463 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.
Anti de Sitter quantum field theory and a new class of hypergeometric identities
We use Anti-de Sitter quantum field theory to prove a new class of identities
between hypergeometric functions related to the K\"all\'en-Lehmann
representation of products of two Anti-de Sitter two-point functions. A rich
mathematical structure emerges. We apply our results to study the decay of
unstable Anti-de Sitter particles. The total amplitude is in this case finite
and Anti-de Sitter invariant
The Reeh-Schlieder property for thermal field theories
We show that the Reeh-Schlieder property w.r.t. the KMS-vector is a direct
consequence of locality, additivity and the relativistic KMS-condition. The
latter characterises the thermal equilibrium states of a relativistic quantum
field theory. The statement remains vaild even if the given equilibrium state
breaks spatial translation invariance.Comment: plain tex, 10 page
Thermal behavior induced by vacuum polarization on causal horizons in comparison with the standard heat bath formalism
Modular theory of operator algebras and the associated KMS property are used
to obtain a unified description for the thermal aspects of the standard heat
bath situation and those caused by quantum vacuum fluctuations from
localization. An algebraic variant of lightfront holography reveals that the
vacuum polarization on wedge horizons is compressed into the lightray
direction. Their absence in the transverse direction is the prerequisite to an
area (generalized Bekenstein-) behavior of entropy-like measures which reveal
the loss of purity of the vacuum due to restrictions to wedges and their
horizons. Besides the well-known fact that localization-induced (generalized
Hawking-) temperature is fixed by the geometric aspects, this area behavior
(versus the standard volume dependence) constitutes the main difference between
localization-caused and standard thermal behavior.Comment: 15 page Latex, dedicated to A. A. Belavin on the occasion of his 60th
birthda
Two-point Functions and Quantum Fields in de Sitter Universe
We present a theory of general two-point functions and of generalized free
fields in d-dimensional de Sitter space-time which closely parallels the
corresponding minkowskian theory. The usual spectral condition is now replaced
by a certain geodesic spectral condition, equivalent to a precise thermal
characterization of the corresponding ``vacuum''states. Our method is based on
the geometry of the complex de Sitter space-time and on the introduction of a
class of holomorphic functions on this manifold, called perikernels, which
reproduce mutatis mutandis the structural properties of the two-point
correlation functions of the minkowskian quantum field theory. The theory
contains as basic elementary case the linear massive field models in their
``preferred'' representation. The latter are described by the introduction of
de Sitter plane waves in their tube domains which lead to a new integral
representation of the two-point functions and to a Fourier-Laplace type
transformation on the hyperboloid. The Hilbert space structure of these
theories is then analysed by using this transformation. In particular we show
the Reeh-Schlieder property. For general two-point functions, a substitute to
the Wick rotation is defined both in complex space-time and in the complex mass
variable, and substantial results concerning the derivation of Kallen-Lehmann
type representation are obtained.Comment: 51 p, uuencoded, LaTex, epsf, 2 figures include
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
How far does the analogy between causal horizon-induced thermalization with the standard heat bath situation go?
After a short presentation of KMS states and modular theory as the unifying
description of thermalizing systems we propose the absence of transverse vacuum
fluctuations in the holographic projections as the mechanism for an area
behavior (the transverse area) of localization entropy as opposed to the volume
dependence of ordinary heat bath entropy. Thermalization through causal
localization is not a property of QM, but results from the omnipresent vacuum
polarization in QFT and does not require a Gibbs type ensemble avaraging
(coupling to a heat bath).Comment: 10 pages, based on talk given at the 2002 Londrina Winter Schoo
The asymptotic symmetry of de Sitter spacetime
We show how to construct a set of Euclidean conformal correlation functions
on the boundary of a de Sitter space from an interacting bulk quantum field
theory with a certain asymptotic behaviour. We discuss the status of the
boundary theory w.r.t. the reflection positivity and conclude that no obvious
physical holographic interpretation is available.Comment: 12 pages, late
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