Spectrum of two-dimensional su(2)su(2) gauge theories coupled to massless fermions in integer representations

The spectra of two-dimensional $su(2)$ gauge theories coupled to a single massless Majorana fermion in integer representations, $J$, are numerically investigated using the Discrete Light-Cone Hamiltonian. The primary aim is to understand the presence of massless states for $J>2$ in spite of the absence of a continuous symmetry. After comparing to existing results for $J=1$ (adjoint fermions), we present results for $J=2,3,4$. As expected, for $J=2$ there are no massless states but in contrast to the $J=1$ theory, the lightest state is a boson. We find exact zero modes in the bosonic and fermionic sector for all values of total momentum for $J=3$ and $J=4$ and, in each sector, the number of zero modes grows with the value of the total momentum. In addition to the spectrum, we present results on the particle number and momentum fraction distributions and argue for a separation of bulk states from edge states.Comment: 21 pages, 6 figure

Approaching the conformal WZW behavior in the infrared limit of two-dimensional massless QCD: a lattice study

Two-dimensional QCD with $N_c$ colors and $N_f$ flavors of massless fermions in the fundamental representation is expected to exhibit conformal behavior in the infrared governed by a $u(N_f)$ WZW model with level $N_c$. Using numerical analysis within the lattice formalism with exactly massless overlap fermions, we show the emergence of such behavior in the infrared limit. Both the continuum extrapolated low-lying eigenvalues of the massless Dirac operator and the propagator of scalar mesons exhibit a flow from the ultraviolet to the infrared. We find that the amplitude of the conserved current correlator remains invariant under the flow, while the amplitude of the scalar correlator approaches $N_f$-independent values in the infrared.Comment: 19 pages, 7 figures, revised version matches the accepted version in PRD and includes small change

Physiological and lipidomic characterization of high temperature stress and traits associated with tolerance in wheat

Doctor of PhilosophyDepartment of AgronomyP. V. Vara PrasadHigh temperature is a major environmental factor that limits wheat productivity. Climate models predict greater increases in night temperature than in day temperature. The objectives of this research were to quantify the effects of high day and night temperatures during anthesis on physiological (chlorophyll fluorescence, chlorophyll concentration, leaf level photosynthesis, lipid peroxidation and membrane damage), biochemical (reactive oxygen species [ROS] concentration and antioxidant capacity in leaves) and yield traits and membrane lipid profile and identify the lipids that are associated with high temperature response in wheat. Winter wheat genotypes Ventnor (heat tolerant) and Karl 92 (heat susceptible) were grown at optimum temperatures (25/15°C, maximum/minimum) until the onset of anthesis. Thereafter, plants were exposed to high night (HN, 25/24°C), high day (HD, 35/15°C), high day and night (HDN, 35/24°C) or optimum temperatures. Compared with optimum temperature, HN, HD and HDN increased ROS concentration, lipid peroxidation and membrane damage and decreased antioxidant capacity, photochemical efficiency, photosynthesis, seed set, grain number and grain yield. Impact of HN and HD was similar on all traits, when stress was imposed for seven days. High day and night temperatures resulted in significant changes in the amount of plastidic and extra-plastidic lipids and lipids with oxidized acyl chains (ox-lipids) in both genotypes. The decrease in lipid unsaturation levels of complex lipids at high temperatures was predominantly due to decrease in 18:3 fatty acid and increase in 18:1 and 16:0 fatty acids. We identified novel odd-numbered long-chain fatty acid-containing phospholipids, which were highly responsive to high temperature stress. Ventnor had higher amounts of sterol glycosides (SG) and lower amounts of ox-lipids at high temperatures than Karl 92; thus SGs and ox-lipids may be potential biomarkers for heat tolerance and susceptibility, respectively, in wheat. Co-occurring lipids, which are up-or-down-regulated together through time under high day and night temperatures formed groups, which were experiencing coordinated metabolism. These results suggest that high day and night temperatures during anthesis cause damage of a similar magnitude to wheat, if stress is imposed for a short term (seven days) and compositional changes in lipid profile in response to high temperature contribute to heat tolerance

