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