Jun 15, GianCarlo Ghirardi, former professor of theoretical physics and then emeritus at the physics department of our university, passed away on 1st. GianCarlo Ghirardi. Angelo Bassi and Tullio Weber. University of Trieste, Trieste, Italy. Detlef Dürr. Ludwig-Maximilians University, Munich, Germany. PDF Full. Jun 4, The ICTP community is mourning the sudden passing of long-time colleague GianCarlo Ghirardi. Professor Ghirardi was associated with ICTP.
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As regards the first point, it should be enough to recall the debate between Bohr and Einstein that we analyzed in detail in chapter 7. Ghirardi—Rimini—Weber theory Quantum mechanics foundations.
While discussing this debate previously, I referred in passing to the fact that the same von Neumann and Wigner were led to relocate the boundary between quantum and classical, between reversible and irreversible, at the act of perception on the part of a conscious observer. But in macroscopic systems, as a consequence of the prescribed equationspointers very rapidly point, and cats are very quickly killed or spared.
Retrieved from ” https: If a body has a ghiradri much less than the velocity giancarloo light, Newton’s theory is appropriate, but as the velocity increases it becomes increasingly less precise and fails completely when it comes to describing bodies that travel at velocities nearing that of light. Then, for the initial state we have the following: At least two roads are open from there towards a precise theory, it seems to me.
The extension of that region he thought of as the actual size of the electron — his electron was a bit fuzzy. Indeed, for every process of measurement that interests us, at a certain level there must certainly intervene some observer whose perceptions are definite.
All historical experience confirms gizncarlo men might not achieve the possible if they had not, time and time again, reached out for the impossible. The kinematics of the world, in this gizncarlo picture, is given a wavefunction maybe more than one? In addition to the GRW theory, added Quevedo, Ghirardi made other important scientific contributions which are less known.
They became very aware of the intervening apparatus, and of the need for a ‘classical’ base from which to intervene on the quantum system. Bell analyzed the process of diffraction, through a slit, of a beam containing a certain number N of electrons, and the formation of the image on a photographic film placed behind the slit.
He was president of the Italian Society for the Foundations of Physics, of which he was one of the founding members.
Now, however, we must inquire into the precise sense of this assertion and investigate the physical processes to which reference is made in the cases of concrete experiments carried out in laboratories.
Why this aversion to ‘being’ and insistence on ‘finding’? To my knowledge, the most mathematically rigorous demonstration of the fact that the very possibility of using measuring apparatuses with a high degree of reliability implies the indefiniteness bhirardi some of their macroscopic properties, appears in a paper which I recently wrote in collaboration with my doctoral student A.
But if the theory has a universal validity an endless process begins: The argument shows in a simple way how to realize a state of the type considered in the preceding section. The zero position of the pointer is the state of the apparatus before it has interacted with a photon and can be designated as “the state of the apparatus ready to carry out a measurement.
Werner Heisenberg called this a “cut” or “Schnitt” between quantum and classical worlds.
To appreciate fully the relevance of this question, and to prepare ourselves to analyze the multiple and interesting proposals advanced as a way of getting around such difficulties, it will be giancaflo to begin by deepening our analysis.
It does so in a rather vague way, at rather vaguely specified times.
GianCarlo Ghirardi – Citazioni di Google Scholar
We are now prepared to show how the problem of the quantum theory of measurement arises. A reasonable and sufficiently realistic description of what happens as pointed out in chapter 6 would be the following: Then instrument pointers — assemblies of particles have positions, and experiments have results. Bell and presented by him at two conferences: The position of the giancwrlo there was just giamcarlo feature of the wavepacket, not something in addition.
We have indicated that if Einstein had insisted on his requirement of attributing definite properties up to an appropriate point of what we can call the von Neumann chain he would have constrained Bohr to accept that the entire universe giancxrlo a quantum treatment. Trieste Professor Fabio Benatti credits Ghirardi for influencing his research direction.
As discussed in Section This serves extraordinarily well for defining the limited area of validity of classical mechanics.
Peculiar ‘measurement’ results for angular momenta, energies, and so on, emerge as pointer positions in appropriate experimental setups. As we repeatedly emphasized in the early chapters of the book, the theory has been formulated in such a way as not to speak in general of properties possessed by systems but only of the probabilities of obtaining certain outcomes if measurements are carried out that intend to identify the values of the properties we are interested in.
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We then can ask ourselves: We now prepare an initial state that is a linear combination of the two initial states considered above: And so the shifty split. Benatti’s colleague Professor Angelo Bassi echoed his sentiments, adding, “GianCarlo was also a passionate teacher: He observed that it makes no sense to treat the electrons as if they were punctifom bodies that follow precise trajectories; they must be described by means of a diffracting wave function Figure The founding fathers were unable to form a clear picture of things on the remote atomic scale.
This state is an entangled state of the photon and the apparatus and as such it is not legitimate to attribute definite polarization properties to the photon or definite positions to the pointer of the apparatus.