Pauline BESSERVE - From Everett to Born: Do We Really Understand Probabilities in Quantum Mechanics?
In 1957, Hugh Everett proposed in his Many Worlds Interpretation of quantum mechanics to set aside the collapse postulate when dealing with isolated systems. Therefore, Born's probability rule is no longer an assumption and has to be derived from the fundamental features of the quantum theory. We will present some derivations of the rules, and point out that they are based on two different understandings of what the concept of probability may refer to : limits of relative frequencies when performing an experiment multiple times on the one hand, degrees of belief concerning the outcome of one single experiment on the other hand. But should physicists be satisfied with such ways for probabilities to enter the quantum realm?
-----------------------------------------------------------------------------------
Titouan CARETTE - Computer Scientist Megalomania
He said: "I think it is pretty obvious that physical phenomena do nothing more than processing information. So, our universe should be quite close to a giant quantum computer, shouldn't it? I think I can deal with it."
Let's dive deep into the sweet hubris of a megalomaniac computer scientist's mind. Inspired by the world of programs, we'll discuss what meaning could be given to physical processes around us. Along the way, we'll discover the semantics of quantum programming languages and their underlying twisted logic.
-----------------------------------------------------------------------------------
Eliana FORIELLI - Open Quantum Systems Interacting with a Macroscopic Magnetic Moment
Open Quantum Systems made of several components feature properties which are essential for understanding foundational aspects as well as implementing quantum computation and communication, one of the most relevant being the possible generation of entanglement between the components themselves. However, the dynamical generation of quantum correlations between a principal quantum system and its environment has usually a detrimental effect upon the entanglement between the components of the former. What happens when the environment is a Macroscopic Magnetic Moment?
-----------------------------------------------------------------------------------
Caterina FOTI - Effective Description of the Short-time Dynamics in Open Quantum Systems
The modeling of any (open) quantum system inherently implies that of its surroundings. But what happens when one considers that such environment is usually big? Several foundational issues immediately arise due to the difficult coexistence of quantum and classical formalism and, as a matter of fact, an effective description of the environment stems from intuitive and phenomenological arguments, rather than from a formal derivation. We dig into the possibilityof building a bridge.
-----------------------------------------------------------------------------------
Lucy KEER - Special Relativity Without the Light Postulate
Special relativity is normally derived from two well-known postulates: the principle that the laws of physics are the same in all inertial reference frames, and the constancy of the speed of light. The first postulate has been familiar since Galileo, whereas the second is less obviously intuitive.
However, it is somewhat less well known that special relativity can be derived without the light postulate, by using symmetry and causality assumptions on space and time. In this talk I will sketch out how this works - in classic special relativity style, this will involve a thought experiment about a train and a platform (and also a fly). I'll also explore the question of whether this is just an interesting reframing, or whether it helps illuminate any features of special relativity.
-----------------------------------------------------------------------------------
Pierre MARTIN-DUSSAUD - To Infinity, and Beyond!
Physicists do not fear divergent series. But mathematicians do. Abel wrote some day: "The divergent series are the invention of the devil, and it is a shame to base on them any demonstration whatsoever." So, how to explain that physicists have been successfully using infinite series for so long? My talk will propose you a healthy walk in the lovely world of infinite sums.
-----------------------------------------------------------------------------------
Robin REUBEN - The Reality of Time: Smolin's Temporal Naturalism
I will discuss some of the key aspects of Lee Smolin’s cosmological programme of temporal naturalism. Smolin traces the current crises within the ruling cosmological paradigm (such as fine-tuning, the problem of initial conditions and the nonchalant propositions of multiverse-theories) back to modern physics’ banishment of time as a mere illusion. Spatialised, with no intrinsic ‘flow’ or ‘arrow’, washed-out by diffeomorphism-invariance and featuring only in time-reversal invariant theories, ‘time’, as we humans intuitively know it, has been all but abolished in modern cosmology. This governing view culminates in the so-called block-universe interpretation of General Relativity in which the history of the universe is taken to be isomorphic to a mathematical object, unchanging in time. Guided by our models’ methodological and metaphysical shortcomings, Smolin suggests a cosmology based on the three propositions: the reality of time, the evolution of the laws of nature with respect to that time, and the uniqueness of the single causally closed universe that unfolds in time.
-----------------------------------------------------------------------------------
Alexandre THOMAS - The Role of Geometry in Physical Theories
The concepts of the geometry of our univers evolved a lot during the centuries, from a flat infinite Euclidean space in Newtonian mechanics to manifolds and fiber bundles in modern theories like general relativity or gauge theories. In the talk, I explain the mathematical concepts of these ideas and why and how these concepts appear in physical theories. In a second part, I discuss possible ways to generalize even further these concepts. Finally, I discuss if geometry is necessary in future theories.
-----------------------------------------------------------------------------------
Alexis TOUMI - Quantum Structures in Human Cognition and Natural Language
Diagrammatic reasoning for quantum computer science allows one to reason about the meaning of natural language, through a homomorphic passage from syntax (given by a pregroup grammar) to semantics (encoded in the category of finite vector spaces).We show how this method can be used to unravel the mysteries of human cognition, showing connections with concept formation and knowledge representation, as well as psychiatric research on schizophrenia. We argue that understanding cognition and language is crucial to our understanding of the physical world.
-----------------------------------------------------------------------------------
Vaclav ZATLOUKAL - Employing Statistical Physics for Description of Biological Neural Networks
Neural network is a collection of a large number of neurons that are interconnected to produce a complex (oriented, weighted) graph. The most natural example is the brain -- the organ that controls behavior of the majority of humans. Although the microscopic mechanism for signal propagation between neurons is relatively well-explored, the great challenge consists in building an efficient mathematical model that would describe the emergence of the complex behavior of the brain we experience. Could statistical physics provide the right tools to address this many-body problem?
