9,615 research outputs found
Quantum corrections to Higher-Dimensional Theories
This is a non-technical summary of the subtleties of quantum corrections on
extra-dimensional theories: should one first renormalize and then mode expand,
or first expand in four-dimensional modes and then renormalize?Comment: 9 pages, based on a talk at IRGAC 2006, Barcelon
Polynomial algebras and exact solutions of general quantum non-linear optical models I: Two-mode boson systems
We introduce higher order polynomial deformations of Lie algebra. We
construct their unitary representations and the corresponding single-variable
differential operator realizations. We then use the results to obtain exact
(Bethe ansatz) solutions to a class of 2-mode boson systems, including the
Boson-Einstein Condensate models as special cases. Up to an overall factor, the
eigenfunctions of the 2-mode boson systems are given by polynomials whose roots
are solutions of the associated Bethe ansatz equations. The corresponding
eigenvalues are expressed in terms of these roots. We also establish the
spectral equivalence between the BEC models and certain quasi-exactly solvable
Sch\"ordinger potentials.Comment: 20 pages, final version to appear in J. Phys. A: Math. Theor
Structure and bonding of halonium compounds
The geometrical parameters and the bonding in [D···X···D]+ halonium compounds, where D is a Lewis base with N as the donor atom and X is Cl, Br, or I, have been investigated through a combined structural and computational study. Cambridge Structural Database (CSD) searches have revealed linear and symmetrical [D···X···D]+ frameworks with neutral donors. By means of density functional theory (DFT), molecular electrostatic potential (MEP), and energy decomposition analyses (EDA) calculations, we have studied the effect of various halogen atoms (X) on the [D···X···D]+ framework, the effect of different nitrogen-donor groups (D) attached to an iodonium cation (X = I), and the influence of the electron density alteration on the [D···I···D]+ halonium bond by variation of the R substituents at the N-donor upon the symmetry, strength, and nature of the interaction. The physical origin of the interaction arises from a subtle interplay between electrostatic and orbital contributions (σ-hole bond). Interaction energies as high as 45 kcal/mol suggest that halonium bonds can be exploited for the development of novel halonium transfer agents, in asymmetric halofunctionalization or as building blocks in supramolecular chemistry
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