Examining California‘s SB 375‘s High Density Sustainable Communities Strategy and What it Means for Cities with their Own Low Density Strategies to Curb the Excesses of Growth: Separate Paths to a Better World?

In 2006, the State of California adopted a pioneering effort by a mere state to address global warming. The law was known in California as Assembly Bill 32. It sought to mandate that local governments in California reduce Greenhouse Gas Emissions to 1990 levels by 2020. Beyond 2020, the law required greater further reductions at specified milestones. The methods adopted to achieve these reductions were set forth in California Senate Bill 375 which, among other strategies, required regional governments in California to herd local governments into adopting an anti-sprawl approach to growth. That strategy is called the Sustainable Communities Strategy. It provides a series of incentives for compact, high density development. Many California local governments have adopted anti-growth measures over the years, but some seem completely incompatible with high density developments. This paper examines these differing urban planning strategies to visualize how these laws will interact and co-exist with each other in the near future. It does so by focusing upon one unique Northern California city, the City of Alameda, with grass-roots laws seeking to keep it in the past and forward looking regional planning efforts [crafted by the Bay Area\u27s Metropolitan Planning Agencies, i.e. the Association of Bay Area Governments (ABAG) and the Metropolitan Planning Commission (MTC)] seeking to thrust it into the future

Direct Detection of Leptophilic Dark Matter in a Model with Radiative Neutrino Masses

We consider an electro-weak scale model for Dark Matter (DM) and radiative neutrino mass generation. Despite the leptophilic nature of DM with no direct couplings to quarks and gluons, scattering with nuclei is induced at the 1-loop level through photon exchange. Effectively, there are charge-charge, dipole-charge and dipole-dipole interactions. We investigate the parameter space consistent with constraints from neutrino masses and mixing, charged lepton-flavour violation, perturbativity, and the thermal production of the correct DM abundance, and calculate the expected event rate in DM direct detection experiments. We show that current data from XENON100 start to constrain certain regions of the allowed parameter space, whereas future data from XENON1T has the potential to significantly probe the model.Comment: 24 pages, 8 figures, 2 tables, discussion of large theta13 added, version to appear in PR

Rayleigh–Taylor instability in two-component relativistic jets

Relativistic jets associated with active galactic nuclei and gamma-ray bursts propagate over huge distances without significant loss of momentum. At the same time they are bright emitters, which is indicative of strong energy dissipation. This points towards a mechanism of internal dissipation which does not result in a global disruption of the flow. One possibility is internal shocks and another one is turbulence driven by local instabilities. Such instabilities can be triggered when a freely expanding jet is reconfined by either the cocoon or external gas pressure. In this paper, we study the dynamics of two-component spine-sheath hydrodynamic jets coming into pressure equilibrium with external gas using 2D computer simulations. We find that the jet oscillations lead to a rapid onset of Rayleigh–Taylor-type instabilities, which results in additional internal dissipation and mixing of the jet components. Although slightly different in details, this outcome holds both for the heavy-spine-light-sheath and light-spine-heavy-sheath configurations. The results may provide an explanation to the spatial flaring observed in some AGN jets on kpc-scales

A possible origin of bimodal duration distribution of gamma-ray bursts

We study the distribution of the durations of gamma-ray bursts (GRBs) in the unified model of short and long GRBs recently proposed by Yamazaki, Ioka, and Nakamura. Monte Carlo simulations show clear bimodal distributions, with lognormal-like shapes for both short and long GRBs, in a power law as well as a Gaussian angulardistr ibution of the subjets. We find that the bimodality comes from the existence of the discrete emission regions (subjets or patchy shells) in the GRB jet

Baryon Loading of AGN Jets Mediated by Neutrons

Plasmas of geometrically thick, black hole (BH) accretion flows in active galactic nuclei (AGNs) are generally collisionless for protons, and involve magnetic field turbulence. Under such conditions a fraction of protons can be accelerated stochastically and create relativistic neutrons via nuclear collisions. These neutrons can freely escape from the accretion flow and decay into protons in dilute polar region above the rotating BH to form relativistic jets. We calculate geometric efficiencies of the neutron energy and mass injections into the polar region, and show that this process can deposit luminosity as high as L_j ~ 2e-3 dot{M} c^2 and mass loading dot{M}_j ~ 6e-4 dot{M} for the case of the BH mass M ~ 1e8 M_sun, where dot{M} is mass accretion rate. The terminal Lorentz factors of the jets are Gamma ~ 3, and they may explain the AGN jets having low luminosities. For higher luminosity jets, which can be produced by additional energy inputs such as Poynting flux, the neutron decay still can be a dominant mass loading process, leading to e.g., Gamma ~ 50 for L_{j,tot} ~ 3e-2 dot{M}c^2.Comment: 7 pages, 6 figures; accepted for publication in Ap