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I think your comment is far behind the times. Directly from QCD we have: computed the low-lying parts of hadronic spectrum, computed the proton-neutron mass sp
by evanb 4y ago
I think your comment is far behind the times. Directly from QCD we have: computed the low-lying parts of hadronic spectrum, computed the proton-neutron mass splitting, made _pre_dictions about hadronic masses that were then found at the LHC, computed the nucleon axial coupling g_A, vacuum polarization and light-by-light, and so on. It requires supercomputers. But so what? Nobody promised that physics should be easy.
We know how to match our effective field theory of protons and neutrons in nuclei to QCD observables. This project has been under way for 20 years. Expect major breakthroughs as the exascale machines mature. If we match our EFTs to QCD calculations then there would be no additional parameters fit to data, and our intellectual edifice will have quantitative predictivity from fundamental particles to neutron stars. It's hard. Nobody promised that physics should be easy.
- deleted 4y ago[deleted]
- adrian_b 4y agoThe values that you mention, e.g. the proton-neutron mass splitting, have been computed only with a precision much lower than such values can be measured experimentally. That means that such computations have little, if any, practical importance. With the current QCD, it is not possible to compute the ratio between the mass of the neutron and the mass of a proton with a useful precision. The mass ratio between the proton and the electron or the mass ratios between light nuclei or their magnetic moments are even less possible to compute. QCD would become a useful theory only when it would be possible to compute things like the probability of fusion of light nuclei with a precision good enough to eliminate the need to measure such values experimentally. QCD would need revolutionary improvements to achieve such goals. Supercomputers are not enough for a progress in this domain. Different solving methods must be discovered.
- evanb 4y agoI'll simply have to disagree. The LQCD calculation of gA, for example, provides the tightest constraint on new right-handed currents beyond the Standard Model. The issue, of course, is that without a calculation the "new physics" is already incorporated into gA. > QCD would need revolutionary improvements to achieve such goals. Make the computers 10x faster and the algorithms / libraries 10x faster and all the things you wish for are within reach. Much more plausible than _overthrowing the standard model with something that offers easier calculations_.