Eldorado Community:
http://hdl.handle.net/2003/22130
2024-04-23T02:27:04ZA Quantum Mechanics without Subjective Element
http://hdl.handle.net/2003/35795
Title: A Quantum Mechanics without Subjective Element
Authors: Blum, Walter
Abstract: It is not easy for practicing physicists to keep track of the ongoing philosophical debate concerning the "reality'' of the entities they manipulate or the "objective validity'' of the results of their work. In addition, the role of the observer and the theory of the measuring process seem to be themselves controversial. Therefore it may be appropriate to present an interpretation of quantum mechanics which corresponds to the perspective of most practicing physicists, although the author makes no claim to possessing any particular knowledge of the literature in this domain. The final four sections present some more specific descriptions of the concepts used, so that they may also serve for more philosophical discussions.2016-12-01T00:00:00ZAgainst the Impossible Picture: Feynman's Heuristics in his Search for a Divergence-free Quantum Electrodynamics
http://hdl.handle.net/2003/29919
Title: Against the Impossible Picture: Feynman's Heuristics in his Search for a Divergence-free Quantum Electrodynamics
Authors: Wüthrich, Adrian
Abstract: I review three early steps of the development of Feynman's proposal for a divergence-free quantum electrodynamics and identify the characteristic feature of his heuristics: the search for alternative formulations of the existing theories. Feynman's reformulations always had precise goals, and in each of the three steps one of them was particularly important. Through reformulation, he tried (1) to extend the domain of application of an existing theory, (2) to provide a model to justify the theory's equations, or (3) to reveal assumptions problematic for the existing theory and in this way find amendments to it.2013-02-15T00:00:00ZAutonomy All the Way Down: Systems and Dynamics in Quantum Bayesianism
http://hdl.handle.net/2003/29402
Title: Autonomy All the Way Down: Systems and Dynamics in Quantum Bayesianism
Authors: Fields, Chris
Abstract: Quantum Bayesianism (``QBism'') has been put forward as an approach to quantum theory that avoids foundational problems by altogether disavowing the objective existence of quantum states. It is shown that QBism suffers its own versions of the familiar foundational problems, and that these QBist versions are illuminating not just for QBism, but for more traditional foundational approaches as well.2012-03-29T00:00:00ZBook review: M. Suárez, Probabilities, Causes and Propensities in Physics
http://hdl.handle.net/2003/29177
Title: Book review: M. Suárez, Probabilities, Causes and Propensities in Physics
Authors: Céspedes, Esteban2011-11-08T00:00:00ZQuantum Gravity: Motivations and Alternatives
http://hdl.handle.net/2003/27496
Title: Quantum Gravity: Motivations and Alternatives
Authors: Hedrich, Reiner
Abstract: The mutual conceptual incompatibility between General Relativity and Quantum Mechanics / Quantum Field Theory is generally seen as the most essential motivation for the development of a theory of Quantum Gravity. It leads to the insight that, if gravity is a fundamental interaction and Quantum Mechanics is universally valid, the gravitational field will have to be quantized, not at least because of the inconsistency of semi-classical theories of gravity. The objective of a theory of Quantum Gravity would then be to identify the quantum properties and the quantum dynamics of the gravitational field. If this means to quantize General Relativity, the general-relativistic identification of the gravitational field with the spacetime metric has to be taken into account. The quantization has to be conceptually adequate, which means in particular that the resulting quantum theory has to be background-independent. This can not be achieved by means of quantum field theoretical procedures. More sophisticated strategies, like those of Loop Quantum Gravity, have to be applied. One of the basic requirements for such a quantization strategy is that the resulting quantum theory has a classical limit that is (at least approximately, and up to the known phenomenology) identical to General Relativity.
However, should gravity not be a fundamental, but an induced, residual, emergent interaction, it could very well be an intrinsically classical phenomenon. Should Quantum Mechanics be nonetheless universally valid, we had to assume a quantum substrate from which gravity would result as an emergent classical phenomenon. And there would be no conflict with the arguments against semi-classical theories, because there would be no gravity at all on the substrate level. The gravitational field would not have any quantum properties to be captured by a theory of Quantum Gravity, and a quantization of General Relativity would not lead to any fundamental theory. The objective of a theory of 'Quantum Gravity' would instead be the identification of the quantum substrate from which gravity results. The requirement that the substrate theory has General Relativity as a classical limit - that it reproduces at least the known phenomenology - would remain.
