Against 'Particle Metaphysics' and 'Collapses' within the Definition of Quantum Entanglement

In this paper we argue against the orthodox definition of quantum entanglement which has been explicitly grounded on several “common sense” (metaphysical) presuppositions and presents today serious formal and conceptual drawbacks. This interpretation which some researchers in the field call “minimal”, has ended up creating a narrative according to which QM talks about “small particles” represented by pure states (in general, superpositions) which —each time someone attempts to observe what is going on— suddenly “collapse” to a single measurement outcome. After discussing the consequences of applying ‘particle metaphysics’ within the definition of entanglement we turn our attention to two recent approaches which might offer an interesting way out of this metaphysical conundrum. Both approaches concentrate their efforts in going beyond the notion of ‘system’. While the first, called device-independent approach, proposes an operational anti-metaphysical scheme in which language plays an essential role; the second approach, takes an essentially metaphysical path which attempts to present a new non-classical representation grounded on intensive relations which, in turn, imposes the need to reconsider the definition and meaning of quantum entanglement

Quantum Field Theory: Where We Are

We comment on the present status, the concepts and their limitations, and the successes and open problems of the various approaches to a relativistic quantum theory of elementary particles, with a hindsight to questions concerning quantum gravity and string theory.Comment: To appear in: An Assessment of Current Paradigms in the Physics of Fundamental Phenomena, to be published by Springer Verlag (2006

Kinematics and hydrodynamics of spinning particles

In the first part (Sections 1 and 2) of this paper --starting from the Pauli current, in the ordinary tensorial language-- we obtain the decomposition of the non-relativistic field velocity into two orthogonal parts: (i) the "classical part, that is, the 3-velocity w = p/m OF the center-of-mass (CM), and (ii) the so-called "quantum" part, that is, the 3-velocity V of the motion IN the CM frame (namely, the internal "spin motion" or zitterbewegung). By inserting such a complete, composite expression of the velocity into the kinetic energy term of the non-relativistic classical (i.e., newtonian) lagrangian, we straightforwardly get the appearance of the so-called "quantum potential" associated, as it is known, with the Madelung fluid. This result carries further evidence that the quantum behaviour of micro-systems can be adirect consequence of the fundamental existence of spin. In the second part (Sections 3 and 4), we fix our attention on the total 3-velocity v = w + V, it being now necessary to pass to relativistic (classical) physics; and we show that the proper time entering the definition of the four-velocity v^mu for spinning particles has to be the proper time tau of the CM frame. Inserting the correct Lorentz factor into the definition of v^mu leads to completely new kinematical properties for v_mu v^mu. The important constraint p_mu v^mu = m, identically true for scalar particles, but just assumed a priori in all previous spinning particle theories, is herein derived in a self-consistent way.Comment: LaTeX file; needs kapproc.st

Non-perturbative \lambda\Phi^4 in D=1+1: an example of the constructive quantum field theory approach in a schematic way

During the '70, several relativistic quantum field theory models in $D=1+1$ and also in $D=2+1$ have been constructed in a non-perturbative way. That was done in the so-called {\it constructive quantum field theory} approach, whose main results have been obtained by a clever use of Euclidean functional methods. Although in the construction of a single model there are several technical steps, some of them involving long proofs, the constructive quantum field theory approach contains conceptual insights about relativistic quantum field theory that deserved to be known and which are accessible without entering in technical details. The purpose of this note is to illustrate such insights by providing an oversimplified schematic exposition of the simple case of $\lambda\Phi^4$ (with $m>0$) in $D=1+1$. Because of the absence of ultraviolet divergences in its perturbative version, this simple example -although does not capture all the difficulties in the constructive quantum field theory approach- allows to stress those difficulties inherent to the non-perturbative definition. We have made an effort in order to avoid several of the long technical intermediate steps without missing the main ideas and making contact with the usual language of the perturbative approach.Comment: 63 pages. Typos correcte

Epistemic modality, particles and the potential optative in Classical Greek

This paper challenges the commonly held view that the Classical Greek potential optative has a subjective epistemic semantics, the result of a conceptual confusion of subjectivity and epistemic modality inherited from our standard grammars. I propose that this view becomes less convincing when the optative’s unique interaction with the subjective particles ἦ and ἄρα is incorporated into the analysis. Rather, the potential optative has a non-subjective epistemic semantics presenting an epistemic judgment as interpersonally accessible to the conversational participants. Frequencies of combination with ἦ and ἄρα, linguistic tests for subjectivity on the potential optative, and contrastive contextual analyses corroborate this view