7,216 research outputs found
A sharpened nuclearity condition for massless fields
A recently proposed phase space condition which comprises information about
the vacuum structure and timelike asymptotic behavior of physical states is
verified in massless free field theory. There follow interesting conclusions
about the momentum transfer of local operators in this model.Comment: 13 pages, LaTeX. As appeared in Letters in Mathematical Physic
The Hartwick Rule: Myths and Facts
We shed light on the Hartwick rule for capital accumulation and resource depletion by providing semantic clarifications and investigating the implications and relevance of this rule.We extend earlier results by establishing that the Hartwick rule does not indicate sustainability and does not require substitutability between man-made and natural capital.We use a new class of simple counterexamples (i) to obtain the novel finding that a negative value of net investments need not entail that utility is unsustainable, and (ii) to point out deficiencies in the literature.natural resources;sustainable development;capital accumulation
There are No Causality Problems for Fermi's Two Atom System
A repeatedly discussed gedanken experiment, proposed by Fermi to check
Einstein causality, is reconsidered. It is shown that, contrary to a recent
statement made by Hegerfeldt, there appears no causality paradoxon in a proper
theoretical description of the experiment.Comment: 6 pages, latex, DESY 94-02
Construction of wedge-local nets of observables through Longo-Witten endomorphisms. II
In the first part, we have constructed several families of interacting
wedge-local nets of von Neumann algebras. In particular, there has been
discovered a family of models based on the endomorphisms of the U(1)-current
algebra of Longo-Witten.
In this second part, we further investigate endomorphisms and interacting
models. The key ingredient is the free massless fermionic net, which contains
the U(1)-current net as the fixed point subnet with respect to the U(1) gauge
action. Through the restriction to the subnet, we construct a new family of
Longo-Witten endomorphisms on the U(1)-current net and accordingly interacting
wedge-local nets in two-dimensional spacetime. The U(1)-current net admits the
structure of particle numbers and the S-matrices of the models constructed here
do mix the spaces with different particle numbers of the bosonic Fock space.Comment: 33 pages, 1 tikz figure. The final version is available under Open
Access. CC-B
Data-Oblivious Stream Productivity
We are concerned with demonstrating productivity of specifications of
infinite streams of data, based on orthogonal rewrite rules. In general, this
property is undecidable, but for restricted formats computable sufficient
conditions can be obtained. The usual analysis disregards the identity of data,
thus leading to approaches that we call data-oblivious. We present a method
that is provably optimal among all such data-oblivious approaches. This means
that in order to improve on the algorithm in this paper one has to proceed in a
data-aware fashion
Nuclearity and Thermal States in Conformal Field Theory
We introduce a new type of spectral density condition, that we call
L^2-nuclearity. One formulation concerns lowest weight unitary representations
of SL(2,R) and turns out to be equivalent to the existence of characters. A
second formulation concerns inclusions of local observable von Neumann algebras
in Quantum Field Theory. We show the two formulations to agree in chiral
Conformal QFT and, starting from the trace class condition for the semigroup
generated by the conformal Hamiltonian L_0, we infer and naturally estimate the
Buchholz-Wichmann nuclearity condition and the (distal) split property. As a
corollary, if L_0 is log-elliptic, the Buchholz-Junglas set up is realized and
so there exists a beta-KMS state for the translation dynamics on the net of
C*-algebras for every inverse temperature beta>0. We include further
discussions on higher dimensional spacetimes. In particular, we verify that
L^2-nuclearity is satisfied for the scalar, massless Klein-Gordon field.Comment: 37 pages, minor correction
Spacelike localization of long-range fields in a model of asymptotic electrodynamics
A previously proposed algebra of asymptotic fields in quantum electrodynamics
is formulated as a net of algebras localized in regions which in general have
unbounded spacelike extension. Electromagnetic fields may be localized in
`symmetrical spacelike cones', but there are strong indications this is not
possible in the present model for charged fields, which have tails extending in
all space directions. Nevertheless, products of appropriately `dressed' fermion
fields (with compensating charges) yield bi-localized observables.Comment: 29 pages, accepted for publication in Annales Henri Poincar\'
- âŠ