page_title: List of unsolved problems in physics
section_title: Nuclear physics
hierarchical_section_title: List of unsolved problems in physics / Unsolved problems by subfield / Nuclear physics
caption_attribution_description: English: A 3-dimensional representation of the theoretical en:Island of stability in en:nuclear physics. This image was created, based on freely available data and images found on the web, intended to be concise and easily understood. See w:Talk:Island of stability #The diagram in the beginning of the article has wrong numbers in the Z(proton number) axis for discussion of the image’s factual accuracy, as well as of the SVG version.
context_page_description: Some of the major unsolved problems in physics are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result. The others are experimental, meaning that there is a difficulty in creating an experiment to test a proposed theory or investigate a phenomenon in greater detail.
  There are still some questions beyond the Standard Model of physics, such as the strong CP problem, neutrino mass, matter–antimatter asymmetry, and the nature of dark matter and dark energy. Another problem lies within the mathematical framework of the Standard Model itself—the Standard Model is inconsistent with that of general relativity, to the point that one or both theories break down under certain conditions.
context_section_description: Quantum chromodynamics: What are the phases of strongly interacting matter, and what roles do they play in the evolution of cosmos? What is the detailed partonic structure of the nucleons? What does QCD predict for the properties of strongly interacting matter? What determines the key features of QCD, and what is their relation to the nature of gravity and spacetime? Do glueballs exist? Do gluons acquire mass dynamically despite having a zero rest mass, within hadrons? Does QCD truly lack CP violations?
  Quark-gluon plasma: Where is the onset of deconfinement: 1) as a function of temperature and chemical potentials? 2) as a function of relativistic heavy-ion collision energy and system size? What is the mechanism of energy and baryon-number stopping leading to creation of quark-gluon plasma in relativistic heavy-ion collisions? Why is sudden hadronization and the statistical-hadronization model a near-to-perfect description of hadron production from quark-gluon plasma? Is quark flavor conserved in quark-gluon plasma? Are strangeness and charm in chemical equilibrium in quark-gluon plasma? Does strangeness in quark-gluon plasma flow at the same speed as up and down quark flavours? Why does deconfined matter show ideal flow?
  Strangelets: Does strange quark matter (Strangelet) exist as stable state?
  Specific models of quark-gluon plasma formation: Do gluons saturate when their occupation number is large? Do gluons form a dense system called Colour Glass Condensate? What are the signatures and evidences for the Balitsky–Fadin–Kuarev–Lipatov, Balitsky–Kovchegov, Catani–Ciafaloni–Fiorani–Marchesini evolution equations?
  Nuclei and nuclear astrophysics: Why is there a lack of convergence in estimates of the mean lifetime of a free neutron based on two separate—and increasingly precise—experimental methods? What is the nature of the nuclear force that binds protons and neutrons into stable nuclei and rare isotopes? What is the nature of exotic excitations in nuclei at the frontiers of stability and their role in stellar processes? What is the nature of neutron stars and dense nuclear matter? What is the origin of the elements in the cosmos? What are the nuclear reactions that drive stars and stellar explosions? What is the heaviest possible chemical element?
caption: The "island of stability" in the proton vs. neutron number plot for heavy nuclei
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