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Perspectives in string theory?
L.Bonora
SISSA,Trieste, Italy
Belgrade, September 2012
Prologue
We have good reasons to believe that there is ‘life’ beyond the standard model:
• dark energy
• dark matter
• inflation
• neutrino mass
• theoretical arguments….
What is beyond the SM?
• Grand unification• Supersymmetry• Supergravity / quantum gravity........... but certainly a renormalizable gauge field theory,
which means UV completeness
- and then ..... superstring theory which offers quantum gravity and UV compleness
….but what string theory?
• At present there are superstring / M-theory in 10/11 D. These theories are formulated perturbatively
• These theories are connected by s- and t-dualities
• There is no unique formulation.
A complete string theory can only be a string field theory
• We have Open Bosonic String Field Theory (à la Witten). It works
• Closed Bosonic SFT (not a field theory)
• Superstring FT’s (incomplete)
Summary
Review of SFT Exact solutions Dp-brane solutions Open-closed duality Prospects: fermions, supersymmetry (based on work done in collaboration with S.Giaccari,
C.Maccaferri, D.D.Tolla)
z z
Prospects
and
Conjectures
Open-closed string duality
D-branes can be expressed in terms of open strings (background independence)
Perturbative closed string states are they limits of S-branes?
Is there a unique string theory, rather than two?
Closed ST does not seem to be a field theory.
Is open SFT the fundamental theory?
Open SFT fundamental?
• It is unstable – is this important?
• It has a tachyon , perhaps two – so what?
• It does not contain gravity – gravity is effective
• It doesn’t contain fermions – this is worrying but not tragic, because….
D=26 or D=10 ?
• 26 = 10 + 16
• Fermions from bosons (old idea)
• Fermions exact solutions of bosonic SFT
• Susy as enhanced symmetry
• SSFT as effective theory of bosonic SFT
• Re-design the landscape….
THANKS