Modern Issues in
Foundations of Physics
Programme
September 26 will be arrival day, with an informal
gathering and drinks in the evening from 8pm.
Venue: h-bar, basement of Sherfield Building, Imperial College. Sherfield building is number 20 on this map.
Talks will take place on the weekend of September
27/28, lecture room: Huxley 311, Department of Physics,
Imperial College London. Huxley building is number 13
on this map.
The conference dinner will take place at the Rembrandt Hotel, 11 Thurloe Place, London SW7 2RS, on
Saturday, September 27, from 19:00. If you registered
for the dinner, please pay £25 upon registration on
Saturday from 8:15 or during the coffee break at
10:45.
Schedule (minor
changes still possible)
Friday, Sep 26
|
Time |
Content |
Remarks |
|
|
|
|
|
20:00—ca. 22:30 |
Informal gathering and drinks, h-bar, Sherfield Building, Imperial College |
All pay for themselves |
Saturday, Sep 27 – all talks in Huxley 311
|
Time |
Content |
Remarks |
|
|
|
|
|
8:15—9:00 |
Registration |
Please pay £25 if you registered for the
conference dinner |
|
9:00—9:15 |
Welcome |
|
|
9:15—10:00 |
Michael Duff, “Yang-Mills origin of
gravitational symmetries” |
|
|
10:00—10:45 |
Peter Knight, “Quantum Rulers – Joint Measurement of Non-commuting
Variables and Observing Uncertainty Relations” |
|
|
10:45—11:15 |
Registration, coffee/tea break |
Please pay £25 if you registered for the
conference dinner |
|
11:15—12:00 |
Roger Penrose, “Twistor
non-locality and EPR effects” |
|
|
12:00—12:45 |
Julian Barbour, “Typical Universes and
their Entropy” |
|
|
12:45—14:15 |
Lunch break |
South Kensington station area or Gloucester
Road, all pay for themselves |
|
14:15—15:00 |
Lee Smolin
(via video link), “Time, causality and law in a cosmological context” |
|
|
15:00—15:45 |
Carlo Rovelli,
“Chris, here is a hope for a quantum gravity effect we might be able to see:
Planck stars” |
|
|
15:45—16:15 |
Coffee/tea break |
16:00 talk by Tom Kibble (by invitation
only) |
|
16:15—18:30 |
Free time/museum? |
|
|
18:30 |
Meeting back at Imperial, walking to
restaurant |
|
|
19:00—ca. 21:30 |
Conference dinner at Rembrandt hotel |
|
Sunday, Sep 28 – all talks in Huxley 311
|
Time |
Content |
Remark |
|
|
|
|
|
9:15—10:00 |
Sarben Sarkar, “Signatures of CPT violation in mesons and neutrinos” |
|
|
10:00—10:45 |
Tim Palmer, “Bell's Conspiracy,
Schrödinger's Black Cat and Global Invariant Sets” |
|
|
10:45—11:15 |
Coffee/tea break |
|
|
11:15—12:00 |
Andreas Döring, “Topos,
Ou Topos? Some Progress
and Some Partial Truths” |
|
|
12:00—12:45 |
Renate Loll |
|
|
12:45—14:15 |
Lunch break |
South Kensington station area or
Gloucester Road, all pay for themselves |
|
14:15—15:00 |
Jonathan Halliwell,
“Negative Probabilities, Fine's Theorem and Quantum Histories” |
|
|
15:00—15:30 |
Coffee/tea break |
|
|
15:30—16:15 |
Steve Weinstein, “Degrees of Freedom” |
|
|
16:15—17:00 |
Stanley Deser
(via video link), “Massive Gravities, or how I got tenure by destroying Isham's models” |
|
|
17:00—17:15 |
Closing remarks by Chris |
|
Abstracts:
Julian Barbour,
Oxford: Typical Universes and their Entropy
It is shown in
ArXiv:1409.0917 (PRL 26/09/14; JB, T Koslowski, and F Mercati) that a
gravitational
arrow of
time arises solely by virtue of the law of gravity and does not require any
special initial
condition.
Building on the methods of that paper, we have created a framework of
gravitational
statistical
mechanics for dynamically closed universes. It allows us to define an entropy
of the
universe
and establish the nature of typical universes. I will explain the basic ideas
and surprising
conclusions of
our theory using the Newtonian N-body problem. General relativity shares the
key
structural
features that underlie N-body theory, so our results should extend to Einstein
gravity.
Stanley Deser, Brandeis: Massive
Gravities, or how I got tenure by destroying Isham's
models
Andreas Döring, Erlangen: Topos, Ou Topos? Some Progress and Some
Partial Truths
I will present
aspects of my joint work with Chris between 2006 and 2011 on the topos approach to
the
formulation of physical theories, emphasising how
radically the topos approach departs from
established
theories and theory-making. I will then present some recent developments and
pose the
question:
is there hope that this approach will actually lead to some progress in
foundations, or will
topos-based
physics stay a utopia?
Michael Duff,
Imperial: Yang-Mills origin of
gravitational symmetries
By regarding
gravity as the convolution of left and right Yang-Mills theories, we derive in
linearised
approximation the gravitational symmetries of general covariance, p-form gauge
invariance,
local Lorentz invariance and local supersymmetry from
the flat space Yang-Mills
symmetries of
local gauge invariance and global super-Poincare. Turning to global symmetries
we
give a division algebra R,C,H,O description of Yang-Mills with N(L/R) = 1,2,4,8
and hence, by
tensoring
left and right multiplets, a Freudenthal
magic square RR, CR, CC, HR, HC, HH, OR, OC,
OH, OO
description of N=N(L)+N(R)
supergravity.
