<div dir="ltr"><div><div><div><div>Dear all,<br><br></div>please find the minutes for today's call below. <br></div><div>@Bishop: thanks a lot for leading today's discussion!</div><div>@all: Let me know if you have any additions or comments to the minutes.</div><br>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.<br><br></div>cheers,<br></div>Helvi<br><br>Call: Einstein Toolkit Working group ``Cosmology and Particles'', 25 June 2018<br><br>Participants:<br>Katy Clough, Isabel Cordero, Michele Grasso, Bishop Mongwane, Daniele Vernieri, Helvi Witek<br><br>1) Reminder: EU Einstein Toolkit and school in Lisbon, September 2018<br> - Website: <a href="https://centra.tecnico.ulisboa.pt/network/grit/einsteintoolkit2018/">https://centra.tecnico.ulisboa.pt/network/grit/einsteintoolkit2018/</a><br> - Deadlines: 1 July 2018 (abstract submission); 15 July 2018 (registration)<br><br>2) Summer calls:<br> - maybe have a call in July; NO call in August;.<br> - next regular working group call: September 2018<br><br>3) Discussion: Bishop Mongwane on 3+1 formulation and hyperbolicity of f(R) theories<br> - based on papers:.<br> <a href="https://arxiv.org/abs/1610.07224">https://arxiv.org/abs/1610.07224</a><br> <a href="https://arxiv.org/abs/1707.05757">https://arxiv.org/abs/1707.05757</a><br><br> - motivation<br> - f(R) gravity captures class of interesting cosmological models<br> - e.g. Starobinsky model of inflation<br> - under certain conditions equivalent to scalar-tensor theories ($f'(R) \sim \phi$)<br> - achievements<br> - derive time evolution formulation for f(R) gravity, specifically ADM and BSSNOK formulation<br> - neat trick: use the 4-dimensional Ricci scalar $^{(4)}R$ and its time derivative $\psi=\p_{t} ^{(4)}R$ as<br> independent variables<br> - showed strong-hyperbolicity for BSSN-type formulation<br> - numerical tests still problematic, maybe future work<br> - Comments<br> - BSSN only valid for $\det\tilde{\gamma}=1$; maybe reference metric formulation for spherically symmetric spacetimes<br> - numerical issues related to gauge choice?<br> - future numerical tests (a la ``apples with apples'') of non-trivial cosmological or black hole spacetimes<br> - references for non-trivial or cosmological boundary conditions:<br> - <a href="https://arxiv.org/abs/1409.3476">https://arxiv.org/abs/1409.3476</a><br> - <a href="https://arxiv.org/abs/1509.08354">https://arxiv.org/abs/1509.08354</a><br> - <a href="https://arxiv.org/abs/1204.2019">https://arxiv.org/abs/1204.2019</a><br> - general discussion on constraint evolution vs free evolution in future working group call (Isa)<br><div><div><div><br></div></div></div></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><span><div><div><div><span>===========================================<br>
Dr. Helvi Witek<br></span></div><span>Royal Society University Research Fellow<br></span></div><span>Theoretical Particle Physics and Cosmology <br></span></div><div><span>Department of Physics<br></span></div><span>King's College London</span></span><span></span><br><span></span><span><span></span></span><span><div><div><div><div><span>
===========================================</span></div></div></div></div></span></div></div></div></div></div>
<br><div class="gmail_quote">On Mon, Jun 25, 2018 at 3:22 PM, Bishop Mongwane <span dir="ltr"><<a href="mailto:astrobish@gmail.com" target="_blank">astrobish@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>Hi all,</div><div><br></div><div>I'll be talking mostly from these 2 papers:</div><div><br></div><div>-> <a href="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" target="_blank">https://arxiv.org/abs/1610.<wbr>07224</a></div><div>-> <a href="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" target="_blank">https://arxiv.org/abs/1707.<wbr>05757</a></div><div><br></div><div>See you in a moment.</div><div><br></div><div><br></div><div>Cheers,</div><div>Bishop<br></div></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Mon, Jun 25, 2018 at 11:31 AM, helvi witek <span dir="ltr"><<a href="mailto:helvi.witek@kcl.ac.uk" target="_blank">helvi.witek@kcl.ac.uk</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><div dir="ltr"><div><div><div><div>Dear all,<br></div><div><br></div><div>this is a reminder for today's call at 4:30pm (BST, i.e. UK/Portugal) / 5:30pm (CDT).<br></div></div><span>You can attend the meeting via the google hangout:<br><a href="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" class="m_9043144916800266214m_8838193773649786440gmail-m_-6448806102055406978gmail-m_-375831684634530944gmail-m_-5795550683140244530external m_9043144916800266214m_8838193773649786440gmail-m_-6448806102055406978gmail-m_-375831684634530944gmail-m_-5795550683140244530gmail-free" title="https://hangouts.google.com/hangouts/_/tce4j4gzcfcormnadoauiqcvg4e" rel="nofollow" target="_blank">https://hangouts.google.com/ha<wbr>ngouts/_/tce4j4gzcfcormnadoaui<wbr>qcvg4e</a><div><span class="m_9043144916800266214m_8838193773649786440gmail-m_-6448806102055406978gmail-m_-375831684634530944gmail-m_-5795550683140244530gmail-im"><div><br></div><div>Bishop Mongwane will discuss his work on "3+1 formulation of and hyperbolicity in $f(R)$ theories".