The paper tries to give an overview over the main options for theory construction in the field of Quantum Gravity. Because of the still unclear status of gravity and spacetime, it pleads for the necessity of a plurality of conceptually different approaches to Quantum Gravity.2010-11-24T00:00:00ZExperimental Noise, Idealizations and the Classical-Quantum Relation
http://hdl.handle.net/2003/27252
Title: Experimental Noise, Idealizations and the Classical-Quantum Relation
Authors: von Oppen, Gebhard
Abstract: Classical dynamics and the classical concept of space-time reality is based on the assumption that the objects of physics can be observed continuously. The discrete structure of matter (atoms) and fields (quanta), however, implies that the process of observation is quantized. In this paper we discuss the consequences of this paradigm change from continuity to discreteness and from determinism to chance. By taking into account the quantized structure of observation, we are led to the conclusion that the classical concept of reality has to be replaced by a quantum concept of observability. It implies that quantum dynamics is not a generalization of classical dynamics. Rather, the two theories apply to complementary idealizations of nature representing opposite extremes on a scale of observability. They are related by correspondence rules. Both theories disregard experimental noise. Statistical and thermal noise provide the experimental foundation for statistical physics.2010-06-03T18:32:45ZVagueness in Philosophy -- "Unbestimmtheit" in Physics
http://hdl.handle.net/2003/27246
Title: Vagueness in Philosophy -- "Unbestimmtheit" in Physics
Authors: Pirner, Hans J.
Abstract: Unbestimmtheit is discussed with three connotations: indefiniteness-vagueness, uncertainty and indeterminacy. Vagueness is a term in philosophy, the two other meanings are found in physics. I will study several physics cases: experimental errors, natural
borderline cases, quantum indeterminacy, uncertainty and indeterminacy in statistical and stochastic physics. Characteristically, the three classes are often found to be mixed. A very sketchy discussion concludes the article: How should one handle Unbestimmtheit? When and how should one clarify, classify, define limits, use fuzzy logic?2010-05-27T19:12:55ZQuantum Holism, Superluminality, and Einstein Causality
http://hdl.handle.net/2003/25801
Title: Quantum Holism, Superluminality, and Einstein Causality
Authors: Mittelstaedt, Peter
Abstract: Within the framework of the EPR Gedankenexperiment we show that
quantum mechanics is not incomplete but nonlocal and holistic.
The attempt to use this quantum non-locality for the transmission
of superluminal signals is exposed to serious objections which
are based on very general theorems. However, we show that one
of the theorems is equivalent to the impossibility of superluminal
signals. Hence, the question whether superluminal EPR signals
are possible can not be decided in this way.2008-09-11T22:05:08ZTime in Philosophy of Physics
http://hdl.handle.net/2003/25146
Title: Time in Philosophy of Physics
Authors: Lyre, Holger
Abstract: The paper provides a survey of problems and debates about time and temporal
directedness in theories of modern physics on an almost introductory level.
We start from general notions of the metaphysics of time and then move on to
special and general relativity theory, thermodynamics and quantum mechanics.
The paper as well as its bibliography should be useful as an entry to further
studies for anybody interested in issues of time in the philosophy of physics.2008-03-26T16:39:58ZScientific Realism in the Age of String Theory
http://hdl.handle.net/2003/24724
Title: Scientific Realism in the Age of String Theory
Authors: Dawid, Richard
Abstract: String theory currently is the only viable candidate for a unified
description of all known natural forces. This article tries to demonstrate
that the fundamental structural and methodological differences that set
string theory apart from other physical theories have important
philosophical consequences. Focusing on implications for the realism debate
in philosophy of science, it is argued that both poles of that debate face
new problems in the context of string theory. On the one hand, the claim of
underdetermination of scientific theory by the available empirical data,
which is a pivotal element of empiricism, loses much of its plausibility. On
the other hand, the dissolution of any meaningful notion of an external
ontological object destroys the basis for conventional versions of
scientific realism. String theory seems to suggest an intermediate position
akin to Structural Realism that is based on a newly emerging principle, to
be called the principle of theoretical uniqueness.2007-09-16T12:04:33ZDecoherence: An Introduction
http://hdl.handle.net/2003/24483
Title: Decoherence: An Introduction
Authors: Joos, Erich
Abstract: In this paper I review the fundamentals of decoherence theory. Decoherence is
viewed as a straightforward application of the general kinematical concept of
a quantum wave function. Classical notions (such as ``particle") as well as
secondary quantum concepts (such as ``observable'', superselection rule etc.)
