QM foundations & nature of time
seminar
relaxed discussions about the foundations
of physics
every Tuesday at 18 Warsaw time
Paweł Błasiak, Jarosław
Duda, contact: jaroslaw.duda@uj.edu.pl
2020-08-18 |
Robert
Close (Clark College) Classical Wave Mechanics This is an attempt to describe elementary particles using classical
continuum mechanics. First, a wave equation is derived for infinitesimal
shear waves in an elastic solid. Next, a change of variables is used to
describe the waves in terms of classical spin angular momentum density, which
is the field whose curl is equal to twice the classical momentum density. The
second-order wave equation is then converted to a first-order Dirac equation.
Plane wave solutions are presented, and the dynamical operators of
relativistic quantum mechanics are derived. Wave interference gives rise to
the Pauli exclusion principle and electromagnetic potentials. (draft) https://us02web.zoom.us/j/86307810379?pwd=TU5aRm5ZaTVJNTFLdW8rZkdSdVlzdz09 Passcode: 9m6Ndh |
2020-08-11 |
Christopher
Halcrow (Leeds) Nuclei as Skyrmions In standard models of nuclear
physics, nuclei are described as point particles with spin and isospin
degrees of freedom. The baryon number (the number of protons plus the
number of neutrons) is conserved in nuclear interactions - this fact is
usually put in “by hand”. In contrast, the Skyrme
model describes nuclei as topological solitons. The baryon number is
conserved due to a topological invariant of the theory while spin and isospin
appear as quantised isometries of the system.
This talk is in two parts: first, I will try and convince you that the Skyrme model is a reasonable model of nuclear
physics. It reproduces several known phenomena: nuclear
clustering, isospin symmetry and rotational bands in energy spectra. I
will then show that the Skyrme model is very
different than standard nuclear models: the notion of position breaks
down, the Deuteron is a torus and novel scatterings can take place.
These surprising facts can give new explanations for some nuclear properties.
For instance, the existence of a toroidal Skyrmion
explains the attractive spin-orbit force in the nucleon-nucleon interaction
as shown recently in arXiv:2007.01304. I will explain this
phenomena assuming no background knowledge of Skyrmions
or nuclear physics. (article,
slides) |
2020-08-04 |
Krzysztof Pomorski (UC
Dublin) From superfluidity to cosmology and elementary particles (based on
"The
universe in helium droplet" by G. Volovik”) |
2020-07-28 |
Jarek Duda (JU) Discussion: are there
experiments proving or disproving time symmetry? Time/CPT symmetry is at heart of many models of physics, like unitary
evolution in quantum mechanics, or Lagrangian
formalism we use from classical mechanics, electromagnetism, up to general
relativity and quantum field theories. However, this symmetry is quite
nonintuitive, very difficult to really accept – mainly due to thermodynamical counterarguments. Let us try to discuss these arguments, especially experiment-based. I
will present some for us to discuss (adding more is welcomed), for example:
Wheeler’s, delayed choice quantum eraser (DCQE), “asking photons where they
have been”, “photonic quantum routers”, Shor algorithm as more sophisticated
DCQE, also: Anderson localization (starting with rho~sin^2 in [0,1]), Born
rule, Bell violation. (slides, video) |
2020-07-21 |
Kenneth Wharton (SJSU) Bell's Theorem: Implications and
Misapprehensions Despite the fact that Bell’s
Theorem tells us something profound about our universe, there are still many
misapprehensions about exactly what it means, even among physicists. For example, it is often incorrectly
characterized as disproving hidden variables, or proving
action-at-a-distance. Even experts in
quantum foundations are sometimes unaware of subtleties concerning the role
of an “arrow of time” in Bell’s analysis and the possibilities of using retrocausation to model quantum entanglement in a
locally-mediated, spacetime-based framework.
This talk will attempt to clarify these and other issues, detailing an
explicit retrocausal model which accounts for
maximally entangled states. (article,
slides) |
2020-07-14 |
Arkadiusz Jadczyk (Toulouse, CNRS) Order
out of chaos. Fractals out of qubits. Theory can predict what happens when several non-commuting observables
are being simultaneously measured. The results of such repetitive measurements are random and
chaotic, but distinct and organized fractal attractors may arise. We study
quantum iterated function systems for a qubit, where measurements and quantum
jumps are implemented by Moebius transformations of the Bloch sphere. As an
example, a quantum fractal resulting from non-commuting parabolic
transformations is discussed in detail. (slides,
book) |
2020-07-07 |
Robert Brady (Cambridge) In memoriam: Yves Couder Yves Couder
died on 2 April 2019. He showed how to make droplets of oil bounce on an oil
surface, spawning a renewed interest in the net forces between oscillating
systems. Bouncing droplets are governed by the ordinary equations of
Newtonian mechanics, yet experimentally their motion mimics the known
equations of special relativity, electromagnetism, and quantum mechanics. I
will show why this is the case, in an idealised
system where the pumping acceleration can be neglected. I will then briefly
discuss my ongoing research in a related system in superfluid helium, where
pumping is superfluous and the predictions may be tested against experiment. In order to maintain your
interest, and to pay respect to Yves, I will give an interpretation of his
work which is controversial. If his results had been known 100 years ago,
they would probably have changed the debate, from 1905 to 1922, between
Einstein and Lorentz on how to interpret the equations of special relativity.
