Absence of a Lower Limit on Omega_b in Inhomogeneous Primordial Nucleosynthesis

We show that a class of inhomogeneous big bang nucleosynthesis models exist which yield light-element abundances in agreement with observational constraints for baryon-to-photon ratios significantly smaller than those inferred from standard homogeneous big bang nucleosynthesis (HBBN). These inhomogeneous nucleosynthesis models are characterized by a bimodal distribution of baryons in which some regions have a local baryon-to-photon ratio eta=3*10e-10, while the remaining regions are baryon-depleted. HBBN scenarios with primordial (2H+3He)/H<9*10e-5 necessarily require that most baryons be in a dark or non-luminous form, although new observations of a possible high deuterium abundance in Lyman-alpha clouds may relax this requirement somewhat. The models described here present another way to relax this requirement and can even eliminate any lower bound on the baryon-to-photon ratio.Comment: 13 pages, 2 figures (available upon request by email), plain te

Baryon Number Transport in a Cosmic QCD-Phase Transition

We investigate the transport of baryon number across phase boundaries in a putative first order QCD-phase transition. Two independent phenomenological models are employed to estimate the baryon penetrability at the phase boundary: chromoelectric flux tube models; and an analogy to baryon-baryon coalescence in nuclear physics. Our analysis indicates that baryon transport across phase boundaries may be order of magnitude more efficient than other work has suggested. We discuss the substantial uncertainties involved in estimating baryon penetrability at phase boundaries.Comment: 25 pages, 4 figures (available upon request by mail or fax), plain tex, UCRL-JC-00000

The surprising influence of late charged current weak interactions on Big Bang Nucleosynthesis

The weak interaction charged current processes ($\nu_e+n\leftrightarrow p+e^-$, $\bar\nu_e +p\leftrightarrow n+e^+$, $n\leftrightarrow p+e^-+\bar\nu_e$) interconvert neutrons and protons in the early universe and have significant influence on Big Bang Nucleosynthesis (BBN) light-element abundance yields, particulary that for $^{4}{\rm He}$. We demonstrate that the influence of these processes is still significant even when they operate well below temperatures $T\sim0.7\,{\rm MeV}$ usually invoked for "weak freeze-out," and in fact down nearly into the alpha-particle formation epoch ($T \approx 0.1\,{\rm MeV}$). This physics is correctly captured in commonly used BBN codes, though this late-time, low-temperature persistent effect of the isospin-changing weak processes, and the sensitivity of the associated rates to lepton energy distribution functions and blocking factors are not widely appreciated. We quantify this late-time influence by analyzing weak interaction rate dependence on the neutron lifetime, lepton energy distribution functions, entropy, the proton-neutron mass difference, and Hubble expansion rate. The effects we point out here render BBN a keen probe of any beyond-standard-model physics that alters lepton number/energy distributions, even subtly, in epochs of the early universe all the way down to near $T=100\,{\rm keV}$.Comment: 27 pages, 8 figure

Transformations to achieve the Sustainable Development Goals Includes the SDG Index and Dashboards. Sustainable Development Report 2019

The Sustainable Development Report 2019 presents an updated SDG Index and Dashboards with a refined assessment of countries’ distance to SDG targets. The report has been successfully audited for the first time by the European Commission Joint Research Centre. New indicators have been included, primarily to refine the indicator selection on agriculture, diets, gender equality and freedom of speech. We have also added more metrics for international spillovers, including on fatal work accidents. A new website and data visualization tools are available (http://sustainabledevelopment.report). Once again, Nordic countries – Denmark, Sweden and Finland – top the SDG Index. Yet, even these countries face major challenges in implementing one or several SDGs. No country is on track for achieving all 17 goals with major performance gaps even in the top countries on SDG 12 (Responsible Consumption and Production), SDG 13 (Climate Action), SDG 14 (Life Below Water) and SDG 15 (Life on Land). Income and wealth inequalities, as well as gaps in health and education outcomes by population groups also remain important policy challenges in developing and developed countries alike. The Sustainable Development Report 2019 generates seven major findings: 1. High-level political commitment to the SDGs is falling short of historic promises In September 2019, heads-of-states and governments will convene for the first time in person at the UN in New York to review progress on their promises made four years after the adoption of the 2030 Agenda. Yet, our in-depth analyses show that many have not taken the critical steps to implement the SDGs. Out of 43 countries surveyed on SDG implementation efforts, including all G20 countries and countries with a population greater than 100 million, 33 countries have endorsed the SDGs in official statements since January 1st, 2018. Yet in only 18 of them do central budget documents mention the SDGs. This gap between rhetoric and action must be closed. 2. The SDGs can be operationalized through six SDG Transformations SDG implementation can be organized along the following Transformations: 1. Education, Gender, and Inequality; 2. Health, Wellbeing, and Demography; 3. Energy Decarbonization and Sustainable Industry; 4. Sustainable Food, Land, Water, Oceans; 5. Sustainable Cities and Communities; and 6. Digital Revolution for Sustainable Development. The transformations respect strong interdependencies across the SDGs and can be operationalized by well-defined parts of governments in collaboration with civil society, business, and other stakeholders. They must be underpinned and guided by the principles of Leave No One Behind and Circularity and Decoupling of resource use from human wellbeing. 3. Trends on climate (SDG 13) and biodiversity (SDG 14 and SDG 15) are alarming On average, countries obtain their worst scores on SDG 13 (Climate Action), SDG 14 (Life Below Water) and SDG 15 (Life on Land). No country obtains a “green rating” (synonym of SDG achieved) on SDG 14 (Life Below Water). Trends on greenhouse gas emissions and, even more so, on threatened species are moving in the wrong direction. These findings are in line with the recent reports from the IPCC and IPBES on climate change mitigation and biodiversity protection, respectively. 4. Sustainable land-use and healthy diets require integrated agriculture, climate and health policy interventions Land use and food production are not meeting people’s needs. Agriculture destroys forests and biodiversity, squanders water and releases one-quarter of global greenhouse-gas emissions. In total, 78% of world nations for which data are available obtain a “red rating” (synonym of major SDG challenge) on sustainable nitrogen management; the highest number of “red” rating across all indicators included in the report. At the same time, one-third of food is wasted, 800 million people remain undernourished, 2 billion are deficient in micronutrients, and obesity is on the rise. New indicators on nations’ trophic level and yield gap closure highlight the depth of the challenge. Transformations towards sustainable landuse and food systems are required to balance efficient and resilient agriculture and forestry with biodiversity conservation and restoration as well as healthy diets