Jonathan Halliwell, Imperial: Negative
Probabilities, Fine's Theorem and Quantum Histories
Many situations
in quantum theory and other areas of physics lead to quasi-probabilities which
seem to
be physically useful but can be negative. The interpretation of suchobjects is not at all clear.
We argue that
quasi-probabilities naturally fall into two qualitatively different types,
according to
whether
their non-negative marginals can or cannot be matched
to a non-negative probability. The
former
type, which we call viable, are qualitatively similar to true probabilities,
but the latter type,
which we
call non-viable, may not have a sensible interpretation. Determining the
existence of a
probability
matching given marginals is a non-trivial question in
general. In simple examples, Fine's
theorem
indicates that inequalities of the Bell and CHSH type provide criteria for its
existence. The
proof of
Fine's theorem is briefly discussed. The results have consequences for the linear
positivity
condition of
Goldstein and Page in the context of the histories approach to quantum theory.
Although
it is
a very weak condition for the assignment of probabilities it fails in some
important cases where
our results
indicate that probabilities clearly exist.
This talk is
based on the papers
J.J.Halliwell
and J.M.Yearsley, Phys. Rev. A 87, 022114 (2013)
J.J.Halliwell,
Phys. Lett. A 378, 2945 (2014).
Peter Knight,
Imperial: Quantum Rulers – Joint Measurement
of Non-commuting Variables and
Observing
Uncertainty Relations
Renate Loll,
Nijmegen: tba
Tim Palmer,
Oxford: Bell's Conspiracy,
Schrödinger's Black Cat and Global Invariant Sets
A locally
causal hidden-variable theory of quantum physics need not be constrained by the
Bell
inequalities if
this theory also partially violates the measurement independence condition.
However, such
violation
can appear unphysical, with implausible conspiratorial correlations between the
hidden-variables
of particles
being measured and earlier determinants of instrumental settings. Motivated by
global
properties of
the state space geometry associated with certain nonlinear dynamical systems, a
novel
explanation
for such correlations is proposed. The explanation is based on the proposal
that states of
physical
reality lie precisely on a measure-zero dynamically invariant set in the state
space of the universe:
the
Cosmological Invariant Set Postulate. To illustrate the relevance of the
concept of a global invariant set,
a
simple analogy is considered where a massive object is propelled into a black
hole depending on the decay
of a
radioactive atom: if the global nature of the event horizon (a photonic
invariant set) were not recognised,
this
experiment might also suggest either implausible conspiracy or retrocausality between the atom's
supposed
hidden variables and the size of the black hole at early times. A locally
causal hidden-variable
theory
constrained by the Cosmological Invariant Set Postulate can violate the CHSH
inequality without
being
conspiratorial, superdeterministic, fine-tuned or retrocausal, and the theory readily accommodates
the
classical compatibilist notion of (experimenter) free will. Just as the
application of global geometric
methods revolutionised our understanding of gravitational physics
in the 1960s, here it is proposed that
global
geometric methods in state space may fundamentally change our understanding of
quantum physics
and,
by promoting a more synergistic relationship between quantum physics and
cosmology, lead to new
insights in
the problem of unifying quantum and gravitational physics.
Roger Penrose,
Oxford: Twistor non-locality and EPR effects
The twistor description of wavefunctions
for individual massless particles is fundamentally non-local, being
given in
terms of holomorphic 1st cohomology. This reflects a certain non-locality of
individual quantum
particles.
For n particles we have a twistor description in
terms of holomorphic nth cohomology. The connection
between
this and EPR effects will be explored.
Carlo Rovelli, Marseille: Chris,
here is a hope for a quantum gravity effect we might be able to see: Planck
stars
Where does the
matter falling into a black hole go?
Quantum gravity allows it to bounce around the Planck
density
(at a radius much larger than Planckian) and the hole
might quantum tunnel into a white hole.
An
estimate of
the tunnelling probability indicates that this is
should happen before extensive
Hawking
evaporation. Primordial black holes might be exploding
now, producing signals we might be able to detect.
If so, this
could be an observable quantum gravitational phenomenon. measuring
it would be the best manner
to
celebrate Chris.
Sarben
Sarkar, King’s College London: Signatures
of CPT violation in mesons and neutrinos
Quantum gravity
models based both on decoherence and string theory
backgrounds are examined within
the
context of experiments at meson
factories and leptogenesis (and resultant baryogenesis). The breaking
of
CPT invariance is inherent in the proposals. Signatures in correlations of kaon pairs and oscillation
properties of
Majorana neutrinos are discussed.
Lee Smolin, Perimeter Institute: Time, causality and law in a cosmological context
Steven
Weinstein, Waterloo: Degrees of Freedom
The statistical
independence assumption in Bell's theorem (a.k.a. measurement independence) can
be thought
of as
the requirement that all degrees of freedom are local degrees of freedom. That is, there are no nonlocal
constraints. This suggests the possibility that quantum
correlations might actually arise from correlations in initial
data
encoded in such constraints. Such
constraints, though unfamiliar to many, need not be arcane or exotic.
I'll give three
simple examples.