The Einstein-Podolsky-Rosen Argument and the Bell Inequalities

In 1935 Einstein, Podolsky, and Rosen (EPR) published an important paper in which they claimed that the whole formalism of quantum mechanics together with what they called ``Reality Criterion'' imply that quantum mechanics cannot be complete. That is, there must exist some elements of reality that are not described by quantum mechanics. There must be, they concluded, a more complete description of physical reality behind quantum mechanics. There must be a state, a hidden variable, characterizing the state of affairs in the world in more details than the quantum mechanical state, something that also reflects the missing elements of reality. Under some further but quite plausible assumptions, this conclusion implies that in some spin-correlation experiments the measured quantum mechanical probabilities should satisfy particular inequalities (Bell-type inequalities). The paradox consists in the fact that quantum probabilities do not satisfy these inequalities. And this paradoxical fact has been confirmed by several laboratory experiments in the last three decades. The problem is still open and hotly debated among both physicists and philosophers. It has motivated a wide range of research from the most fundamental quantum mechanical experiments through foundations of probability theory to the theory of stochastic causality as well as the metaphysics of free will

The Einstein-Podolsky-Rosen Argument and the Bell Inequalities

In 1935 Einstein, Podolsky, and Rosen (EPR) published an important paper in which they claimed that the whole formalism of quantum mechanics together with what they called ``Reality Criterion'' imply that quantum mechanics cannot be complete. That is, there must exist some elements of reality that are not described by quantum mechanics. There must be, they concluded, a more complete description of physical reality behind quantum mechanics. There must be a state, a hidden variable, characterizing the state of affairs in the world in more details than the quantum mechanical state, something that also reflects the missing elements of reality. Under some further but quite plausible assumptions, this conclusion implies that in some spin-correlation experiments the measured quantum mechanical probabilities should satisfy particular inequalities (Bell-type inequalities). The paradox consists in the fact that quantum probabilities do not satisfy these inequalities. And this paradoxical fact has been confirmed by several laboratory experiments in the last three decades. The problem is still open and hotly debated among both physicists and philosophers. It has motivated a wide range of research from the most fundamental quantum mechanical experiments through foundations of probability theory to the theory of stochastic causality as well as the metaphysics of free will

Is Quantum Mechanics Compatible with a Deterministic Universe? Two Interpretations of Quantum Probabilities

Two problems will be considered: the question of hidden parameters and the problem of Kolmogorovity of quantum probabilities. Both of them will be analyzed from the point of view of two distinct understandings of quantum mechanical probabilities. Our analysis will be focused, as a particular example, on the Aspect-type EPR experiment. It will be shown that the quantum mechanical probabilities appearing in this experiment can be consistently understood as conditional probabilities without any paradoxical consequences. Therefore, nothing implies in the Aspect experiment that quantum theory is incompatible with a deterministic universe.Comment: REVISED VERSION! ONLY SMALL CHANGES IN THE TEXT! compressed and uuencoded postscript, a uuencoded version of a demo program file (epr.exe for DOS) is attached as a "Figure

A local hidden variable theory for the GHZ experiment

A recent analysis by de Barros and Suppes of experimentally realizable GHZ correlations supports the conclusion that these correlations cannot be explained by introducing local hidden variables. We show, nevertheless, that their analysis does not exclude local hidden variable models in which the inefficiency in the experiment is an effect not only of random errors in the detector equipment, but is also the manifestation of a pre-set, hidden property of the particles ("prism models"). Indeed, we present an explicit prism model for the GHZ scenario; that is, a local hidden variable model entirely compatible with recent GHZ experiments.Comment: 17 pages, LaTeX, 7 eps figures, computer demo: http://hps.elte.hu/~leszabo/GHZ.html, an improper figure is replace

Lytic and mechanical stability of clots composed of fibrin and blood vessel wall components.

Background Proteases expressed in atherosclerotic plaque lesions generate collagen fragments, release glycosaminoglycans (chondroitin sulfate [CS] and dermatan sulfate [DS]) and expose extracellular matrix (ECM) proteins (e.g. decorin) at sites of fibrin formation. Objective Here we address the effect of these vessel wall components on the lysis of fibrin by the tissue plasminogen activator (tPA)/plasminogen system and on the mechanical stability of clots. Methods and results MMP-8-digested collagen fragments, isolated CS, DS, glycosylated decorin and its core protein were used to prepare mixed matrices with fibrin (additives present at a 50-fold lower mass concentration than fibrinogen). Scanning electron microscopy (SEM) showed that the presence of ECM components resulted in a coarse fibrin structure, most pronounced for glycosylated decorin causing an increase in the median fiber diameter from 85 to 187 nm. Rheological measurements indicated that these structural alterations were coupled to decreased shear resistance (1.8-fold lower shear stress needed for gel/fluid transition of the clots containing glycosylated decorin) and rigidity (reduction of the storage modulus from 54.3 to 33.2 Pa). The lytic susceptibility of the modified fibrin structures was increased. The time to 50% lysis by plasmin was reduced approximately 2-fold for all investigated ECM components (apart from the core protein of decorin which produced a moderate reduction of the lysis time by 25%), whereas fibrin-dependent plasminogen activation by tPA was inhibited by up to 30%. Conclusion ECM components compromise the chemical and mechanical stability of fibrin as a result of changes in its ultrastructure

