# Factoid

The first international e-mail in India was sent from TIFR to CERN (Geneva) in October 1988. The email address of TIFR was then TIFR.BITNET.

# Meetings

Lattice 2017 will be held in Granada, Spain on 19--24 June, 2017. A complete list of meetings held in TIFR is available.

# Gauge configurations

Some gauge configurations are available for use on request (see a list). Please request gauge configurations from ilgti at theory fullstop tifr dot res period in.

## What we do

### A short description

We are interested in the physics of matter in extreme conditions. An example of this is matter at temperatures in excess of 2 trillion degrees (2.1012 Kelvin or 175 MeV). Under such conditions matter takes extremely different forms and has peculiar properties. We compute the properties of such matter from a fundamental theory using supercomputers. Our computations are used in predicting results of experiments at CERN (Geneva) and BNL (New York). They also have implications for the evolution of the universe.

We are also interested in the structure and properties of composite particles which have strong interactions. In particular, we examine the properties of particles called glueballs, or particles with four or five quarks, or particles with heavy quarks. Collider experiments look for such exotic particles, and have already found a few.

### Normal matter

To understand why, consider normal matter. This contains molecules, which are made of atoms sharing their electrons (chemical bonds). Each atom contains a heavy nucleus (positively charged) with electrons (negatively charged) going around them. The electrons are held to the nucleus by electromagnetic forces: that is the usual force between charged particles. The nucleus is made up of neutrons and protons, which are held together by forces exerted through mesons. Baryons (of which neutrons and protons are examples) and mesons are constructed from quarks and gluons, which are held together by a force called the strong force.

Almost all forms of matter that we see around us in normal life, solids, liquids and gases, are made up of molecules. Under unusual circumstances, such as in a lightning discharge, atoms and molecules are stripped of their electrons and a new form of matter called a plasma is created. Plasmas of this kind are common elsewhere in the universe: in the upper atmosphere, in the sun and in other stars, in giant gas clouds called nebulae. Such plasmas may come together in ways that seem strange to our earth-bound ways. For example, neutron stars are gigantic atomic nuclei, several kilometers in diameter, surrounded by a cloud of electrons. From the perspective of the matter that we study, all these are examples of "normal matter".

### Extreme matter

Under the extreme conditions that we study, the force between quarks and gluons is modified so that they aggregate in bulk. They are no longer forced to come together in twos and threes to form mesons and baryons, but can aggregate into larger clusters. This form of matter is called the "quark-gluon plasma" (see 1 2 3 4). How large are these clusters? That may depend on how they are formed. There are speculations that in laboratory conditions they can be somewhat larger than the nuclei of heavy atoms such as gold or Uranium. In astrophysical conditions they could be a little smaller than neutron stars, or they could be any size in between. Such matter would also have formed early in the history of the universe, and must have left its subtle imprints on the cold background light that fills the universe even today.

This form of extreme matter is interesting because of many reasons. For example, it helps us to understand the strong force that binds quarks and gluons in normal matter. It also plays a role in helping to understand the early history of the universe. But most exciting is the race to create it in the laboratory. Our aim is to understand and predict the properties of the "quark-gluon plasma" from a theory called "Quantum Chromodynamics". Some aspects of this theory have been very well tested in laboratory experiments. Other aspects will be tested in all the situations that we have outlined above.

### How we compute the properties of extreme matter

Since we believe that we have the complete theory of quarks and gluons, we should be able to compute all properties of extreme matter from this theory. Unfortunately this is a complicated mathematical theory, and its treatment requires computers. The more detailed the question you ask, the more computation is required to answer it. Since experiments are trying to create extreme matter in labs, they ask fairly complicated questions, and we need supercomputers to answer them.

How long will we continue doing this? It is like a game of "know all". If someone in your neighbourhood is known as a walking encyclopaedia, then you keep asking her questions until one of three things happen: you lose interest, she loses interest, or she gives a wrong answer. Exactly the same with us, except that the most exciting thing we can think of is to get something wrong after getting many things right. Then the experiment which asked this question will have made a new discovery.