# Equilibration and hydrodynamics at strong and weak coupling

## Abstract

We give an updated overview of both weak and strong coupling methods to describe the approach to a plasma described by viscous hydrodynamics, a process now called hydrodynamisation. At weak coupling the very first moments after a heavy ion collision is described by the colour-glass condensate framework, but quickly thereafter the mean free path is long enough for kinetic theory to become applicable. Recent simulations indicate thermalization in a time t ~ 40 (η/s) ^{4/3}/ *T*, with $$\tau$$ the temperature at that time and η/s the shear viscosity divided by the entropy density. At (infinitely) strong coupling it is possible to mimic heavy ion collisions by using holography, which leads to a dual description of colliding gravitational shock waves. The plasma formed hydrodynamises within a time of 0.41/$$\tau$$ recent extension found corrections to this result for finite values of the coupling, when is bigger than the canonical value of 1/4$$\pi$$, which leads to t ~ (.41+1.6(η/s-1/4$$\pi$$))/ *T*. Moreover, future improvements include the inclusion of the effects of the running coupling constant in QCD.

- Authors:

- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of Utrecht, Utrecht (Netherlands)

- Publication Date:

- Research Org.:
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC)

- OSTI Identifier:
- 1500558

- Grant/Contract Number:
- [SC0011090]

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Nuclear Physics. A

- Additional Journal Information:
- [ Journal Volume: 967; Journal Issue: C]; Journal ID: ISSN 0375-9474

- Publisher:
- Elsevier

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; hydrodynamisation; holography

### Citation Formats

```
van der Schee, Wilke. Equilibration and hydrodynamics at strong and weak coupling. United States: N. p., 2017.
Web. doi:10.1016/j.nuclphysa.2017.05.003.
```

```
van der Schee, Wilke. Equilibration and hydrodynamics at strong and weak coupling. United States. doi:10.1016/j.nuclphysa.2017.05.003.
```

```
van der Schee, Wilke. Mon .
"Equilibration and hydrodynamics at strong and weak coupling". United States. doi:10.1016/j.nuclphysa.2017.05.003. https://www.osti.gov/servlets/purl/1500558.
```

```
@article{osti_1500558,
```

title = {Equilibration and hydrodynamics at strong and weak coupling},

author = {van der Schee, Wilke},

abstractNote = {We give an updated overview of both weak and strong coupling methods to describe the approach to a plasma described by viscous hydrodynamics, a process now called hydrodynamisation. At weak coupling the very first moments after a heavy ion collision is described by the colour-glass condensate framework, but quickly thereafter the mean free path is long enough for kinetic theory to become applicable. Recent simulations indicate thermalization in a time t ~ 40 (η/s)4/3/T, with $\tau$ the temperature at that time and η/s the shear viscosity divided by the entropy density. At (infinitely) strong coupling it is possible to mimic heavy ion collisions by using holography, which leads to a dual description of colliding gravitational shock waves. The plasma formed hydrodynamises within a time of 0.41/$\tau$ recent extension found corrections to this result for finite values of the coupling, when is bigger than the canonical value of 1/4$\pi$, which leads to t ~ (.41+1.6(η/s-1/4$\pi$))/T. Moreover, future improvements include the inclusion of the effects of the running coupling constant in QCD.},

doi = {10.1016/j.nuclphysa.2017.05.003},

journal = {Nuclear Physics. A},

number = [C],

volume = [967],

place = {United States},

year = {2017},

month = {9}

}

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#### Figures / Tables:

*η/s*(from [11], see also [12]). Even though the

*η/s*ranges from 0.08more »

Figures / Tables found in this record:

*Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.*