Yang-Mills theory from the worldsheet

Abstract

We give a new description of classical Yang-Mills theory by coupling a twodimensional chiral CFT (which gives the tree-level S-matrix of Yang-Mills theory at genus zero) to a background non-abelian gauge field. The resulting model is solvable, and when the gravitational degrees of freedom are decoupled the non-linear Yang-Mills equations are imposed as an exact worldsheet anomaly cancellation condition. When gravitational modes are reinstated, we find gauge anomalies analogous to those appearing in heterotic string theory.

Linear Optical and Third‐Order Nonlinear Optical Properties of Some Fluorenyl‐ and Triarylamine‐Containing Tetracyanobutadiene Derivatives

“…As expected, the match is less satisfactory for electronic transitions involving long-range charget ransfer when employing such afunctional that does not incorporate long-range corrections. [32] The calculations are nevertheless sufficient to provide aq ualitative understandingo ft he origin of the excited states underlying the absorptions of 1-3.Furthermore, we verified in selected cases that the observed discrepanciesd on ot originate from different conformers than the ones computed, ad istributiono ft hese being certainly present in solution. Indeed,anearly similar spectral shape was obtained in each For C1-C3,the HOMO is mostly located on the triphenylamino fragment and the HOMOÀ1e ither on the fluorenyl fragment (C1)o ro nt he triphenylamino fragments (C2-C3), whereas the LUMO and LUMO+ +1a re strongly located on the TCBD fragment(s).…”

“…Note that the calculated transition moments for the (longrange)C Tt ransitions at lowest energy are somewhat overestimated, as is sometimes the case for long-range charge transfer. [32] As ar esult, the red side of the simulated spectrai s slightly more intense than experimentally observed, especially for 2' and 3.T he existence of poorly allowed CT transitions on the red side of the main absorption peak observed in the 600-700 nm spectral range is also attested by the presence of sizeable 2PAi nt he 1200-1400 nm range. In line with literature, [1, 13c] calculations indicate that these will correspond to excitationsf rom the most electropositive triphenylamino donor towardt he TCBD acceptor(s), but for molecules having more energetic conformations than for the GS.…”

Excited State Dynamics of Isocyano Rhenium(I) Phenanthroline Complexes from Time‐Resolved Spectroscopy

“…The emission energies of the complexes were estimated by the vertical energy difference between the optimized triplet state and the ground state. The electronic absorption spectra were simulated by TD-DFT method, [36] by solving the lowest 50 allowed vertical electronic transitions from the ground state.…”

Celestial amplitudes and conformal soft theorems

“…The key tool which enables these calculations is ambitwistor string theory, a class of chiral, constrained worldsheet models which describe massless QFTs [27]. Ambitwistor strings underpin the scattering equations and Cachazo-He-Yuan (CHY) formulae [28,29] for massless scattering in the momentum basis [27,30,31], but they also encode the full non-linearity of the underlying classical equations of motion [32,33] and their spectrum always imposes the free equations of motion [34,35]. Thus, they can equally well describe scattering in the conformal basis, leading to CHY formulae for celestial scattering amplitudes.…”