1999. október 4. (hétfő)
12:30
6. em. 654.

The framework of branching space-time (BST; cf. Belnap 1992, Synthese 92, pp. 385--434) has recently been extended to allow for the introduction of outcomes of events and the analysis of GHZ theorems. (Kowalski & Placek, forthcoming in Brit. J. Phil. Sci. and Int. J. Theor. Phys.)

In BST, space-time and modality are incorporated in the very structure of the models, which consist of a pair , where  is a non-empty set weakly ordered by , which is interpreted as ‘causally accessible from’. Maximal upward directed subsets of  are called ‘histories’, and proper subsets of histories are called ‘events’. Two events are called ‘space-like separated’ if neither causally precedes the other. ‘Atomic outcomes’ of an event  are those parts of the event’s causal future that split in .

The main result of Kowalski & Placek is that the family of outcomes of an event forms a Boolean algebra. The paper also proves that in GHZ setups, there is always a common cause (CC) in the sense of Reichenbach if directions are held fixed, but that there is no single commom common cause (cf. Hofer-Szabó et al., forthcoming in Brit. J. Phil. Sci.) accounting for the outcomes of incompatible settings.

For an analysis of Bell’s theorem, I assign probabilities to outcomes by imposing a classical probability measure on the Boolean algebra of the outcomes of each given event. In the derivation of Bell’s theorem, I use probability measures of the form , , where the subscript indicates that the result is an outcome of the event of measuring the spin projections along directions  on the left and  on the right. Probabilities for single results on the left or on the right are calculated from these measures, allowing us to express correlations as .

Since correlations between space-like separated results appear disturbing, it is natural to look for an explanation in terms of a CC located in the results’ common past. The CC’s outcomes divide histories in such a way that actual runs of a correlation experiment are seen as belonging to two or more varieties differentiated by hidden factors. You may think of these hidden factors as restoring the deterministic order. You may also be more modest and require only that the hidden factors restore the causal order, i.e., that in each sub-population, the correlations disappear.

Formally, for space-like separated events  and  with correlated outcomes  and , respectively, a CC is an event  preceding both  and , such that for every atomic outcome  of ,

where  is defined on the enlarged probability space.

Now, for any correlated pair  we can construct mathematically an enlarged probability space containing such a CC. Moreover, for any finite number of correlations we can construct a single large probability space containing a set of distinct CCs, each CC taking care of one correlation.

However, in the Bell/Clauser-Horne argument, one wants something more: one postulates a single common CC accounting for all the correlated outcomes of , ,  and . Given the standard assumptions of locality and ‘no conspiracy’, which in our framework take the form

we derive the Bell/CH inequalities, which are empirically violated. Thus, there cannot be a common common cause accounting for the Bell/CH correlations.

Tomasz Placek néhany cikke (ps-file) itt letölthető: Outcomes in branching space-time and GHZ-Bell theorems; Stochastic Outcomes in Branching Space-Time: Analysis of Bell's Theorem; On the Issue of Joint Probabilities in Interpretations of Bell's Inequalities
 

1999. október 11. (hétfő)
12:30
6. em. 654.

Úgy tűnik igen, sőt még egy sereg más problémáját a kvantumelméletnek. "Prizma-modell" néven Arthur Fine 1982-ben egy olyan megoldást javasolt az EPR-Bell problémára, és általában a kvantummechanika lokális-realista interpretációjára, amelyről, mint később ő maga kiderítette, már Einstein is említést tett egy 1936-os cikkében, illetve néhány Rosenhez és Schrödingerhez írt levelében. E megoldás nem kapott különösebb visszhangot, sőt maga Fine sem vette igazán komolyan, hiszen későbbi cikkeiben úgy ír a Bell-tételről, mintha az Einstein-Fine-interpretáció nem is létezne. Ennek oka, hogy tévesen, Fine ezt a megoldást a valóságban végrehajtott kísérletekben használt detektorok nem 100%-os hatásfokával hozta kapcsolatba.

Az előadásban az Einstein-Fine-interpretációt egy új megvilágításban mutatom be. Megmutatom, hogy semmi köze nincs a detektorok hatásfokának sokat diszkutált problémájához. A valóságban elvégzett EPR-Bell kísérletek elemzésével megmutatom, hogy e kísérletek logikai szerkezetüknél fogva teljesen kompatibilisek az Einstein-Fine-interpretációval, amely viszont tökéletesen feloldja az EPR-Bell paradoxont.

Az előadás fóliái és az Aspect-kísérletet modellező, az előadást illusztráló  (PC/DOS/full-screen) program letölhető: http://hps.elte.hu/~leszabo/Preprints/einstein.htm
 
 

1999. október 18. (hétfő)
12:30
6. em. 654.

I want to take on the question of what a class of arguments, usually called the Conceivability Arguments, have to say about the mind-body problem. These arguments have two different versions. In one version, considerations of conceivability are taken to support the claim that phenomenal consciousness is not identical, realized by, or supervenient on, physical properties (for example, Kripke 1972, 140-162, Nagel 1974, Robinson 1993, White 1986, Jackson 1998, and Chalmers 1996). According to the other version, there is an explanatory gap between phenomenal and physical levels of description, that does not exist with respect to other higher level descriptions, and that may have metaphysical ramifications. (This argument is formulated by Joseph Levine 1998, although he is himself hesitant to accept the conclusion.) My claim is that these arguments do not succeed in establishing their conclusions. That is because, and I take this to be the primary lesson of the Conceivability Arguments, what they reveal does not have to do with phenomenal consciousness itself, it rather has to do with the nature of phenomenal concepts.

In the paper, I will focus on the most elaborate and sophisticated version of the Conceivability Argument for dualism. I first provide a general exposition of the structure of Conceivability Arguments, then I proceed to describe in greater detail Frank Jackson’s and David Chalmers’ new Conceivability Argument. Finally I construct a reductio that at the same time reveals where the arguments went wrong.
 
 

1999. október 25. (hétfő)
12:30
6. em. 654.

(Az előadás magyarul lesz!)

1. Introduction
1.1. Definition of awareness & consciousness for the non-philosopher
1.2. "Components" of consciousness
1.3. Levels of human consciousness, coma, sleep, awake states
1.4. "Prerequisites" of consciousness

2. Recent results on the brain and mind problem
2.1. Visual consciousness
2.2. Blindsight
2.3. Perception vs. action
2.4. Bistable percepts
2.4.1. Ambiguous figures
2.4.2. Binocular rivalry
2.5. Electrical brain stimulation and conscious behavior
2.6. Subliminal and supraliminal stimulus processing
2.7. Time scale of consciousness

Humans & Monkeys:
2.8. NCC - Neural Correlate of Consciousness

Theories & models

A szeminárium szervezője: Szabó E. László