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Franco Selleri

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Franco Selleri
Franco Selleri
Born(1936-10-09)October 9, 1936
DiedNovember 20, 2013(2013-11-20)
ResidenceBari, Italy
NationalityItalian
Known forQuantum Theory, EPR, Relativity, Selleri (inertial) transformations, absolute simultaneity
Scientific career
FieldsPhysicist
InstitutionsUniversity of Bari; Istituto Nazionale di Fisica Nucleare (INFN)

Franco Selleri (9 October 1936 – 20 November 2013) was an Italian theoretical physicist, professor at the University of Bari, and one of the most persistent and technically serious critics of the foundations of both quantum mechanics and special relativity in the second half of the twentieth century. He is best known for the Selleri transformations — a one-parameter family of transformations between inertial frames which, for the parameter value <math>e_1 = 0</math>, restore absolute simultaneity and a preferred frame while reproducing the experimentally verified predictions of relativity — and for his work on the Einstein-Podolsky-Rosen paradox, Bell's inequalities and the reality of de Broglie's waves. A realist in the tradition of Einstein, de Broglie and Karl Popper, Selleri argued throughout his career that the paradoxes of modern physics are symptoms of wrong conventional choices rather than facts of nature.

Biography

Franco Selleri was born in Bologna, Italy, on 9 October 1936. He received his Ph.D. cum laude from Bologna University in 1958, and from 1959 was a fellow of the Istituto Nazionale di Fisica Nucleare (INFN). He spent the bulk of his academic career at the University of Bari, where he was professor of physics and later professor emeritus.

He held numerous visiting professorships and fellowships, including at CERN, Saclay, the University of Nebraska–Lincoln, Cornell University and the Joint Institute for Nuclear Research at Dubna. He was a member of the New York Academy of Sciences and of the Fondation Louis de Broglie, and served on the Board of Directors of the Italian Physical Society. He was the recipient of a medal from the Gdanskie Towarzystwo Naukowe (Gdansk Scientific Society, Poland).

Selleri published more than 200 papers in particle physics, quantum theory, relativity, and the history and philosophy of physics, and authored or edited a long list of books and conference proceedings on the foundations of physics. He was a central organiser of the international meetings that helped make "foundations of quantum physics" a legitimate research field, including a 1985 conference in Bari attended by the philosopher Karl Popper, with whom Selleri was in close contact, and the 1991 Cesena conference on Bell's theorem. In 2009 he accepted directorships of ECE Science Technology Ltd, Steriwave Plc and Yellow Energy Plc.

He died on 20 November 2013.

Scientific contributions

The Selleri (inertial) transformations

Selleri's best-known result grows out of the well-known fact that the one-way speed of light cannot be measured without first adopting a clock-synchronisation convention, whereas only the two-way (round-trip) speed is directly observable. Starting from a small set of assumptions — homogeneity of space and time, an isotropic "rest" system <math>S_0</math>, the observed invariance of the two-way light speed, and the empirically established time-dilation factor — Selleri derived the most general transformations of space and time variables between inertial systems, and showed that they contain a single free synchronisation parameter, usually written <math>e_1</math>.

The result is a one-parameter family:

  • <math>e_1 = -v/c^2\gamma^2</math> (Einstein's choice) recovers the ordinary Lorentz transformations of special relativity, with relative simultaneity;
  • <math>e_1 = 0</math> gives what Selleri called the inertial transformations — now widely called the Selleri transformations — in which clocks are set by "absolute" synchronisation and simultaneity becomes absolute: two events judged simultaneous in <math>S_0</math> are judged simultaneous in every other inertial system.

The crucial point of Selleri's programme is that all values of <math>e_1</math> give the same predictions for every experiment based on two-way light propagation — Michelson–Morley, Kennedy–Thorndike, time dilation, the transverse Doppler effect and so on. Special relativity is therefore not singled out by experiment at the level of these tests; it is singled out by a convention. Under <math>e_1 = 0</math> the one-way speed of light becomes direction-dependent, <math>c(\theta) = c/(1 - \beta\cos\theta)</math> for an observer moving with <math>\beta = v/c</math> relative to the privileged frame, while the average round-trip value remains exactly <math>c</math>. Length contraction and time dilation survive as real, absolute effects relative to <math>S_0</math> — a structure close in spirit to the Lorentz ether theory, which Selleri explicitly sought to recover.

Why he preferred e₁ = 0: the rotating-platform discontinuity

Selleri did not regard the choice as merely conventional. His central physical argument — presented in "On a Physical and Mathematical Discontinuity in Relativity Theory", "The Zero Acceleration Discontinuity and Absolute Simultaneity" and a series of papers on the Sagnac effect — is now known as the Selleri paradox.

