Domenico Giulini

Quantum tests of the Einstein Equivalence Principle with the STE-QUEST space mission

We present in detail the scientific objectives in fundamental physics of the Space-Time Explorer and QUantum Equivalence Space Test (STE-QUEST) space mission. STE-QUEST was pre-selected by the European Space Agency together with four other missions for the cosmic vision M3 launch opportunity planned around 2024. It carries out tests of different aspects of the Einstein Equivalence Principle using atomic clocks, matter wave interferometry and long distance time/frequency links, providing fascinating science at the interface between quantum mechanics and gravitation that cannot be achieved, at that level of precision, in ground experiments. We especially emphasize the specific strong interest of performing equivalence principle tests in the quantum regime, i.e. using quantum atomic wave interferometry. Although STE-QUEST was finally not selected in early 2014 because of budgetary and technological reasons, its science case was very highly rated. Our aim is to expose that science to a large audience in order to allow future projects and proposals to take advantage of the STE-QUEST experience.

The Superspace of Geometrodynamics

Wheeler’s Superspace is the arena in which Geometrodynamics takes place. I review some aspects of its geometrical and topological structure that Wheeler urged us to take seriously in the context of canonical quantum gravity.

Symmetries, superselection rules, and decoherence

Abstract We discuss the applicability of the programme of decoherence to cases where it was suggested that the presence of symmetries would lead to exact superselection rules. We discuss, in particular, superpositions of states with different charges, as well as with different masses, and suggest how the corresponding interference term, although they exist in principle, become inaccessible through decoherence.

The Schrödinger–Newton equation as a non-relativistic limit of self-gravitating Klein–Gordon and Dirac fields

In this paper, we show that the Schrodinger–Newton equation for spherically symmetric gravitational fields can be derived in a WKB-like expansion in 1/c from the Einstein–Klein–Gordon and Einstein–Dirac systems.

Hunting the White Elephant: When and How did Galileo Discover the Law of Fall?

we present a number of findings concerning galileos major discoveries which question both the methods and the results of dating his achievements by common historiographic criteria. the dating of galileos discoveries is, however, not our primary concern. this paper is intended to contribute to a critical reexamination of the notion of discovery from the point of view of historical epistemology. we claim that the puzzling course of galileos discoveries is not an exceptional comedy of errors but rather illustrates the normal way in which scientific progress is achieved. we argue that scientific knowledge generally develops not as a sequence of independent discoveries accumulating to a new body of knowledge but rather as a network of interdependent activities which only as a whole makes the individual steps understandable as meaningful “discoveries.”

On Galilei invariance in quantum mechanics and the Bargmann superselection rule

Abstract We reinvestigate Bargmanns superselection rule for the overall mass ofnparticles in ordinary quantum mechanics with Galilei invariant interaction potential. We point out that in order for mass to define a superselection rule it should be considered as a dynamical variable. We present a minimal extension of the original dynamics in which mass it treated as dynamical variable. Here the classical symmetry group turns out to be given by anR-extension of the Galilei group. Unlike before, there is now no obstruction to implement an action of the classical symmetry group on Hilbert space. We include some comments of a general nature on formal derivations of superselection rules without dynamical context.

Gravitationally induced inhibitions of dispersion according to a modified Schrödinger-Newton equation for a homogeneous-sphere potential

We modify the time-dependent Schrodinger–Newton equation by using a potential for a solid sphere suggested by Jaaskelainen (2012 Phys. Rev. A 86 052105) as well as a hollow-sphere potential. Compared to our recent paper (Giulini and Grosardt 2011 Class. Quantum Grav. 28 195026) where a single point particle, i.e. a Coulomb potential, was considered, this has been suggested to be a more realistic model for a molecule. Surprisingly, compared to our previous results, inhibitions of dispersion of a Gaussian wave packet occur at even smaller masses for the solid-sphere potential, given that the width of the wave packet is not exceeded by the radius of the sphere.

What is (not) wrong with scalar gravity

On his way to General Relativity (GR) Einstein gave several arguments as to why a special relativistic theory of gravity based on a massless scalar field could be ruled out merely on grounds of theoretical considerations. We re-investigate his two main arguments, which relate to energy conservation and some form of the principle of the universality of free fall. We find that such a theory-based a priori abandonment not to be justified. Rather, the theory seems formally perfectly viable, though in clear contradiction with (later) experiments.

That Strange Procedure Called Quantisation

I discuss the notion of ‘quantisation’ a la Dirac (canonical quantisation) from a general perspective. It is well known that Dirac’s quantisation rules cannot work in general. I present this classic no-go result, which is due to Groenewold and van Hove, with due emphasis on its hypotheses. Finally, I briefly discuss first-class constrained systems with emphasis on the global-geometric and algebraic apsects.

Algebraic and Geometric Structures in Special Relativity

I review, some of the algebraic and geometric structures that underlie the theory of Special Relativity. This includes a discussion of relativity as a symmetry principle, derivations of the Lorentz group, its composition law, its Lie algebra, comparison with the Galilei group, Einstein synchronization, the lattice of causally and chronologically complete regions in Minkowski space, rigid motion (the Noether-Herglotz theorem), and the geometry of rotating reference frames. Representation-theoretic aspects of the Lorentz group are not included. A series of appendices present some related mathematical material.