43 research outputs found
The unmasking of thermal Goldstone bosons
The problem of extracting the modes of Goldstone bosons from a thermal
background is reconsidered in the framework of relativistic quantum field
theory. It is shown that in the case of spontaneous breakdown of an internal
bosonic symmetry a recently established decomposition of thermal correlation
functions contains certain specific contributions which can be attributed to a
particle of zero mass.Comment: 7 pages, LaTeX; new and considerably strengthened results after Eq.
(14); to appear in Phys. Rev.
A Goldstone Theorem in Thermal Relativistic Quantum Field Theory
We prove a Goldstone Theorem in thermal relativistic quantum field theory,
which relates spontaneous symmetry breaking to the rate of space-like decay of
the two-point function. The critical rate of fall-off coincides with that of
the massless free scalar field theory. Related results and open problems are
briefly discussed
Massive Schwinger model and its confining aspects on curved space-time
Using a covariant method to regularize the composite operators, we obtain the
bosonized action of the massive Schwinger model on a classical curved
background. Using the solution of the bosonic effective action, the energy of
two static external charges with finite and large distance separation on a
static curved space-time is obtained. The confining behavior of this model is
also explicitly discussed.Comment: A disscussion about the infrared regularization and also two
references are added. Accepted for publication in Phys. Rev. D (2001
The General Correlation Function in the Schwinger Model on a Torus
In the framework of the Euclidean path integral approach we derive the exact
formula for the general N-point chiral densities correlator in the Schwinger
model on a torusComment: 17 pages, misprints corrected, references adde
The Quest for Understanding in Relativistic Quantum Physics
We discuss the status and some perspectives of relativistic quantum physics.Comment: Invited contribution to the Special Issue 2000 of the Journal of
Mathematical Physics, 38 pages, typos corrected and references added, as to
appear in JM
Spontaneous symmetry breaking in the gl(N)-NLS hierarchy on the half line
We describe an algebraic framework for studying the symmetry properties of
integrable quantum systems on the half line. The approach is based on the
introduction of boundary operators. It turns out that these operators both
encode the boundary conditions and generate integrals of motion. We use this
direct relationship between boundary conditions and symmetry content to
establish the spontaneous breakdown of some internal symmetries, due to the
boundary.Comment: LaTeX2e, 28 pages, no figur
Anomalous Scale Dimensions from Timelike Braiding
Using the previously gained insight about the particle/field relation in
conformal quantum field theories which required interactions to be related to
the existence of particle-like states associated with fields of anomalous
scaling dimensions, we set out to construct a classification theory for the
spectra of anomalous dimensions. Starting from the old observations on
conformal superselection sectors related to the anomalous dimensions via the
phases which appear in the spectral decomposition of the center of the
conformal covering group we explore the possibility
of a timelike braiding structure consistent with the timelike ordering which
refines and explains the central decomposition. We regard this as a preparatory
step in a new construction attempt of interacting conformal quantum field
theories in D=4 spacetime dimensions. Other ideas of constructions based on the
- or the perturbative SYM approach in their relation to the
present idea are briefly mentioned.Comment: completely revised, updated and shortened replacement, 24 pages
tcilatex, 3 latexcad figure
Integrable models: from dynamical solutions to string theory
We review the status of integrable models from the point of view of their
dynamics and integrability conditions. Some integrable models are discussed in
detail. We comment on the use it is made of them in string theory. We also
discuss the Bethe Ansatz solution of the SO(6) symmetric Hamiltonian with SO(6)
boundary.
This work is especially prepared for the seventieth anniversaries of
Andr\'{e} Swieca (in memoriam) and Roland K\"{o}berle.Comment: 24 pages, to appear in Brazilian Journal of Physic
Localization and symmetries
The violation of the Noether relation between symmetries and charges is
reduced to the time dependence of the charge associated to a conserved current.
For the U(1) gauge symmetry a non-perturbative control of the charge
commutators is obtained by an analysis of the Coulomb charged fields. From
this, in the unbroken case we obtain a correct expression for the electric
charge on the Coulomb states, its superselection and the presence of massless
vector bosons; in the broken case, we obtain a general non-perturbative version
of the Higgs phenomenon, i.e. the absence of massless Goldstone bosons and of
massless vector bosons. The conservation of the (gauge dependent) current
associated to the U(1) axial symmetry in QCD is shown to be compatible with the
time dependence of the corresponding charge commutators and a non-vanishing
eta' mass, as a consequence of the non locality of the (conserved) current.Comment: Invited contribution to ``The Quantum Universe'', dedicated to G.
Ghirardi for his 70th birthda
Spin and statistics of quantum kinks
Apart from some brief and inconclusive remarks concerning the problem of spin and statistics of quantum kinks in space-time dimension D>2, a detailed discussion of the D=2 situation is given. The main result is that two-dimensional quantum kinks are statistical 'schizons'; they exist in the same Hilbert space either as bosons or as fermions. In those cases where one can introduce local kink-sector generating operators as in the sine-Gordon model, the Bose and Fermi fields are strictly local fields, which are relatively nonlocal with respect to each other. (20 refs)