24,363 research outputs found
Energy-Conserving Lattice Boltzmann Thermal Model in Two Dimensions
A discrete velocity model is presented for lattice Boltzmann thermal fluid dynamics.
This model is implemented and tested in two dimensions with a finite difference scheme. Comparison with analytical solutions shows an excellent agreement even for wide temperature differences. An alternative approximate approach is then presented for traditional lattice transport schemes
Pressure effects on superconducting properties of single-crystalline Co doped NaFeAs
Resistivity and magnetic susceptibility measurements under external pressure
were performed on single-crystals NaFe1-xCoxAs (x=0, 0.01, 0.028, 0.075,
0.109). The maximum Tc enhanced by pressure in both underdoped and optimally
doped NaFe1-xCoxAs is the same, as high as 31 K. The overdoped sample with x =
0.075 also shows a positive pressure effect on Tc, and an enhancement of Tc by
13 K is achieved under pressure of 2.3 GPa. All the superconducting samples
show large positive pressure coefficient on superconductivity, being different
from Ba(Fe1-xCox)2As2. However, the superconductivity cannot be induced by
pressure in heavily overdoped non-superconducting NaFe0.891Co0.109As. These
results provide evidence for that the electronic structure is much different
between superconducting and heavily overdoped non-superconducting NaFe1-xCoxAs,
being consistent with the observation by angle-resolved photoemission
spectroscopy.Comment: 6 pages, 6 figure
Collapse models with non-white noises II: particle-density coupled noises
We continue the analysis of models of spontaneous wave function collapse with
stochastic dynamics driven by non-white Gaussian noise. We specialize to a
model in which a classical "noise" field, with specified autocorrelator, is
coupled to a local nonrelativistic particle density. We derive general results
in this model for the rates of density matrix diagonalization and of state
vector reduction, and show that (in the absence of decoherence) both processes
are governed by essentially the same rate parameters. As an alternative route
to our reduction results, we also derive the Fokker-Planck equations that
correspond to the initial stochastic Schr\"odinger equation. For specific
models of the noise autocorrelator, including ones motivated by the structure
of thermal Green's functions, we discuss the qualitative and qantitative
dependence on model parameters, with particular emphasis on possible
cosmological sources of the noise field.Comment: Latex, 43 pages; versions 2&3 have minor editorial revision
- …