CORE: Frustrated Magnets, Charge Fractionalization, and QCD

I explain how to use a simple method to extract the physics of lattice Hamiltonian systems which are not easily analyzed by exact or other numerical methods. I will then use this method to establish the relationship between QCD and a special class of generalized, highly frustrated anti-ferromagnets.     

Observation of structural anisotropy and the onset of liquidlike motion during the nonthermal melting of InSb

The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.     

The Hamiltonian structure of the Maxwell-Vlasov equations

Morrison [25] has observed that the Maxwell-Vlasov and Poisson-Vlasov equations for a collisionless plasma can be written in Hamiltonian form relative to a certain Poisson bracket. We derive another Poisson structure for these equations by using general methods of symplectic geometry. The main ingredients in our construction are the symplectic structure on the co-adjoint orbits for the group of canonical transformations, and the symplectic structure for the phase space of the electromagnetic field regarded as a gauge theory. Our Poisson bracket satisfies the Jacobi identity, whereas Morrison's does not [37]. Our construction also shows where canonical variables can be found and can be applied to the Yang-Mills-Vlasov equations and to electromagnetic fluid dynamics.     

Pressure dependent optical phonon anharmonicity in GaP

The asymmetric Raman line shape of the TO(Γ) phonon in GaP has been carefully measured under hydrostatic pressure up to 87 kbar (room temperature). At high pressure the peak becomes symmetric and a weak sideband emerges. These results can be explained as due to the third order anharmonic interaction of TO(Γ) with the combination modes TA + LA(≈ X). A calculation of this effect, based on the measured phonon dispersion of GaP, is successful in fitting the observed line shape at all pressures. The anharmonic coupling strength for the decay TO(Γ) → TA + LA(≈ X) is found to decrease linearly with pressure by an appreciable amount.     

On a class of partial differential equations of even order

Summary The general solution for a class of equations of even order is expressed as a sum of solutions of equations of second order. To Mauro Picone on his 70^th birthday. This research was supported in part by the United States Air Force under Contract N^o. AF(600)-573 — monitored by the Office of Scientific Research, Air Research and Development Command.     

Observation of the Hadronic transitions chi(b1,2)(2P)-->omegaUpsilon(1S)

The CLEO Collaboration has made the first observations of hadronic transitions among bottomonium (bbmacr;) states other than the dipion transitions among Upsilon(nS) states. In our study of Upsilon(3S) decays, we find a significant signal for Upsilon(3S)-->gammaomegaUpsilon(1S) that is consistent with radiative decays Upsilon(3S)-->gammachi(b1,2)(2P), followed by chi(b1,2)(2P)-->omegaUpsilon(1S). The branching ratios we obtain are B[chi(b1)(2P)-->omegaUpsilon(1S)]=(1.63(+0.35+0.16)(-0.31-0.15))% and B[chi(b2)(2P)-->omegaUpsilon(1S)]=(1.10(+0.32+0.11)(-0.28-0.10))%, in which the first error is statistical and the second is systematic.