can be derived. Special emphasis is put on a precise and consistent
interpretation of quantum states and processes.2007-07-25T13:31:58ZThe Controversial Universe
http://hdl.handle.net/2003/24422
Title: The Controversial Universe
Authors: Kragh, Helge
Abstract: The domain of cosmology is the universe, a singular concept, and basically
for this reason cosmology is a science that differs from other sciences. For a long
time there have been critical voices which argue that cosmology cannot be a
proper science on par with, say, nuclear physics or hydrodynamics. This kind of
critique goes a long way back in time, and I review it here in a historical
perspective, focusing on the century from 1870 to 1970. I suggest that there
are no good reasons to deny cosmology the status of a proper science. On the
other hand, I also consider it natural, and a sign of health, that such
foundational questions continue to be part of the cosmological discourse.2007-07-06T20:52:05ZQuantum Logic versus Alternative Approaches
http://hdl.handle.net/2003/24420
Title: Quantum Logic versus Alternative Approaches
Authors: Mittelstaedt, Peter
Abstract: In the present paper we will discuss the following problem: Is
the external reality primarily a quantum world such that in
macroscopic dimensions classical properties evolve by decoherence
and emergency? -- Or is there only a classical, macroscopic world
of apparatuses and observers, and what we can say about the
quantum world is nothing but a consistent way of speaking which
illustrates without any ontological commitments merely the
formalism of quantum mechanics?2007-07-05T20:04:53ZEinstein and the Laws of Physics
http://hdl.handle.net/2003/24280
Title: Einstein and the Laws of Physics
Authors: Weinert, Friedel
Abstract: The purpose of this paper is to highlight the importance of constraints
in the theory of relativity and, in particular, what philosophical
work they do for Einstein's views on the laws of physics. Einstein
presents a view of local ``structure laws'' which he characterizes
as the most appropriate form of physical laws. Einstein was committed
to a view of science, which presents a synthesis between rational
and empirical elements as its hallmark. If scientific constructs
are free inventions of the human mind, as Einstein, held, the
question arises how such rational constructs, including the symbolic
formulation of the laws of physics, can represent physical reality. Representation
in turn raises the question of realism. Einstein uses a number
of constraints in the theory of relativity to show that by imposing
constraints on the rational elements a certain ``fit'' between theory
and reality can be achieved. Fit is to be understood as satisfaction
of constraint. His emphasis on reference frames in the STR and
more general coordinate systems in the GTR, as well as his emphasis
on the symmetries of the theory of relativity suggests that Einstein's
realism is akin to a certain form of structural realism. His
version of structural realism follows from the theory of relativity
and is independent of any current philosophical debates about
structural realism.2007-05-03T14:25:37ZLight Quanta
http://hdl.handle.net/2003/24257
Title: Light Quanta
Authors: Klaus, Hentschel
Abstract: I will begin by identifying 12 layers of meaning of the concept of light
quanta as it is understood today. The main part of this contribution will then
discuss some of the earlier layers. I will also briefly discuss the extreme
skepticism with which the concept of light quanta was received between 1905
and 1922 and close with a thesis on what makes Einstein's thinking so
exceptional.2007-04-19T19:51:48ZString Theory - From Physics to Metaphysics
http://hdl.handle.net/2003/23603
Title: String Theory - From Physics to Metaphysics
Authors: Hedrich, Reiner
Abstract: Currently, string theory represents the only advanced approach to a
unification of all interactions, including gravity. In spite of the more
than thirty years of its existence, the sequence of metamorphosis it ran
through, and the ever more increasing number of involved physicists, until
now, it did not make any empirically testable predictions. Because there are
no empirical data incompatible with the quantum field theoretical standard
model of elementary particle physics and with general relativity, the only
motivations for string theory rest in the mutual incompatibility of the
standard model and of general relativity as well as in the metaphysics of
the unification program of physics, aimed at a final unified theory of all
interactions including gravity. But actually, it is completely unknown
which physically interpretable principles could form the basis of string
theory. At the moment, ''string theory'' is no theory at all, but rather a
labyrinthic structure of mathematical procedures and intuitions which get
their justification from the fact that they, at least formally, reproduce
general relativity and the standard model of elementary particle physics as
