2,772 research outputs found
Faddeev-Jackiw formalism for a topological-like oscillator in planar dimensions
The problem of a harmonic oscillator coupling to an electromagnetic potential
plus a topological-like (Chern-Simons) massive term, in two-dimensional space,
is studied in the light of the symplectic formalism proposed by Faddeev and
Jackiw for constrained systems.Comment: 17 pages, Latex file, to appear in Mod. Phys. Let.
Low-Dimensional Spin Systems: Hidden Symmetries, Conformal Field Theories and Numerical Checks
We review here some general properties of antiferromagnetic Heisenberg spin
chains, emphasizing and discussing the role of hidden symmetries in the
classification of the various phases of the models. We present also some recent
results that have been obtained with a combined use of Conformal Field Theory
and of numerical Density Matrix Renormalization Group techniques.Comment: To be published in the proceedings of the XIII Conference on
"Symmetries in Physics", held in Bregenz (Voralberg, Austria), 21-24/7/2003.
Plain LaTeX2e, 4 EPS figure
Generalized partition functions and interpolating statistics
We show that the assumption of quasiperiodic boundary conditions (those that
interpolate continuously periodic and antiperiodic conditions) in order to
compute partition functions of relativistic particles in 2+1 space-time can be
related with anyonic physics. In particular, in the low temperature limit, our
result leads to the well known second virial coefficient for anyons. Besides,
we also obtain the high temperature limit as well as the full temperature
dependence of this coefficient.Comment: 12 pages, Latex, updated and enlarged versio
On critical phases in anisotropic spin-1 chains
Quantum spin-1 chains may develop massless phases in presence of Ising-like
and single-ion anisotropies. We have studied c=1 critical phases by means of
both analytical techniques, including a mapping of the lattice Hamiltonian onto
an O(2) nonlinear sigma model, and a multi-target DMRG algorithm which allows
for accurate calculation of excited states. We find excellent quantitative
agreement with the theoretical predictions and conclude that a pure Gaussian
model, without any orbifold construction, describes correctly the low-energy
physics of these critical phases. This combined analysis indicates that the
multicritical point at large single-ion anisotropy does not belong to the same
universality class as the Takhtajan-Babujian Hamiltonian as claimed in the
past. A link between string-order correlation functions and twisting vertex
operators, along the c=1 line that ends at this point, is also suggested.Comment: 9 pages, 3 figures, svjour format, submitted to Eur. Phys. J.
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