TY  - JOUR
A1  - Hoffmann, H.
A1  - Boström, Kim
A1  - Felbinger, Timo
T1  - Comment on Secure direct communication with a quantum one-time pad
N2  - In the paper [Phys. Rev. A 69, 052319 (2004)], a quantum direct communication protocol is proposed which is claimed to be unconditionally secure even for the case of a noisy channel. We show that this is not the case by giving an undetectable attack scheme
Y1  - 2005
ER  - 
TY  - JOUR
A1  - Hoffmann, H.
A1  - Seiß, Martin
A1  - Spahn, Frank
T1  - Vertical relaxation of a moonlet propeller in Saturn's a ring
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
N2  - Two images, taken by the Cassini spacecraft near Saturn's equinox in 2009 August, show the Earhart propeller casting a 350 km long shadow, offering the opportunity to watch how the ring height, excited by the propeller moonlet, relaxes to an equilibrium state. From the shape of the shadow cast and a model of the azimuthal propeller height relaxation, we determine the exponential cooling constant of this process to be lambda = 0.07 +/- 0.02 km(-1), and thereby determine the collision frequency of the ring particles in the vertically excited region of the propeller to be omega(c)/Omega = 0.9 +/- 0.2.
KW  - planets and satellites: individual (Saturn)
KW  - planets and satellites: rings
Y1  - 2013
U6  - https://doi.org/10.1088/2041-8205/765/1/L4
SN  - 2041-8205
VL  - 765
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -