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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Physics > History and Philosophy of Physics
The mean frequency of the localisations is extremely small, and the localisation width is large on an atomic scale. For Teachers To hide this material, click on the Normal link.
In the information physics solution to the problem of measurementthe timing and location of the Heisenberg “cut” are identified with the interaction between quantum system and classical apparatus that leaves the apparatus in an irreversible stable state providing information to the observer.
In other words, the theory is not in a position to explain how it could ever come about, in an interaction between a system and a measuring apparatus, that the peculiar process leading to a definite outcome could emerge — that is, how an apparatus could ever behave in the manner it is supposed to do! Where do we locate this boundary? Inhe was awarded the Spirit of Salam prize for his extraordinary contributions to the development of the International Centre for Theoretical Physics during its budding years, both at its scientific and organizational fronts.
And so what can be wrong with this simple, clear argument?
First, since the two processes described above involve physical systems that are completely normal for the theory in question the apparatus is composed of electrons, protons, neutrons, etc. We know very well that every time we watch one of the computers of the ensemble we read something definite and we do not end up in a state of mental confusion in which we have “potentially” read both expressions, leaving it ambiguous what we have actually seen.
His research interests related to a variety of topics of theoretical physics, but focused beginning in mainly on the foundations of quantum mechanics. Trieste Professor Fabio Benatti credits Ghirardi for influencing his research direction. The position of the particle there was just a feature of the wavepacket, not something in addition.
Gaincarlo Heisenberg called this a “cut” or “Schnitt” between quantum and classical worlds.
And this is in fact what we would experience if we actually looked at the apparatus. GianCarlo Ghirardi on Measurement In his elegantly written and nicely illustrated book, Sneaking a Look at God’s CardsGhirardi starts his discussion of the measurement problem by noting that the principle of superposition of states means that some observables lack a precise expectation value, so we can speak only of the probability of outcomes.
The GRW scheme represents a proposal aimed to overcome the difficulties of quantum mechanics discussed by John Bell in his article “Against Measurement. Indeed, for every process of measurement that interests us, at a certain level there must certainly intervene some observer whose perceptions are definite. If we want to describe which signals actually reach the brain, we would once more have to relocate the boundary between the vague quantum world and the world of definite events, and we are then led to place it between the optic nerve and the brain.
He was president of the Italian Society for the Foundations of Physics, of which he was one of the founding members.
Giancarlo Ghirardi – Wikipedia
In order to ghidardi this point, we need to recall that the theory in its general formulation includes a postulate that becomes operative every time a process of measurement is carried out, and that is the postulate of the reduction or collapse of the wave packet. Obviously these modifications must leave practically unaltered all standard quantum predictions about microsystems. Particles are not attributed angular momenta, energies, etc.
This serves extraordinarily well for defining the limited area of validity of classical mechanics. This reasoning can in principle be extended until it involves the entire universe, and it implies that even the universe would have only potentialities. He became a full professor of quantum mechanics at the University, as well as director of the Department of Theoretical Physics there.
By contrast, the reduction of the wave packet is a fundamentally stochastic and nonlinear physical process: The dynamics is not very precisely formulated either.
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 requires a quantum treatment.
Ghirardi had two great personal passions beyond his scientific research.
Since the number of the electrons is very large but still finite, what we see on the film will be a series of N black dots that correspond to the positions in which they are, so to speak, “revealed” by that object, which can be thought of as a measuring device.
The foregoing arguments might seem to point toward the number of particles as a possible candidate, but that does not work: Now, however, we must ginacarlo into the precise sense of this assertion and investigate the physical processes to which reference ghieardi made in the cases of concrete experiments carried out in laboratories.
Broad Michael Burke C. Then, for the initial state we have the following: Information increases, but entropy increases even more, to satisfy the second law. Peculiar ‘measurement’ results for angular momenta, energies, and so on, emerge as pointer positions in appropriate experimental setups.
Nevertheless, as observed in the preceding section, this does not have any consequences for what concerns the fact that any assertion about the position of the pointer is illegitimate, and it is even not permitted us to think that it has a precise position.
And we think there is nothing but the wavefunction.
GianCarlo Ghirardi – Citazioni di Google Scholar
The simple and clear answer is that nobody has as yet been able to find it. All historical experience confirms that men might not achieve the possible if they had not, time and ghigardi again, reached out for the impossible. 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 We have dislodged the boundary from the microcosm of the electron beam to the macrocosm of the film, as shown in the second stage of the figure.
But if the theory has a universal validity an endless process begins: As already mentioned, the difficulties that appear do not derive from our idealizations or simplifications introduced into the interpretation.