21st-Century directions in
28th August - 4th September 2010
de Broglie-Bohm theory and beyond
For a week at the end of August 2010, a disparate - or should that be desperate - collection of physicists
and philosophers gathered in Valllico Sotto to discuss the meaning of a
partial differential equation, and related matters. Not very exciting you
might think. But the wearying, childish, relentless six-month media and internet storm
which preceded it - concerning who should or should not be invited to
attend - depressed many of the thousands of people that were dragged into it,
almost always against their will.. the personal threats, the badly-spelled diatribes from internet
psychics and telepaths, the conspiracy theories concerning precisely which
of the worlds' intelligence agencies were controlling events at TTI (MI6, since you ask - and definitely not the CIA)..
Not a good start, by us or them.
Which made it all the more remarkable that what followed was almost
certainly the best physics conference in the world that year (not that I went to
all the others, but it's probably true.). The aim was to imitate the 1927
Solvay conference - sadly with 19 fewer Nobel prize winners -
discuss the theory of quantum mechanics first presented by French physicist Louis de Broglie at that meeting. With the
considerable advantage of not having Wolfgang 'Not Even Wrong' Pauli around to make
fun of us.
De Broglie-Bohm theory is a 'hidden variables' formulation of quantum
mechanics initially developed by de Broglie from 1923-1927 and clarified
and extended by American physicist David Bohm beginning in 1952. Just by the simple expedient of
refusing to believe that particles cease to exist if you stop looking at
them, it is easy to show that - contrary to popular belief - quantum
mechanics can be interpreted as a dynamical theory of particle
trajectories rather than as a statistical theory of observation. In such a
formalism the standard paradoxes related to measurement, observation and
wave function collapse (Schrödinger's cat, and so on) largely evaporate.
The classical limit does not have to be presupposed and emerges from the
theory in a relatively clear way. All the 'talk' is replaced by
sharply-defined mathematics, it becomes possible to 'visualize' the
reality of most quantum events, and - most importantly - the theory is
completely consistent with the full range of QM predictive-observational
data. The theory also gives rise to the possibility of
new physics - and of new mathematical and philosophical ideas - and considerable emphasis was placed on this during the meeting.
One of the most common remarks by the participants, many of whom work in
relative isolation, was an expression of surprise that there were all these other
people out there working on topics related to de Broglie-Bohm theory. The number of scientists
apparently unaware of each others' work was consistently surprising, and
the meeting led to a number of new collaborations. The overall quality of the talks and of the accompanying discussions was very high - the only problem being the overall tendency to talk too much, leading to many unscheduled early afternoon sessions to fit in all the talks that people wanted to give.
We were also fortunate to enjoy the presence of many of Bohm's former friends and colleagues - including Basil Hiley, Chris Dewdney, Paavo Pylkkänen and almost, but not quite, David Peat and Georg Wikman. Their personal reminscences of Bohm - who died in 1992 - were extremely interesting.
As with all events at TTI, afternoon
athletic achievements were strongly encouraged. The week kicked off with a couragous and successful
bid by Lev Vaidman, Shantena Sabbadini,
Wayne Myrvold, and Ilja Schmelzer - menaced by the threat of thunderstorms - to reach the summit of the giant and very vertical peak of Pizzo d'Uccello. Other expeditions traversed the
Turrite di San Rocco canyon, scaled Monte Procinto and Monte Matanna,
crossed the giant rock arch of Monte Forato, penetrated the depths of the
Tana di Cascaltendine cave, and er.. sat around by Bagni di Lucca and
Barga swimming pools eating ice cream.
