Basic Concepts for Simple and Complex Liquids , Jean-Louis Barrat , Jean-Pierre Hansen Cambridge U. Press, New York, 2003. $110.00, $55.00 paper (296 pp.). ISBN 0-521-78344-5, ISBN 0-521-78953-2 paper
Liquids are strongly interacting but disordered systems whose very existence arises from a delicate balance between energy and entropy. They exist over a much smaller range of temperature and density than do solids, in which energy usually dominates, or gases, in which entropy dominates. Because liquids are relevant in everyday life and essential in biology and biophysics, physicists need to gain a better understanding of this elusive state of matter and the ideas that researchers in the field have developed in the past 50 years. However, some of those ideas are difficult and involve new concepts and approximations not usually taught in standard physics courses. Basic Concepts for Simple and Complex Liquids , a concise, very well-written textbook by two experts in the field, should help fill this gap in the physics curriculum.
The book by Jean-Louis Barrat and Jean-Pierre Hansen describes and connects formal work and simulations of atomic-scale properties of mostly simple fluids to the coarse-grained mesoscopic models and scaling arguments used to explain critical phenomena and to describe complex fluids such as liquid crystals and polymers. Coarse-grained models and scaling ideas are familiar to most physicists, and their integration with standard topics in condensed matter physics was well presented in the textbook Principles of Condensed Matter Physics (Cambridge U. Press, 1995) by Paul M. Chaikin and Tom C. Lubensky. Barrat and Hansen’s book covers some of the same ground from a different perspective, with more emphasis on polymers and ionic solutions, and relates the mesoscopic-scale physics most physicists know to the less familiar molecular-scale physics of liquids. These connections should help researchers in many different fields get a succinct overview of the conceptual issues in liquid-state science. The authors’ inclusive approach is quite different from that taken in most earlier books on liquids: In those books, the emphasis is mainly on simple atomic liquids and on the detailed, formal development of specialized techniques for such systems.
To get an idea of how Barrat and Hansen’s approach works, consider their treatment of phase transitions. That part of the book begins with a general discussion of mean-field approaches, which includes a detailed discussion of the Landau theory of phase transitions, followed by specific applications to the van der Waals equation of state, to the Flory–Huggins theory of polymer blends, and to the isotopic–nematic transition in liquid crystals as described by Lars Onsager’s hard-rod model. Next, the authors present a discussion on critical fluctuations and scaling ideas that includes a short, one-page description of Leo Kadanoff’s block-spin picture. However, no attempt is made to describe renormalization group ideas; instead, the authors give an application of the Ginzburg criterion to polymer blends and show why mean-field ideas are more generally applicable in the study of these blends than in simple molecular liquids. The authors then cover scaling ideas for polymer solutions and briefly describe finite-size scaling.
In subsequent parts of the book describing interfaces, nonuniform fluids, and dynamics, Barrat and Hansen follow the same approach. They first introduce general theoretical concepts like density functional theory and Langevin and Fokker–Planck methods and then illustrate those concepts by many different and sometimes surprising applications.
A wealth of material is covered in fewer than 300 pages. This textbook is the only one I know of that succinctly tackles such a diverse set of topics and attempts to find common viewpoints and theoretical approximations. The tradeoff is that the discussions can be very terse at times. The authors get to the essential ideas quickly, with little discussion of mathematical difficulties or physical subtleties that might arise. As a result, the book is not—nor is it intended to be—the place to learn about the weaknesses in the various theoretical methods presented or to gain detailed physical insight into specific applications. The level of treatment should be understandable to graduate students, provided they are aware that the authors waste few words. The book has a few well-chosen but rather difficult exercises that will help students gauge their level of understanding.
I enjoyed reading Basic Concepts for Simple and Complex Liquids and have used it in my own research group to introduce students to new research areas and ideas. The authors should be commended for an impressive pedagogical achievement.
