QM foundations & nature of time seminar

relaxed discussions about the foundations of physics

Tuesdays at 18 Warsaw time

Paweł Błasiak, Jarosław Duda, contact: jaroslaw.duda@uj.edu.pl, speakers are welcomed

 

2020-10-06

Dagomir Kaszlikowski (NUS), Pawel Kurzynski (UAM) Another take on negative probabilities?

We present preliminary studies of basic information-theoretic and computational properties of negative binary probability distribution called nebit: p(0)=1+\delta, p(1)=-\delta. We show an interesting computational model based on quasi-stochastic processes between an ordinary bit and nebit. Finally, we show that some classical information processing protocols can be more effective with an access to nebits.  (article)

2020-09-29

Álvaro García López (URJC) On an electrodynamic origin of quantum fluctuations

We use the LiénardWiechert potential to show that very violent fluctuations are experienced by an electromagnetic charged extended particle when it is perturbed from its rest state. The feedback interaction of Coulombian and radiative fields among different charged parts of the particle makes uniform motion unstable. Then, we show that radiative fields and radiation reaction produce dissipative and antidamping effects, triggering a self-oscillation. Finally, we compute the self-potential, which in addition to rest and kinetic energy, gives rise to a new contribution that shares features with the quantum potential. We suggest that this contribution to self-energy produces a symmetry breaking of the Lorentz group, bridging classical electromagnetism and quantum mechanics (article, slides).

2020-09-15

Fritz W.  Bopp (Siegen U.) How to Avoid Absolute Determinismin Two Boundary Quantum Dynamics

Arguments for a two boundary theory are outlined. A quantum statistical effect plays a central role. Plausible concepts of how in such a theory an approximate causal macroscopic theory can emerge are presented. A problem with simple implementations of the two boundary theory is that effective or real willful decisions can not be added as there is no consecutive macroscopic time ordering of such effective or real willful decision points.  We present a somewhat drastic but somehow beautiful way to avoid it (article, slides)

2020-09-01

Jarek Duda (JU) Maximal Entropy Random Walk: repairing diffusion-QM disagreement

Considering diffusion or chaos in [0,1] range leads to uniform stationary probability distribution rho=1. In contrast, QM predicts localized rho~sin^2 there. This disagreement is crucial e.g. for semiconductors – standard diffusion would predict nearly uniform electron distribution, allowing them to flow – incorrectly expecting it to be a conductor. In contrast, QM predicts strong e.g. Anderson localization preventing conductance.

Maximal Entropy Random Walk (MERW) allows to understand and repair this disagreement - turns out that standard random walk often only approximates the (Jaynes) principle of maximal entropy, which is crucial for statistical physics models – MERW is the most random among random walk, thanks of it leading to stationary probability distribution exactly as quantum ground state – with localization property. In contrast to standard random walk, MERW is also scale-free, time symmetric and nonlocal. It also has many other applications (~160 citations).  (Wikipedia, article, thesis, conductance simulator, video, slides).

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, slides, videos)

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”)
There are fundamental relations between three vast areas of physics: particle physics, cosmology, and condensed matter physics.  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 3He A–B interface provides an unprecedented type of superfluid boundary between two degenerate macroscopically coherent quantum systems which display different broken symmetries and rich family of topological defects. (slides)

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 briey 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 R3 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 HerbigHaro 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?"