Eldorado Collection:
http://hdl.handle.net/2003/25945
2024-03-26T08:54:57ZLight 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