# Download PDF Field theory, quantum gravity and strings I

Ziqi Yan. Liujun Zou. Simon Caron-Huot. Visiting Fellow. Bartek Czech. Jerome Gauntlett. Zohar Komargodski. Emil Mottola. Quantum Foundations ,. Quantum Gravity ,. Quantum Information ,. Strong Gravity ,. Tibra Ali.

PSI Fellow. Jacob Abajian. Resident PhD Student. Alvaro Ballon Bordo.

## Conferences - String Theory Wiki

Strong Gravity. Hong Zhe Chen. Frank Coronado. Diego Delmastro. Adrian Franco Rubio. Alfredo Guevara. Juan Hernandez. Alexandre Homrich. Qi Hu. Nafiz Ishtiaque. Justin Kulp. Ji Hoon Lee. Raeez Lorgat. Hugo Marrochio. But the line of thoughts has been pretty linear all this time. The String Theory challenges the basic approach and presents us with a mind-blowing new perspective to see the reality. But first, let's see what makes String Theory revolutionary and so interesting. Physicists were having a good time explaining the observable universe with Galilean laws of motion.

Newton added to their arsenal gravitational force and things started making more sense. A major breakthrough was made by Maxwell when he unified the electric and magnetic forces into electromagnetism. He even explained the carriers of the force that are photons. But we were still clueless about the gravitational force.

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What brings it into being? Einstein was the first to make advancement in this direction with his theory of special and general relativity. He tried to explain gravity solely in terms of geometry and it went pretty well. But the world of science was completely turned upside-down by Heisenberg and others when they added the quintessential chapter of quantum physics.

Till this point, the classical model and electromagnetism were doing a great job, explaining the phenomenon and interactions at the macroscopic level. Quantum Physics now enabled physicists to explain the microscopic world as well. Later on, weak and strong nuclear forces were discovered and we got our four fundamental forces. Along the way, we discovered a lot of really small particles which seemed to make up the Universe.

Later on, electrons, protons, and neutron grabbed that spot. As of now, we consider bosons like gluons, Higgs and fermions like quarks, leptons to be the elementary particles. These fundamental particles and their interaction with each other illustrated the nature of reality quite precisely with gravity being the only exception. Now, we do not want to delve deep into the mathematics behind these discoveries, but you must know that our knowledge about them comes from mere speculations and calculation. Elementary particles are so small, of the order of a Planck dimension that is 10 , that we cannot experiment or even observe them.

- String theory?
- General relativity: Quantum gravity;
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- Quantum Fields and Strings.

So, how do we play with them? Moreover, these points have quantum states which we call mass, charge, etc. But you cannot do much with these point particles. This proved to be a major hurdle while formulating the interaction between different particles. However, his theoretical model of strings failed for hadrons, but it was later revived to describe all the elementary particles.

Remember our little problem with point particles being unable to account for interactions?

### Introduction

Well, the String Theory proposed to generalize the idea of the fundamental constituent entity to 1-dimension. What it means is that String Theory suggests that little strings of the size of the Planck length are the elementary objects, not the elementary particles. All the elementary particles can be described as strings with different quantum states. There is a rather famous analogy of these theoretical strings to the strings of a violin.

As different vibrations of a string on a violin produce different notes, in a similar way, different quantum states of a string give rise to all the possible elementary particles, be it an electron or a quark or a gluon.

## Loop Quantum Gravity

On a larger scale, you do not see strings, they look like the elementary particles, which we are well familiar with. You may ask what these strings are made up of. Well, they are not made of anything but they themselves make everything.

For example, in a Standard Model, a chair is made up of wood, which in turn comprise different molecules, which themselves are made of different atoms comprising of electrons, protons made of quarks and neutrons also formed by quarks. But what are these quarks and electrons have in their ultimate breakdown? Explorations of new avatars of the mysterious "moonshine" relating mock modular forms, sporadic simple groups, algebraic geometry, and string vacua has been a subject of significant recent interest at Stanford.

String theory has enjoyed tremendously fruitful interactions with modern mathematics. Some of the simplest and most interesting questions in number theory and geometry involve counting for instance, determining numbers of integer solutions to certain equations. Many mathematical concepts trace their origins to everyday experience, from astronomy to mechanics. Remarkably, ideas from quantum theory turn out to carry tremendous mathematical power too, even though we have little intuition dealing with elementary particles.

He received his Ph. D from the University of Texas at Austin in His research interests range from phenomenological questions in cosmology and particle physics to formal questions in quantum field theory and string theory. Currently, he is interested in extracting clues about fundamental physics from cosmological observations.

Liam McAllister is a professor at Cornell University. D from Stanford University in He is interested in using string theory to understand the early universe, and in developing compactifications of string theory that lead to realistic four-dimensional physics. Two dimensional conformal field theories CFTs have a very powerful property called modular invariance, which relates the high and low temperature limits of the theory.

This can give nontrivial relations between the low-energy spectrum of the theory and the high-energy spectrum.