26,006 research outputs found
AdS/CFT Correspondence and Quotient Space Geometry
We consider a version of the correspondence, in which the
bulk space is taken to be the quotient manifold with a
fairly generic discrete group acting isometrically on . We
address some geometrical issues concerning the holographic principle and the
UV/IR relations. It is shown that certain singular structures on the quotient
boundary can affect the underlying physical spectrum. In
particular, the conformal dimension of the most relevant operators in the
boundary CFT can increase as becomes ``large''. This phenomenon also
has a natural explanation in terms of the bulk supergravity theory. The scalar
two-point function is computed using this quotient version of the AdS/CFT
correspondence, which agrees with the expected result derived from conformal
invariance of the boundary theory.Comment: 28 pages, Latex, no figures. Minor changes, version to appear in JHE
Optical spectroscopy of molecular junctions: Nonequilibrium Green's functions perspective
We consider optical spectroscopy of molecular junctions from the quantum
transport perspective when radiation field is quantized and optical response of
the system is simulated as photon flux. Using exact expressions for photon and
electronic fluxes derived within the nonequilibrium Green function (NEGF)
methodology and utilizing fourth order diagrammatic perturbation theory in
molecular coupling to radiation field we perform simulations employing
realistic parameters. Results of the simulations are compared to the bare
perturbation theory (PT) usually employed in studies on nonlinear optical
spectroscopy to classify optical processes. We show that the bare PT violates
conservation laws, while flux conserving NEGF formulation mixes optical
processes.Comment: 10 pages, 6 figure
Simulation of optical response functions in molecular junctions
We discuss theoretical approaches to nonlinear optical spectroscopy of
molecular junctions. Optical response functions are derived in the form
convenient for implementation of Green function techniques, and their
expressions in terms of pseudoparticle nonequilibrium Green functions are
proposed. The formulation allows to account for both intra-molecular
interactions and hybridization of molecular states due to coupling to contacts.
Two-dimensional optical spectroscopy in junctions is considered as an example.Comment: 11 pages, 7 figure
Regioselective Formation of α-Vinylpyrroles from the Ruthenium-Catalyzed Coupling Reaction of Pyrroles and Terminal Alkynes Involving C–H Bond Activation
The cationic ruthenium catalyst Ru3(CO)12/NH4PF6 was found to be highly effective for the intermolecular coupling reaction of pyrroles and terminal alkynes to give gem-selective α-vinylpyrroles. The carbon isotope effect on the α-pyrrole carbon and the Hammett correlation from a series of para-substituted N-arylpyrroles (ρ = −0.90) indicate a rate-limiting C−C bond formation step of the coupling reaction
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