When must fermions be antisymmetrized?
K. Sunko
Department of Physics, Faculty of Science, University of Zagreb, dks@phy.hr
Abstract
Quantum coherence is a consequence of the indistinguishability of identical particles, implemented in the case of fermions by requiring that the total wave function be antisymmetric. The scope of this requirement is a function of the concrete physical environment, in which decoherence and thermalization effects are distinct. Some illuminating examples are discussed, comparing in particular large molecules with elemental metals. In the former case, even comparatively few electrons can behave like distinguishable particles, while in the latter a mole of electrons remain coherent over macroscopic distances. Feynman’s model of indistinguishability—physical exchange of particles in real space—is compared with the standard permutational one. It is argued that Feynman’s is clearly superior. Some technical issues involved in implementing it are discussed.
To Interpret QM “Follow the Math”: Math of QM = Linearized Partition Math
David Ellerman
The purpose of this talk is to show that the mathematics of quantum mechanics (QM) is the mathematics of partitions linearized to vector spaces, particularly Hilbert spaces. Since partitions are the mathematical concept to describe distinctions and indistinctions–or definiteness and indefiniteness–at the set level, this shows that the math of QM is the vector space math to describe a reality of objective indefiniteness that is quite different from the classical physics and common sense view of reality as being “definite all the way down.”. This follow-the-math approach thus supports the Objective Indefiniteness or Literal Interpretation of QM–as advocated by Abner Shimony among others. In contrast to other realistic interpretations such as the Bohmian, spontaneous localization, and many worlds interpretations, this approach takes the formalism of QM as being complete without other variables, other equations, or other-worldly ideas.
On the Emergence of Relativistic Structure from Discrete Space-Time with a Global Foliation
Tim Maudlin, NYU, New York
Abstract: The empirical success of Special and General Relativity, and of theories that incorporate Relativistic symmetries, argues that the Relativistic account of space-time structure must approximate the truth. But on the other hand, the confirmed violations of Bell’s Inequality for experiments done at space-like separation equally appears to argue for some global foliation of space-time that does not appear in the Relativistic theory.
Relativistic QFT from a Bohmian perspective: A proof of concept
Hrvoje Nikolić, Ruđer Bošković Institute, Zagreb
Abstract: Since Bohmian mechanics is explicitly nonlocal, it is widely believed that it is very hard, if not impossible, to make Bohmian mechanics
compatible with relativistic quantum field theory (QFT).
I explain, in simple terms, that it is not hard at all to construct a Bohmian theory that lacks Lorentz covariance, but makes the same measurable predictions as relativistic QFT.All one has to do is to construct a Bohmian theory that makes the same measurable predictions as QFT in one Lorentz frame, because then standard relativistic QFT itself guarantees that those predictions are Lorentz invariant.
I first explain this in general terms, then I describe a simple Bohmian model that makes the same measurable predictions as the Standard Model of elementary particles, after which I give some hints towards a more fundamental theory beyond Standard Model.
Superluminal Propagation and Causality
Neven Bilić, Ruđer Bošković Institute, Zagreb
Abstract: Does superluminal propagation necessarily violate causality? It will be demonstrated that a superluminal signal will not violate causality provided a condition on allowed Lorentz transformations is imposed. A necessary condition for the prevention of causality loops will be derived. A related fluid analog and classical field theory will be discussed in the context of causality.
Classical Electromagnetics from Variational Principles
Dragan Poljak, University of Split, FESB
Laws of nature can be derived from following fundamental principles; the action principle, locality, Lorentz invariance and gauge invariance. the least action principle, for classical mechanics states that a particle, among all of the trajectories between fixed time instants t1 and t2, follows the path which minimizes the action (time integral of the difference between the kinetic and potential energy, respectively) thus requiring the time averages of the kinetic energy and potential energy to distribute as equally as possible.
This lecture deals with an extension of variational principle in classical mechanics to classical electromagnetics by studying the motion of single charged particle. From the corresponding Lagrangians, featuring Noether’s theorem and gauge invariance equation of continuity for the charge, Lorentz force and Maxwell’s equations are derived.
Finally, the application of variational approach in developing a base for the numerical solution methods in electromagnetics are given.