Thursday saw the latest and greatest installment of the regular "Vallico Sotto
against the World" football match. At the last minute we learned that
Vallico's Team Captain and inpirational talisman Marco was crippled with a
broken arm, and that Michele and Luca (the 2nd and 3rd best players) were
similarly unable to play. Hence it was a team largely made up of balding,
middle-aged reserves that took the field against the best that the Rest of
the World could offer. Within minutes, the World - led by the skilful and
quick Benincasa twins - were stuffing Vallico 6-0. Taking full advantage
of the fact that Vallico lacked any substitutes whatever and were quickly
exhausted, the World team substituted players at will every few minutes
whenever they felt a bit out of breath, and continued to press home their
advantage. And then, and then.. a speculative shot from the Vallichese
nearly blew out the back of the net, and slowly the tiny village (average
age of inhabitants: 87) began to creep back into the game. After an hour's
play, the score was - unbelievably - only 11-10 to the World yet victory
was within the physicists' grasp. Then, with only 5 seconds to go, the funny
little Vallico guy in the white vest skipped past three defenders and equalized. The
resulting tense Golden Goal period came to a sudden end when the Mysterious Stranger
now playing for Vallico in the blue and red
stripey shirt blasted the ball into the top corner. The humiliation
of the World was complete. The Benincasas, Batelaan, Struyve, Derakhshani,
Oriols, Ip, Schmelzer and Norsen skulked off, crying.. All the pretty
Vallico girls looked pityingly at the inept and cowardly foreigners, and
cheered the victors to the skies. Then everyone mucked in at the old
village restaurant to make pizza, and everything was alright in the end, but the World boys won't forget that in a hurry..
MDT congratulates the winners of 'Vallico Sotto against the World': the Vallico reserves
The meeting concluded with some of the best talks of the week, a trip to
the beautiful city of Lucca, dinner in a high mountain village, late-night fireworks, the Best
Cheese in Italy (soaked in barolo, by God), and some Warre's 1991 port in
the back garden.
It all seemed so far from the email I received from Guardian
journalist Jonathan Margolis last April:
"Dear Mike. I was having a very nice afternoon sitting in the directors'
box at Nottingham Forest with [UK Justice Secretary] Kenneth Clarke when
Uri Geller called, and I thought it was such a funny combination of
Herman Batelaan, Dionigi Benincasa, Gregorio Benincasa, Andrew Bennett, Howard Burton, John Bush, Jeremy Butterfield, Murray Daw, Maaneli Derakhshani, Chris Dewdney, Christos Efthimiopoulos, Lucien Hardy, Richard Havery, Basil Hiley, Kris Krogh, Alberto Montina, Wayne Myrvold, Gillie Naaman-Marom, Hrvoje Nikolic, Travis Norsen, Xavier Oriols, Pedro Naranjo Pérez, Patrick Peter, Nelson Pinto-Neto, Enrico Prati, Paavo Pylkkänen, Anton Ramsak, Peter Riggs, Joshua Rosaler, Shantena Sabbadini, Ilja Schmelzer, Rafael Sorkin, Ward Struyve, Mike Towler, Jos Uffink, Lev Vaidman, Wouter Valentin, Antony Valentini, James Yearsley, Michael Naaman-Marom, Elaine Bennett, Mari Hirano, Glenys Dewdney, Irena Burton, Louis Burton, Emma Burton, Elina Pylkkänen, Kasper Pylkkänen, Ester Pylkkänen, Vanessa Hardy, Vivienne Hardy, Branka Ramsak, Samantha Keil, Saska Towler, Samuel Denny, Daniel Thorpe, Pui Ip.
Guido Bacciagaluppi, Jeffrey Bub, Maurice de Gosson, Jonathan Halliwell, Tim Maudlin, David Peat, Roger Penrose, Carlo Rovelli, Simon Saunders, Maximilian Schlosshauer, Lee Smolin, Rob Spekkens, Georg Wikman.
Official conference material
Background material and references
"21st-century directions in de Broglie-Bohm theory and beyond - an introduction" [PDF]
- Movie: 1927 Solvay conference [MP4]
- Movie: The central dogma of molecular biology [MP4]
"Introduction to current research in de Broglie-Bohm pilot-wave theory" [PDF]
"Particle diffraction from a double slit and a phase grating; can random electrodynamics provide a physical picture for the de Broglie-Bohm pilot wave?" (NOT AVAILABLE)
"Lorentz-invariant relaxation to quantum thermal equilibrium" [PDF]
"'Advice' from the Founding Director of the Perimeter Institute" [AUDIO FILE AVAILABLE]
"Pilot waves and the quantum behaviour of bouncing droplets"
[PDF of relevant paper - too many videos in talk slides.]