(slides) |
2020-06-30 |
Łukasz Stępień (PUK) This and that on solitons and some their
applications I am going to talk about solitons.
I will remind brieﬂy their history and some fundamental facts from soliton theory. Next,
I will say about one of the important tools for investigation of soliton
equations: Bogomolny (Bogomol’nyi)
equations, called also as Bogomolny decomposition,
and I will present also an example - Bogomolny
equations in the so-called baby BPS Skyrme model.
Later I will say about a soliton model of particle. |
2020-06-23 |
Jarek Duda (JU) Topological charge
as electric charge – can we get all particles this way? We can repair Gauss law to return only integer charges (as in nature)
by interpreting EM field as curvature of some e.g. vector field, this way
counting winding number (topological charge) using Gauss-Bonnet theorem as
Gauss law (Faber’s model). I will lightly introduce it and would like to
discuss if we could expand it to a field which excitations (e.g. topological)
agree with the entire particle physics, could be effectively described by
something close to the Standard Model. Kind of superfuid
biaxial nematic: 3 distinguishable axes in every
point (using tensor field instead of molecules) seems quite promising here.
They can form hedgehog configuration with one of 3 axes, getting 3 leptons
(as spatial dimensions), trying to align the second axis for it we cannot do
it due to the hairy ball theorem (no naked charges – leptons need magnetic
dipoles), then baryon-like configurations enforcing some positive charge:
needed to be compensated in neutron (hence it is heavier than proton), charge
is shared in deuteron for binding (leading to observed electric quadrupole
moment). (slides,
video) |
2020-06-16 |
Manfried Faber (TU Wien) Topological
excitations of a scalar SO(3)-theory We discuss a model with only three degrees of freedom in Minkowski space-time. This model is related to Dirac
monopoles, one can see it as a generalisation of
the Sine-Gordon model from 1D to 3D, or a modification of the Skyrme model. Starting from a Lagrangian,
the intention of the model is to provide a geometrical description of
electromagnetic phenomena. The model has three topological quantum numbers
which can be compared to the properties of charge, spin and photon number. We
discuss stable solitonic solutions and compare them
to the properties of electrons and photons. (slides,
article) |
2020-06-09 |
Ilan Roth (Berkeley) From Braids
to Knots; Topological features in Solar Magnetic Fields – and beyond… The
generally accepted structure of magnetic fields depicts them as field lines
in R^{3} with curvature, rotation and wiggles, satisfying divB=0. Their observed configuration allows us to
implement the powerful topological methods, opening a new venue for an
interpretation of various solar, interplanetary and astrophysical phenomena.
Direct imaging of the coronal fields pinpoints to their braiding structure,
large solar wind field reversal (switchback) and intermittent fading of
energetic flare ions suggest that coronal braided field may have been carried
by the solar wind. The interconnection between the mathematical braids and
knots is applied to the topologically non-trivial magnetized structures and
their dynamics, from solar corona and the interplanetary medium to the
astrophysical Herbig – Haro
jets. The topological invariants attached to a given knot/braid become the
crucial factor in the evolution and interpretation of the phenomena in space.
The methods involved cover classical as well as analogues of quantum
procedures. The analysis results in conjectures regarding (i) stability of coronal magnetic loops under large
oscillations, (ii) their evolution through successive emergence/decay of
heated magnetic braids, (iii) their morphism into the solar wind knotty
structures and (iv) large scale narrow jets emitted in star-forming regions.
These conjectures may contribute significantly to the understanding of
physical processes in the lab and in solar/astrophysical medium, particularly
in the dynamo produced magnetic structures as observed by Parker Solar Probe.
