33,941 research outputs found
Entropy Bound for the Classical Capacity of a Quantum Channel Assisted by Classical Feedback
We prove that the classical capacity of an arbitrary quantum channel assisted
by a free classical feedback channel is bounded from above by the maximum
average output entropy of the quantum channel. As a consequence of this bound,
we conclude that a classical feedback channel does not improve the classical
capacity of a quantum erasure channel, and by taking into account energy
constraints, we conclude the same for a pure-loss bosonic channel. The method
for establishing the aforementioned entropy bound involves identifying an
information measure having two key properties: 1) it does not increase under a
one-way local operations and classical communication channel from the receiver
to the sender and 2) a quantum channel from sender to receiver cannot increase
the information measure by more than the maximum output entropy of the channel.
This information measure can be understood as the sum of two terms, with one
corresponding to classical correlation and the other to entanglement.Comment: v2: 6 pages, 1 figure, final version published in conference
proceeding
Three realizations of quantum affine algebra
In this article we establish explicit isomorphisms between three realizations
of quantum twisted affine algebra : the Drinfeld ("current")
realization, the Chevalley realization and the so-called realization,
investigated by Faddeev, Reshetikhin and Takhtajan.Comment: 15 page
Lepton flavor violating and conversion in unparticle physics
We have studied lepton flavor violation processes and
conversion in nuclei induced by unparticle. Both and conversion rate strongly
depend on the scale dimension and the unparticle coupling
(K=V, A, S, P). Present experimental upper bounds on
, and put stringent constraints on the parameters of unaprticle physics. The
scale dimensions around 2 are favored for the unparticle scale
of and the unparticle coupling of
. is proportional to
for the pure vector and scalar couplings between
unparticle and SM fermions, this peculiar atomatic number dependence can be
used to distinguish unparticle from other theoretical models.Comment: 16 pages, 5 figure
Heavy Quark diffusion from lattice QCD spectral functions
We analyze the low frequency part of charmonium spectral functions on large
lattices close to the continuum limit in the temperature region as well as for . We present evidence for the
existence of a transport peak above and its absence below . The
heavy quark diffusion constant is then estimated using the Kubo formula. As
part of the calculation we also determine the temperature dependence of the
signature for the charmonium bound state in the spectral function and discuss
the fate of charmonium states in the hot medium.Comment: 4 pages, Proceedings for Quark Matter 2011 Conference, May 23-28,
2011, Annecy, Franc
Cusp-scaling behavior in fractal dimension of chaotic scattering
A topological bifurcation in chaotic scattering is characterized by a sudden
change in the topology of the infinite set of unstable periodic orbits embedded
in the underlying chaotic invariant set. We uncover a scaling law for the
fractal dimension of the chaotic set for such a bifurcation. Our analysis and
numerical computations in both two- and three-degrees-of-freedom systems
suggest a striking feature associated with these subtle bifurcations: the
dimension typically exhibits a sharp, cusplike local minimum at the
bifurcation.Comment: 4 pages, 4 figures, Revte
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