How to make plasma of helium nucleus, electrons and positrons?4 answersTo create a plasma of helium nucleus, electrons, and positrons, one possible method is to use pulsed electron cyclotron resonance discharge in a poloidal heliotron type magnetic field. This method allows for the production of helium plasmas with low fluctuation and a uniform radial density distribution. Another approach is to generate an electron-positron plasma by trapping externally injected, low energy electrons and positrons using electron cyclotron resonance heating in a magnetic mirror. By balancing the positron flux from a commercial Na-22 source, it is expected that an equilibrium density of 10^6-10^8 cm^-3 can be achieved. These methods provide potential ways to create plasmas consisting of helium nucleus, electrons, and positrons.
What are the challenges in separating particles in dense media?5 answersThe challenges in separating particles in dense media include the dependence of grades and throughputs of concentrates on volume fractions occupied by particles, physical properties of components in the slurry, particle size and density distributions, and the sensitivity of finer particles to the motion of larger particles. Additionally, the separation of particles in dense media can be influenced by the magnitude and direction of velocity of larger particles, which affects particles in the "near density" range. Other challenges include the need for specific arrangements and techniques to separate particles based on their sizes or refractive indices, such as using interfering light or light gradient forces. Furthermore, the design of apparatus for separating particles in dense media requires careful consideration of factors such as fluid flow direction, capturing means, and the ability to adapt to changes in fluid velocity or particle composition.
Parametric photon production from axion?5 answersParametric photon production from axions can occur through various mechanisms. One such mechanism is the axion-photon-photon interaction, which modifies Maxwell's equations and leads to a new parametric instability. This instability results in the decay of a strong pump into a scattered light wave and an axion, with the axion mode growing exponentially in time. This growth leads to a change in the polarization of the initial laser beam, providing a signal for detection. Additionally, axion clumps can undergo parametric resonance into photons, especially for clumps above a critical mass. Mergers of sub-critical mass clumps can also lead to super-critical clumps that undergo parametric resonance into photons. These processes have implications for cosmology and may have observable signatures, making them of interest for further study.
What would be the consequences of being able to generate new matter?5 answersThe consequences of being able to generate new matter would have significant implications in various areas of physics. In the context of neutrino oscillation experiments, the existence of a new force mediated by a light scalar particle could lead to neutrino masses and mixings with a much stronger matter dependence than the MSW effect. In cosmology, the continuous creation of matter associated with the production of particles by the gravitational field could have implications for the cosmic microwave background power spectrum and the validity of the generalized second law of thermodynamics. The evolution of matter in the expanding universe during different phases, such as the end of inflation and the radiation-dominated era, would also be affected by the presence of matter creation and energy exchange. Additionally, the generation of new matter could impact the formation of nonlinear structures and the timing of the first star forming halos in the early Universe.
What is the relationship between particle creation and the superfluid universe?5 answersParticle creation in the context of the superfluid universe has been studied in several papers. Singh et al. examined the effect of particle creation on the evolution of the FRW cosmological model and considered the universe as an open thermodynamic system, where particle creation leads to supplementary negative creation pressure in addition to the thermodynamic pressure. Navarro-Salas discussed the entwining relationship between particle creation and quantum anomalies, specifically relating chiral anomalies with the process of particle creation. They argued that the symmetry under electric-magnetic duality rotations of the source-free Maxwell theory is anomalous in curved spacetime, which could lead to a change in the net polarization of photons propagating in a gravitational field. Hong et al. examined particle production during tunneling in quantum cosmology and found that the creation of the universe from nothing can be understood as a limit of tunneling from a small recollapsing universe. Pathinayake and Ford investigated the creation of quanta of a self-coupled scalar field due to the time dependence of the classical scalar field and discussed its implications for inflationary cosmology. Nikolic discussed the inconsistency between the time dependence of raising and lowering operators in particle creation and the field equations and conservation of the stress-energy tensor, and explored possible resolutions to this inconsistency.
How does particle creation occur in a superfluid universe?5 answersParticle creation in a superfluid universe occurs through various mechanisms. One mechanism is the interaction of a weakly incident gravitational perturbation with a weakly interacting static one-dimensional domain wall. Another mechanism is the effect of particle creation on the evolution of the universe, where particle creation leads to supplementary negative creation pressure in addition to the thermodynamic pressure. Additionally, particle creation can arise from scattering and mode conversion in a background curved spacetime, including spacetimes with a black hole. Furthermore, the creation of particles can occur during tunneling in quantum cosmology, where a minisuperspace model with a scalar field and a radiation background is considered. These different mechanisms contribute to the overall process of particle creation in a superfluid universe.