Collisions between heavy atomic nuclei at ultrarelativistic energies are carried out at particle colliders to produce the quark–gluon plasma, a state of matter where quarks and gluons are not confined into hadrons, and colour degrees of freedom are liberated. This state is thought to be produced as a transient phenomenon before it fragments into thousands of particles that reach the particle detectors. Despite two decades of investigations, one of the big open challenges is to obtain an experimental determination of the temperature reached in a heavy-ion collision, and a simultaneous determination of another thermodynamic quantity, such as the entropy density, that would give access to the number of degrees of freedom.

In a Letter published recently in Nature Physics, two physicists from IPhT, Jean-Yves Ollitrault  and Giuliano Giacalone, in collaboration with Fernando Gardim, from Federal University of Alfenas (Brazil), in sabbatical at IPhT, and Matthew Luzum, from the University of São Paulo (Brazil), obtain such a determination. Using experimental data, they show that the matter created in lead–lead collisions at the Large Hadron Collider reaches a temperature of 2.6 trillion degrees, the hottest ever achieved in the laboratory. They determine the corresponding entropy density and the speed of sound, which is half the speed of light in this state of matter. Results inferred from experiment agree with first principles calculations and confirms that a deconfined phase of matter is indeed produced.

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DESCRIPTION

This pedagogical and self-contained text describes the modern mean field theory of simple structural glasses. The book begins with a thorough explanation of infinite-dimensional models in statistical physics, before reviewing the key elements of the thermodynamic theory of liquids and the dynamical properties of liquids and glasses. The central feature of the mean field theory of disordered systems, the existence of a large multiplicity of metastable states, is then introduced. The replica method is then covered, before the final chapters describe important, advanced topics such as Gardner transitions, complexity, packing spheres in large dimensions, the jamming transition, and the rheology of glass. Presenting the theory in a clear and pedagogical style, this is an excellent resource for researchers and graduate students working in condensed matter physics and statistical mechanics…

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A guide to the theoretical and computational toolkits for the modern study of molecular kinetics in condensed phases

Molecular Kinetics in Condensed Phases: Theory, Simulation and Analysis puts the focus on the theory, algorithms, simulations methods and analysis of molecular kinetics in condensed phases. The authors – noted experts on the topic – offer a detailed and thorough description of modern theories and simulation methods to model molecular events. They highlight the rigorous stochastic modelling of molecular processes and the use of mathematical models to reproduce experimental observations, such as rate coefficients, mean first passage times and transition path times.

The book’s exploration of simulations examines atomically detailed modelling of molecules in action and the connections of these simulations to theory and experiment. The authors also explore the applications that range from simple intuitive examples of one and two-dimensional systems to complex solvated macromolecules. 

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