Quantum field theory – the universe as a field.

6 min readAug 15, 2020

Image credit : edukite.org

Introduction

We humans have come a long way in exploring things but the urge to explore and what is ought there to explore still remains the same. Human evolution was possible only due to the urge to explore new things, from being hunter gatherers to farmers, then forming civilizations around river banks and delta regions, to the Europeans trying a new way to India, which helped Christopher Columbus reach the New world as they called it.., As humans got connected in this way thier different ideas emerged to give rise to a greater understanding of nature and physics. Let’s go to the 1800s to the empire where the sun never sets, Michael Faraday started explaining electromagnetism in terms of fields, it was a new concept at that time but everyone felt it when bringing like poles of a simple bar magnet, Faraday once demonstrated the “field phenomena” by a simple experiment he made a current to pass through a solenoid and then dipped another one the compass which had no contact, deflected. This proved the magnetic /electric field concept of Faraday. That concept was taken by quantum physicists to describe particles as a quanta(packet) of fields let’s see more about these fields..

Michael Faraday. Image credit- britannica.com.

Quantum field theory – an overview.

It all starts with Niels bohr, Schrodinger and Heisenberg who stated or supported electrons or sub atomic particles as waves at its peak.Then Paul Dirac came up with a equation which almost described every phenomena that we know, it can be called as a equation which describes everything we know,This resulted in the development of the string theory, the Supersymmetry postulates etc. But still we couldn’t explain things which were still incomplete, physicists knew something else is there, which they left due to our incomplete understanding, the quantum field theory in a way helps us to better explain the universe. Quantum field theory states everything as fields, the sub atomic fundamental particles, quarks – the up quark, down quark, top quark, bottom quark, strange quark, charm quark are all fields as a quanta or a like lump of the charecteristic field. The three nuetrinos, muons and taus, electrons are all the basic fundamental fields or the twelve fundamental fields. Peter Higgs in 1960s predicted the presence of the Higgs boson, the Higgs as we know now is basically another field known as Higgs field which is assumed to be throughout the cosmos, the Higgs field is never zero, the interference of these fundamental fields with the Higgs field gives the so called particles its mass. The discovery of the Higgs in 2012 at Cern is a major break through as it is somewhat impossible as the Higgs quickly decays into various fundamental particles.

Credit :quantamagazine.org

The bump in the graph is the Higgs boson.

Quantum field theory (QFT) is a theoretical framework that combines classical field theory, special relativity and quantum mechanics, but not general relativity’s description of gravity. Quantum field theory is used in particle physics to construct physical models of subatomic particles and in condensed matter physics to construct models of quasiparticles.QFT treats particles as excited states (also called quanta) of their underlying fields, which are more fundamental than the particles. Interactions between particles are described by interaction terms in the Lagrangian involving their corresponding fields. Each interaction can be visually represented by Feynman diagrams according to perturbation theory in quantum mechanics.

Paul Dirac Image credit :wikipedia

Peter Higgs Image credit : britannica.com

Quantum vacuum fluctuations

Credit : physics.adelaide.edu.au
The above gif is a computer simulation which shows how an empty vaccum looks like even after removing every material particles, this simulation explains the quantum field theory, now when we observe the cosmic microwave background of the universe we get a similar image or similar kind of flickers just after big bang, it might not have being the bang after all but to simplify the issue.

Cosmic microwave background.

Credit :cosmology.berkerley.edu
Quantum field theory postulates that the field formed after big bang might be the parent of the fundamental fields resulting due to the condensation of the field as the field fluctuated into individual fields or might be everything is the same field even now but the differentiation is solely due to our perspective of these fields. The computer simulation predicting the field is known as quantum vacuum fluctuations. quantum fluctuation ( vacuum state fluctuation) is the temporary random change in the amount of energy in a point in space, as prescribed by Werner Heisenberg’s uncertainty principle. They are tiny random fluctuations in the values of the fields which represent elementary particles, such as electric and magnetic fields which represent the electromagnetic force carried by photons, W and Z fields which carry the weak force, and gluon fields which carry the strong force.

Image credit – azquotes.com

Feynman diagrams

Image credit – britannica.com
Feynman diagrams are used to solve problems related to the quantum field theory, explains the matter collisions such as the above depicting the EM field waves when two electrons collide with each other, there are actually infinite ways at which the collision charecterizes it can be either transformed into photon and from photon to electron positron pair and again back to photons. In a more detailed way, A Feynman diagram has lines in different shapes-straight, dotted, which meet up at points called vertices. The vertices are where the lines begin and end. The points in Feynman diagrams where the lines meet represent two or more particles that happen to be at the same point in space at the same time. The lines in a Feynman diagram represent the probability amplitude for a particle to go from one place to another.

Image credit – quantamagazine.org

Richard Feynman. Image credit – Wikipedia

Perturbation theory

This theory states that (in a simple way) if you are not getting a solution of a problem then take a similar problem whose solution we know and make modifications to it. This is incredibly important in solving quantum field theory problems.

Image credit – slideserve.com

Conclusion

The depiction of the universe as a field have given a better way of interpreting the physics, but the thing is we cannot be sure that this is the truth, but as of now we don’t get anything wrong with what we know while using quantum field theory, and a better understanding of supersymmetry, dark matter and dark energy, quantum gravity will lead to a theory of everything but the thing we still don’t understand the universe as it is…