41,251 research outputs found
Collective Motion of Polarized Dipolar Fermi Gases in the Hydrodynamic Regime
Recently, a seminal STIRAP experiment allowed the creation of 40K-87Rb
molecules in the rovibrational ground state [K.-K. Ni et al., Science 322, 231
(2008)]. In order to describe such a polarized dipolar Fermi gas in the
hydrodynamic regime, we work out a variational time-dependent Hartree-Fock
approach. With this we calculate dynamical properties of such a system as, for
instance, the frequencies of the low-lying excitations and the time-of-flight
expansion. We find that the dipole-dipole interaction induces anisotropic
breathing oscillations in momentum space. In addition, after release from the
trap, the momentum distribution becomes asymptotically isotropic, while the
particle density becomes anisotropic
Charge migration mechanisms in the DNA at finite temperature revisited; from quasi-ballistic to subdiffusive transport
Various charge migration mechanisms in the DNA are studied within the
framework of the Peyrard-Bishop-Holstein model which has been widely used to
address charge dynamics in this macromolecule. To analyze these mechanisms we
consider characteristic size and time scales of the fluctuations of the
electronic and vibrational subsystems. It is shown, in particular, that due to
substantial differences in these timescales polaron formation is unlikely
within a broad range of temperatures. We demonstrate that at low temperatures
electronic transport can be quasi-ballistic. For high temperatures, we propose
an alternative to polaronic charge migration mechanism: the
fluctuation-assisted one, in which the electron dynamics is governed by
relatively slow fluctuations of the vibrational subsystem. We argue also that
the discussed methods and mechanisms can be relevant for other organic
macromolecular systems, such as conjugated polymers and molecular aggregates
Lightweight Security for Network Coding
Under the emerging network coding paradigm, intermediate nodes in the network
are allowed not only to store and forward packets but also to process and mix
different data flows. We propose a low-complexity cryptographic scheme that
exploits the inherent security provided by random linear network coding and
offers the advantage of reduced overhead in comparison to traditional
end-to-end encryption of the entire data. Confidentiality is achieved by
protecting (or "locking") the source coefficients required to decode the
encoded data, without preventing intermediate nodes from running their standard
network coding operations. Our scheme can be easily combined with existing
techniques that counter active attacks.Comment: Proc. of the IEEE International Conference on Communications (ICC
2008), Beijing, China, May 200
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