ABSTRACT Perturbation theory is combined with spin-wave techniques to study the large-U one-band ... more ABSTRACT Perturbation theory is combined with spin-wave techniques to study the large-U one-band Hubbard model near half filling. It is shown that the antiferromagnetic order is preserved for finite doping fractions. A uniform magnetization perpendicular to the staggered one is predicted for doping fractions above some critical value. This critical value is zero for d=2 and nonzero for d>2.
We explore possible extensions of the $t$-channel and $s$-channel unitary model of high energy ev... more We explore possible extensions of the $t$-channel and $s$-channel unitary model of high energy evolution in zero transverse dimensions appropriate to very high energy/atomic number where the dipole density in a toy hadron is parametrically high.We suggest that the appropriate generalization is to allow emission of more than one dipole in a single step of energy evolution. We construct explicitly such a model that preserves the $t$-channel and s-channel unitarity and have the correct low density limit, and study the particle multiplicity distribution resulting from this evolution. We consider initial conditions of a single dipole and many dipoles at initial rapidity. We observe that the saturation regime in this model is preceded by a parametric range of rapidities $\frac{1}{\alpha_s}\ln\frac{1}{\alpha_s}
The variational Gaussian approximation is generalized to the time-dependent approach capable of g... more The variational Gaussian approximation is generalized to the time-dependent approach capable of giving time-dependent Green's functions. This covariant Gaussian approximation is represented, in full analogy with the classical approximation, as an initial truncation of the Dyson-Schwinger equations followed by functional differentiation of the effective action. Intuitively simple Schroedinger and Heisenberg pictures of the approximation are also discussed.
ABSTRACT Perturbation theory is combined with spin-wave techniques to study the large-U one-band ... more ABSTRACT Perturbation theory is combined with spin-wave techniques to study the large-U one-band Hubbard model near half filling. It is shown that the antiferromagnetic order is preserved for finite doping fractions. A uniform magnetization perpendicular to the staggered one is predicted for doping fractions above some critical value. This critical value is zero for d=2 and nonzero for d>2.
We explore possible extensions of the $t$-channel and $s$-channel unitary model of high energy ev... more We explore possible extensions of the $t$-channel and $s$-channel unitary model of high energy evolution in zero transverse dimensions appropriate to very high energy/atomic number where the dipole density in a toy hadron is parametrically high.We suggest that the appropriate generalization is to allow emission of more than one dipole in a single step of energy evolution. We construct explicitly such a model that preserves the $t$-channel and s-channel unitarity and have the correct low density limit, and study the particle multiplicity distribution resulting from this evolution. We consider initial conditions of a single dipole and many dipoles at initial rapidity. We observe that the saturation regime in this model is preceded by a parametric range of rapidities $\frac{1}{\alpha_s}\ln\frac{1}{\alpha_s}
The variational Gaussian approximation is generalized to the time-dependent approach capable of g... more The variational Gaussian approximation is generalized to the time-dependent approach capable of giving time-dependent Green's functions. This covariant Gaussian approximation is represented, in full analogy with the classical approximation, as an initial truncation of the Dyson-Schwinger equations followed by functional differentiation of the effective action. Intuitively simple Schroedinger and Heisenberg pictures of the approximation are also discussed.
Uploads
Papers by A. Kovner