Andrew Zimmerman Jones

This Cheat Sheet is intended to supplement Quantum Physics For Dummies, 3rd edition, by Andrew Zimmerman Jones. It begins by reviewing some useful operators used in quantum mechanics calculations. Then it covers a useful method for solving the Schrödinger equation for the quantum wave function, and then how you can use that wave function to calculate probabilities in quantum physics.

String theory, often called the “theory of everything,” is a relatively young science that includes such unusual concepts as superstrings, branes, and extra dimensions. Scientists are hopeful that string theory will unlock one of the biggest mysteries of the universe, namely how gravity and quantum physics fit together.

In string theory, the multiverse is a theory in which our universe is not the only one; many universes exist parallel to each other. These distinct universes within the multiverse theory are called parallel universes. A variety of different theories lend themselves to a multiverse viewpoint. In some theories, there are copies of you sitting right here right now reading this in other universes and other copies of you that are doing other things in other universes.

Albert Einstein was influenced by the concept of an unchanging universe. His general theory of relativity predicted a dynamic universe — one that changed substantially over time — so he introduced a term, called the cosmological constant, into the theory to make the universe static and eternal. This term represented a form of repulsive gravity that exactly balanced out the attractive pull of gravity, and it would prove to be a mistake when, several years later, astronomer Edwin Hubble discovered that the universe was expanding.

String theory is a type of high-energy theoretical physics, practiced largely by particle physicists. It’s a quantum field theory that describes the particles and forces in our universe based on the way that special extra dimensions within the theory are wrapped up into a very small size (a process called compactification).

A hologram is a 2-dimensional image that contains all the 3-dimensional information of an object. When viewing a hologram, you can tilt the image and see the orientation of the shape move. It’s as if you see the object in the picture from a different angle. The process of making a hologram is called holography.

In the light of all of the recent criticisms of string theory, many of which have some measure of validity or logic to them, you may be wondering how anyone could continue working on string theory. How could some of the most brilliant physicists in the world devote their careers to exploring a field that is apparently a house of cards?