Four wave mixing with self-phase matching due to collective atomic recoil

We describe a method for non-degenerate four-wave mixing in a cold sample of 4-level atoms. An integral part of the four-wave mixing process is a collective instability which spontaneously generates a periodic density modulation in the cold atomic sample with a period equal to half of the wavelength of the generated high-frequency optical field. Due to the generation of this density modulation, phase-matching between the pump and scattered fields is not a necessary initial condition for this wave-mixing process to occur, rather the density modulation acts to "self phase-match" the fields during the course of the wave-mixing process. We describe a one-dimensional model of this process, and suggest a proof-of-principle experiment which would involve pumping a sample of cold Cs atoms with three infra-red pump fields to produce blue light.Comment: to appear in Physical Review Letter

Inducing strong density modulation with small energy dispersion in particle beams and the harmonic amplifier free electron laser

We present a possible method of inducing a periodic density modulation in a particle beam with little increase in the energy dispersion of the particles. The flow of particles in phase space does not obey Liouville's Theorem. The method relies upon the Kuramoto-like model of collective synchronism found in free electron generators of radiation, such as Cyclotron Resonance Masers and the Free Electron Laser. For the case of an FEL interaction, electrons initially begin to bunch and emit radiation energy with a correlated energy dispersion which is periodic with the FEL ponderomotive potential. The relative phase between potential and particles is then changed by approximately 180 degrees. The particles continue to bunch, however, there is now a correlated re-absorption of energy from the field. We show that, by repeating this relative phase change many times, a significant density modulation of the particles may be achieved with only relatively small energy dispersion. A similar method of repeated relative electron/radiation phase changes is used to demonstrate supression of the fundamental growth in a high gain FEL so that the FEL lases at the harmonic only

Crystallization processes and solubility of columbite-(Mn), tantalite-(Mn), microlite, pyrochlore, wodginite and titanowodginite in highly fluxed haplogranitic melts

Niobium and tantalum are critical metals that are necessary for many modern technologies such as smartphones, computers, cars, etc. Ore minerals of niobium and tantalum are typically associated with pegmatites and include columbite, tantalite, wodginite, titanowodginite, microlite and pyrochlore. Solubility and crystallization mechanisms of columbite-(Mn) and tantalite-(Mn) have been extensively studied in haplogranitic melts, with little research into other ore minerals. A new method of synthesis has been developed enabling synthesis of columbite-(Mn), tantalite-(Mn), hafnon, zircon, and titanowodginite for use in experiments at temperatures ≤ 850 °C and 200 MPa, conditions attainable by cold seal pressure vessels. Solubilities of wodginite, titanowodginite, microlite and pyrochlore are compared to those for columbite-(Mn) and tantalite-(Mn) in a flux-rich haplogranitic melt of alumina saturation index (ASI) 1.0 at 700 – 850 °C and 200 MPa. The effect of melt composition on solubilities of wodginite, titanowodginite, and microlite compared to tantalite-(Mn) is also investigated in highly fluxed haplogranitic melts of ASI 1.0, 1.10, and 1.24, at 700 °C and 800 °C and 200 MPa. The log solubility product (logKsp) for tantalite-(Mn) is highest (-2.32 mol2/kg2) followed by columbite-(Mn) (-2.68 mol2/kg2), and pyrochlore (-3.71 mol3/kg3) titanowodginite (-3.73 mol3/kg3), wodginite (-3.77 mol3/kg3), and microlite (-3.78 mol3/kg3) are almost identical within error at 750 °C. However, the tantalum mineral-melt partition coefficient solubilities of wodginite, titanowodginite, and tantalite-(Mn) are identical within error; microlite is different because it contains a major melt cation, sodium, and columbite-(Mn) is less soluble than pyrochlore. Wodginite, titanowodginite, and pyrochlore have similar temperature and compositional dependences to columbite-(Mn) and tantalite-(Mn), as described in previous studies, and microlite solubility conversely increases with ASI. Experiments crystallizing columbite-(Mn) through the interaction of a manganese-rich hydrothermal fluid with a niobium-rich pegmatite melt have demonstrated that fluid-melt interactions are a plausible mechanism for the crystallization of niobium and tantalum ore minerals. These experiments show that saturation can be reached from lower, more reasonable niobium melt concentrations than previous experiments and from higher concentrations of manganese in a hydrothermal fluid. This is significant because natural pegmatites contain evidence of hydrothermal processes during rare metal crystallization stages

