# Simple-tens!

Useful article for guitarists.

# A bouquet of particles

Theoretical physics is like a bouquet of roses (or particles you may say!). It has an enticing fragrance, which forces you to follow its fume, no matter how far you may have to go. And like a simpleton child you follow this fume with firm belief that you will, at the end, find a beautiful heaven-like garden of roses. But the fragrance is omnipresent, everywhere. There is not just one narrow path. The fragrance will some time take you to the notations of tensors, the principles of quantum world, the groups of Lie, the topology of rubber sheet, the geometry of Riemann, the relativity of Einstein, the standard model of Salam, the diagrams of Feynman, the symmetries of Noether, the diagrams of Dynkin.

# If d/dt is velocity, what is d/dx ?

Well, it is easy to understand if we regard time as a dimension, which it is according to relativity. Further, space and time are on equal footing, i.e., what you can say about time you can also say that about space, and vice versa. Pictorially we draw the 3-dimensional coordinate system and add one more (4th) dimension to include time. So as the time derivative d/dt tells us the rate of change of U w.r.t. time (t-axis), in the same way, d/dx tells us the rate of change of U w.r.t x-axis.

# Interesting Example

Let $\bold{A}=A_1 \hat{i} + A_2 \hat{j} +A_3 \hat{k}$ is be a vector in 3-dimensional space. Is the set of all vectors with $A_1 = 7$ a vector space?

# Main theorem of Tensors

If two tensors have all their components equal in one coordinate system, then their components are equal in any of the coordinate systems.