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The World of Physics: Constituents

1. The particle zoo: In the 1950s, in experiments more and more kinds of 'elementary' particles were observed. At the beginning of the 1960s, one had discovered 200 of them. [bdw 5/2004]
2. A hypothesis: To get order into the particle zoo, Murray Gell-Mann (CalTec, Pasadena, USA) and Georg Zweig (Los Alamos Nat. Lab., USA) suggested that protons and neutrons are in fact not elementary and hypothesized quarks as their components (Up, Down, and Strange). [bdw 5/2004]
3. Non-elementarity: 1968, collision experiments at the Stanford Linear Collider (Califorina, USA) showed that protons must have an innner structure. [bdw 5/2004]
4. The "November revolution": 1974, experiments at the Stanford Linear Collider and at Brookhaven Nat. Lab. (USA) showed that there must be another quark, called Charm [shortly after it was predicted by Sheldon Glashow (Harward Univ, USA)] [bdw 5/2004]
5. 1979. Gluon - carrier of strong interaction between quarks discovered in PETRA ring at DESY (Hamburg, Germany). [bdw 5/2004]
...
6. 1995. Experiments at Fermilab (Chicago, USA) produced the Top quark (after it was predicted from the standard model and several phenomena had shown hints of it).
6. 2002. The neutrino observatory in Sudbury (Canada) confirms the explanation for the missing sun neutrio problem: The sun's emitted neutrinos oszillate between the three neutrino kinds. This oszillation presupposes that neutrinos are not completely mass-less. [bdw 4/2005]
7. 2003. After 30 years of searching, pentaquarks are first produced in Japan [bdw 10/2003]

 

OPEN QUESTION: The Great Unifying Theory (GUT): unify quantum theory and relativity theory in one theory
(a) Strings / Branes
  • Bring order into the lepton zoo: Are all the 24+ types of lepton really elementary or are they manifestations of different oszillations of 1 type of more basic strings in 9D-space or of branes in 10D-space? [bdw 5/2004]
  • Enable the quanted explanation of gravitation [bdw 4/2005]

    1 string idea/theory - 5 string models/theories (with 9D-space) - can be explained as different facets of one M-theory (with 10D-space) [bdw 4/2005]

    		•      (b) Quantum-geometry
    (eg. Martin Bojowald, Max-Planck Institute, Potsdam)
  • Focus on the quanted explanation of gravitation.

    Quantificates spacetime: There are smallest spatial and temporal distances!

    • :
    :
    Leptons - the elementary physical objects (in the current standard model):

  • The building stones of matter [subject to Pauli principle -> they are Fermions]
    • 2×6 quarks
    [subject to strong interaction
    - the reason why we never observe an isolated quark?]     		2×3 neutrinos
    (the neutral leptons)
    [subject to weak interaction]     		2×3 charged leptons
    [subject to el-mag force]     		 
    Up [+2/3]   Down [-1/3]
    anti-Up   anti-Down
    e-neutrino
    anti-e-neutrino
    electron [-1]
    positron [+1]
    		 
    Strange   Charm (1974)
    anti-Strange   anti-Charm
    μ-neutrino
    anti-μ-neutrino
    myon
    anti-myon
    		 
    Bottom   Top (1995)
    anti-Bottom   anti-Top
    τ-neutrino
    anti-τ-neutrino
    tauon
    anti-tauon
    		 
  • The carriers (exchange particles) of the quanted forces between fermions [not subject to Pauli principle -> they are Bosons]
    Quantication - and thus integration in quantum theory - of the first three forces works well; only gravitation resists. String theory[^] is an attempt to include it. [bdw 4/2005]
    • gluon (1979)

    strong interaction
    (keeps quarks together in hadrons, and these in nuclei)
    (name?)

    weak interaction
    (explains beta-decay, reaches no further than 1/100 of proton diameter)
    photon?

    el.-mag. force
    (explains electrical attraction/repulsion between charged particals, and magnetic field established by moving charged particles [different views of the same by relativity])
    graviton
    - not found yet!

    gravitation
    Hadrons - composites of quarks held together by strong interaction (gluons)
    OPEN QUESTION: Where does all the mass in the universe come from?

