QCD and Light-Front Holography

The soft-wall AdS/QCD model, modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics. The model predicts a zero-mass pion for zero-mass quarks and a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum $L$ of hadrons and the radial quantum number $N$. Light-Front Holography maps the amplitudes which are functions of the fifth dimension variable $z$ of anti-de Sitter space to a corresponding hadron theory quantized on the light front. The resulting Lorentz-invariant relativistic light-front wave equations are functions of an invariant impact variable $\zeta$ which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. The result is a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryon light-quark bound states, which in turn predict the behavior of the pion and nucleon form factors. The effects of chiral symmetry breaking increase as one goes toward large interquark separation, consistent with spectroscopic data, and the hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L=0 and L=1 light-front Fock components with equal probability. The soft-wall model also predicts the form of the non-perturbative effective coupling $\alpha_s^{AdS}(Q)$ which agrees with the effective coupling extracted from the Bjorken sum rule. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms. A new perspective on quark and gluon condensates is also reviewed.Comment: Invited talk, presented by SJB at the 50th Crakow School, Zakopane, Poland; final version to appear in proceeding

OFF-FARM INCOME, TECHNOLOGY ADOPTION, AND FARM ECONOMIC PERFORMANCE

The economic well-being of most U.S. farm households depends on income from both onfarm and off-farm activities. Consequently, for many farm households, economic decisions (including technology adoption and other production decisions) are likely to be shaped by the allocation of managerial time among such activities. While time allocation decisions are usually not measured directly, we observe the outcomes of such decisions, such as onfarm and off-farm income. This report finds that a farm operator’s off-farm employment and off-farm income vary inversely with the size of the farm. Operators of smaller farm operations improve their economic performance by compensating for the scale disadvantages of their farm business with more off-farm involvement. Off-farm work reduces farm-level technical efficiency, but increases household-level technical efficiency. And adoption of agricultural innovations that save managerial time is associated with higher off-farm income.Off-farm income, farm households, economic performance, managerial time, scale economies, scope economies, technical efficiency, technology adoption, farm size, Agricultural Finance, Farm Management,

Freeman Honors Newsletter, Fall 2020 Issue

Fall 2020 Newsletterhttps://digitalscholarship.tsu.edu/freeman_honors/1000/thumbnail.jp

Freeman Honors Newsletter, Fall 2019 Issue

Fall 2019 Newsletterhttps://digitalscholarship.tsu.edu/freeman_honors/1002/thumbnail.jp

Freeman Honors Newsletter, Spring 2019 Issue

Spring 2019 Newsletterhttps://digitalscholarship.tsu.edu/freeman_honors/1003/thumbnail.jp

Low-Temperature Excitations of Dilute Lattice Spin Glasses

A new approach to exploring low-temperature excitations in finite-dimensional lattice spin glasses is proposed. By focusing on bond-diluted lattices just above the percolation threshold, large system sizes $L$ can be obtained which lead to enhanced scaling regimes and more accurate exponents. Furthermore, this method in principle remains practical for any dimension, yielding exponents that so far have been elusive. This approach is demonstrated by determining the stiffness exponent for dimensions $d=3$, $d=6$ (the upper critical dimension), and $d=7$. Key is the application of an exact reduction algorithm, which eliminates a large fraction of spins, so that the reduced lattices never exceed $\sim10^3$ variables for sizes as large as L=30 in $d=3$, L=9 in $d=6$, or L=8 in $d=7$. Finite size scaling analysis gives $y_3=0.24(1)$ for $d=3$, significantly improving on previous work. The results for $d=6$ and $d=7$, $y_6=1.1(1)$ and $y_7=1.24(5)$, are entirely new and are compared with mean-field predictions made for d>=6.Comment: 7 pages, LaTex, 7 ps-figures included, added result for stiffness in d=7, as to appear in Europhysics Letters (see http://www.physics.emory.edu/faculty/boettcher/ for related information

Freeman Honors Newsletter, Spring/Summer 2020 Issue

Spring/Summer 2020 Newsletterhttps://digitalscholarship.tsu.edu/freeman_honors/1001/thumbnail.jp

Absence of aging in the remanent magnetization in Migdal-Kadanoff spin glasses

We study the non-equilibrium behavior of three-dimensional spin glasses in the Migdal-Kadanoff approximation, that is on a hierarchical lattice. In this approximation the model has an unique ground state and equilibrium properties correctly described by the droplet model. Extensive numerical simulations show that this model lacks aging in the remanent magnetization as well as a maximum in the magnetic viscosity in disagreement with experiments as well as with numerical studies of the Edwards-Anderson model. This result strongly limits the validity of the droplet model (at least in its simplest form) as a good model for real spin glasses.Comment: 4 pages and 3 figures. References update

Monte Carlo Study of an Extended 3-State Potts Model on the Triangular Lattice

By introducing a chiral term into the Hamiltonian of the 3-state Potts model on a triangular lattice additional symmetries are achieved between the clockwise and anticlockwise states and the ferromagnetic state. This model is investigated using Monte Carlo methods. We investigate the full phase diagram and find evidence for a line tricritical points separating the ferromagnetic and antiferromagnetic phases.Comment: 6 pages, 10 figure