26,018 research outputs found
Neutral triplet Collective Mode as a new decay channel in Graphite
In an earlier work we predicted the existence of a neutral triplet collective
mode in undoped graphene and graphite [Phys. Rev. Lett. {\bf 89} (2002) 16402].
In this work we study a phenomenological Hamiltonian describing the interaction
of tight-binding electrons on honeycomb lattice with such a dispersive neutral
triplet boson. Our Hamiltonian is a generalization of the Holstein polaron
problem to the case of triplet bosons with non-trivial dispersion all over the
Brillouin zone. This collective mode constitutes an important excitation branch
which can contribute to the decay rate of the electronic excitations. The
presence of such collective mode, modifies the spectral properties of electrons
in graphite and undoped graphene. In particular such collective mode, as will
be shown in this paper, can account for some part of the missing decay rate in
a time-domain measurement done on graphite
On the Approximability and Hardness of the Minimum Connected Dominating Set with Routing Cost Constraint
In the problem of minimum connected dominating set with routing cost
constraint, we are given a graph , and the goal is to find the
smallest connected dominating set of such that, for any two
non-adjacent vertices and in , the number of internal nodes on the
shortest path between and in the subgraph of induced by is at most times that in . For general graphs, the only
known previous approximability result is an -approximation algorithm
() for by Ding et al. For any constant , we
give an -approximation
algorithm. When , we give an -approximation
algorithm. Finally, we prove that, when , unless , for any constant , the problem admits no
polynomial-time -approximation algorithm, improving
upon the bound by Du et al. (albeit under a stronger hardness
assumption)
Uniqueness of Nash equilibria in quantum Cournot duopoly game
A quantum Cournot game of which classical form game has multiple Nash
equilibria is examined. Although the classical equilibria fail to be Pareto
optimal, the quantum equilibrium exhibits the following two properties, (i) if
the measurement of entanglement between strategic variables chosen by the
competing firms is sufficiently large, the multiplicity of equilibria vanishes,
and, (ii) the more strongly the strategic variables are entangled, the more
closely the unique equilibrium approaches to the optimal one.Comment: 7 pages, 2 figure
CP Violating Rate Difference Relations for and in Broken SU(3)
Within the standard model there exist certain relations between CP violating
rate differences in B decays in the SU(3) limit. We study SU(3) breaking
corrections to these relations in the case of charmless, hadronic, two body
decays using the improved factorization model of Ref.\cite{3}. We consider the
cases and for both and mesons. We present an
estimate for in terms of .Comment: Latex 13 pages, no figure
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