Primordial Black Holes, Hawking Radiation and the Early Universe

The 511 keV gamma emission from the galactic core may originate from a high concentration ($\sim 10^{22}$) of primordial black holes (PBHs) in the core each of whose Hawking radiation includes $\sim 10^{21}$ positrons per second. The PBHs we consider are taken as near the lightest with longevity greater than the age of the universe (mass $\sim 10^{12}$ kg; Schwarzschild radius $\sim 1$ fm). These PBHs contribute only a small fraction of cold dark matter, $\Omega_{PBH} \sim 10^{-8}$. This speculative hypothesis, if confirmed implies the simultaneous discovery of Hawking radiation and an early universe phase transition.Comment: 4 Page

Human Factors of Flight-deck Automation: NASA/Industry Workshop

The scope of automation, the benefits of automation, and automation-induced problems were discussed at a workshop held to determine whether those functions previously performed manually on the flight deck of commercial aircraft should always be automated in view of various human factors. Issues which require research for resolution were identified. The research questions developed are presented

Torn between legal claiming and privatized remedy: rights mobilization against gold mining in Chile

This is the author accepted manuscript. The final version is available from Cambridge University Press via the DOI in this recordMany academic authors, policymakers, NGOs and corporations have focused on top-down human rights global norm-making, such as the United Nations Guiding Principles for Business and Human Rights (UNGPs). What is often missing are contextual and substantive analyses that interrogate rights mobilization and linkages between voluntary transnational rules and domestic governance. Deploying a socio-legal approach and using a combination of longitudinal field and archival data, this article investigates how a local, indigenous community in Northern Chile mobilized their rights over a period of almost two decades. We found that rights mobilization was largely shaped by tensions between the different logics of legality and the business organization. In our case, the UNGP implementation process has been ineffective in giving rightsholders access to genuine remedy. On the contrary, it has led to weakened rights mobilization, dividing the local community. We conclude that greater attention to rights mobilization and domestic governance dynamics should be given in the Business and Human Rights debate.European Union Horizon 202

On Evidence-based Risk Management in Requirements Engineering

Background: The sensitivity of Requirements Engineering (RE) to the context makes it difficult to efficiently control problems therein, thus, hampering an effective risk management devoted to allow for early corrective or even preventive measures. Problem: There is still little empirical knowledge about context-specific RE phenomena which would be necessary for an effective context- sensitive risk management in RE. Goal: We propose and validate an evidence-based approach to assess risks in RE using cross-company data about problems, causes and effects. Research Method: We use survey data from 228 companies and build a probabilistic network that supports the forecast of context-specific RE phenomena. We implement this approach using spreadsheets to support a light-weight risk assessment. Results: Our results from an initial validation in 6 companies strengthen our confidence that the approach increases the awareness for individual risk factors in RE, and the feedback further allows for disseminating our approach into practice.Comment: 20 pages, submitted to 10th Software Quality Days conference, 201

Resolution of puzzles from the LSND, KARMEN, and MiniBooNE experiments

This work has attempted to reconcile puzzling neutrino oscillation results from the LSND, KARMEN and MiniBooNE experiments. We show that the LSND evidence for $\bar{\nu}_\mu \to \bar{\nu}_e$ oscillations, its long-standing disagreement with the results from KARMEN, and the anomalous event excess observed by MiniBooNE in $\nu_\mu$ and $\bar{\nu}_\mu$ data could all be explained by the existence of a heavy sterile neutrino ($\nu_h$). All these results are found to be consistent with each other assuming that the $\nu_h$ is created in $\nu_\mu$ neutral-current interactions and decays radiatively into a photon and a light neutrino. Assuming the $\nu_h$ is produced through mixing with $\nu_\mu$, the combined analysis of the LSND and MiniBooNe excess events suggests that the $\nu_h$ mass is in the range from 40 to 80 MeV, the mixing strength is $|U_{\mu h}|^2 \simeq 10^{-3}-10^{-2}$, and the lifetime is $\tau_{\nu_h} \lesssim 10^{-9}$ s. Surprisingly, this LSND-MiniBooNE parameters window is found to be unconstrained by the results from the most sensitive experiments searching for heavy neutrino. We set new limits on $|U_{\mu h}|^2$ for the LSND-MiniBooNE favorable mass region from the precision measurements of the Michel spectrum by the TWIST experiment. The results obtained provide a strong motivation for a sensitive search for the $\nu_h$ in a near future $K$ decay or neutrino experiments, which fit well in the existing/planned experimental programs at CERN or FNAL. The question of whether the heavy neutrino is Dirac or Majorana particle is briefly discussed.Comment: 24 pages, 28 figures, version to appear in PR

