Can You Obtain New Physics from the use of Fractional Derivatives? I was curious if anyone could give me an example of the use of fractional derivatives in physics and explain what they offer that "conventional" mathematics does not (in terms of new physics and not just another method to work the problem)? 
If you look at the conservation of mass example on the wikipedia page they cite the paper http://www.stt.msu.edu/~mcubed/fcom.pdf they derive a general equation for conservation of mass in equation 13. It seems like the fractional derivative is then used as a method to approach their problem, but I dont think it includes new physics (correct me if I'm wrong on this). Is there anything gained by stating that fractional conservation of mass holds in this case (apart from gaining another way to approach the problem)?  
Any thoughts on this example or others would be appreciated! 
 A: All our sophisticated mathematical tools - Derivatives and Integrals, Fourier Transforms, Groups and Representations, Riemann Tensors, Kähler manifolds, etc. are merely descriptive techniques.  What exists is what exists, independent of how we try to describe it.  
New mathematical ideas often help us see known phenomena more clearly, or deal with the mathematical analysis more easily.   Imagine studying the gravitational field of a planet or star in rectangular coordinates instead of spherical. Ugh!  (A good exercise for undergrad students...hee hee!) 
A well-aligned mathematical view will let us see phenomena otherwise hidden in messy data or a blizzard of algebraic terms.  I think of the moons of Saturn and waves induced in the rings - a very complex system requiring wise choices of coordinate systems. In high energy physics, prediction of the Omega hadron as the final piece of a puzzle was allowed by use of group representation theory.
So, application of innovative mathematics to physics can certainly facilitate discovery of physical phenomena.
Specifically for fractional derivatives, though, it's unlikely to help.  Any interesting peaks, wiggles, jumps in the semi-derivative of a function or in numerical analysis of raw data, is unlikely to show anything not already clearly visible in the data or its plain first-order derivative.   
If you can think of some type of feature in data or an expression that's easily visible the way it is, but hard to notice in the semi-derivative or semi-integral, you'd be onto something.   Good luck finding such a thing.
