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<p class="MsoNormal">Dear Physical Sciences Division member,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We wish to invite you to attend two special seminars next week. Dates, times, titles, and abstracts are below for your information.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We hope to see you there!<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-CA">****<o:p></o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-CA">Monday, 29 March 2021, at 10 am<o:p></o:p></span></b></p>
<p class="MsoNormal"><span lang="EN-CA">Ragnar Stroberg (U Washington)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA">Title: Are you sure? The quest for error bars in nuclear theory<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA">Abstract: Perhaps the greatest benefit of the recent advances in ab initio nuclear theory is the possibility to make predictions with meaningful uncertainties. This is especially valuable for quantities that are difficult
or impossible to access experimentally, such as those that arise in astrophysics or in searches for physics beyond the standard model. However, just because uncertainty quantification is possible does not mean that it is easy. In many cases, converged ab initio
calculations of the quantities of interest, in the nuclei of interest, have only recently been achieved and efforts at rigorous uncertainty quantification are still in early stages. I will discuss some developments which enabled the ab initio calculations
to be done at all and some initial efforts to make good on the promise of error bars for nuclei.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA"><a href="https://ca01web.zoom.us/j/66543046629?pwd=aVh4aWs4ZjlxOUFPOGhVNWVoM3Fxdz09">https://ca01web.zoom.us/j/66543046629?pwd=aVh4aWs4ZjlxOUFPOGhVNWVoM3Fxdz09</a><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA"> <o:p></o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-CA">Wednesday, 31 March 2021, at 10 am<o:p></o:p></span></b></p>
<p class="MsoNormal"><span lang="EN-CA">Gaute Hagen (ORNL)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA">Title: Advances in ab initio computations of nuclei<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA">Abstract:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA">High performance computing, machine learning techniques, many-body methods with polynomial scaling, and ideas from effective-field-theory have revolutionized computations of nuclei. In addition, with a lot of interest
and funding coming from industry and research institutions, fault tolerant quantum computers could potentially transform the way ab-initio computations are performed in the future. Here I report on recent advances in ab-initio coupled-cluster computations
of nuclei starting from chiral Hamiltonians with two- and three-nucleon forces. Using state-of-the-art ab-initio methods we addressed a 50-year old quenching puzzle of β-decays in nuclei [1]. Performing a systematic study of this decay in light and medium-mass
nuclei including the heavy nucleus 100Sn, we showed that this quenching can be explained by a proper treatment of two-body currents and many-body correlations. Continuing along these lines we have computed the neutrino-less double-beta decay in 48Ca [2]. We
found a relatively small matrix element for the neutrino-less double-beta decay, while the two-neutrino matrix element is consistent with data. I will also show predictions for radii and binding energies of exotic neon and magnesium isotopes using a deformed
coupled-cluster approach with chiral interactions with delta degrees of freedom [3]. Using this approach, we provided support for the discovery of a two-neutron halo in 29F [4], and recent charge radii measurements in neutron-rich potassium isotopes [5]. The
measurements challenge ab initio theory and the magic character of the neutron shell closures at N = 20 and N = 32. Last, but not least, I will present a new method that emulates exact coupled-cluster computations and allows for the computation of nuclear
properties for millions of different model parameters in less than one hour on a standard laptop, once the emulator is trained. The equivalent set of ab-initio coupled-cluster computations would require about 20 years. This speedup enables statistical computing
of the chiral nuclear Hamiltonian, and entirely new ways to use experimental data across the nuclear chart to generate new knowledge about the strong nuclear interaction [6].<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA">[1] P. Gysbers, et al, Nature Physics 15, 428–431 (2019)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA">[2] S. J. Novario, et al., arXiv:2008.09696 (2020)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA">[3] S. J. Novario, et al., Phys. Rev. C 102, 051303(R) (2020)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA">[4] S. Bagchi, et al., Phys. Rev. Lett. 124, 222504 (2020)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA">[5] Á. Koszorús, et al., Nature Physics, Open Access (2021)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA">[6] A. Ekström and G. Hagen, Phys. Rev. Lett. 123, 252501 (2019)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA"><a href="https://ca01web.zoom.us/j/67452392983?pwd=T1AzSVlmSFoxL25wRjFlaTdNV0wrQT09">https://ca01web.zoom.us/j/67452392983?pwd=T1AzSVlmSFoxL25wRjFlaTdNV0wrQT09</a><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA">****<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b><span style="font-family:"HelveticaNeueLT Pro 55 Roman",sans-serif">Allayne McGowan<o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"HelveticaNeueLT Pro 55 Roman",sans-serif">Administrative Assistant – Physical Sciences Division<br>
Assistant to Dr. Jens Dilling – Associate Laboratory Director<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"HelveticaNeueLT Pro 55 Roman",sans-serif">t 604-222-7438<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"HelveticaNeueLT Pro 55 Roman",sans-serif"><a href="mailto:amcgowan@triumf.ca">amcgowan@triumf.ca</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"HelveticaNeueLT Pro 55 Roman",sans-serif"><a href="mailto:sciencediv@triumf.ca">sciencediv@triumf.ca</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"HelveticaNeueLT Pro 55 Roman",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"HelveticaNeueLT Pro 55 Roman",sans-serif;color:#00B0F0">TRIUMF</span></b><span style="font-size:10.0pt;font-family:"HelveticaNeueLT Pro 55 Roman",sans-serif;color:#00B0F0"> Canada’s particle
accelerator centre<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"HelveticaNeueLT Pro 55 Roman",sans-serif"><a href="http://www.triumf.ca/">www.triumf.ca</a> @TRIUMFLab<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"HelveticaNeueLT Pro 55 Roman",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"HelveticaNeueLT Pro 55 Roman",sans-serif">4004 Wesbrook Mall<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"HelveticaNeueLT Pro 55 Roman",sans-serif">Vancouver, BC V6T 2A3<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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