Critical O(N) - vector nonlinear sigma - models: A resume of their field structure

The classification of quasi - primary fields is outlined. It is proved that the only conserved quasi - primary currents are the energy - momentum tensor and the O(N) - Noether currents. Derivation of all quasi - primary fields and the resolution of degeneracy is sketched. Finally the limits d=2 and d=4 of the space dimension are discussed. Whereas the latter is trivial the former is only almost so.Comment: 16 pages, Latex. To appear in the Proceedings of the XXII Conference on Differential Methods in Theoretical Physics, Ixtapa, Mexico, September 20-24, 199

The Effect of Luxury Taxes on Competitive Balance, Club Profits, and Social Welfare in Sports Leagues

This paper provides a game-theoretic model of a professional sports league and analyzes the effect of luxury taxes on competitive balance, club profits and social welfare. We show that a luxury tax increases aggregate salary payments in the league as well as produces a more balanced league. Moreover, a higher tax rate increases the profits of large-market clubs, whereas the profits of small-market clubs only increase if the tax rate is not set inadequately high. Finally, we show that social welfare increases with a luxury tax.Sports League, Luxury Tax, Social Welfare, Competitive Balance

Chandra and FUSE spectroscopy of the hot bare stellar core H1504+65

H1504+65 is an extremely hot hydrogen-deficient white dwarf with an effective temperature close to 200,000 K. We present new FUV and soft X-ray spectra obtained with FUSE and Chandra, which confirm that H1504+65 has an atmosphere primarily composed of carbon and oxygen. The Chandra LETG spectrum (60-160 Angstroem) shows a wealth of photospheric absorption lines from highly ionized oxygen, neon, and - for the first time identified in this star - magnesium and suggests relatively high Ne and Mg abundances. This corroborates an earlier suggestion that H1504+65 represents a naked C/O stellar core or even the C/O envelope of an O-Ne-Mg white dwarf.Comment: 15 pages, 10 figures, accepted for publication in A&

Efficient DMFT-simulation of the Holstein-Hubbard Model

We present a method for solving impurity models with electron-phonon coupling, which treats the phonons efficiently and without approximations. The algorithm is applied to the Holstein-Hubbard model in the dynamical mean field approximation, where it allows access to strong interactions, very low temperatures and arbitrary fillings. We show that a renormalized Migdal-Eliashberg theory provides a reasonlable description of the phonon contribution to the electronic self energy in strongly doped systems, but fails if the quasiparticle energy becomes of order of the phonon frequency.Comment: Published versio

Monopole currents and Dirac sheets in U(1) lattice gauge theory

We show that the phases of the 4-dimensional compact U(1) lattice gauge theory are unambiguously characterized by the topological properties of minimal Dirac sheets as well as of monopole currents lines. We obtain the minimal sheets by a simulated-annealing procedure. Our results indicate that the equivalence classes of sheet structures are the physical relevant quantities and that intersections are not important. In conclusion we get a percolation-type view of the phases which holds beyond the particular boundary conditions used.Comment: 13 pages, latex, 5 figures include

The group approach to AdS space propagators

We show that AdS two-point functions can be obtained by connecting two points in the interior of AdS space with one point on its boundary by a dual pair of Dobrev's boundary-to-bulk intertwiners and integrating over the boundary point.Comment: 23 page

Low-energy models for correlated materials: bandwidth renormalization from Coulombic screening

We provide a prescription for constructing Hamiltonians representing the low energy physics of correlated electron materials with dynamically screened Coulomb interactions. The key feature is a renormalization of the hopping and hybridization parameters by the processes that lead to the dynamical screening. The renormalization is shown to be non-negligible for various classes of correlated electron materials. The bandwidth reduction effect is necessary for connecting models to materials behavior and for making quantitative predictions for low-energy properties of solids.Comment: 4 pages, 2 figure

On the proposed AdS dual of the critical O(N) sigma model for any dimension 2<d<4

We evaluate the 4-point function of the auxiliary field in the critical O(N) sigma model at O(1/N) and show that it describes the exchange of tensor currents of arbitrary even rank l>0. These are dual to tensor gauge fields of the same rank in the AdS theory, which supports the recent hypothesis of Klebanov and Polyakov. Their couplings to two auxiliary fields are also derived.Comment: 14 page

Fractional Multi-Trace Fields of N=4 SYM_4 from AdS/CFT

We prove inductively that every k-trace operator of SO(6)_R irrep with Young tableau partition {r_1,r_2,r_3}, constructed out of k chiral primaries in the twenty dimensional SO(6)_R irrep, leads to a quasi primary field with protected conformal dimension. Our argument is based on perturbative evaluations of certain four point functions up to order 1/N^2.Comment: 14 pages, 6 figures, revised version, essential changes, to appear in Physics Letters

Social Welfare in Sports Leagues with Profit-Maximizing and/or Win-Maximizing Clubs

This paper develops a contest model to compare social welfare in homogeneous leagues in which all clubs maximize identical objective functions with mixed leagues in which clubs maximize different objective functions. We show that homogeneous leagues in which all clubs are profit-maximizers dominate all other leagues whereas mixed leagues in which small-market clubs are profit- and large-market clubs are win-maximizers (type-I mixed leagues) are dominated by all other leagues. In addition, we show that, from a welfare perspective, large-market clubs win too often in (purely) win-maximizing and type-I mixed leagues whereas small-market clubs win too many games in (purely) profit-maximizing leagues and in mixed leagues in which large-market clubs are profit- and small-market clubs are win-maximizers (type-II mixed leagues). These results have important policy implications: Social welfare will increase if clubs are reorganized from non-profit members associations to profit-maximizing corporations. Moreover, it is socially desirable to reorganize large-market clubs first because, in mixed leagues, it is better if large-market clubs maximize profits instead of small-market clubs. Finally, we show that the invariance proposition does not hold in any league. In mixed (homogeneous) leagues, revenue sharing decreases (increases) social welfare. Given these results, homogeneous leagues should introduce revenue sharing; mixed leagues should not.Social welfare, team sports leagues, objective functions, mixed leagues, competitive balance