A high-reflectivity high-Q micromechanical Bragg-mirror

We report on the fabrication and characterization of a micromechanical oscillator consisting only of a free-standing dielectric Bragg mirror with high optical reflectivity and high mechanical quality. The fabrication technique is a hybrid approach involving laser ablation and dry etching. The mirror has a reflectivity of 99.6%, a mass of 400ng, and a mechanical quality factor Q of approximately 10^4. Using this micromirror in a Fabry Perot cavity, a finesse of 500 has been achieved. This is an important step towards designing tunable high-Q high-finesse cavities on chip.Comment: 3 pages, 2 figure

Gamow-Teller transitions and deformation in the proton-neutron random phase approximation

We investigate reliability of Gamow-Teller transition strengths computed in the proton-neutron random phase approximation, comparing with exact results from diagonalization in full $0\hbar\omega$ shell-model spaces. By allowing the Hartree-Fock state to be deformed, we obtain good results for a wide variety of nuclides, even though we do not project onto good angular momentum. We suggest that deformation is as important or more so than pairing for Gamow-Teller transitions.Comment: 8 pages, 5 figures; added references, clarified discussion with regards to stabilit

MeV-mass dark matter and primordial nucleosynthesis

The annihilation of new dark matter candidates with masses $m_X$ in the MeV range may account for the galactic positrons that are required to explain the 511 keV $\gamma$-ray flux from the galactic bulge. We study the impact of MeV-mass thermal relic particles on the primordial synthesis of $^2$H, $^4$He, and $^7$Li. If the new particles are in thermal equilibrium with neutrinos during the nucleosynthesis epoch they increase the helium mass fraction for m_X\alt 10 MeV and are thus disfavored. If they couple primarily to the electromagnetic plasma they can have the opposite effect of lowering both helium and deuterium. For $m_X=4$--10 MeV they can even improve the overall agreement between the predicted and observed $^2$H and $^4$He abundances.Comment: 11 pages, 10 figures, references and two appendices added, conclusions unchanged; accepted for publication in Phys.Rev.

Self-cooling of a micro-mirror by radiation pressure

We demonstrate passive feedback cooling of a mechanical resonator based on radiation pressure forces and assisted by photothermal forces in a high-finesse optical cavity. The resonator is a free-standing high-reflectance micro-mirror (of mass m=400ng and mechanical quality factor Q=10^4) that is used as back-mirror in a detuned Fabry-Perot cavity of optical finesse F=500. We observe an increased damping in the dynamics of the mechanical oscillator by a factor of 30 and a corresponding cooling of the oscillator modes below 10 K starting from room temperature. This effect is an important ingredient for recently proposed schemes to prepare quantum entanglement of macroscopic mechanical oscillators.Comment: 11 pages, 9 figures, minor correction

Glutamate receptor exocytosis and spine enlargement during chemically induced long-term potentiation

The changes in synaptic morphology and receptor content that underlie neural plasticity are poorly understood. Here, we use a pH-sensitive green fluorescent protein to tag recombinant glutamate receptors and monitor their dynamics onto dendritic spine surfaces. We show that chemically induced long-term potentiation (chemLTP) drives robust exocytosis of AMPA receptors. In contrast, the same stimulus produces a small reduction of NMDA receptors from the spine surface. chemLTP produces similar modification of small and large spines. Interestingly, during chemLTP induction, spines increase in volume before accumulation of AMPA receptors on their surface, indicating that distinct mechanisms underlie changes in morphology and receptor content