Sorry for the confusion, bad syntax on my part, I was meaning the point at which a variable in a denominator approaches zero, or becomes zero. For example in the phase transitions in ferroelectric and ferromagnetic materials, when the material changes from para(electric/magnetic) to ferro(electric/magnetic). The material variable (permitivity or permeability) is given by E = C/(Tc - T), where E is the material variable, C is a material constant, and Tc is the phase transition temperature, and T is the material temperature. Clearly when T approaches Tc from above E gets increasingly larger, until at T = Tc it spikes since you now have a 1/0 term (i.e. it becomes discontinuous in the mathematical sense). This is the region where interesting physics takes place since in some materials the transition remains mathematically continuous (2nd order phase transition) instead of discontinuous 91st order phase transition), and indeed, when one goes to reduced length scales, materials with first order phase transitions can become second order phase transitions.

I suppose arguing with a mathematician wife can create interesting physics too. Friction for example, and on rare occasions direct testing of Newtons laws via projectile motion.

jonny

The path to good scholarship is paved with imagined patterns. - David M Raup