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Lecture

Entropy: Microscopic View

In course

PHYS-106(a): General physics : thermodynamics

Le but du cours de Physique générale est de fournir les notions de base nécessaires à la compréhension des phénomènes physiques. L'objectif est atteint lorsqu'il est possible de prévoir quantitativement les conséquences de ces phénomènes avec des outils th ...

Description

This lecture delves into the microscopic perspective of entropy, emphasizing the equilibrium of a system in various energy states and the statistical entropy definition. It explores the concept of maximum entropy in isolated systems and the irreversibility of natural processes, discussing the arrow of time and the implications of the second law of thermodynamics. The presentation includes the Boltzmann formula for isolated systems and the analysis of irreversible phenomena through an entropic lens.

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Instructors (2)

Cécile Hébert

Cécile Hébert was born in France in 1970. She obtained her Ingeneer degree (physics) and her PhD degree (design of a new energy filter for transmission electron microscopy, under the direction of Prof. B. Jouffrey) at the Ecole Centrale in Paris. As a post doc with Prof. P. Schattschneider, she was working on the calculation of the fine structure of ionisation edges in EELS. As a research assistant at the Vienna University of Technology, she was one of the main participant to the CHIRALTEM project dealing with the measurement of magnetic circular dichroism in the electron microscope.

Romuald Houdré

Curriculum Vitae CV 2011 Appointed as Adjunct Professor 2006 Appointed as Maitre d'Enseignement et de Recherche 2004 Joins the "Laboratory of Quantum Electronics" led by Prof. B. Deveaud-Plédran 2001-2004 Appointed as "Adjoint Scientifique" at the Institute for Quantum Photonics and Electronics (previously Institute for Micro and Optoelectronics led by Prof. M. Ilegems) 1998 Habilitation, University Pierre et Marie Curie, Paris 6 (France) 1997 Invited researcher at NTT, Optoelectronics Department (Atsugi, Japan) 1988-2000 "Collaborateur scientifique" at the Institut for Micro and Optoelectronics with Prof. M.Ilegems at the Swiss Federal Institut of Technology in Lausanne (Switzerland). In charge of the Molecular Beam Epitaxy (1988-1996) and the research on optical microcavities (1996-2000) 1987-1988 Laboratoire de Physique de la Matière Condensée at Ecole Polytechnique (France). 1986-1987 Postdoctoral fellow at the University of Illinois at Urbana-Champaign (U.S.A.) with Prof. H.Morkoç in the molecular beam epitaxy group 1983-1985 Ph.D. thesis on the photoemission from quantum wells and superlattices under negative electron affinity at Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique (France), G.Lampel and C.Hermann as advisors

Official source

Ontological neighbourhood

Physics

Thermodynamics: Statistical mechanics

Related concepts (32)

Entropy

Entropy is a scientific concept, as well as a measurable physical property, that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamics, where it was first recognized, to the microscopic description of nature in statistical physics, and to the principles of information theory.

Entropy (statistical thermodynamics)

The concept entropy was first developed by German physicist Rudolf Clausius in the mid-nineteenth century as a thermodynamic property that predicts that certain spontaneous processes are irreversible or impossible. In statistical mechanics, entropy is formulated as a statistical property using probability theory. The statistical entropy perspective was introduced in 1870 by Austrian physicist Ludwig Boltzmann, who established a new field of physics that provided the descriptive linkage between the macroscopic observation of nature and the microscopic view based on the rigorous treatment of large ensembles of microstates that constitute thermodynamic systems.

Boltzmann's entropy formula

In statistical mechanics, Boltzmann's equation (also known as the Boltzmann–Planck equation) is a probability equation relating the entropy , also written as , of an ideal gas to the multiplicity (commonly denoted as or ), the number of real microstates corresponding to the gas's macrostate: where is the Boltzmann constant (also written as simply ) and equal to 1.380649 × 10−23 J/K, and is the natural logarithm function (also written as , as in the image above).

Irreversible process

In science, a process that is not reversible is called irreversible. This concept arises frequently in thermodynamics. All complex natural processes are irreversible, although a phase transition at the coexistence temperature (e.g. melting of ice cubes in water) is well approximated as reversible. In thermodynamics, a change in the thermodynamic state of a system and all of its surroundings cannot be precisely restored to its initial state by infinitesimal changes in some property of the system without expenditure of energy.

Entropy (information theory)

In information theory, the entropy of a random variable is the average level of "information", "surprise", or "uncertainty" inherent to the variable's possible outcomes. Given a discrete random variable , which takes values in the alphabet and is distributed according to : where denotes the sum over the variable's possible values. The choice of base for , the logarithm, varies for different applications. Base 2 gives the unit of bits (or "shannons"), while base e gives "natural units" nat, and base 10 gives units of "dits", "bans", or "hartleys".

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