# Extreme State Physics at the University of Rochester

Welcome to the Gourdain Research Group website.

Extreme states of matter are most uncommon on Earth. However they are quite common in the Universe and include all its visible matter, especially in the x-ray and gamma-ray ranges. As matter is pulled away from peaceful environments such as Earth or the intergalactic space, it becomes stars, brown dwarves or even black holes. During this migration, it changes its physical properties. In turn these properties define the macroscopic scales of astrophysical systems and understanding universal mechanics requires knowing these properties.

So what is so extreme about these states. Their particle density is usually much larger than solid densities of materials found on Earth ($$~10^{21} cm^{-3}$$) or their temperature is much higher than the 300 K. The difficulty to study these states is overwhelming because these states do not exist naturally. They have to be created in the laboratory using pulsed-power machines, high power lasers, heavy ion beams or free electron lasers. Once created they have to be confined long enough to be studied. The power involved to generate a single sample of extreme state matter is on the order of a terawatt, a power similar to electrical grids of most technologically advanced countries.

So how do we do it? We deliver relatively amount of energy (>1 kJ) to a target sample in less than 1 nanosecond ($$10^{-9}$$s). That's a terawatt... During this time, the laboratory tuns into a real astrophysical experimental playground where the properties of matter can be measured and novel physical models can be developed. In these states, most electrons are dissociated from the nucleus of the atoms.

As a result chemistry becomes quite unconventional. If the ions and electrons are far apart, the matter is weakly coupled and the matter is in a plasma state. However if the ions and electrons are packed together then we are in the warn dense matter regime. Our group uses pulsed systems (principally lasers and pulsed-power generators) to study the properties of matter under extreme conditions. Our primary focus is to:

• explore the fundamental laws of strongly interacting systems;
• study the formation of flows and shocks under extreme conditions;
• validate competing physical models by comparing numerical simulations to experimental measurements.

Our group welcomes anyone who is interested to study extreme states of matter: undergraduate students, graduate students, postdoctoral researchers and senior researchers.