Richard Kenway Everything is a computer Richard Kenway
May 2006Richard Kenway2 Theory of Everything TOE is unique: no free parameters – one Universe (God is a mathematician) TOE is not unique: various parameter values are allowed – a Multiverse (anthropic), or – one Universe is chosen (intelligent design) conjecture 1: our Universe is completely described by a mathematical model † † includes quantum mechanics and so does not obviously exclude consciousness, free will, time travel, …
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May 2006Richard Kenway4 objective of physics guided by mathematical beauty/symmetry falsification by experiment/observation …reverse engineering the TOE TOE today: General Relativity + Standard Model reality = TOE today 25 free parameters … unlikely to be fundamental constants –our existence is very sensitive to their values not fully quantum … gravity weird enough discrepancies with experiment → new physics = progress
May 2006Richard Kenway5 Standard Model matter, as we know it, is made of quarks and leptons interacting through four forces QCD
May 2006Richard Kenway6 u u u d unified theory … consequences all particles are manifestations of one fundamental entity → quarks can change into leptons … protons decay u u d
May 2006Richard Kenway7 do protons decay? watch 50 kton of water 1km underground (1 kton = protons) none observed
May 2006Richard Kenway8 calculating the proton lifetime if we compute the ‘QCD factor’, the experimental lifetime bound constrains theories of new physics this requires simulating how quarks and gluons make a proton u ? u
May 2006Richard Kenway9 simulation for imaginary time ~ a probability → Monte Carlo generation of quantum fields works for QCD other theories have a sign problem → the motivation for quantum computers conjecture 2: the TOE may be simulated to arbitrary precision on a computer † † may need a quantum computer … ‡ many worlds and their consequences enter here … ‡
May 2006Richard Kenway10 simulation of QCD integral over anti-commuting quarks and SU(3) gluons we cannot measure experimentally quark masses or mixings, only hadron masses and decays … reverse engineer quark masses (& mixings) + gauge coupling properties of hadrons Lattice QCD
May 2006Richard Kenway11 computational cost and parallel computing a L lattice spacing must be extrapolated to zero keeping box large enough –halving lattice spacing 500 computing speed performance number of processors Moore’s law: microprocessor speeds double every months
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May 2006Richard Kenway13 determination of Standard Model parameters depressingly self-consistent only the Higgs boson is missing
May 2006Richard Kenway14 but most of our Universe is also missing! dark energy → atoms + dark matter → atoms 4% dark matter 23% –inflaton, neutralino, axion, … dark energy 73%
May 2006Richard Kenway15 effective theories simulation bridges between short ( L ) and long scale ( L' ) computational cost of virtual reality is bounded but very large conjecture 3: reality is described by a finite set of effective theories each of which can be simulated † † beginning with the TOE
May 2006Richard Kenway16 reverse engineer our Universe today visible matter → dark matter → Millennium simulation 10,077,696,000 particles ?
May 2006Richard Kenway17 the challenge for computing Higgs boson or new physics must be found at LHC –the next layer in the onion –QCD is an effective theory will classical digital computers be sufficient? conjecture 4: everything can be simulated † † everything is a simulation? QCDOC … the last pre-LHC machine
May 2006Richard Kenway18 life, the Universe, everything… nuclei … neutron stars fusion … solar weather chemistry … designer materials complex molecules … living organisms brain … mind