17 open problems across every field of physics
The problem In general relativity, vacuum energy gravitates like a cosmological constant: a Lorentz-invariant vacuum has, contributing to the effective Observations (CMB, BAO, SNe…
Neutrino oscillations fix the mass-squared differences but not the absolute scale or the sign of. What are the absolute neutrino masses, is the ordering normal or inverted, and…
General relativity describes gravity as spacetime curvature, while the other interactions are described by quantum field theory. Naively quantizing the Einstein–Hilbert action…
QCD allows a CP-violating term yet the neutron electric dipole moment forces. Why is so unnaturally small? The Peccei–Quinn axion is the leading proposal, but the axion has not…
Prove that for any compact simple gauge group, a non-trivial quantum Yang–Mills theory exists on and has a mass gap. The classical Yang–Mills action describes massless gauge…
Kolmogorov's 1941 theory predicts an inertial-range energy spectrum but intermittency produces measurable deviations in the scaling exponents. Can the statistics of fully…
The measured muon anomaly has differed from some Standard Model predictions at the few-sigma level, Is the tension a signal of new physics, or an artifact of hadronic…
For the incompressible Navier–Stokes equations in three dimensions, do smooth, globally defined solutions exist for all smooth divergence-free initial data with finite energy — or…
The microscopic laws are (nearly) time-symmetric, yet entropy increases, This macroscopic arrow is usually traced to an extraordinarily low-entropy initial state of the universe…
Hawking radiation appears thermal, with temperature suggesting that a black hole formed from a pure state evaporates into a mixed state — violating unitarity. How is quantum…
Radiative corrections to the Higgs mass scale quadratically with the cutoff, so keeping against a Planck-scale cutoff requires enormous fine-tuning. Why is the electroweak scale…
Muonic-hydrogen spectroscopy measured a proton charge radius several standard deviations smaller than the older electron-scattering and hydrogen-spectroscopy values. Is the…
Galactic rotation curves stay flat, , far beyond the visible mass, and gravitational lensing plus the CMB power spectrum all point to roughly five times more non-luminous matter…
In cuprates and related materials, superconductivity survives to, far above the BCS phonon-mediated ceiling. What is the pairing mechanism that binds electrons into Cooper pairs…
Quantum field theory predicts a vacuum energy density that, cut off at the Planck scale, exceeds the observed value by up to 120 orders of magnitude — "the worst theoretical…
Unitary evolution keeps a system in superpositions, yet a measurement yields a single definite outcome with probability. What physical process — if any — selects a single outcome,…
The observed baryon-to-photon ratio is yet the Big Bang should have produced equal matter and antimatter. The Standard Model satisfies Sakharov's three conditions only far too…