TY  - JOUR
A1  - Grätz, Fabio M.
A1  - Seiss, Martin
A1  - Spahn, Frank
T1  - Formation of moon-induced gaps in dense planetary rings
BT  - application to the rings of saturn
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We develop an axisymmetric diffusion model to describe radial density profiles in the vicinity of tiny moons embedded in planetary rings. Our diffusion model accounts for the gravitational scattering of the ring particles by an embedded moon and for the viscous diffusion of the ring matter back into the gap. With test particle simulations, we show that the scattering of the ring particles passing the moon is larger for small impact parameters than estimated by Goldreich & Tremaine and Namouni. This is significant for modeling the Keeler gap. We apply our model to the gaps of the moons Pan and Daphnis embedded in the outer A ring of Saturn with the aim to estimate the shear viscosity of the ring in the vicinity of the Encke and Keeler gap. In addition, we analyze whether tiny icy moons whose dimensions lie below Cassini's resolution capabilities would be able to explain the gap structure of the C ring and the Cassini division.
KW  - diffusion
KW  - planets and satellites: rings
KW  - scattering
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4357/aace00
SN  - 0004-637X
SN  - 1538-4357
VL  - 862
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - GEN
A1  - Bouchoule, Isabelle
A1  - Schemmer, Max
A1  - Henkel, Carsten
T1  - Cooling phonon modes of a Bose condensate with uniform few body losses
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - We present a general analysis of the cooling produced by losses on condensates or quasi-condensates. We study how the occupations of the collective phonon modes evolve in time, assuming that the loss process is slow enough so that each mode adiabatically follows the decrease of the mean density. The theory is valid for any loss process whose rate is proportional to the jth power of the density, but otherwise spatially uniform. We cover both homogeneous gases and systems confined in a smooth potential. For a low-dimensional gas, we can take into account the modified equation of state due to the broadening of the cloud width along the tightly confined directions, which occurs for large interactions. We find that at large times, the temperature decreases proportionally to the energy scale mc2, where m is the mass of the particles and c the sound velocity. We compute the asymptotic ratio of these two quantities for different limiting cases: a homogeneous gas in any dimension and a one-dimensional gas in a harmonic trap.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1029 
KW  - 3 body recombination
KW  - gas
KW  - scattering
KW  - Bose-Einstein condensates (BECs)
KW  - harmonic traps
KW  - one-dimensional Bose gas
KW  - phonon modes
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-468811
SN  - 1866-8372
IS  - 1029
ER  -