Search results for "spectral representation"
showing 4 items of 14 documents
Two-flavour lattice QCD correlation functions in the deconfinement transition region
2013
We report on a lattice QCD calculation with two dynamical flavors of the isovector vector correlator in the high-temperature phase. We analyze the correlator in terms of the associated spectral function by performing a fit for the difference of the thermal and vacuum spectral functions, using also an exact sum rule that constrains this difference. Additonally we carry out a direct fit for the thermal spectral function, and obtain good agreement between the two analyses for frequencies below the two-pion threshold. Under the assumption that the spectral function is smooth in that region, we give an estimate of the electrical conductivity.
Charmonium dissociation and heavy quark transport in hot quenched lattice QCD
2012
We study the properties of charmonium states at finite temperature in quenched lattice QCD on large and fine isotropic lattices. We perform a detailed analysis of charmonium correlation and spectral functions both below and above Tc. Our analysis suggests that the S wave states disappear at about 1.5 Tc. The charm diffusion coefficient is estimated and found to be approximately 1/{\pi}T at 1.5Tc {\leq} T {\leq} 3Tc.
Working group on hadron polarizabilities and form factors
1998
Covariant Operator Formalism for Quantized Superfields
1988
The Takahashi-Umezawa method of deriving the free covariant quantization relations from the linear equations of motion is extended to superfields. The Cauchy problem for free superfields is solved, and an expression for the time independent scalar product is given. For the case of interacting fields, we give the general Kallen-Lehmann spectral representation for the two-point superfield Green functions and, after the introduction of the asymptotic condition for superfields, we give the superfield extension of the Yang-Feldman equation. The case of the D = 2 real scalar superfield and the case of the D = 4 chiral superfield are discussed in detail.