Resource Type

The Conformal Template and New Perspectives for Quantum Chromodynamics (open access)

The Conformal Template and New Perspectives for Quantum Chromodynamics

Conformal symmetry provides a systematic approximation to QCD in both its perturbative and nonperturbative domains. One can use the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. For example, there is an exact correspondence between the fifth-dimensional coordinate of AdS space and a specific impact variable which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. One can also use conformal symmetry as a template for perturbative QCD predictions where the effects of the nonzero beta function can be systematically included in the scale of the QCD coupling. This leads to fixing of the renormalization scale and commensurate scale relations which relate observables without scale or scheme ambiguity. The results are consistent with the renormalization group and the analytic connection of QCD to Abelian theory at N{sub C} {yields} 0. I also discuss a number of novel phenomenological features of QCD. Initial- …
Date: March 6, 2007
Creator: Brodsky, Stanley J.
System: The UNT Digital Library
Proof that stable monotonic equilibrium distributions in a continuous focusing channel are necessarily axisymmetric (open access)

Proof that stable monotonic equilibrium distributions in a continuous focusing channel are necessarily axisymmetric

The transverse Vlasov equilibrium distribution function of an unbunched ion beam propagating in a continuous focusing channel is specified by a function f{perpendicular} (H{perpendicular}), where H{perpendicular} is the single-particle Hamiltonian. In standard treatments of continuous focusing equilibria in Vlasov-Poisson electrostatic models, it is assumed that a stable beam equilibrium specified by monotonic f{perpendicular}(H{perpendicular}) with {partial_derivative}f{perpendicular}(H{perpendicular})/{partial_derivative}H{perpendicular} {le} 0 is axisymmetric (no variation in azimuthal angle, i.e., with {partial_derivative}/{partial_derivative}{theta} = 0). In this paper a simple, but rigorous, proof is presented that only axisymmetric equilibrium solutions are possible in Vlasov-Poisson models for any physical choice of f{perpendicular}(H{perpendicular}) with {partial_derivative}f{perpendicular}(H{perpendicular})/{partial_derivative}H{perpendicular} {le} 0 if the confining boundary of the system (the beam pipe) is axisymmetric or if the geometry is radially unbounded.
Date: March 28, 2007
Creator: Lund, S M
System: The UNT Digital Library
The rest-frame K-band luminosity function of galaxies in clusters to z = 1.3 (open access)

The rest-frame K-band luminosity function of galaxies in clusters to z = 1.3

We derive the rest-frame K-band luminosity function for galaxies in 32 clusters at 0.6 < z < 1.3 using deep 3.6 {micro}m and 4.5 {micro}m imaging from the Spitzer Space Telescope InfraRed Array Camera (IRAC). The luminosity functions approximate the stellar mass function of the cluster galaxies. Their dependence on redshift indicates that massive cluster galaxies (to the characteristic luminosity M*{sub K}) are fully assembled at least at z {approx} 1.3 and that little significant accretion takes place at later times. The existence of massive, highly evolved galaxies at these epochs is likely to represent a significant challenge to theories of hierarchical structure formation where such objects are formed by the late accretion of spheroidal systems at z < 1.
Date: March 20, 2007
Creator: De Propris, R.; Stanford, S. A.; Eisenhardt, P. R.; Holden, B. P. & Rosati, P.
System: The UNT Digital Library
Mesotron Decays and the Role of Anomalies (open access)

Mesotron Decays and the Role of Anomalies

None
Date: March 1, 2007
Creator: Bardeen, William A.
System: The UNT Digital Library
Near-Infrared Properties of Moderate-Redshift Galaxy Clusters: Halo Occupation Number, Mass-to-Light Ratios and Omega(M) (open access)

Near-Infrared Properties of Moderate-Redshift Galaxy Clusters: Halo Occupation Number, Mass-to-Light Ratios and Omega(M)

Using K-band imaging for 15 of the Canadian Network for Observational Cosmology (CNOC1) clusters we examine the near-infrared properties of moderate-redshift (0.19 < z < 0.55) galaxy clusters. We find that the number of K-band selected cluster galaxies within R{sub 500} (the Halo Occupation Number, HON) is well-correlated with the cluster dynamical mass (M{sub 500}) and X-ray Temperature (T{sub x}); however, the intrinsic scatter in these scaling relations is 37% and 46% respectively. Comparison with clusters in the local universe shows that the HON-M{sub 500} relation does not evolve significantly between z = 0 and z {approx} 0.3. This suggests that if dark matter halos are disrupted or undergo significant tidal-stripping in high-density regions as seen in numerical simulations, the stellar mass within the halos is tightly bound, and not removed during the process. The total K-band cluster light (L{sub 200},K) and K-band selected richness (parameterized by B{sub gc,K}) are also correlated with both the cluster T{sub x} and M{sub 200}. The total (intrinsic) scatter in the L{sub 200,K}-M{sub 200} and B{sub gc,K}-M{sub 200} relations are 43%(31%) and 35%(18%) respectively and indicates that for massive clusters both L{sub 200,K} and B{sub gc,K} can predict M{sub 200} with similar accuracy as …
Date: March 1, 2007
Creator: Muzzin, Adam; Yee, H. K. C.; Hall, Patrick B. & Lin, Huan
System: The UNT Digital Library