A domain wall is a type of topological soliton that occurs whenever a discrete symmetry is spontaneously broken. Domain walls also sometimes called kinks in analogy with closely related kink solution of the sine-Gordon model. Unstable domain walls can also appear if spontaneously broken discrete symmetry is approximate and there is the metastable vacuum.
A domain (hyper volume) is extended in three spatial dimensions and one time dimension. A domain wall is the boundary between two neighboring domains. Thus a domain wall is extended in two spatial dimensions and one time dimension.
Besides these important cases similar solitons appear in wide spectrum of the models. Here are other examples:
Spontaneous breaking of discrete symmetries at early cosmological epochs can produce domain wall. Formation of domain wall network influence on the late stages of cosmological inflation and the cosmic microwave background radiation. Observations impose severe constraints on the existence of stable domain walls. Those constraints should be accounted for by the models of the beyond Standard Model physics. Unstable cosmic domain walls decay also should produce potentially observable radiation.
Domain first impressed fans of melodic metal back in the 1980s with their first works, "Lost In The City" (still under the old band name Kingdom), "Before The Storm" and "Crack in The Wall", as well as with their hit songs such as 'Lost In The City' and ‚ 'I Don’t Wanna Die'. Single "Heart Of Stone was a title song of german mini-serial "Bastard".
But it was their next albums, "One Million Lightyears From Home" (2001), "The Artefact" (2002) and "The Sixth Dimension" (2003) as well as a successful tour with the rock legends, Glenn Hughes and Joe Lynn Turner (HTP) that secured the quintet a place in the European Melodic Metal scene. With a harder edged sound, Domain still had a good following. And that was when the career of the guitarist Axel "Ironfinger" Ritt (Grave Digger), ex-vocalist Carsten Lizard Schulz (Evidence One et al.), and the long-term band mates keyboarder Erdmann Lange, ex-bass player Jochen Mayer (Boysvoice, Demon Drive, Casanova) and the ex-drummer Stefan Köllner really began…