    The concordance model:
  		• normal (ie. baryonic) matter: 5%
  		• dark matter: 25% - but what is it?
  		• dark energy: 70% - but what is it?

    ... some bosons [but are they mesons?]:
    hyperon   pion   kaon
    W-boson   Z-boson

    OPEN QUESTION: How does mass work?
    Peter Higgs: Particles get mass through the Higgs field that slows them down
    (more or less, dep. on ... - their mass?)
    Higgs field is created by:
    Higgs-Boson
    - has itself a "mass" of estimated 117GeV (earlier estimate was 96GeV) - to produce it, one needs more than Genevea's 114GeV collider [bdw 4/2005]

    Higgs field
  • Mesons - made of a quark and an anti-quark (plus quantum soup)
    [not subject to Pauli principle -> they are Bosons]
    K+-meson   ...
  • Baryons - made of 3 quarks (plus quantum soup)
    [subject to Pauli principle -> they are Fermions]
    proton [1]
    Up
    [+2/3]     		Up
    [+2/3]     		Down
    [-1/3]
    		  neutron [0]
    Up
    [+2/3]     		Down
    [-1/3]     		Down
    [-1/3]
    		• Somehow related to weak interaction:
  • Beta decay: neutron --> proton + electron + anti-[e?]-neutrino
         [does this mean Up --> Down + electron + anti-[e?]-neutrino ???]
  • inverse Beta decay: proton + electron --> neutron + neutrino [which neutrino?]
  • Pentaquarks - made of 5 quarks [Bild der Wissenschaft 10 2003]
    pentaquark (2003)
    Up Up Down Down anti-Strange
    		• neutrons + hi-energy gamma rays
    --> pentaquark (stable for 10-20 sec)
    --> neutron + K+-meson
    Nuclei - composites of protons and neutrons held together by more strong interaction
    nucleus [element:n, isotop:n+m]
    n × proton [1] m × neutron [1]
    Composites of nuclei and electrons held together by electro-magentic force
    atom [ionization:n+n', element:n, isotop:n+m]
    nucleus [n, n+m] n' × electron [-1]
    		 
    Bose-Einstein condensate
    - a cloud of gas atoms cooled down to fractions of degrees above 0K (up to several micrometer in size)
    - behaves like one large atom [bdw 4/2005]

    Through an "optical lattice" formed by light waves, the atoms can be arranged regularly in space, like atoms in a crystal (the BE-c becomes a Mott-isolator). [bdw 4/2005]

    OPEN QUESTION: How does the "decoherence" from non-deterministic, quantum state of microscopic objects to deterministic, classical state of macroscopic objects work? Where exactly is the boundary?

    		 
    metal
    [ionization:(Sum ni)+n']
    combined from metal atoms
    N × nucleus
    [ni, ni+mi]
    n' × electron [-1]

    OPEN QUESTION: How do "memory metals" work?

    OPEN QUESTION: How does super-conductivity work?
    - in ultra-cold metals (-269C) discovered 1911, or "high temp." sup.-cond. in ceramics discovered 1986 (-196C)

    Ionized atoms held together by el-mag force
    molecule
    N × atom [ni, ni+mi]
    		 
    crystal
    N × atom [ni, ni+mi]
    BUT: ice crystal
    = crystal made of H2O molecules?
    micro-cosmos
    |
    |
    meso-cosmos
    |
    ...
    |
    macro-cosmos
    Composites of (otherwise held-together) parts with mass held together by gravitation
    celestrial body
    ...

       planetary system
    planet n × moon
    		   solar system
    N × star n × planetary system m × planetoids, asteroids, comets

       galaxy
    N × solar system interstelar dust
    		   galaxy cluster
    N × galaxy dark matter

     
    Sources: Bild der Wissenschaft 4/2005, 5/2004, 10/2003. Spektrum der Wissenschaft March 2004.
    Location: http://www.cs.mun.ca/~ulf/two/phy.html © Ulf Schünemann; ulf@cs.mun.ca; 180604, 120505