(some materials: coronal
loop, magnetic reconnections, article1, article2, book) |
2020-06-02 |
Krzysztof Pomorski (UC Dublin) Review of
book "The universe in helium
droplet" by G. Volovik There are fundamental relations between three vast areas of physics:
particle physics, cosmology, and condensed matter physics. The fundamental
links between the first two areas — in other words, between micro- and
macro-worlds — have been well established. There is a unified system of laws
governing the scales from subatomic particles to the cosmos and this
principle is widely exploited in the description of the physics of the early
universe. This book aims to establish and define the connection of these two
fields with condensed matter physics. According to the modern view,
elementary particles (electrons, neutrinos, quarks, etc.) are excitations of
a more fundamental medium called the quantum vacuum. This is the new ‘aether’ of the 21st century. Electromagnetism, gravity,
and the fields transferring weak and strong interactions all represent
different types of the collective motion of the quantum vacuum. Among the
existing condensed matter systems, a quantum liquid called superfluid 3He-A
most closely represents the quantum vacuum. Its quasiparticles are very
similar to the elementary particles, while the collective modes are analogues
of photons and gravitons. The fundamental laws of physics, such as the laws
of relativity (Lorentz invariance) and gauge invariance, arise when the
temperature of the quantum liquid decreases (slides) |
2020-05-26 |
Arkadiusz Jadczyk (Toulouse, CNRS) Time of
arrival in quantum theory While all our knowledge of the outside world is based on observation
of events, the standard quantum theory does not have tools allowing us to
model events arising in real time, as in all our experiments. A typical example
are events in a particle cloud chamber. A simple extension of the quantum
theory is proposed that fixes this serious shortcoming. In particular the new
solution to the problem of time of arrival in quantum theory is presented. It
allows for computer simulation of particle counters and it implies Born's interpretation (slides) |
2020-05-19 |
Radosław Kycia (CUT) Cartan Connection for Schrodinger equation. The nature of
vacuum I will present the Schrodinger equation's factorization into the
(elliptic) background and an (evolutionary) part moving on this background.
It is a slightly generalized picture than in the pilot-wave theory. Moreover,
if the Schrodinger equation is interpreted as a continuity equation, then the
Cartan connection appearing in this equation is
precisely the background. Therefore, the equation and the background can be
interpreted geometrically. The vital role in this approach plays the
scaling/dilation group of the wave function. This corresponds to the original
idea of Weyl that leads to the concept of the gauge principle. The talk is based on arXiv:2004.04622
[math-ph] (slides) |
2020-05-12 |
Jarek Duda (JU) Hydrodynamical
analogues of some quantum phenomena As our understanding of quantum mechanics might be not satisfactory,
it could be helpful to search and study more accessible analogues of its
phenomena. Hydrodynamics contains many of them, for example of Casimir and Aharonov-Bohm effect, and many others with the popular
wave-particle duality “walking droplets”: double slit interference,
tunneling, many types of orbit quantization (including double quantization
(radius + angular momentum) and Zeeman effect), path statistics agreeing with
wavefunction. Let us look closer and discuss applicability of these
analogues. (article, slides) |
2020-05-05 |
Kenneth Wharton (SJSU) How Time-Symmetry
is compatible with the Second Law: A Discussion All fundamental physics
appears to be governed by time-symmetric laws. (Actually, CPT-symmetric, but this detail
is a red herring.) And yet our
observable universe is dominated by time-asymmetric thermodynamic
behavior. There is a simple but still
widely-misunderstood resolution of this apparent contradiction. I will attempt to briefly sort out this
resolution in various domains (cosmological, computational, etc.), and
carefully identify where causal reasoning does and doesn't belong in our
analysis. A general discussion will follow (article). |
2020-04-28 |
Paweł Błasiak (IFJ PAN) Entanglement by identity, or interaction without ever
touching What is interaction and when does it
occur? Intuition suggests that the necessary condition for the interaction of
independently created particles is their direct touch or contact through
physical force carriers. In quantum mechanics, the result of the interaction
is entanglement — the appearance of non-classical correlations in the system.
It seems that quantum theory allows entanglement of independent particles
without any contact. The fundamental identity of particles of the same kind
is responsible for this phenomenon. (article, slides) |
2020-04-21 |
Manfried Faber (TU Wien) Violation of Mermin's version of a Bell inequality in a classical
statistical model We investigate a classical statistical model
and show that Mermin's version of a Bell inequality
is violated. We get this violation, if the measurement modifies the ensemble,
a feature, which is also characteristic for measurement processes for quantum
systems. (slides) |
2020-04-14 |
Bell theorem
discussion, short presentations: Richard Gill - continuation (additional
slides). Jarek Duda:
4 slides: 1)
derivation of Born rule for probability distribution inside Ising sequence, 2) Schrödinger equation from path
ensembles, 3) how to use it to violate Bell-like inequalities, 4) how to save
(local realistic) Lagrangian formalism from
conflict with Bell theorem (extended video) |
2020-04-06 |
Richard Gill (Leiden Univ.) Some thoughts on
Bell’s theorem and on Bell denialism I think that Bell’s theorem is a
true, simple (easy) mathematical theorem. NB Bell’s inequality(-ies) is (are) simple lemmas in the proof of the theorem.
I have learnt a whole lot more about the whole complex of mathematical,
physical and philosophical issues, by getting into fights with both
respectable established scientists with non-mainstream views, and with
manifest amateur crackpots. This has given me both mathematical and
scientific insights, and insights into human psychology; it feeds my amateur
interests in psychology and metaphysics (philosophy) and even religion. (slides) |
2020-03-30 |
Organizational
meeting, initial discussion: "Can
electrons objectively be in two places at once?" |