arXiv subjects

Daniel Segel

Publications and source records attributed to Daniel Segel.

2 recordsLinked to original sources

arXiv1996

Extended Self-Similarity in Turbulent Systems: an Analytically Soluble Example

In turbulent flows the $n$'th order structure functions $S_n(R)$ scale like $R^{ζ_n}$ when $R$ is in the "inertial range". Extended Self-Similarity refers to the substantial increase in the range of power law behaviour of $S_n(R)$ when they are plotted as a function of $S_2(R)$ or $S_3(R)$. In this Letter we demonstrate this phenomenon analytically in the context of the ``multiscaling" turbulent advection of a passive scalar. This model gives rise to a series of differential equations for the structure functions $S_n(R)$ which can be solved and shown to exhibit extended self similarity. The phenomenon is understood by comparing the equations for $S_n(R)$ to those for $S_n(S_2)$.

chao-dyn↗

arXiv1993

Neutrino Energy Loss from the Plasma Process at all Temperatures and Densities

We present a unified approach which is accurate at all temperatures and densities for calculating the energy loss from a stellar plasma due to the plasma process, the decay of photons and plasmons into neutrino pairs. To allow efficient numerical calculations, an analytic approximation to the dispersion equations for photons and plasmons is developed. It is correct to order $α$ in the classical, degenerate, and relativistic limits for all momenta $k$ and is correct at small $k$ for all temperatures and electron densities. Within the same approximations, concise expressions are derived for the transverse, longitudinal, and axial vector components of the neutrino emissivity.

hep-ph↗