Deforming Soft Algebras for Gauge Theory

Symmetry algebras deriving from towers of soft theorems can be deformed by a short list of higher-dimension Wilsonian corrections to the effective action. We study the simplest of these deformations in gauge theory arising from a massless complex scalar coupled to $F^2$. The soft gauge symmetry '$s$-algebra', compactly realized as a higher-spin current algebra acting on the celestial sphere, is deformed and enlarged to an associative algebra containing soft scalar generators. This deformed soft algebra is found to be non-abelian even in abelian gauge theory. A two-parameter family of central extensions of the $s$-subalgebra are generated by shifting and decoupling the scalar generators. It is shown that these central extensions can also be generated by expanding around a certain non-trivial but Lorentz invariant shockwave type background for the scalar field.Comment: 13 pages, 1 figur

Evaluation of soybean [\u3ci\u3eGlycine max\u3c/i\u3e (L.) Merr.] genotypes for yield, water use efficiency, and root traits

Drought stress has been identified as the major environmental factor limiting soybean [Glycine max (L.) Merr.] yield worldwide. Current breeding efforts in soybean largely focus on identifying genotypes with high seed yield and drought tolerance. Water use efficiency (WUE) that results in greater yield per unit rainfall is an important parameter in determining crop yields in many production systems, and is often related with crop drought tolerance. Even though roots are major plant organs that perceive and respond to drought stress, their utility in improving soybean yield and WUE under different environmental and management conditions are largely unclear. The objectives of this research was to evaluate soybean cultivars and breeding and germplasm lines for yield, WUE, root penetrability of hardpan, and root morphology. Field experiments were conducted at two locations in South Carolina (southeastern United States) during the 2017 cropping season to test the genotypes for yield and root morphology under irrigated and non-irrigated conditions. Two independent controlled-environmental experiments were conducted to test the genotypes for WUE and root penetrability of synthetic hardpans. The slow wilting lines NTCPR94-5157 and N09-13890 had equal or greater yield than the checks- cultivar NC-Raleigh and the elite South Carolina breeding line SC07-1518RR, under irrigated and non-irrigated conditions. The high yielding genotypes NTCPR94-5157, N09-13890, and SC07-1518RR exhibited root parsimony (reduced root development). This supported the recent hypothesis in literature that root parsimony would have adaptational advantage to improve yield under high input field conditions. The high yielding genotypes NTCPR94-5157, N09-13890, NC-Raleigh, and SC07-1518RR and a cultivar Boggs (intermediate in yield) possessed high WUE and had increased root penetrability of hardpans. These genotypes offer useful genetic materials for soybean breeding programs for improving yield, drought tolerance, and/or hardpan penetrability

Alterations in Wheat Pollen Lipidome during High Day and Night Temperature Stress

Understanding the adaptive changes in wheat pollen lipidome under high temperature (HT) stress is critical to improving seed set and developing HT tolerant wheat varieties. We measured 89 pollen lipid species under optimum and high day and/or night temperatures using electrospray ionization-tandem mass spectrometry in wheat plants. The pollen lipidome had a distinct composition compared to that of leaves. Unlike in leaves, 34:3 and 36:6 species dominated the composition of extraplastidic phospholipids in pollen under optimum and HT conditions. The most HT-responsive lipids were extraplastidic phospholipids, PC, PE, PI, PA, and PS. The unsaturation levels of the extraplastidic phospholipids decreased through the decreases in the levels of 18:3 and increases in the levels of 16:0, 18:0, 18:1, and 18:2 acyl chains. PC and PE were negatively correlated. Higher PC:PE at HT indicated possible PE-to-PC conversion, lower PE formation, or increased PE degradation, relative to PC. Correlation analysis revealed lipids experiencing coordinated metabolism under HT and confirmed the HT-responsiveness of extraplastidic phospholipids. Comparison of the present results on wheat pollen with results of our previous research on wheat leaves suggests that similar lipid changes contribute to HT adaptation in both leaves and pollen, though the lipidomes have inherently distinct compositions