W boson mass measurement with the D0 detector

We have measured the W boson mass using the D0 detector and a data sample of 82 pb^-1 from the Tevatron collider. This measurement used W -> e nu decays, where the electron is close to a boundary of a central electromagnetic calorimeter module. Such 'edge' electrons have not been used in any previous D0 analysis, and represent a 14% increase in the W boson sample size. For these electrons, new response and resolution parameters are determined, and revised backgrounds and underlying event energy flow measurements are made. When the current measurement is combined with previous D0 W boson mass measurements, we obtain M_W = 80.483 +/- 0.084 GeV. The 8% improvement from the previous D0 measurement is primarily due to the improved determination of the response parameters for non-edge electrons using the sample of Z bosons with non-edge and edge electrons.Comment: submitted to Phys. Rev. D; 20 pages, 18 figures, 9 table

Wholesale pricing in a small open economy

This paper addresses the empirical analysis of wholesale profit margins using data of the Dutch wholesale sector, 1986. At the heart of the analysis is the typical nature of wholesale production: wholesalers do not produce a tangible product, but offer a service capacity. This has an immediate impact on the identification, interprelation and measurement of determinants of profit variations. A model is set up to explain variations in wholesale profit margins, which is inspired by two widely applied approaches to industry pricing: the behavioural mark-up model and the marginalist price-cost model

Searching for the low-energy resonances in the 12C( 12C,n)23Mg reaction cross section relevant for s-process nucleosynthesis

The 12C(12C,n) reaction (Q=-2.6 MeV) is a potential neutron source for the weak s-process occurring in shell-carbon burning of massive stars. The uncertainty in this reaction rate limits our understanding of the production of elements in the range 60 < A < 110. Current stellar models must rely on the smooth extrapolation of a dubious statistical model calculation based on experimental data taken at energies well above the Gamow window which lies below 3.2 MeV. At Notre Dame, this reaction cross section has been measured in finer steps at energies above 3.5 MeV, while successful measurements down to 3.1 MeV have just recently been achieved. In addition, a new extrapolation based on measurements of the mirror system has been developed which predicts a number of low-energy resonances while accounting well for the high-energy resonances. An overview of this work along with the most recent results and astrophysical implications are presented

Dust Devil Sediment Transport: From Lab to Field to Global Impact

The impact of dust aerosols on the climate and environment of Earth and Mars is complex and forms a major area of research. A difficulty arises in estimating the contribution of small-scale dust devils to the total dust aerosol. This difficulty is due to uncertainties in the amount of dust lifted by individual dust devils, the frequency of dust devil occurrence, and the lack of statistical generality of individual experiments and observations. In this paper, we review results of observational, laboratory, and modeling studies and provide an overview of dust devil dust transport on various spatio-temporal scales as obtained with the different research approaches. Methods used for the investigation of dust devils on Earth and Mars vary. For example, while the use of imagery for the investigation of dust devil occurrence frequency is common practice for Mars, this is less so the case for Earth. Modeling approaches for Earth and Mars are similar in that they are based on the same underlying theory, but they are applied in different ways. Insights into the benefits and limitations of each approach suggest potential future research focuses, which can further reduce the uncertainty associated with dust devil dust entrainment. The potential impacts of dust devils on the climates of Earth and Mars are discussed on the basis of the presented research results

Test of Lorentz and CPT violation with Short Baseline Neutrino Oscillation Excesses

The sidereal time dependence of MiniBooNE electron neutrino and anti-electron neutrino appearance data are analyzed to search for evidence of Lorentz and CPT violation. An unbinned Kolmogorov-Smirnov test shows both the electron neutrino and anti-electron neutrino appearance data are compatible with the null sidereal variation hypothesis to more than 5%. Using an unbinned likelihood fit with a Lorentz-violating oscillation model derived from the Standard Model Extension (SME) to describe any excess events over background, we find that the electron neutrino appearance data prefer a sidereal time-independent solution, and the anti-electron neutrino appearance data slightly prefer a sidereal time-dependent solution. Limits of order 10E-20 GeV are placed on combinations of SME coefficients. These limits give the best limits on certain SME coefficients for muon neutrino to electron neutrino and anti-muon neutrino to anti-electron neutrino oscillations. The fit values and limits of combinations of SME coefficients are provided.Comment: 14 pages, 3 figures, and 2 tables, submitted to Physics Letters

Properties of the Top Quark

The top quark was discoverd at the CDF and D0 experiments in 1995. As the partner of the bottom quark its properties within the Standard Model are fully defined. Only the mass is a free parameter. The measurement of the top quark mass and the verification of the expected properties have been an important topic of experimental top quark physics since. In this review the recent results on top quark properties obtained by the Tevatron experiments CDF and D0 are summarised. At the advent of the LHC special emphasis is given to the basic measurement methods and the dominating systematic uncertainties.Comment: Habilitation thesis, revised and updated for publication in EPJ