[Cosmoparticle-wg] ET "Cosmology and particles" working group call

Mon Jun 25 13:09:20 CDT 2018

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.

cheers,
Helvi

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)

===========================================
Dr. Helvi Witek
Royal Society University Research Fellow
Theoretical Particle Physics and Cosmology
Department of Physics
King's College London
===========================================

On Mon, Jun 25, 2018 at 3:22 PM, Bishop Mongwane <astrobish at gmail.com>
wrote:

> Hi all,
>
> I'll be talking mostly from these 2 papers:
>
> -> https://arxiv.org/abs/1610.07224
> <https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Farxiv.org%2Fabs%2F1610.07224&data=01%7C01%7Chelvi.witek%40kcl.ac.uk%7Cdc1f5f0064244e9904a808d5daaf68a0%7C8370cf1416f34c16b83c724071654356%7C0&sdata=w55IrYoihCipghj7TpYUl4RtGZf%2FPPulnFqVDHdfj0I%3D&reserved=0>
> -> https://arxiv.org/abs/1707.05757
> <https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Farxiv.org%2Fabs%2F1707.05757&data=01%7C01%7Chelvi.witek%40kcl.ac.uk%7Cdc1f5f0064244e9904a808d5daaf68a0%7C8370cf1416f34c16b83c724071654356%7C0&sdata=F8uJt%2F3%2F%2BK%2BmkqfgCHB2UCjScYWo4Rt%2BvuqQuhLYNYY%3D&reserved=0>
>
> See you in a moment.
>
>
> Cheers,
> Bishop
>
> On Mon, Jun 25, 2018 at 11:31 AM, helvi witek <helvi.witek at kcl.ac.uk>
> wrote:
>
>> Dear all,
>>
>> this is a reminder for today's call at 4:30pm (BST, i.e. UK/Portugal) /
>> 5:30pm (CDT).
>> You can attend the meeting via the google hangout:
>> https://hangouts.google.com/hangouts/_/tce4j4gzcfcormnadoauiqcvg4e
>> <https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fhangouts.google.com%2Fhangouts%2F_%2Ftce4j4gzcfcormnadoauiqcvg4e&data=01%7C01%7Chelvi.witek%40kcl.ac.uk%7Cdc1f5f0064244e9904a808d5daaf68a0%7C8370cf1416f34c16b83c724071654356%7C0&sdata=i54YG1gRzkngvduxiPLF8EYoCH9ZWB9a00avOEgYW0Y%3D&reserved=0>
>>
>> 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:
>> https://docs.einsteintoolkit.org/et-docs/Cosmology_and_Particles
>> <https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.einsteintoolkit.org%2Fet-docs%2FCosmology_and_Particles&data=01%7C01%7Chelvi.witek%40kcl.ac.uk%7Cdc1f5f0064244e9904a808d5daaf68a0%7C8370cf1416f34c16b83c724071654356%7C0&sdata=DJ8U9lYk6TzqAjjb9ZTrVBfQm9f%2FugX40dx1yPBvBMQ%3D&reserved=0>
>> or reply to this email if you also have difficulties to edit the wiki.
>>
>> Best wishes,
>> Helvi
>>
>> ===========================================
>> Dr. Helvi Witek
>> Royal Society University Research Fellow
>> Theoretical Particle Physics and Cosmology
>> Department of Physics
>> King's College London
>> ===========================================
>>
>> On Mon, Jun 18, 2018 at 6:32 PM, helvi witek <helvi.witek at kcl.ac.uk>
>> wrote:
>>
>>> 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).
>>> You can attend the meeting via the google hangout:
>>> https://hangouts.google.com/hangouts/_/tce4j4gzcfcormnadoauiqcvg4e
>>> <https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fhangouts.google.com%2Fhangouts%2F_%2Ftce4j4gzcfcormnadoauiqcvg4e&data=01%7C01%7Chelvi.witek%40kcl.ac.uk%7Cdc1f5f0064244e9904a808d5daaf68a0%7C8370cf1416f34c16b83c724071654356%7C0&sdata=i54YG1gRzkngvduxiPLF8EYoCH9ZWB9a00avOEgYW0Y%3D&reserved=0>
>>>
>>> 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:
>>> https://docs.einsteintoolkit.org/et-docs/Cosmology_and_Particles
>>> <https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.einsteintoolkit.org%2Fet-docs%2FCosmology_and_Particles&data=01%7C01%7Chelvi.witek%40kcl.ac.uk%7Cdc1f5f0064244e9904a808d5daaf68a0%7C8370cf1416f34c16b83c724071654356%7C0&sdata=DJ8U9lYk6TzqAjjb9ZTrVBfQm9f%2FugX40dx1yPBvBMQ%3D&reserved=0>
>>> or reply to this email if you also have difficulties to edit the wiki.
>>>
>>> cheers,
>>> Helvi
>>> ===========================================
>>> Dr. Helvi Witek
>>> Royal Society University Research Fellow
>>> Theoretical Particle Physics and Cosmology
>>> Department of Physics
>>> King's College London
>>> ===========================================
>>>
>>>
>>
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>> <https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.einsteintoolkit.org%2Fmailman%2Flistinfo%2Fcosmoparticle-wg&data=01%7C01%7Chelvi.witek%40kcl.ac.uk%7Cdc1f5f0064244e9904a808d5daaf68a0%7C8370cf1416f34c16b83c724071654356%7C0&sdata=goyNp6Fu6%2FhoLHKH8JWCgoypaCY%2F8t4DYf4lBQNLD34%3D&reserved=0>
>>
>>
>
>
> --
>
>
>
> .. with two they covered their face, with two they covered their feet,
> with two they did fly and one cried unto the other
> `Masina, masina, masina'
>
>
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