11,005 research outputs found
Resummed Perturbation Theory of Galaxy Clustering
The relationship between observed tracers such as galaxies and the underlying
dark matter distribution is crucial in extracting cosmological information. As
the linear bias model breaks down at quasi-linear scales, the standard
perturbative approach of the nonlinear Eulerian bias model (EBM) is not
accurate enough in describing galaxy clustering. In this paper, we discuss such
a model in the context of resummed perturbation theory, and further generalize
it to incorporate the subsequent gravitational evolution by combining with a
Lagrangian description of galaxies' motion. The multipoint propagators we
constructed for such model also exhibit exponential damping similar to their
dark matter counterparts, therefore the convergence property of statistics
built upon these quantities is improved. This is achieved by applying both
Eulerian and Lagrangian resummation techniques of dark matter field developed
in recent years. As inherited from the Lagrangian description of galaxy density
evolution, our approach automatically incorporates the non-locality induced by
gravitational evolution after the formation of the tracer, and also allows us
to include a continuous galaxy formation history by temporally
weighted-averaging relevant quantities with the galaxy formation rate.Comment: 19 pages, 18 figures, submitted to PR
Electron confinement by laser-driven azimuthal magnetic fields during direct laser acceleration
A laser-driven azimuthal plasma magnetic field is known to facilitate
electron energy gain from the irradiating laser pulse. The enhancement is due
to changes in the orientation between the laser electric field and electron
velocity caused by magnetic field deflections. Transverse electron confinement
is critical for realizing this concept experimentally. We find that the phase
velocity of the laser pulse has a profound impact on the transverse size of
electron trajectories. The transverse size remains constant below a threshold
energy that depends on the degree of the superluminosity and it increases with
the electron energy above the threshold. This increase can cause electron
losses in tightly focused laser pulses. We show using 3D particle-in-cell
simulations that the electron energy gain can be significantly increased by
increasing laser power at fixed intensity due to the increased electron
confinement. This finding makes a strong case for designing experiments at
multi-PW laser facilities
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