348 research outputs found
Particle decays and stability on the de Sitter universe
We study particle decay in de Sitter space-time as given by first order
perturbation theory in a Lagrangian interacting quantum field theory. We study
in detail the adiabatic limit of the perturbative amplitude and compute the
"phase space" coefficient exactly in the case of two equal particles produced
in the disintegration. We show that for fields with masses above a critical
mass there is no such thing as particle stability, so that decays
forbidden in flat space-time do occur here. The lifetime of such a particle
also turns out to be independent of its velocity when that lifetime is
comparable with de Sitter radius. Particles with mass lower than critical have
a completely different behavior: the masses of their decay products must obey
quantification rules, and their lifetime is zero.Comment: Latex, 38 pages, 1 PostScript figure; added references, minor
corrections and remark
Discrete Symmetries for Spinor Field in de Sitter Space
Discrete symmetries, parity, time reversal, antipodal, and charge conjugation
transformations for spinor field in de Sitter space, are presented in the
ambient space notation, i.e. in a coordinate independent way. The PT and PCT
transformations are also discussed in this notation. The five-current density
is studied and their transformation under the discrete symmetries is discussed.Comment: 13 pages, LaTeX; appendices adde
Microlocal analysis of quantum fields on curved spacetimes: Analytic wavefront sets and Reeh-Schlieder theorems
We show in this article that the Reeh-Schlieder property holds for states of
quantum fields on real analytic spacetimes if they satisfy an analytic
microlocal spectrum condition. This result holds in the setting of general
quantum field theory, i.e. without assuming the quantum field to obey a
specific equation of motion. Moreover, quasifree states of the Klein-Gordon
field are further investigated in this work and the (analytic) microlocal
spectrum condition is shown to be equivalent to simpler conditions. We also
prove that any quasifree ground- or KMS-state of the Klein-Gordon field on a
stationary real analytic spacetime fulfills the analytic microlocal spectrum
condition.Comment: 31 pages, latex2
Massless scalar field in two-dimensional de Sitter universe
We study the massless minimally coupled scalar field on a two--dimensional de
Sitter space-time in the setting of axiomatic quantum field theory. We
construct the invariant Wightman distribution obtained as the renormalized
zero--mass limit of the massive one. Insisting on gauge invariance of the model
we construct a vacuum state and a Hilbert space of physical states which are
invariant under the action of the whole de Sitter group. We also present the
integral expression of the conserved charge which generates the gauge
invariance and propose a definition of dual field.Comment: 13 page
Braid group statistics implies scattering in three-dimensional local quantum physics
It is shown that particles with braid group statistics (Plektons) in
three-dimensional space-time cannot be free, in a quite elementary sense: They
must exhibit elastic two-particle scattering into every solid angle, and at
every energy. This also implies that for such particles there cannot be any
operators localized in wedge regions which create only single particle states
from the vacuum and which are well-behaved under the space-time translations
(so-called temperate polarization-free generators). These results considerably
strengthen an earlier "NoGo-theorem for 'free' relativistic Anyons".
As a by-product we extend a fact which is well-known in quantum field theory
to the case of topological charges (i.e., charges localized in space-like
cones) in d>3, namely: If there is no elastic two-particle scattering into some
arbitrarily small open solid angle element, then the 2-particle S-matrix is
trivial.Comment: 25 pages, 4 figures. Comment on model-building added in the
introductio
Universality of low-energy scattering in (2+1) dimensions
We prove that, in (2+1) dimensions, the S-wave phase shift, , k
being the c.m. momentum, vanishes as either as . The constant is universal and .
This result is established first in the framework of the Schr\"odinger equation
for a large class of potentials, second for a massive field theory from proved
analyticity and unitarity, and, finally, we look at perturbation theory in
and study its relation to our non-perturbative result. The
remarkable fact here is that in n-th order the perturbative amplitude diverges
like as , while the full amplitude vanishes as . We show how these two facts can be reconciled.Comment: 23 pages, Late
De Sitter Waves and the Zero Curvature Limit
We show that a particular set of global modes for the massive de Sitter
scalar field (the de Sitter waves) allows to manage the group representations
and the Fourier transform in the flat (Minkowskian) limit. This is in
opposition to the usual acceptance based on a previous result, suggesting the
appearance of negative energy in the limit process. This method also confirms
that the Euclidean vacuum, in de Sitter spacetime, has to be preferred as far
as one wishes to recover ordinary QFT in the flat limit.Comment: 9 pages, latex no figure, to appear in Phys. Rev.
Conformally invariant wave-equations and massless fields in de Sitter spacetime
Conformally invariant wave equations in de Sitter space, for scalar and
vector fields, are introduced in the present paper. Solutions of their wave
equations and the related two-point functions, in the ambient space notation,
have been calculated. The ``Hilbert'' space structure and the field operator,
in terms of coordinate independent de Sitter plane waves, have been defined.
The construction of the paper is based on the analyticity in the complexified
pseudo-Riemanian manifold, presented first by Bros et al.. Minkowskian limits
of these functions are analyzed. The relation between the ambient space
notation and the intrinsic coordinates is then studied in the final stage.Comment: 21 pages, LaTeX, some details adde
N=1 de Sitter Supersymmetry Algebra
Recalling the universal covering group of de Sitter, the transformation
properties of the spinor fields and , in the ambient
space notation, are presented in this paper. The charge conjugation symmetry of
the de Sitter spinor field is then discussed in the above notation. Using this
spinor field and charge conjugation, de Sitter supersymmetry algebra in the
ambient space notation has been established. It is shown that a novel
dS-superalgebra can be attained by the use of spinor field and charge
conjugation in the ambient space notation.Comment: 8 pages, LaTeX, some details 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
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