Prospects for Detecting Supernova Neutrino Flavor Oscillations

The neutrinos from a Type II supernova provide perhaps our best opportunity to probe cosmologically interesting muon and/or tauon neutrino masses. This is because matter enhanced neutrino oscillations can lead to an anomalously hot nu_e spectrum, and thus to enhanced charged current cross sections in terrestrial detectors. Two recently proposed supernova neutrino observatories, OMNIS and LAND, will detect neutrons spalled from target nuclei by neutral and charged current neutrino interactions. As this signal is not flavor specific, it is not immediately clear whether a convincing neutrino oscillation signal can be extracted from such experiments. To address this issue we examine the responses of a series of possible light and heavy mass targets, 9Be, 23Na, 35Cl, and 208Pb. We find that strategies for detecting oscillations which use only neutron count rates are problematic at best, even if cross sections are determined by ancillary experiments. Plausible uncertainties in supernova neutrino spectra tend to obscure rate enhancements due to oscillations. However, in the case of 208Pb, a signal emerges that is largely flavor specific and extraordinarily sensitive to the nu_e temperature, the emission of two neutrons. This signal and its flavor specificity are associated with the strength and location of the first-forbidden responses for neutral and charge current reactions, aspects of the 208Pb neutrino cross section that have not been discussed previously. Hadronic spin transfer experiments might be helpful in confirming some of the nuclear structure physics underlying our conclusions.Comment: 27 pages, RevTeX, 2 figure

The Influence of Nuclear Composition on the Electron Fraction in the Post-Core-Bounce Supernova Environment

We study the early evolution of the electron fraction (or, alternatively, the neutron-to-proton ratio) in the region above the hot proto-neutron star formed after a supernova explosion. We study the way in which the electron fraction in this environment is set by a competition between lepton (electron, positron, neutrino, and antineutrino) capture processes on free neutrons and protons and nuclei. Our calculations take explicit account of the effect of nuclear composition changes, such as formation of alpha particles (the alpha effect) and the shifting of nuclear abundances in nuclear statistical equilibrium associated with cooling in near-adiabatic outflow. We take detailed account of the process of weak interaction freeze-out in conjunction with these nuclear composition changes. Our detailed treatment shows that the alpha effect can cause significant increases in the electron fraction, while neutrino and antineutrino capture on heavy nuclei tends to have a buffering effect on this quantity. We also examine the effect on weak rates and the electron fraction of fluctuations in time in the neutrino and antineutrino energy spectra arising from hydrodynamic waves. Our analysis is guided by the Mayle & Wilson supernova code numerical results for the neutrino energy spectra and density and velocity profiles.Comment: 38 pages, AAS LaTeX, 8 figure

Neutrinos in Cosmology and Astrophysics

We briefly review the recent developments in neutrino physics and astrophysics which have import for frontline research in nuclear physics. These developments, we argue, tie nuclear physics to exciting developments in observational cosmology and astrophysics in new ways. Moreover, the behavior of neutrinos in dense matter is itself a fundamental problem in many-body quantum mechanics, in some ways akin to well-known issues in nuclear matter and nuclei, and in some ways radically different, especially because of nonlinearity and quantum de-coherence. The self-interacting neutrino gas is the only many body system driven by the weak interactions.Comment: 7 pages, 1 figur

Nuclear neutrino energy spectra in high temperature astrophysical environments

Astrophysical environments that reach temperatures greater than $\sim$ 100 keV can have significant neutrino energy loss via both plasma processes and nuclear weak interactions. We find that nuclear processes likely produce the highest-energy neutrinos. Among the important weak nuclear interactions are both charged current channels (electron capture/emission and positron capture/emission) and neutral current channels (de-excitation of nuclei via neutrino pair emission). We show that in order to make a realistic prediction of the nuclear neutrino spectrum, one must take nuclear structure into account; in some cases, the most important transitions may involve excited states, possibly in both parent and daughter nuclei. We find that the standard technique of producing a neutrino energy spectrum by using a single transition with a Q-value and matrix element chosen to fit published neutrino production rates and energy losses will not accurately capture important spectral features.Comment: 11 pages, 17 figure

The measurement of velocity gradients in laminar flow by homodyne light-scattering spectroscopy

A technique for measuring velocity gradients in laminar flows by homodyne light scattering is presented. A theory which describes the light-scattering spectrum is derived that includes the effects of different types of linear flow fields, particle diffusion and the intensity profile in the scattering volume. The conditions which must be satisfied in order that the theory describe the experimental situation are outlined and complementary experiments are performed which both verify the theory and apply the technique. Verification is provided using the flow in a Couette device, and the flow due to single rotating cylinder in a large bath of fluid. The technique is then applied to measure the spatial variation of the shear rate in a four-roll mill