Final answer:
The non-time-ordered Wightman function's perturbative expansion in quantum field theory, while conceptually different from the time-ordered correlation function, also pertains to the probability distributions and measurement effects described by quantum mechanics, particularly in the context of the Born and Copenhagen interpretations.
Step-by-step explanation:
In the context of quantum field theory, specifically φ4 theory, the perturbative expansion of the time-ordered 2-point correlation function ⟨Ω|Tφ(x₁)φ(x₂)|Ω⟩ is known. The non-time-ordered 2-point Wightman function ⟨Ω|φ(x₁)φ(x₂)|Ω provides a different perspective, and its perturbative expansion can be quite insightful. While both functions describe interactions between quantum fields at two different points in space-time, the lack of time-ordering in the Wightman function results in different types of contributions to the series expansion. Moreover, it directly relates to measurements and probability density distributions in quantum mechanics.
Quantum mechanics teaches us that the square of the wave function, |Y(x, t)|2 , is proportional to the probability of finding a particle at a certain location. This culminates in what is known as the Born interpretation. According to the Copenhagen interpretation, a particle is not confined to a specific location until a measurement is made, suggesting that prior to measurement, a particle's location is described by a probability distribution rather than a specific position. When the wave function is measured or observed, it collapses to a specific value, pinpointing the particle's location within a narrow interval.