Bohmian mechanics is a quantum theory without observers. This means that neither the act of observation nor the notion of observer play any role in defining the theory, the theory is not about observers and observation, and it explains all non relativistic quantum phenomena. The theory is about something primitive', the basic ontology, and the laws for that are given. Bohmian mechanics is a deterministic theory of point particles. Like Newtonian mechanics it is invariant under Galilei transformations, but unlike Newtonian (...) mechanics it is a first-order theory, acceleration is not a concept entering the law of motion. Rather this law directly determines the velocities of the particles as follows. (shrink)
Quantum philosophy, a peculiar twentieth-century malady, is responsible for most of the conceptual muddle plaguing the foundations of quantum physics. When this philosophy is eschewed, one naturally arrives at Bohmian mechanics, which is what emerges from Schrodinger's equation for a nonrelativistic system of particles when we merely insist that 'particles' means particles. While distinctly non-Newtonian, Bohmian mechanics is a fully deterministic theory of particles in motion, a motion choreographed by the wave function. The quantum formalism emerges when measurement situations are (...) analyzed according to this theory. When the quantum formalism is regarded as arising in this way, the paradoxes and perplexities so often associated with quantum theory simply evaporate.Bohr's ... approach to atomic problems ... is really remarkable. He is completely convinced that any understanding in the usual sense of the word is impossible. Therefore the conversation is almost immediately driven into philosophical questions, and soon you no longer know whether you really take the position he is attacking, or whether you really must attack the position he is defending. (shrink)
It is well known that density matrices can be used in quantum mechanics to represent the information available to an observer about either a system with a random wave function or a system that is entangled with another system. We point out another role, previously unnoticed in the literature, that a density matrix can play: it can be the “conditional density matrix,” conditional on the configuration of the environment. A precise definition can be given in the context of Bohmian mechanics, (...) whereas orthodox quantum mechanics is too vague to allow a sharp definition, except perhaps in special cases. In contrast to statistical and reduced density matrices, forming the conditional density matrix involves no averaging. In Bohmian mechanics with spin, the conditional density matrix replaces the notion of conditional wave function, as the object with the same dynamical significance as the wave function of a Bohmian system. (shrink)
Bohmian mechanics is a theory about point particles moving along trajectories. It has the property that in a world governed by Bohmian mechanics, observers see the same statistics for experimental results as predicted by quantum mechanics. Bohmian mechanics thus provides an explanation of quantum mechanics. Moreover, the Bohmian trajectories are defined in a non-conspiratorial way by a few simple laws.
A source of much difficulty and confusion in the interpretation of quantum mechanics is a naive realism about operators. By this we refer to various ways of taking too seriously the notion of operator-as-observable, and in particular to the all too casual talk about measuring operators that occurs when the subject is quantum mechanics. Without a specification of what should be meant by measuring a quantum observable, such an expression can have no clear meaning. A definite specification is provided by (...) Bohmian mechanics, a theory that emerges from Schrödinger's equation for a system of particles when we merely insist that particles means particles. Bohmian mechanics clarifies the status and the role of operators as observables in quantum mechanics by providing the operational details absent from standard quantum mechanics. It thereby allows us to readily dismiss all the radical claims traditionally enveloping the transition from the classical to the quantum realm — for example, that we must abandon classical logic or classical probability. The moral is rather simple: Beware naive realism, especially about operators! (shrink)
The emerging concept of food sovereignty refers to the right of communities, peoples, and states to independently determine their own food and agricultural policies. It raises the question of which type of food production, agriculture and rural development should be pursued to guarantee food security for the world population. Social movements and non-governmental organizations have readily integrated the concept into their terminology. The concept is also beginning to find its way into the debates and policies of UN organizations and national (...) governments in both developing and industrialized countries. Beyond its relation to civil society movements little academic attention has been paid to the concept of food sovereignty and its appropriateness for international development policies aimed at reducing hunger and poverty, especially in comparison to the human right to adequate food (RtAF). We analyze, on the basis of an extensive literature review, the concept of food sovereignty with regard to its ability to contribute to hunger and poverty reduction worldwide as well as the challenges attached to this concept. Then, we compare the concept of food sovereignty with the RtAF and discuss the appropriateness of both concepts for national public sector policy makers and international development policies. We conclude that the impact on global food security is likely to be much greater if the RtAF approach predominated public policies. While the concept of food sovereignty may be appropriate for civil society movements, we recommend that the RtAF should obtain highest priority in national and international agricultural, trade and development policies. (shrink)
Detlef Breitenband gibt in seinem Buch einen problemorientierten Überblick über die Rechtstheorien von Immanuel Kant und Jürgen Habermas. Im Zentrum steht die Frage nach der Leistungsfähigkeit beider Rechtstheorien, da diese den Konsens aller Rechtsadressaten zur Grundlage haben, aber nicht davon ausgegangen wird, dass jemals über eine Rechtsnorm ein faktischer Konsens erzeugt wird. Der Autor arbeitet die radikal-demokratischen Implikationen des Kantischen Republikanismus heraus und leistet einen wichtigen Beitrag zur Klärung des Begriffs der Legitimation von Rechtsnormen.
Classical physics is about real objects, like apples falling from trees, whose motion is governed by Newtonian laws. In standard quantum mechanics only the wave function or the results of measurements exist, and to answer the question of how the classical world can be part of the quantum world is a rather formidable task. However, this is not the case for Bohmian mechanics, which, like classical mechanics, is a theory about real objects. In Bohmian terms, the problem of the classical (...) limit becomes very simple: when do the Bohmian trajectories look Newtonian? (shrink)
We analyze the origin of quantum randomness within the framework of a completely deterministic theory of particle motion—Bohmian mechanics. We show that a universe governed by this mechanics evolves in such a way as to give rise to the appearance of randomness, with empirical distributions in agreement with the predictions of the quantum formalism. Crucial ingredients in our analysis are the concept of the effective wave function of a subsystem and that of a random system. The latter is a notion (...) of interest in its own right and is relevant to any discussion of the role of probability in a deterministic universe. (shrink)
This article was found among the papers left by Prof. Laugwitz. The following abstract is extracted from a lecture he gave at the Fourth Austrain Symposion on the History of Mathematics.About 100 years ago, the Cantor-Veronese controversy found wide interest and lasted for more than 20 years. It is concerned with “actual infinity” in mathematics. Cantor, supported by Peano and others, believed to have shown the non-existence of infinitely small quantities, and therefore he fought against the infinitely large and small (...) numbers in Veronese’s geometry, but also against the non-archimedean systems of Thomae, du Bois-Reymond, and Stolz. As a positive consequence of the controversy the distinction between Cantor’s transfinite arithmetic and the theory of ordered algebraic structures becomes clear. (shrink)
We criticize speculations to the effect that quantum mechanics is fundamentally about information. We do this by pointing out how unfounded such speculations in fact are. Our analysis focuses on the dubious claims of this kind recently made by Anton Zeilinger.