P-A Measurements in the 48-Ca(p,n)48-Sc Reaction at 135 MeV

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Fragmentation of High-spin Stretched States in the (p,n) Reaction on 36-Ar and 40-Ca

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Search for a State at E_x = 2.6MeV in 20-Na via the 20-Ne(p,n)20-Na Reaction and Possible Breakout from the Hot CNO Cycle

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Black holes and Hawking radiation in spacetime and its analogues

These notes introduce the fundamentals of black hole geometry, the thermality of the vacuum, and the Hawking effect, in spacetime and its analogues. Stimulated emission of Hawking radiation, the trans-Planckian question, short wavelength dispersion, and white hole radiation in the setting of analogue models are also discussed. No prior knowledge of differential geometry, general relativity, or quantum field theory in curved spacetime is assumed.Comment: 31 pages, 9 figures; to appear in the proceedings of the IX SIGRAV School on 'Analogue Gravity', Como (Italy), May 2011, eds. D. Faccio et. al. (Springer

Engineering strong chiral light-matter interactions in a waveguide-coupled nanocavity

Spin-dependent, directional light-matter interactions form the basis of chiral quantum networks. In the solid state, quantum emitters commonly possess circularly polarised optical transitions with spin-dependent handedness. We demonstrate theoretically that spin-dependent chiral coupling can be realised by embedding such an emitter in a waveguide-coupled nanocavity, which supports two near-degenerate, orthogonally-polarised cavity modes. The chiral behaviour arises due to direction-dependent interference between the cavity modes upon coupling to two single-mode output waveguides. Notably, an experimentally realistic cavity design simultaneously supports near-unity chiral contrast, efficient (β>0.95) waveguide coupling and enhanced light-matter interaction strength (Purcell factor FP>60). In combination, these parameters could enable the development of highly coherent spin-photon interfaces, and may even allow access to the chiral strong-coupling regime using integrated nano-photonic devices

High-Spin Stretched States in Nuclei Excited via (p,n) Reactions

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

A microscopic model for d-wave charge carrier pairing and non-Fermi-liquid behavior in a purely repulsive 2D electron system

We investigate a microscopic model for strongly correlated electrons with both on-site and nearest neighbor Coulomb repulsion on a 2D square lattice. This exhibits a state in which electrons undergo a ``somersault'' in their internal spin-space (spin-flux) as they traverse a closed loop in external coordinate space. When this spin-1/2 antiferromagnetic (AFM) insulator is doped, the ground state is a liquid of charged, bosonic meron-vortices, which for topological reasons are created in vortex-antivortex pairs. The magnetic exchange energy of the distorted AFM background leads to a logarithmic vortex-antivortex attraction which overcomes the direct Coulomb repulsion between holes localized on the vortex cores. This leads to the appearance of pre-formed charged pairs. We use the Configuration Interaction (CI) Method to study the quantum translational and rotational motion of various charged magnetic solitons and soliton pairs. The CI method systematically describes fluctuation and quantum tunneling corrections to the Hartree-Fock Approximation (HFA). We find that the lowest energy charged meron-antimeron pairs exhibit d-wave rotational symmetry, consistent with the symmetry of the cuprate superconducting order parameter. For a single hole in the 2D AFM plane, we find a precursor to spin-charge separation in which a conventional charged spin-polaron dissociates into a singly charged meron-antimeron pair. This model provides a unified microscopic basis for (i) non-Fermi-liquid transport properties, (ii) d-wave preformed charged carrier pairs, (iii) mid-infrared optical absorption, (iv) destruction of AFM long range order with doping and other magnetic properties, and (v) certain aspects of angled resolved photo-emission spectroscopy (ARPES).Comment: 14 pages, 17 figure

Anthropogenic Space Weather

Anthropogenic effects on the space environment started in the late 19th century and reached their peak in the 1960s when high-altitude nuclear explosions were carried out by the USA and the Soviet Union. These explosions created artificial radiation belts near Earth that resulted in major damages to several satellites. Another, unexpected impact of the high-altitude nuclear tests was the electromagnetic pulse (EMP) that can have devastating effects over a large geographic area (as large as the continental United States). Other anthropogenic impacts on the space environment include chemical release ex- periments, high-frequency wave heating of the ionosphere and the interaction of VLF waves with the radiation belts. This paper reviews the fundamental physical process behind these phenomena and discusses the observations of their impacts.Comment: 71 pages, 35 figure

Global impacts of the 1980s regime shift

Despite evidence from a number of Earth systems that abrupt temporal changes known as regime shifts are important, their nature, scale and mechanisms remain poorly documented and understood. Applying principal component analysis, change-point analysis and a sequential t-test analysis of regime shifts to 72 time series, we confirm that the 1980s regime shift represented a major change in the Earth's biophysical systems from the upper atmosphere to the depths of the ocean and from the Arctic to the Antarctic, and occurred at slightly different times around the world. Using historical climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and statistical modelling of historical temperatures, we then demonstrate that this event was triggered by rapid global warming from anthropogenic plus natural forcing, the latter associated with the recovery from the El Chichón volcanic eruption. The shift in temperature that occurred at this time is hypothesized as the main forcing for a cascade of abrupt environmental changes. Within the context of the last century or more, the 1980s event was unique in terms of its global scope and scale; our observed consequences imply that if unavoidable natural events such as major volcanic eruptions interact with anthropogenic warming unforeseen multiplier effects may occur

Calibration of a Neutron Polarimeter

This research was sponsored by the National Science Foundation Grant NSF PHY-931478