A first order iteration process for simultaneous equations

First order iteration process for solutions of simultaneous equation

Adjacent face scattering of electrons on a square Fermi surface

Interacting electrons with a square Fermi surface is investigated from a bosonic point of view taking into account electron scattering between all faces of the square. Fermion operators are classified according to their dimensions and the stability of the boson fixed-point is investigated. In particular we find, in contrast to previous studies, that the square Fermi surface is unstable to doping in the case of no spin gap and microscopic Hubbard interactions.Comment: Revtex 6 pages, 1 Figur

Bosonization in Higher Dimensions

Using the recently discovered connection between bosonization and duality transformations (hep-th/9401105 and hep-th/9403173), we give an explicit path-integral representation for the bosonization of a massive fermion coupled to a U(1) gauge potential (such as electromagnetism) in d space (D=d+1 spacetime) dimensions. The bosonic theory is described by a rank d-1 antisymmetric Kalb-Ramond-type gauge potential. We construct the bosonized lagrangian explicitly in the limit of large fermion mass. We find that the resulting action is local for d=2 (and given by a Chern-Simons action), but nonlocal for d larger than 3. By coupling to a statistical Chern-Simons field for d=2, we obtain a bosonized formulation of anyons. The bosonic theory may be further dualized to a theory involving purely scalars, for any d, and we show this to be governed by a higher-derivative lagrangian for which the scalar decouples from the U(1) gauge potential.Comment: (We had omitted some references and had misspelled `aficionados') plain TeX, 11 pages, McGill-94/33, NEIP-94-006, OSLO-TP 10-9

Excitations in one-dimensional S=1/2 quantum antiferromagnets

The transition from dimerized to uniform phases is studied in terms of spectral weights for spin chains using continuous unitary transformations (CUTs). The spectral weights in the S=1 channel are computed perturbatively around the limit of strong dimerization. We find that the spectral weight is concentrated mainly in the subspaces with a small number of elementary triplets (triplons), even for vanishing dimerization. So, besides spinons, triplons may be used as elementary excitations in spin chains. We conclude that there is no necessity to use fractional excitations in low-dimensional, undoped or doped quantum antiferromagnets.Comment: 4 pages, 1 figure include

Keystone XL Pipeline: Overview and Recent Developments

[Excerpt] This report describes the Keystone XL Pipeline Project and the process that the State Department must complete to decide whether it will approve or deny TransCanada’s permit application. The report also discusses key energy security, economic, and environmental issues relevant to the State Department’s national interest determination. Some of these issues include perspectives among various stakeholders both in favor of and opposed to the construction of the pipeline. Finally, the report discusses the constitutional basis for the State Department’s authority to issue a Presidential Permit, and opponents’ possible challenges to this authority