2,034 research outputs found
H
An H-function with complex parameters is defined by a
Mellin-Barnes type integral. Necessary and sufficient conditions
under which the integral defining the H-function converges
absolutely are established. Some properties, special cases, and an
application to integral transforms are given
The Link Between Shocks, Turbulence and Magnetic Reconnection in Collisionless Plasmas
Global hybrid (electron fluid, kinetic ions) and fully kinetic simulations of the magnetosphere have been used to show surprising interconnection between shocks, turbulence and magnetic reconnection. In particular collisionless shocks with their reflected ions that can get upstream before retransmission can generate previously unforeseen phenomena in the post shocked flows: (i) formation of reconnecting current sheets and magnetic islands with sizes up to tens of ion inertial length. (ii) Generation of large scale low frequency electromagnetic waves that are compressed and amplified as they cross the shock. These \u27wavefronts\u27 maintain their integrity for tens of ion cyclotron times but eventually disrupt and dissipate their energy. (iii) Rippling of the shock front, which can in turn lead to formation of fast collimated jets extending to hundreds of ion inertial lengths downstream of the shock. The jets, which have high dynamical pressure, \u27stir\u27 the downstream region, creating large scale disturbances such as vortices, sunward flows, and can trigger flux ropes along the magnetopause. This phenomenology closes the loop between shocks, turbulence and magnetic reconnection in ways previously unrealized. These interconnections appear generic for the collisionless plasmas typical of space, and are expected even at planar shocks, although they will also occur at curved shocks as occur at planets or around ejecta
Satellite-based Quantum Network: Security and Challenges over Atmospheric Channel
The ultra-secure quantum network leverages quantum cryptography to deliver
unsurpassed data transfer security. In principle, the well-known quantum key
distribution (QKD) achieves unconditional security, which raises concerns about
the trustworthiness of 6G wireless systems in order to mitigate the gap between
practice and theory. The long-distance satellite-to-ground evolving quantum
network distributes keys that are ubiquitous to the node on the ground through
low-orbit satellites. As the secret key sequence is encoded into quantum
states, it is sent through the atmosphere via a quantum channel. It still
requires more effort in the physical layer design of deployment ranges,
transmission, and security to achieve high-quality quantum communication. In
this paper, we first review the quantum states and channel properties for
satellite-based quantum networks and long-range quantum state transfer (QST).
Moreover, we highlight some challenges, such as transmissivity statistics,
estimation of channel parameters and attack resilience, quantum state transfer
for satellite-based quantum networks, and wavepacket shaping techniques over
atmospheric channels. We underline two research directions that consider the
QST and wavepacket shaping techniques for atmospheric transmission in order to
encourage further research toward the next generation of satellite-based
quantum networks.Comment: 6 pages, 1 figure, conferenc
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