Monday, January 3, 2022

Unsolved Physics Problems

As we begin a new year, it is helpful to consider what is on our plate, not just in one's personal and professional lives, but in the disciplines we are interested in. In physics, these include the following. 

* Determine the seven Standard Model parameters related to neutrinos with greater precision (especially the neutrino masses and the CP violating parameter of the PMNS matrix).

* Rule out non-standard interactions and sterile neutrino hypotheses further.

* Determine how neutrino mass arises (Majorana, Dirac, other, and in any scenario, how this happens).

* Determine how to determine the entire hadron spectrum from first principles, especially scalar mesons, axial vector mesons, and hadrons with four or more valance quarks.

* Are free glueballs possible?

* Determine if there are any relatively stable hadrons other than protons and bound neutrons (some people have suggested that there may be such a hexaquark, but most are skeptical of this possibility).

* Determine if there is a hypothetical upper limit to the scale of hadrons beyond which there is not sufficient energy to bind additional quarks.

* Determine if lepton universality is a correct Standard Model law of physics, and if not, to develop a phenomenological understanding of the deviations from it and the mechanism behind that deviation.

* Do the sphaleron interactions of the Standard Model actually happen?

* Is the value of the QCD coupling constant zero or non-zero in the limit of zero momentum transfer?

* Determine which of the leading predictions for the anomalous magnetic moment of the muon (muon g-2) is closest to being correct.

* Determine the source of dark matter phenomena (probably some subtle tweak to the laws of gravity)

* Determine the magnitude and source of dark energy phenomena (probably the laws of gravity combined with understated uncertainty in measurements of it)

* Resolve the Hubble tension or determine that it arises from new physics.

* Determine if the LP & C relationship, that the sum of the squares of the fundamental particle masses in the Standard Model is equal to the Higgs vacuum expectation value continues to hold at greater precision.

* Determine if Koide's rule for charged leptons continues to hold true.

* Identify better phenomenological relationships between the Standard Model experimentally measured parameters.

* Determine with greater precision, all Standard Model experimentally measured physical parameters.

* Determine how gravity affects the high energy running of the parameters of the Standard Model.

* Improve the precision with which we known Newton's constant "G".

* Better develop means of calculating Standard Model physics parameters that do not rely on infinite series approximations.

* Determine if there are aspects of string theory that can be salvaged in the absence of supersymmetry and supergravity.

* Bring about greater recognition that the LambdaCDM Standard Model of Cosmology is beyond salvaging.

* Better determine the critical maximum mass of a neutron star without turning into a black hole with greater precision, both theoretically and observationally, and in so doing, determine more about whether neutron stars contain matter other than ordinary but highly compressed neutrons.

* Determine if Planet 9 exists in our solar system, and if so, where it is and what properties it has.

* Determine if four neutron resonances (basically element-0) can be created in laboratories and exist briefly (two, three and five neutron resonances cannot be created in this way).

* Precisely what triggers wave function collapse?

* Is gravity quantum or classical? Is a quantum gravity transmitted by a carrier boson or a function of the discreteness of space-time?

* Is entanglement really a non-local phenomena? Is physics causal?


websterling said...

In the last point, should neutrino actually be neutron?

andrew said...

Thanks for catching the error. Fixed.

neo said...

four-neutron bound state could explain third peak in the cmb?

andrew said...

Very unlikely. Even if it was "stable" it would have a mean lifetime on the order of less than two minutes, due to beta decay of neutrons which a four neutron bound state would not mitigate the way that an atom with a mix of protons and neutrons in a bound nucleus does.

neo said...

how much time did the third peak in the cmb take ?

neo said...

this may be of interest on the JWST Primordial black holes at high redshift

The James Webb telescope’s mission will be to find the first galaxies that formed in the early universe and see stars forming planetary systems.

Best of all, the existence of primordial black holes can be proven—or disproven—in the near future, courtesy of the James Webb Space Telescope and ESA’s Laser Interferometer Space Antenna (LISA) mission announced for the 2030s.

If dark matter is comprised of primordial black holes, more stars and galaxies would have formed around them in the early universe—precisely the epoch that the James Webb telescope will be able to see.

could dark matter is comprised of primordial black holes and MOND both be correct ?

andrew said...

"how much time did the third peak in the cmb take ?"

10-17 million years.

"could dark matter is comprised of primordial black holes and MOND both be correct?"

No. The PBH distribution couldn't possibly be correct in that combination (i.e. there is no way that PBH's could be so highly concentrated in clusters). Also, PBH's are already all but ruled out.