Consider a platform of radius <math>R</math> rotating with angular velocity <math>\omega</math>. Light sent around the rim in the two opposite directions takes different times, as measured by a single clock on the rim: this is the Sagnac effect, and it implies a rim-frame light-speed anisotropy. Now take the limit <math>\omega \to 0</math> and <math>R \to \infty</math> while holding the peripheral velocity <math>v = \omega R</math> fixed. The acceleration <math>\omega^2 R</math> tends to zero and the rim becomes locally indistinguishable from a straight inertial frame moving at <math>v</math> — yet the ratio of the two global light speeds does not tend to 1. Selleri argued that special relativity, which asserts light-speed isotropy in every inertial frame, therefore contains a genuine discontinuity at zero acceleration, whereas the <math>e_1 = 0</math> inertial transformations give a smooth, continuous limit that matches the rotating case exactly. He concluded that the observable success of the Sagnac effect, of the rotating Michelson–Gale experiment and of GPS clock synchronisation constitutes positive evidence for absolute simultaneity and a privileged frame.

Defenders of special relativity have replied that the discontinuity reflects only the use of different synchrony conventions in different frames rather than a physical inconsistency; Selleri's response was that this reply concedes his main point — that the standard theory's simultaneity is a convention, and one that produces an unphysical jump where the alternative does not.

Weak relativity

Selleri gathered this programme in Weak Relativity: The Physics of Space and Time Without Paradoxes (2009). "Weak" relativity retains a relativity principle in a weakened form: physical laws are the same in all inertial frames as regards two-way experiments, but there exists one privileged isotropic frame with respect to which absolute simultaneity is defined. The claimed payoff is the elimination of the paradoxes of the standard theory — the clock (twin) paradox, the causal paradoxes generated by superluminal signalling, and the rotating-disc/Ehrenfest difficulties — while leaving every confirmed relativistic prediction, from time dilation and relativistic beaming to Thomas precession, intact. He argued in "Superluminal Signals Imply Absolute Simultaneity" that if superluminal propagation exists at all (as some quantum-tunnelling and EPR-correlation experiments have been read to suggest) then only absolute simultaneity keeps causality safe.

Quantum foundations, EPR and Bell's inequalities

Selleri's earlier work was in particle physics and then, from the 1960s onward, in the foundations of quantum mechanics, where he was one of the small group of physicists who kept the interpretation question alive when it was professionally unfashionable. He was a realist: he held that quantum objects exist independently of observation and that the Copenhagen renunciation of a description of microphysical reality was a philosophical, not an empirical, commitment. His Die Debatte um die Quantentheorie (1983) and its Spanish edition became widely read statements of this view.

Technically, Selleri worked on Bell's inequalities and the Einstein-Podolsky-Rosen problem. He derived strengthened forms of the inequalities, analysed carefully what the atomic-cascade experiments (Aspect and others) actually establish once detection efficiency and other auxiliary assumptions are taken into account, and argued that the experiments then available did not conclusively refute local realism — the "detection loophole" line of criticism. He also constructed and studied nonlocal theories satisfying Bell's inequality, showing that the logical map of the problem is more complicated than the standard textbook dichotomy suggests.

A related long-running interest was the physical reality of the de Broglie wave. Following Louis de Broglie's double-solution and pilot-wave ideas, Selleri defended the possibility of directly detecting empty waves — the wave component of a split quantum system travelling along a path in which no particle is found — and proposed experiments to look for them ("On the Direct Observability of Quantum Waves"). He was a member of the Fondation Louis de Broglie and edited the memorial volume Fundamental Questions in Quantum Physics and Relativity: Collected Papers in Honor of Louis de Broglie (1993).

Discussed in CNPS talks

Selleri's transformations are an active line of research within the CNPS community. Stephan J G Gift has published extensively on the Selleri transformations and the one-way speed of light (including "The Selleri transformations and the one-way speed of light", Physics Essays 28, 2015, and later work using GPS range and synchronisation equations), and Roger J Anderton devoted a livestream to Gift's Selleri paper.

Abstracts

Books

Selected journal papers

  • F. Selleri, "Noninvariant One-Way Speed of Light and Locally Equivalent Reference Frames", Foundations of Physics Letters 10 (1), 73–83 (1997)
  • F. Selleri, "Noninvariant One-Way Velocity of Light", Foundations of Physics 26, 641 (1996)
  • F. Selleri, "Sagnac Effect: End of the Mystery", Apeiron 11 (2004)
  • F. Selleri, "On the Anisotropy of the Speed of Light on a Rotating Platform" (with related discussion), Foundations of Physics Letters (2004)

Media

External links

See also

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