Please note that the content of this book primarily consists of articles
available from Wikipedia or other free sources online. n physics,
spontaneous symmetry breaking occurs when a system that is symmetric
with respect to some symmetry group goes into a vacuum state that is not
symmetric. When that happens, the system no longer appears to behave in
a symmetric manner. It is a phenomenon that naturally occurs in many
situations.The symmetry group can be discrete, such as the space group
of a crystal, or continuous (e.g., a Lie group), such as the rotational
symmetry of space. However if the system contains only a single spatial
dimension then only discrete symmetries may be broken in a vacuum state
of the full quantum theory, although a classical solution may break a
continuous symmetry.