"On the phase-quantization problem in stochastic mechanics" [PDF]
"The role of chaos in the de Broglie-Bohm quantum theory" [PPT]
"Why we should consider situating the de Broglie-Bohm model in the context of a much more general framework for hidden variable theories?" [BLACKBOARD TALK]
"Moyal and Clifford algebras and the Bohm approach" [PDF]
"Resource cost in the classical simulation of a quantum preparation-measurement process" [PDF]
"Are corpuscle trajectories idle wheels?" [PDF]
"The validity of a naive approximating formula for Bohmian velocity" [PPTX]
"Making Bohmian mechanics compatible with relativity and quantum field theory" [PDF]
"Out of this world ontology" [PPTX]
"Quantum many-particle computations with Bohmian trajectories" [PDF]
"Cosmological problems and a possible non-inflationary solution in the framework of de Broglie-Bohm quantum cosmology" [PDF]
"The de Broglie-Bohm interpretation of quantum cosmology" [PPT]
"From classical to quantum observables in mesoscopic electron systems" [NOT AVAILABLE]
"The philosophical relevance of Bohm's interpretation of quantum theory" [PDF]
"De Broglie-Bohm analysis of entangled qubit pairs" [PDF]
"Testing de Broglie-Bohm theory with 21st-century technology" [PPT]
"Decoherence and the emergence of deterministic classical behaviour in de Broglie-Bohm theory" [PDF]
"About pilot wave field theory" [PDF].
More information here.
"A re-formulation of quantum theory in which events really do (or do not) happen." [BLACKBOARD TALK]
"Pilot wave theory and quantum fields" [PDF]
"The origin of the Born rule: dynamical relaxation to quantum equilibrium" [PDF]
- Movie: Approach to quantum equilibrium. [GIF]
"Bohm vs. Everett" [PPTX]
"In search of a breakdown in quantum theory" [PDF]
"Comparing solutions to the arrival time problem in de Broglie-Bohm theory and decoherent histories: What can we learn?" [PDF]
Additional volunteered talks
"A New Paradigm?" [MP4] (Video filmed in Cambridge)
"Persistence of information in the quantum measurement problem" [PDF]
"Beyond the theory / wrapping up" [PPT]
"Well, words fail me really! That was a stupendous
conference; a real feat by Mike if I may say so: to keep so many people
feeling welcome, and intellectually stimulated; and so much more than that. Truly an amazing week, and we all owe you a big debt of gratitude."
"It was a great privilege to be invited to the Towler Institute and to enjoy that blissful week in the beautiful surroundings with such good company, intellectual stimulation and, not least, exercise! I think you and Samantha have made a wonderful home of that delightful monastery - to hear (and see) lectures in the twelfth-century church was most exciting. I am lost in admiration for your organizational capacity and energy - the diversity of all the things you have to think about is enormous. You are playing a great part in promoting pilot wave theory among the physics community. May it flourish!"
"Thank you for a wonderful visit and conference. I have learned more than I can express, and made many new friends, among whom I am glad to include the Towlers. I hope to see you in [my town] soon. In the meantime, I hope you'll enjoy this adventure, the story of discovery which reminds me of what we have spent the week sharing. See you in the New World." [inscribed inside the cover of "Undaunted Courage" by Stephen Ambrose]
"Thanks so much for a wonderful week, with a well-organized workshop, interesting talks, lovely venue, great excursions, gorgeous food, and welcome environment. I can't believe how you're doing this all by yourselves! Take care and best wishes."
"Many, many thanks for organising such an excellent conference. Thank you
for being such good hosts. Mike, I felt exhausted just watching you dealing
with all the schedule and the many problems that must arise when such a
group gather. Congratulations!"
