Tuesday, April 17, 2007

Probabilities of various theories: fundamental physics

This is the first set of estimates what are the probabilities that various theories are correct. The precise numbers don't mean much - the *exact* answer is actually either 0% or 100% in each case, nothing in between - but they may express a kind of "qualified guess". Everyone can add entries and/or comment on (vastly) different estimates of various numbers below. Let me start with fundamental physics.
  • 99.9999% - The Standard Model is a perturbatively consistent quantum theory, from a mathematics viewpoint
  • 99.9995% - Pure QCD is a non-perturbatively consistent quantum theory
  • 99.999% - String theory is a mathematically consistent theory including quantum gravity, even non-perturbatively, at least in some highly supersymmetric vacua
  • 99.999% - General relativity correctly predicts phenomena such as frame dragging and classical gravitational waves in the real world, at reasonable distance and other scales
  • 99.995% - Black holes exist
  • 99.99% - The Standard Model with neutrino masses is the correct description for all interactions of currently known particles in particle physics below 100 GeV with errors that can be parameterized as small corrections
  • 99.99% - The semiclassical approach to general relativity is correct and its predictions such as the black hole entropy and the existence of gravitons and similar concepts may in principle be verified




  • 99.95% - String theory in principle allows one to calculate properties of a supersymmetry-breaking semirealistic vacuum arbitrarily accurately
  • 99.9% - The Big Bang, an expansion of the Universe from a very small size and huge density, is a correct description of its history, at least from the age of one minute or so
  • 99.5% - The LHC will find a Higgs boson, elementary, composite, or otherwise - neutral, charged SUSY, or any other boson of this type
  • 99% - Evaporating neutral black holes in the real world preserve information when described by the exact correct quantum mechanical model
  • 95% - The standard model of cosmology including the cold dark matter and dark energy is correct up to small corrections - no qualitatively new large terms or concepts are necessary to explain the data
  • 90% - Inflationary cosmology is a correct effective description of an earlier era of cosmology
  • 85% - String theory is the correct unifying theory, i.e. when dust is settled, it will be clear that the same equations that describe our Universe more accurately than any other theory also imply the existence of the well-known 10-dimensional and 11-dimensional vacua
  • 70% - Supersymmetry exists at the GUT scale or lower
  • 60% - At very high energy scales, a GUT theory with unified gauge interactions becomes more natural zeroth approximation: GUT is correct
  • 50% - Supersymmetry will be found at the LHC
  • 40% - The Hartle-Hawking wavefunction or its generalization that will require the author(s) to cite Hartle and Hawking correctly predicts non-trivial features of the initial conditions of the Universe
  • 35% - Eternal inflation can either be rigorously proven to be necessary from a complete theory, or it will lead to correct and verifiable quantitative predictions
  • 30% - New elementary fermions or Z' gauge bosons will be identified below the TeV scale
  • 20% - The anthropic selection will remain the only constraint on the value of the cosmological constant that will be accessible to theorists by 2100
  • 15% - Cosmic strings exist and will be observed or produced by 2100
  • 10% - The Higgs sector is described by a theory capturing the main ideas of the little Higgs theories and its variations
  • 5% - Light axions exist and are responsible for some phenomena observed by 2100
  • 2% - Features of the Randall-Sundrum warped geometry will be detected by the LHC or the following collider
  • 2% - The acceleration of the Universe or the Pioneer anomaly or similar observable effects may be explained by a dramatic modification of general relativity at very long distances comparable to the Hubble scale, or very small accelerations at the same scale
  • 1% - Some predictions of old large dimensions by ADD will be experimentally supported in the next 20 years
  • 0.5% - Noncommutative geometry constructions at the level qualitatively not exceeding Alain Connes' existing papers can tell us something correct about particle physics that doesn't follow from effective field theory
  • 0.2% - The LHC will produce evaporating black holes
  • 0.2% - The LHC will produce excited string modes with a clear stringy pattern
  • 0.1% - A model of cyclic or ekpyrotic Universe will be experimentally shown much more correct than any inflation-based cosmological model in the next 100 years
  • 0.05% - New unknown light neutrino flavors exist
  • 0.02% - Torsion or similar tensors generalizing minimal general relativity that seem unnatural from a particle physics perspective is physically relevant for our Universe
  • 0.01% - Quasinormal modes "know" about characteristic quantum-gravitational phenomena that are not seen semiclassically
  • 0.005% - Locality is violated more than by small higher-dimensional operators or exponentially tiny correlations associated with Hawking evaporation
  • 0.002% - A discrete model without a continuum limit is strictly more fundamental and accurate a description of the world than any continuous model
  • 0.002% - A model that studies quantum gravity separately from other sources and assumes that nothing beyond pure gravity exists will lead to true and valuable insights about the workings of the real world by 2100
  • 0.001% - Doubly special relativity is a refinement of special relativity that becomes much more accurate in a wide class of phenomena
  • 0.0005% - Basic postulates of quantum mechanics such as superposition principle and the method to obtain probabilities as squared amplitudes will be modified and the extension will describe a class of phenomena much more accurately than orthodox quantum mechanics
  • 0.0002% - Loop quantum gravity is able to describe physics whose low-energy limit is general relativity while avoiding an infinite number of fine-tunings
  • 0.0001% - Loop quantum gravity, with the metric as the only and well-defined degree of freedom and with quantized area, is a correct description of gravity in the real world at the Planck scale
  • 0.000001% - One of the ESP phenomena measured in the Princeton lab actually exists and can be measured again with a similar equipment
If you carefully negate the sentences and subtract the numbers from 100%, you get new estimates. ;-)

See also climate change probabilities.

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