2,383 research outputs found
An Evaluable Theory for a Class of Migration Problems
A master equation formulation for a class of migration problems describing the spatio-temporal dynamics of a system of regions is introduced. The transition probabilities are functions of trend parameters, which characterize preferences, growth pool and saturation effects. The trend parameters can be determined by regression analysis from the empirical migration matrix. The solution of meanvalue equations yields a nonlinear migration prognosis. The relation between trend parameters and motivation factors, e.g., income per capita, infrastructure and transportation costs, is also discussed. Numerical simulations illustrate the influence of the superposition of migration trends on the evolution of the system
Wightman Functions' Behaviour on the Event Horizon of an Extremal Reissner-Nordstr\"om Black Hole
A weaker Haag, Narnhofer and Stein prescription as well as a weaker Hessling
Quantum Equivalence Principle for the behaviour of thermal Wightman functions
on an event horizon are analysed in the case of an extremal
Reissner-Nordstr\"{o}m black hole in the limit of a large mass. In order to
avoid the degeneracy of the metric in the stationary coordinates on the
horizon, a method is introduced which employs the invariant length of geodesics
which pass the horizon. First the method is checked for a massless scalar field
on the event horizon of the Rindler wedge, extending the original procedure of
Haag, Narnhofer and Stein onto the {\em whole horizon} and recovering the same
results found by Hessling. Afterwards the HNS prescription and Hessling's
prescription for a massless scalar field are analysed on the whole horizon of
an extremal Reissner-Nordstr\"{o}m black hole in the limit of a large mass. It
is proved that the weak form of the HNS prescription is satisfyed for all the
finite values of the temperature of the KMS states, i.e., this principle does
not determine any Hawking temperature. It is found that the
Reissner-Nordstr\"{o}m vacuum, i.e., does satisfy the weak HNS
prescription and it is the only state which satisfies weak Hessling's
prescription, too. Finally, it is suggested that all the previously obtained
results should be valid dropping the requirements of a massless field and of a
large mass black hole.Comment: 27 pages, standard LaTex, no figures, final version containing the
results following from Hessling's principle as they appeared in the other
paper gr-qc/9510016, minor changes in the text and in references, it will
appear on Class. Quant. Gra
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
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
Pion-Nucleon Scattering in Kadyshevsky Formalism: I Meson Exchange Sector
In a series of two papers we present the theoretical results of /meson-baryon scattering in the Kadyshevsky formalism. In this paper the
results are given for meson exchange diagrams. On the formal side we show, by
means of an example, how general couplings, i.e. couplings containing multiple
derivatives and/or higher spin fields, should be treated. We do this by
introducing and applying the Takahashi-Umezawa and the Gross-Jackiw method. For
practical purposes we introduce the method. We also show how the
Takashashi-Umezawa method can be derived using the theory of Bogoliubov and
collaborators and the Gross-Jackiw method is also used to study the
-dependence of the Kadyshevsky integral equation. Last but not least we
present the second quantization procedure of the quasi particle in Kadyshevsky
formalism.Comment: 29 page
Relational interpretation of the wave function and a possible way around Bell's theorem
The famous ``spooky action at a distance'' in the EPR-szenario is shown to be
a local interaction, once entanglement is interpreted as a kind of ``nearest
neighbor'' relation among quantum systems. Furthermore, the wave function
itself is interpreted as encoding the ``nearest neighbor'' relations between a
quantum system and spatial points. This interpretation becomes natural, if we
view space and distance in terms of relations among spatial points. Therefore,
``position'' becomes a purely relational concept. This relational picture leads
to a new perspective onto the quantum mechanical formalism, where many of the
``weird'' aspects, like the particle-wave duality, the non-locality of
entanglement, or the ``mystery'' of the double-slit experiment, disappear.
Furthermore, this picture cirumvents the restrictions set by Bell's
inequalities, i.e., a possible (realistic) hidden variable theory based on
these concepts can be local and at the same time reproduce the results of
quantum mechanics.Comment: Accepted for publication in "International Journal of Theoretical
Physics
Causality and dispersion relations and the role of the S-matrix in the ongoing research
The adaptation of the Kramers-Kronig dispersion relations to the causal
localization structure of QFT led to an important project in particle physics,
the only one with a successful closure. The same cannot be said about the
subsequent attempts to formulate particle physics as a pure S-matrix project.
The feasibility of a pure S-matrix approach are critically analyzed and their
serious shortcomings are highlighted. Whereas the conceptual/mathematical
demands of renormalized perturbation theory are modest and misunderstandings
could easily be corrected, the correct understanding about the origin of the
crossing property requires the use of the mathematical theory of modular
localization and its relation to the thermal KMS condition. These new concepts,
which combine localization, vacuum polarization and thermal properties under
the roof of modular theory, will be explained and their potential use in a new
constructive (nonperturbative) approach to QFT will be indicated. The S-matrix
still plays a predominant role but, different from Heisenberg's and
Mandelstam's proposals, the new project is not a pure S-matrix approach. The
S-matrix plays a new role as a "relative modular invariant"..Comment: 47 pages expansion of arguments and addition of references,
corrections of misprints and bad formulation
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
A Bisognano-Wichmann-like Theorem in a Certain Case of a Non Bifurcate Event Horizon related to an Extreme Reissner-Nordstr\"om Black Hole
Thermal Wightman functions of a massless scalar field are studied within the
framework of a ``near horizon'' static background model of an extremal R-N
black hole. This model is built up by using global Carter-like coordinates over
an infinite set of Bertotti-Robinson submanifolds glued together. The
analytical extendibility beyond the horizon is imposed as constraints on
(thermal) Wightman's functions defined on a Bertotti-Robinson sub manifold. It
turns out that only the Bertotti-Robinson vacuum state, i.e. , satisfies
the above requirement. Furthermore the extension of this state onto the whole
manifold is proved to coincide exactly with the vacuum state in the global
Carter-like coordinates. Hence a theorem similar to Bisognano-Wichmann theorem
for the Minkowski space-time in terms of Wightman functions holds with
vanishing ``Unruh-Rindler temperature''. Furtermore, the Carter-like vacuum
restricted to a Bertotti-Robinson region, resulting a pure state there, has
vanishing entropy despite of the presence of event horizons. Some comments on
the real extreme R-N black hole are given
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