Spontaneous symmetry breaking in a solvable nuclear model

Chuang Liu, Gérard G. Emch

Jasper van Wezel, Jeroen van den Brink, Jan Zaanen

We investigate the influence of spontaneous symmetry breaking on the decoherence of a many-particle quantum system. This decoherence process is analyzed in an exactly solvable model system that is known to be representative of symmetry broken macroscopic systems in equilibrium. It is shown that spontaneous symmetry breaking imposes a fundamental limit to the time that a system can stay quantum coherent. This universal time scale is t(spon) approximately = 2piNH/(kBT), given in terms of the number of microscopic degrees of freedom N, temperature T, and the constants of Planck (h) and Boltzmann (kB).

Cheng-Ju Lin, Liujun Zou

A spontaneous symmetry-breaking order is conventionally described by a tensor-product wavefunction of some few-body clusters; some standard examples include the simplest ferromagnets and valence bond solids. We discuss a type of symmetry-breaking orders, dubbed entanglement-enabled symmetry-breaking orders, which cannot be realized by any such tensor-product state. Given a symmetry breaking pattern, we propose a criterion to diagnose if the symmetry-breaking order is entanglement-enabled, by examining the compatibility between the symmetries and the tensor-product description. For concreteness, we present an infinite family of exactly solvable gapped models on one-dimensional lattices with nearest-neighbor interactions, whose ground states exhibit entanglement-enabled symmetry-breaking orders from a discrete symmetry breaking. In addition, these ground states have gapless edge modes protected by the unbroken symmetries. We also propose a construction to realize entanglement-enabled symmetry-breaking orders with spontaneously broken continuous symmetries. Under the unbroken symmetries, some of our examples can be viewed as symmetry-protected topological states that are beyond the conventional classifications.

Franco Strocchi

Ernest Grodner

Spontaneous time-reversal symmetry breaking in the system of an atomic nucleus is discussed on the basis of nuclear chirality phenomenon. The mechanism of nuclear chirality i.e. existence of three aplanar angular momenta vectors seems to be applicable in other fields of physics, for example in classical physics as coupling of three gyroscopes. Here, possible application of spontaneous time-reversal symmetry breaking in the design of a digital logic is discussed as an interesting curiosity.

Spartak T. Belyaev