low energy approximations. However, there are now strong indications that
string theory does not only reproduce the dynamics and symmetries of our
standard model, but a plethora of different scenarios with different low
energy nomologies and symmetries. String theory seems to describe not only
our world, but an immense landscape of possible worlds. So far, all
attempts to find a selection principle which could be motivated
intratheoretically remained without success. So, recently the idea that the
low energy nomology of our world, and therefore also the observable
phenomenology, could be the result of an anthropic selection from a vast
arena of nomologically different scenarios entered string theory. Although
multiverse scenarios and anthropic selection are not only motivated by
string theory, but lead also to a possible explanation for the fine tuning
of the universe, they are concepts which transcend the framework defined by
the epistemological and methodological rules which conventionally form the
basis of physics as an empirical science.2007-03-16T21:54:30ZThe Phase of a Bose-Einstein Condensate
http://hdl.handle.net/2003/23109
Title: The Phase of a Bose-Einstein Condensate
Authors: Dürr, Stephan
Abstract: If two
Bose-Einstein condensates are prepared independently and then overlapped, a
spatial interference pattern is observed. This prompts the question what
determines the phase of the fringe pattern, and whether a condensate has a
well-defined value of the phase. This problem has been studied in the
literature in detail. The objective of this article is, to present an
introduction to the subject and to summarize the discussion for a wider
audience.2006-11-30T14:32:27ZWhat You Always Wanted to Know about Bohmian Mechanics but Were Afraid to Ask
http://hdl.handle.net/2003/23108
Title: What You Always Wanted to Know about Bohmian Mechanics but Were Afraid to Ask
Authors: Passon, Oliver
Abstract: Bohmian mechanics is an alternative
interpretation of quantum mechanics. We outline the main characteristics of
its non-relativistic formulation. Most notably it does provide a simple
solution to the infamous measurement problem of quantum mechanics. Presumably
the most common objection against Bohmian mechanics is based on its
non-locality and its apparent conflict with relativity and quantum field
theory. However, several models for a quantum field theoretical
generalization do exist. We give a non-technical account of some of these
models.2006-11-30T14:26:28ZDetection of High-Energy Particles
http://hdl.handle.net/2003/23058
Title: Detection of High-Energy Particles
Authors: Lohse, Thomas
Abstract: In spite of quantum field theoretical and philosophical problems to
define the concept of elementary particles and to understand
their localizability, particles become intuitively apparent
by the traces they leave in particle detectors.
Today, experimental particle physicists have reached a high degree
of perfection in measuring and visualizing particles up to highest
energies using a variety of high technology detection devices and
sophisticated, powerful particle accelerators. The paper reviews the
basic detection techniques and puts the microscopic quantum field
theoretical processes of interest into perspective with the
measurements performed at macroscopic scales. It is shown that particle
detectors and accelerators are highly classical devices which localize
particles without significantly affecting the tails of their wave
functions. It is discussed which properties of particles can be
measured and how these measurements relate to the dynamics of
elementary particles at microscopic length scales.2006-11-08T20:40:23ZEinstein's Objections against Quantum Mechanics
http://hdl.handle.net/2003/22995
Title: Einstein's Objections against Quantum Mechanics
Authors: Mittelstaedt, Peter
Abstract: After the discovery of quantum
mechanics by Heisenberg and Schrödinger in 1925, Einstein raised
again and again objections to this theory. Obviously, he had the
impression that (a) quantum mechanics does not adequately grasp
reality, that it is (b) based on probabilistic laws of nature and
that it is (c) for this reason incomplete. Einstein must have
obtained this impression from many presentations of quantum
mechanics in the first decade after its discovery. -- However,
technical refutations of Einstein's objections were not possible
when these arguments were put forward, since the necessary formal
tools were not yet available at this time. Instead, the advocates
of quantum mechanics tried to disprove Einstein merely by
intuitive and less rigorous arguments. -- In the light of current
physics we find that the objections (a) and (b) are irrelevant
since, in accordance with Einstein's intentions, quantum mechanics
does refer to reality and is not based on probabilistic laws. Only
the incompleteness argument is incorrect. However, for technical
reasons a convincing refutation of this objection only became
possible thirty years after its formulation and ten years after
Einstein's death.2006-10-12T18:57:33Z