Kaon Condensation in a Nambu--Jona-Lasinio (NJL) Model at High Density

We demonstrate a fully self-consistent microscopic realization of a kaon-condensed colour-flavour locked state (CFLK0) within the context of a mean-field NJL model at high density. The properties of this state are shown to be consistent with the QCD low-energy effective theory once the proper gauge neutrality conditions are satisfied, and a simple matching procedure is used to compute the pion decay constant, which agrees with the perturbative QCD result. The NJL model is used to compare the energies of the CFLK0 state to the parity even CFL state, and to determine locations of the metal/insulator transition to a phase with gapless fermionic excitations in the presence of a non-zero hypercharge chemical potential and a non-zero strange quark mass. The transition points are compared with results derived previously via effective theories and with partially self-consistent NJL calculations. We find that the qualitative physics does not change, but that the transitions are slightly lower.Comment: 21 pages, ReVTeX4. Clarified discussion and minor change

Game situation information in video-based perceptual decision making : the influence of criticality of decisions

This study examined the effects of game situation information, manipulated in terms of time and score, on decisions made in a video-based perceptual test in basketball. The participants were undergraduate university students (n=159) who viewed 21 offensive basketball plays, under two test conditions (low decision criticality; high decision criticality). To manipulate the conditions, prior to each clip, theparticipants were presented with a description of the remaining time and score differential. High decision criticality situations were characterised by a remaining time of 60 seconds or less and score differentials of 2 points or less. Low decision criticality situations were characterised by remaining time of 5 minutes or more and score differentials of 5 points or more. The participants indicated their decision (pass, shoot, dribble) after the visual display had been occluded for each clip. The results indicated that decision profiles differed under the low and high decision criticality conditions. More pass decisions were made under high decision criticality situations and more shoot decisions under low decision criticality situations. These variations differed according to the type of main sport played but not for the basketball competition level. It was concluded that game situation information does influence decision making and should be considered in video-based testing and training.<br /

Zero Temperature Thermodynamics of Asymmetric Fermi Gases at Unitarity

The equation of state of a dilute two-component asymmetric Fermi gas at unitarity is subject to strong constraints, which affect the spatial density profiles in atomic traps. These constraints require the existence of at least one non-trivial partially polarized (asymmetric) phase. We determine the relation between the structure of the spatial density profiles and the T=0 equation of state, based on the most accurate theoretical predictions available. We also show how the equation of state can be determined from experimental observations.Comment: 10 pages and 7 figures. (Minor changes to correspond with published version.

Induced P-wave Superfluidity in Asymmetric Fermi Gases

We show that two new intra-species P-wave superfluid phases appear in two-component asymmetric Fermi systems with short-range S-wave interactions. In the BEC limit, phonons of the molecular BEC induce P-wave superfluidity in the excess fermions. In the BCS limit, density fluctuations induce P-wave superfluidity in both the majority and the minority species. These phases may be realized in experiments with spin-polarized Fermi gases.Comment: published versio

V1647 Ori (IRAS 05436-0007) in Outburst: the First Three Months

We report on photometric (BVRIJHK) and low dispersion spectroscopic observations of V1647 Ori, the star that drives McNeil's Nebula, between 10 February and 7 May 2004. The star is photometrically variable atop a general decline in brightness of about 0.3-0.4 magnitudes during these 87 days. The spectra are featureless, aside from H-alpha and the Ca II infrared triplet in emission, and a Na I D absorption feature. The Ca II triplet line ratios are typical of young stellar objects. The H-alpha equivalent width may be modulated on a period of about 60 days. The post-outburst extinction appears to be less than 7 mag. The data are suggestive of an FU Orionis-like event, but further monitoring will be needed to definitively characterize the outburst.Comment: Accepted for publication in the Astronomical Journa