In today’s Academic Minute, Dr. Ali Nayeri of Chapman University discusses the explanatory power of string theory cosmology.
Ali Nayeri is an assistant professor of physics in the Schmid College of Science and Technology at Chapman University in Orange, California. His teaching and research interests are focused on string theory and string cosmology. He is also a member of Chapman’s Institute for Quantum Studies.
Dr. Ali Nayeri – Cosmology and String Theory
Cosmology is the study of the universe. The universe is usually described by the most successful framework in particle physics – inflation. But inflation is not as fundamental as string theory.
String theory is when the role of a particle is replaced by the role of a concentration of energies in the form of string.
To explain the universe using string theory, we begin with some assumptions that the universe is flat and not a sphere; the topology of the universe is compact and torus – shaped like a doughnut; there are only three dimensions; and there is lots of entropy or disorder in the universe.
Strings provide more degrees of freedom. One of these is winding – so strings can be wound around space. There is symmetry in the nature appreciated by this winding of the strings called T-duality.
Because strings have finite lengths, when they vibrate the vibrations are very limited, which creates an upper limit of the temperature that the strings can achieve. Conversely, there is no thermal limit to a particle.
There is a duality between smallness and bigness – so the physics for small objects is the same as the physics for large ones. If you add these features into cosmology you will see there is a dual to our universe. Our universe is expanding; the other universe is contracting. These two universes are connected through a self-dual zone which mimics the Big Bang. So for everyone – there is a dual to you in the dual universe.
The difference between string cosmology and inflationary cosmology is in the former the radius of the universe goes through a huge expansion. But in string cosmology, instead, the fluctuations generated by strings will exit the radius of the observable universe and then re-enter at some later time.
It is the only theory which offers why we are living in three dimensions.