16,974 research outputs found
The physical foundations for the geometric structure of relativistic theories of gravitation. From General Relativity to Extended Theories of Gravity through Ehlers-Pirani-Schild approach
We discuss in a critical way the physical foundations of geometric structure
of relativistic theories of gravity by the so-called Ehlers-Pirani-Schild
formalism. This approach provides a natural interpretation of the observables
showing how relate them to General Relativity and to a large class of Extended
Theories of Gravity. In particular we show that, in such a formalism, geodesic
and causal structures of space-time can be safely disentangled allowing a
correct analysis in view of observations and experiment. As specific case, we
take into account the case of f(R) gravity.Comment: 11 pages, 2 figure
Common Axioms for Inferring Classical Ensemble Dynamics and Quantum Theory
The same set of physically motivated axioms can be used to construct both the
classical ensemble Hamilton-Jacobi equation and Schrodingers equation. Crucial
roles are played by the assumptions of universality and simplicity (Occam's
Razor) which restrict the number and type of of arbitrary constants that appear
in the equations of motion. In this approach, non-relativistic quantum theory
is seen as the unique single parameter extension of the classical ensemble
dynamics. The method is contrasted with other related constructions in the
literature and some consequences of relaxing the axioms are also discussed: for
example, the appearance of nonlinear higher-derivative corrections possibly
related to gravity and spacetime fluctuations. Finally, some open research
problems within this approach are highlighted.Comment: Final proceedings version. 6 pages. Presented at the 3rd QTRF
conference at Vaxjo, Sweden, June6-11 200
Quantum Theory and Human Perception of the Macro-World
We investigate the question of 'why customary macroscopic entities appear to
us humans as they do, i.e. as bounded entities occupying space and persisting
through time', starting from our knowledge of quantum theory, how it affects
the behavior of such customary macroscopic entities, and how it influences our
perception of them. For this purpose, we approach the question from three
perspectives. Firstly, we look at the situation from the standard quantum
angle, more specifically the de Broglie wavelength analysis of the behavior of
macroscopic entities, indicate how a problem with spin and identity arises, and
illustrate how both play a fundamental role in well-established experimental
quantum-macroscopical phenomena, such as Bose-Einstein condensates. Secondly,
we analyze how the question is influenced by our result in axiomatic quantum
theory, which proves that standard quantum theory is structurally incapable of
describing separated entities. Thirdly, we put forward our new 'conceptual
quantum interpretation', including a highly detailed reformulation of the
question to confront the new insights and views that arise with the foregoing
analysis. At the end of the final section, a nuanced answer is given that can
be summarized as follows. The specific and very classical perception of human
seeing -- light as a geometric theory -- and human touching -- only ruled by
Pauli's exclusion principle -- plays a role in our perception of macroscopic
entities as ontologically stable entities in space. To ascertain quantum
behavior in such macroscopic entities, we will need measuring apparatuses
capable of its detection. Future experimental research will have to show if
sharp quantum effects -- as they occur in smaller entities -- appear to be
ontological aspects of customary macroscopic entities.Comment: 28 page
Is nature OO?
What exists "out there"? What does "doing physics" mean? What are the
axiomatic ideas for microphysics? What is a particle? What is an apparatus made
of? We show that Quantum Mechanics textbooks cannot truly answer this kind of
question whereas they should. By adopting a pure "hitological" point of view
for microphysics, we introduce the Hit in Apparatuses Theory (HAT) and the
Vacuum of Apparatuses (VA) that restore, through Object Orientation (OO), an
intuitive ontology to deal with this kind of physics. Through a review of what
it means to "observe" and what relativism means in Special and General
Relativities (SR and GR), we address the problem of finding common maths for GR
and QM. Finally, with our new HAT, we address the measurement problem in QM and
propose two possible approaches.Comment: 26 page
Axiomatic Foundations for Metrics of Distributive Justice Shown by the Example of Needs-Based Justice
Distributive justice deals with allocations of goods and bads within a group. Different principles and results of distributions are seen as possible ideals. Often those normative approaches are solely framed verbally, which complicates the application to different concrete distribution situations that are supposed to be evaluated in regard to justice. One possibility in order to frame this precisely and to allow for a fine-grained evaluation of justice lies in formal modelling of these ideals by metrics. Choosing a metric that is supposed to map a certain ideal has to be justified. Such justification might be given by demanding specific substantiated axioms, which have to be met by a metric. This paper introduces such axioms for metrics of distributive justice shown by the example of needs-based justice. Furthermore, some exemplary metrics of needs-based justice and a three dimensional method for visualisation of non-comparative justice axioms or evaluations are presented. Therewith, a base worth discussing for the evaluation and modelling of metrics of distributive justice is given
Axiomatic approach to the cosmological constant
A theory of the cosmological constant Lambda is currently out of reach.
Still, one can start from a set of axioms that describe the most desirable
properties a cosmological constant should have. This can be seen in certain
analogy to the Khinchin axioms in information theory, which fix the most
desirable properties an information measure should have and that ultimately
lead to the Shannon entropy as the fundamental information measure on which
statistical mechanics is based. Here we formulate a set of axioms for the
cosmological constant in close analogy to the Khinchin axioms, formally
replacing the dependency of the information measure on probabilities of events
by a dependency of the cosmological constant on the fundamental constants of
nature. Evaluating this set of axioms one finally arrives at a formula for the
cosmological constant that is given by Lambda = (G^2/hbar^4) (m_e/alpha_el)^6,
where G is the gravitational constant, m_e is the electron mass, and alpha_el
is the low energy limit of the fine structure constant. This formula is in
perfect agreement with current WMAP data. Our approach gives physical meaning
to the Eddington-Dirac large number hypothesis and suggests that the observed
value of the cosmological constant is not at all unnatural.Comment: 7 pages, no figures. Some further references adde
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