On the Persistence of the Electromagnetic Field

According to the standard realistic interpretation of classical electrodynamics, the electromagnetic field is conceived as a real physical entity existing in space and time. The problem we address in this paper is how to understand this spatiotemporal existence, that is, how to describe the persistence of a field-like physical entity like electromagnetic field. First, we provide a formal description of the notion of persistence: we derive an “equation of persistence” constituting a necessary condition that the spatiotemporal distributions of the fundamental attributes of a persisting physical entity must satisfy. We then prove a theorem according to which the vast majority of the solutions of Maxwell's equations, describing possible spatiotemporal distributions of the fundamental attributes of the electromagnetic field, violate the equation of persistence. Finally, we discuss the consequences of this result for the ontology of the electromagnetic field

Csatolt diszkrét és folytonos dinamikai rendszerek stabilitása és nemlineáris rezgései = Stability and nonlinear vibrations of coupled discrete and continuous dynamical systems

Gépészmérnöki feladatok megoldásakor, ahol mozgások leírása, tervezése a cél, hagyományosan folytonos szemlélet dominál. A műszaki-technológiai fejlesztés azonban sok olyan rezgési problémába ütközött az utóbbi évtizedben, ahol a fejlődés további korlátját jelentő rezgéseket diszkrét hatások okozzák. Ennek alappéldái a robotika rezgési jelenségei, ahol a newtoni dinamikával leírható, folytonosan viselkedő rendszert mikroprocesszorok segítségével szabályoznak, és így a mintavételezésen és kerekítési hibákon keresztül időbeli és térbeli digitális hatásokat kapcsolnak hozzá. Diszkrét és folytonos rendszerek dinamikájának együttes vizsgálatára szükség van akkor is, ha a fizikai rendszer maga szabályozza a folytonos rendszert diszkrét módon, mint a nagy amplitúdójú szerszámgéprezgések, a gyorsan forgó tengelyek rubbing jelensége, vagy a kerekek térbeli gördülése és csúszása során jelentkező kapcsolgatás esetén. Olyan algoritmusokat dolgoztunk ki, amelyek a lehető legkevesebb numerikus közelítést tartalmazva, pontosan és egyszerűen adják meg az ilyen rendszerek stabilitásának feltételeit, illetve a stabilitásvesztéskor kialakuló rezgések jellegét, frekvenciáit, amplitúdóit. Ezekkel a módszerekkel sikerült pl. robotok emberekkel való érintkezéséhez szükséges erőszabályozásokat terveznünk az EU rehabilitációs robot projektjében, új nagysebességű marási technológiákat javasolnunk, magyarázatot adnunk kerekek fékezéskor kialakuló laterális (simmiző) rezgésére. | Time-continuous approach dominates the solution of those problems of mechanical engineering where the goal is the analysis or design of certain motions. The technological development, however, has often been set back during the last decade by vibration problems originated in discrete effects. Basic example is the vibration phenomenon of robots, where the continuous physical system described the Newtonian laws is subjected to control by means of microprocessors. These introduce digital effects both in time and space via the sampling and the round-off, respectively. The coupled discrete and continuous systems dynamics are in the focus of critical vibration phenomena also in those cases when the physical system regulates itself in a discrete way. This happens during the large amplitude oscillations of machine tools, the rubbing phenomenon of rotors, or the subsequent switches between the rolling and sliding dynamics of wheels. We developed algorithms that give the stability conditions of these systems in a reliable, efficient and still simple way. Moreover, these methods also describe the nature of these vibrations, provide their frequency content and amplitude range. This way, for example, we designed the force control of rehabilitation robots in an EU project where human and robot must interact by touching each other, suggested new technological parameter domains for high-speed milling, or explained the lateral vibrations (shimmy) of wheels during braking

Meaning, Truth, and Physics

A physical theory is a partially interpreted axiomatic formal system (L,S), where L is a formal language with some logical, mathematical and physical axioms, and with some derivation rules, and the semantics S is a relationship between the formulas of L and some states of affairs in the physical world. In our ordinary discourse, the formal system L is regarded as an abstract object or structure, the semantics S as something which involves the mental/conceptual realm. This view is of course incompatible with physicalism. How can physical theory be accommodated in a purely physical ontology? The aim of this paper is to outline an account for meaning and truth of physical theory, within the philosophical framework spanned by three doctrines: physicalism, empiricism, and the formalist philosophy of mathematics