Books received

Two losing gambling games, when alternated in a periodic or random fashion, can produce a winning game. This paradox has been inspired by certain physical systems capable of rectifying fluctuations: the so-called Brownian ratchets. In this paper we review this paradox, from Brownian ratchets to the most recent studies on collective games, providing some intuitive explanations of the unexpected phenomena that we will find along the way.     

Books received

This article is a colloquium-level review of the idea of supersymmetry and why so many physicists expect it to soon be a major discovery in particle physics. Supersymmetry is the hypothesis, for which there is indirect evidence, that the underlying laws of nature are symmetric between matter particles (fermions) such as electrons and quarks, and force particles (bosons) such as photons and gluons.     

Books received

Equations are derived to enable the two components of magnetic field at a corner of a cross-section through a long straight conductor to be calculated, and it is shown how the field components at any point in or near the conductor can be obtained by combining contributions calculated using these equations.     

Books received

Most of the universe is in. the plasma state and for a long time astrophysicists have been making measurements on extraterrestrial plasmas. More recently high temperature plasmas have been produced in the laboratory and this has led to the development of new techniques for the determination of plasma parameters.

This article describes the more important techniques which are being used for measurements on laboratory plasmas. High temperature plasmas are extremely difficult to contain for times of only a few milliseconds. Consequently it is essential for any successful technique to be able to provide adequate resolution in time so that the mechanisms controlling the growth and decay of the plasma may be understood.     

Books received

A new kind of experiment is described which measures the ‘effective mass’ of mobile electrons in semiconductors and metals. Samples are placed in a magnetic field which causes the charge carriers to move in circular paths, and a microwave oscillating electric field accelerates them in the same way as charged particles in a vacuum are accelerated in a cyclotron. The effective mass thus determined measures the momentum transfer between the crystal lattice and the electron waves and thus gives detailed information about the nature of the conduction electron states.