On 25 Jun 2018, at 20:09, helvi witek <helvi.witek@kcl.ac.uk> wrote:Helvicheers,Dear all,please find the minutes for today's call below.@Bishop: thanks a lot for leading today's discussion!@all: Let me know if you have any additions or comments to the minutes.
Btw, I still have problems to edit the wiki. Would you all agree to use a shared googledoc? I am asking because of the new EU data protection laws, which led KCL to warn us against using google. As long as we do not share any personal data, however, it should be fine.
Call: Einstein Toolkit Working group ``Cosmology and Particles'', 25 June 2018
Participants:
Katy Clough, Isabel Cordero, Michele Grasso, Bishop Mongwane, Daniele Vernieri, Helvi Witek
1) Reminder: EU Einstein Toolkit and school in Lisbon, September 2018
- Website: https://centra.tecnico.ulisboa.pt/network/grit/einsteintoolkit2018/
- Deadlines: 1 July 2018 (abstract submission); 15 July 2018 (registration)
2) Summer calls:
- maybe have a call in July; NO call in August;.
- next regular working group call: September 2018
3) Discussion: Bishop Mongwane on 3+1 formulation and hyperbolicity of f(R) theories
- based on papers:.
https://arxiv.org/abs/1610.07224
https://arxiv.org/abs/1707.05757
- motivation
- f(R) gravity captures class of interesting cosmological models
- e.g. Starobinsky model of inflation
- under certain conditions equivalent to scalar-tensor theories ($f'(R) \sim \phi$)
- achievements
- derive time evolution formulation for f(R) gravity, specifically ADM and BSSNOK formulation
- neat trick: use the 4-dimensional Ricci scalar $^{(4)}R$ and its time derivative $\psi=\p_{t} ^{(4)}R$ as
independent variables
- showed strong-hyperbolicity for BSSN-type formulation
- numerical tests still problematic, maybe future work
- Comments
- BSSN only valid for $\det\tilde{\gamma}=1$; maybe reference metric formulation for spherically symmetric spacetimes
- numerical issues related to gauge choice?
- future numerical tests (a la ``apples with apples'') of non-trivial cosmological or black hole spacetimes
- references for non-trivial or cosmological boundary conditions:
- https://arxiv.org/abs/1409.3476
- https://arxiv.org/abs/1509.08354
- https://arxiv.org/abs/1204.2019
- general discussion on constraint evolution vs free evolution in future working group call (Isa)_______________________________________________Theoretical Particle Physics and Cosmology===========================================Royal Society University Research Fellow
Dr. Helvi WitekDepartment of PhysicsKing's College London===========================================On Mon, Jun 25, 2018 at 3:22 PM, Bishop Mongwane <astrobish@gmail.com> wrote:Hi all,I'll be talking mostly from these 2 papers:See you in a moment.Cheers,BishopOn Mon, Jun 25, 2018 at 11:31 AM, helvi witek <helvi.witek@kcl.ac.uk> wrote:______________________________HelviBest wishes,You can attend the meeting via the google hangout:Dear all,this is a reminder for today's call at 4:30pm (BST, i.e. UK/Portugal) / 5:30pm (CDT).
https://hangouts.google.com/hangouts/_/tce4j4gzcfcormnadoaui qcvg4e or reply to this email if you also have difficulties to edit the wiki.Bishop Mongwane will discuss his work on "3+1 formulation of and hyperbolicity in $f(R)$ theories".If you have any further suggestions for topics to be discussed in the meeting, please add them to the meeting agenda:Theoretical Particle Physics and Cosmology==============================Royal Society University Research Fellow=============
Dr. Helvi WitekDepartment of PhysicsKing's College London=========================================== On Mon, Jun 18, 2018 at 6:32 PM, helvi witek <helvi.witek@kcl.ac.uk> wrote:You can attend the meeting via the google hangout:Dear all,please consider joining our working group call next Monday, 25 June 2018, at 4:30pm (BST, i.e. UK/Portugal) / 5:30pm (CDT).
https://hangouts.google.com/hangouts/_/tce4j4gzcfcormnadoaui qcvg4e Bishop Mongwane will discuss his work on "3+1 formulation of and hyperbolicity in $f(R)$ theories".If you have any further suggestions for topics to be discussed in the meeting, please add them to the meeting agenda:or reply to this email if you also have difficulties to edit the wiki.cheers,HelviTheoretical Particle Physics and Cosmology==============================Royal Society University Research Fellow=============
Dr. Helvi WitekDepartment of PhysicsKing's College London=========================================== _________________
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