Strange matter
In extreme environments, strange matter is hypothesized to occur in the core of neutron stars, or, more speculatively, as isolated droplets that may vary in size from femtometers (strangelets) to kilometers, as in the hypothetical strange stars.In particle physics and astrophysics, the term 'strange matter' is used in two different contexts, one broader and the other more specific and hypothetical:[1][2] In the general context, strange matter might occur inside neutron stars, if the pressure at their core is high enough to provide a sufficient gravitational force (i.e. above the critical pressure).The Pauli exclusion principle forbids fermions such as quarks from occupying the same position and energy level.However, it is difficult to know whether hybrid stars really exist in nature because physicists currently have little idea of the likely value of the critical pressure or density.But a more precise estimate is not yet available, because the strong interaction that governs the behavior of quarks is mathematically intractable, and numerical calculations using lattice QCD are currently blocked by the fermion sign problem.