"Really enjoyed the meeting in
Vallico Sotto. I also enjoyed tremendously seeing your house/monastery. It
is amazing what you have done with it. We were blown away with Sam's
sculptures. Seeing them "in the flesh" was much better than seeing photos
of them. She is really good. ... Thanks very much for a fantastic meeting. It was very satifying to see an
approach to pilot wave that is fully engaged with the big problems in
physics. Meetings in quantum foundations can be depressing. This was
"The conference was excellent in every way, both [my wife] and I thoroughly
enjoyed it and wanted to convey our thanks for all the work that you did. We
were particularly sorry to leave without saying goodbye to Sam as she was
such good company during our "lazy" afternoons by the pool. Please give her
our best wishes.
Unfortunately it is wet and windy in [my town] and I have spent the day
doing very boring administrative tasks for our new Applied Physics degree -
with much more to do. It is a hard contrast with talking physics in the
sunshine in Tuscany!"
"A quick note to thank you for the fantastic visit to Tuscany.
I apologize for my less than graceful exit, but I think someone must have
put something in my Ouzo! It was a tough day...
I really enjoyed the meeting, and getting to know you and yours. Hopefully our paths will
cross again before too long.. With many thanks for everything, a great meeting, and some great fun - a
wonderful exclamation point
on a mad summer!"
"I'd like to express my sincere gratitude for the wonderful week I've
spent at TTI. The atmosphere surrounding the conference was just
I've had the chance to talk a bit with Sam and she's told me about
the difficulties you've being through in order to organise this
meeting. I really appreciate what you both are doing. It's simply
..it's definitely very encouraging to know that
there are some people out there making huge efforts to allow people
meet each other (in some cases young people having the opportunity to
learn techniques that are then developed at their countries),
irrespective of whether financial support happens to exist."
"Thanks again for the kickass conference. I hope you got -- and
are still getting -- some much deserved rest."
"I would like to congratulate you for an excellent organization of the meeting
and thank you again for the acceptance of my late application. It was really
fruitful for me, in particular to discuss with Basil Hiley."
"It was good to meet you and the others at the conference. All in all a
great success, I think."
"I want to thank you, once more, for you hospitality sharing your house and
your life with us during this week. For me, apart from a very fruitful
scientific conference, it was also a wonderful and unique experience.
I do also hope to be in touch with you in the future to discuss."
"I want to thank you again for this very enjoyable conference!
It was extremely fruitful from my point of view at least."
"I'd like to thank you and Sam for opening up your
home and organising such an interesting conference. This has been without a
doubt the peak of my summer!"
"Thanks again for the wonderful conference."
"I have been impressed by your personal
dedication to the goal of creating such conditions that people can get the
out of themselves and of discussing new and interesting physics. You and
your family created an atmosphere which I felt very friendly from the start.
I am sure that all participants will recognise owing a lot to your efforts."
"I keep rereading your conference report. Every time it brings a
smile to my face or makes me laugh out loud. I agree it must have
been the best physics conference this year -- and maybe the most fun
The best surprise for me was the number of friends made. Thanks to
you and Sam for a fabulous time and regards to my 'niece' Saska!"
"The pleasure is mutual. It was the all-around best conference I've
been to in my short career."
"I am still enjoying my memories from the wonderful, indeed amazing workshop you organized."
"It was lovely meeting you and Samantha, you have a
wonderful place there, the conference was great, the outings spectacular,
the Alpi Apuane a real discovery... what more to ask?"
"Thanks for the warm words and your general hospitality. That's a
pretty special place you have there."
"Thank you very much for an excellent conference & for your
tremendous hospitability! [My wife], I & the kids truly enjoyed meeting you all
and seeing Vallico Sotto. And sorry for breaking the electric wall socket
in Doctor's house while trying to charge my laptop 4.30 in the morning - I
hope it was possible to fix!"
"Thanks again for the great time last week. I'm still in complete
awe of the fact that you not only organized the conference, but chaired all
the talks, led tours every afternoon, coordinated 3 meals a day for 50
people, emceed the football match, kept your daughter alive and your wife
(mostly) happy, get a little drunk as needed, purchase and light fireworks,
etc. And that you did all that 3 times already in one summer. You should
find a way to bottle your energy and sell it."
"That is one fantastic house to chill in. I certainly envy you that!"