The Null Energy Condition and its violation
V.A. Rubakov a, b
a Institute for Nuclear Research, Russian Academy of Sciences, prosp. 60-letiya Oktyabrya 7a, Moscow, 117312, Russian Federation
b Lomonosov Moscow State University, Department of Physics, Leninskie Gory 1 build. 2, Moscow, 119991, Russian Federation
A brief review is given of scalar field theories with second-derivative Lagrangians yielding second order field equations. Some of these theories admit solutions that violate the Null Energy Condition but which otherwise show no obvious inconsistencies. The use of these theories in constructing cosmological scenarios and in the context a laboratory-created universe is illustrated with examples.