# Pawel Danielewicz

## Professor of Physics

**About**

- Joined the laboratory in September 1988
- Theoretical nuclear physics
- Contact information

**Education and training**

- MS, Physics, Warsaw University, 1977
- PhD, Physics, Warsaw University, 1981

**Research**

My research is in nuclear reaction theory. Primarily I am

interested in the central energetic reactions of heavy nuclei.

These reactions test bulk nuclear properties such as the

Equation of State (EoS) of nuclear matter. Particular focus

is now on determining the dependence of nuclear pressure

on temperature and the symmetry energy that describes

changes in the matter with changes in neutron-proton

imbalance. Insights into the symmetry energy would allow

to extrapolate from large nuclei explored in the laboratory,

with low neutron-over-proton excess, to neutron stars, with

large excess. I am interested in the many-body theory tied

to the central reactions, such as the semiclassical transport

theory and the quantum nonequilibrium Green’s function

theory. I use the theory to understand what happens in the

reactions and to learn about the bulk nuclear properties,

by analyzing reaction measurements. When more

information can be gained from data in an adjacent field or

any methods are not there for my use, I often dive into the

adjacent fields and tackle challenges there, to move the

overall efforts forward.

Current research projects I am engaged in include the

use of the so-called charge-exchange reactions to learn

about the symmetry energy at the densities characteristic

for nuclei, the use of the charged pion yields from central

reactions to learn about the symmetry energy at higher

densities than in the nuclei, and the use of central reactions

to create transient rings out of nuclear matter. Moreover,

I am engaged in the development of quantum transport

theory suitable for studying collisions of heavy nuclei

and of other systems. Charge exchange reactions, where

proton incident on a nucleus turns into a neutron, probe

the relative distributions of neutrons vs protons in a

nucleus. The latter distribution is largely governed by the

symmetry energy. The rings out of nuclear matter form in

the transport theory simulations of collisions at modest

incident energy, in effect of a low-density instability in

the nuclear EoS, while the matter expands, mimicking the

formation of smoke rings. Experimental observation of

such rings would validate the current understanding of the

low-density EoS and give insight into phenomena in the

crusts of neutron stars.

Possible incoming student projects, of different difficulty,

include:

- Exploring impacts of a medium-modification of pion

production and absorption rates on pion yields from

central collisions of heavy nuclei - Generalizing error analysis to produce faithful errors

on the conclusions drawn from charge-exchange and

elastic scttering reactions. The traditional analysis

falters due to a serious difference in the accuracy of

measuring charged protons and neutral neutrons - Constructing and implementing modern energy

functional for exploring EoS in central reactions - Advancing quantum transport theory for central

reactions, based on nonequilibrium Green’s functions

**Scientific publications**

- Dynamics of one-dimensional correlated nuclear systems

within non-equilibrium Green’s function theory, Hao Lin,

Hossein Mahzoon, Arnau Rios and Pawel Danielewicz,

Ann. Phys. (N.Y.) 420, 168272 (2020) - Shear viscosity from nuclear stopping, Brent Barker and

Pawel Danielewicz, Phys. Rev. C 99, 034607 (2019) - Symmetry Energy III: Isovector Skins, Pawel Danielewicz,

Pardeep Singh and Jenny Lee, Nucl. Phys. A 958, 147

(2017)