45,093 research outputs found
Spectral Singularities of Complex Scattering Potentials and Infinite Reflection and Transmission Coefficients at real Energies
Spectral singularities are spectral points that spoil the completeness of the
eigenfunctions of certain non-Hermitian Hamiltonian operators. We identify
spectral singularities of complex scattering potentials with the real energies
at which the reflection and transmission coefficients tend to infinity, i.e.,
they correspond to resonances having a zero width. We show that a wave guide
modeled using such a potential operates like a resonator at the frequencies of
spectral singularities. As a concrete example, we explore the spectral
singularities of an imaginary PT-symmetric barrier potential and demonstrate
the above resonance phenomenon for a certain electromagnetic wave guide.Comment: Published versio
Hunting for the alpha: , ,
The hypothesis of the smallness of penguin contribution to charmless
strangeless decays allows to determine with high accuracy the
value of angle from the currently available , and decay data.Comment: 9 page
Possible large direct CP asymmetry in hadronic B+- -> \pi+- \eta' decays
We calculate the branching ratio and direct CP asymmetry in nonleptonic two
body B decays B^+- ->\pi^+- \eta'. It is shown that the tree diagram and gluon
fusion mechanism via penguin diagram have comparable contributions to these
decays which, as a result, could provide an interesting venue for investigating
CP violation. Our estimate shows that the direct CP asymmetry in the above
decays could be as large as 75% which along with a branching ratio B(B^-
->\pi^- \eta')=3.4 X 10^{-6} should be accessible to experiment in the near
future.Comment: 13 pages, Revtex, 4 figures (included
Tight lower bound to the geometric measure of quantum discord
Dakic, Vedral and Brukner [Physical Review Letters \tf{105},190502 (2010)]
gave a geometric measure of quantum discord in a bipartite quantum state as the
distance of the state from the closest classical quantum (or zero discord)
state and derived an explicit formula for a two qubit state. Further, S.Luo and
S.Fu [Physical Review A \tf{82}, 034302 (2010)] obtained a generic form of this
geometric measure for a general bipartite state and established a lower bound.
In this brief report we obtain a rigorous lower bound to the geometric measure
of quantum discord in a general bipartite state which dominates that obtained
by S.Luo and S.Fu.Comment: 10 pages,2 figures. In the previous versions, a constraint was
ignored while optimizing the second term in Eq.(5), in which case, only a
lower bound on the geometric discord can be obtained. The title is also
consequently changed. Accepted in Phys.Rev.
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