</div><div><br><div>If you have any further suggestions for topics to be discussed in the meeting, please add them to the meeting agenda:</div><div><a href="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" target="_blank">https://docs.einsteintoolkit.o<wbr>rg/et-docs/Cosmology_and_Parti<wbr>cles</a></div></div></span></div>or reply to this email if you also have difficulties to edit the wiki.<br><br></span></div>Best wishes,<br></div>Helvi<br></div><div class="gmail_extra"><span><br clear="all"><div><div class="m_9043144916800266214m_8838193773649786440gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><span><div><div><div><span>==============================<wbr>=============<br>
Dr. Helvi Witek<br></span></div><span>Royal Society University Research Fellow<br></span></div><span>Theoretical Particle Physics and Cosmology <br></span></div><div><span>Department of Physics<br></span></div><span>King's College London</span></span><span></span><br><span></span><span><span></span></span><span><div><div><div><div><span>
==============================<wbr>=============</span></div></div></div></div></span></div></div></div></div></div>
<br></span><div><div class="m_9043144916800266214h5"><div class="gmail_quote">On Mon, Jun 18, 2018 at 6:32 PM, helvi witek <span dir="ltr"><<a href="mailto:helvi.witek@kcl.ac.uk" target="_blank">helvi.witek@kcl.ac.uk</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div>Dear all,<br></div><div><br></div><div>please consider joining our working group call next Monday, 25 June 2018, at 4:30pm (BST, i.e. UK/Portugal) / 5:30pm (CDT).<br></div></div>You can attend the meeting via the google hangout:<br><a href="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" class="m_9043144916800266214m_8838193773649786440m_-6448806102055406978gmail-m_-375831684634530944gmail-m_-5795550683140244530external m_9043144916800266214m_8838193773649786440m_-6448806102055406978gmail-m_-375831684634530944gmail-m_-5795550683140244530gmail-free" title="https://hangouts.google.com/hangouts/_/tce4j4gzcfcormnadoauiqcvg4e" rel="nofollow" target="_blank">https://hangouts.google.com/ha<wbr>ngouts/_/tce4j4gzcfcormnadoaui<wbr>qcvg4e</a><div><span class="m_9043144916800266214m_8838193773649786440m_-6448806102055406978gmail-m_-375831684634530944gmail-m_-5795550683140244530gmail-im"><div><br></div><div>Bishop Mongwane will discuss his work on "3+1 formulation of and hyperbolicity in $f(R)$ theories".</div><div><br><div>If you have any further suggestions for topics to be discussed in the meeting, please add them to the meeting agenda:</div><div><a href="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" target="_blank">https://docs.einsteintoolkit.o<wbr>rg/et-docs/Cosmology_and_Parti<wbr>cles</a></div></div></span></div><div>or reply to this email if you also have difficulties to edit the wiki.<br></div><div><br></div><div>cheers,</div>Helvi<div><div class="m_9043144916800266214m_8838193773649786440m_-6448806102055406978gmail_signature"><div dir="ltr"><div><div dir="ltr"><span><div><div><div><span>==============================<wbr>=============<br>
Dr. Helvi Witek<br></span></div><span>Royal Society University Research Fellow<br></span></div><span>Theoretical Particle Physics and Cosmology <br></span></div><div><span>Department of Physics<br></span></div><span>King's College London</span></span><span></span><br><span></span><span><span></span></span><span><div><div><div><div><span>
==============================<wbr>=============</span></div></div></div></div></span></div></div></div></div></div>
<div dir="ltr"><br></div></div>
</blockquote></div><br></div></div></div>
<br></div></div>______________________________<wbr>_________________<br>
Cosmoparticle-wg mailing list<br>
<a href="mailto:Cosmoparticle-wg@einsteintoolkit.org" target="_blank">Cosmoparticle-wg@einsteintoolk<wbr>it.org</a><br>
<a href="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" rel="noreferrer" target="_blank">http://lists.einsteintoolkit.o<wbr>rg/mailman/listinfo/cosmoparti<wbr>cle-wg</a><br>
<br></blockquote></div><span class="HOEnZb"><font color="#888888"><br><br clear="all"><br>-- <br><div class="m_9043144916800266214gmail_signature" data-smartmail="gmail_signature"><br><br><br><div style="text-align:center">.. with two they covered their face, with two they covered their feet, <br>with two they did fly and one cried unto the other<br>`Masina, masina, masina'<br></div><br></div>
</font></span></div>
</blockquote></div><br></div>