String theory is the only known theory that consistently unifies all four fundamental interactions: the electromagnetic, gravitational and strong and weak nuclear forces. Its consistency with quantum mechanics makes it also the leading candidate for quantum gravity theory. String theory faces two major
challenges which might be related to each other: it can allow our universe to have too many distinct physical properties (such as the masses and coupling constants of elementary particles) and therefore lack of clear experimental predictions. The second major challenge is a lack of proper non-perturbative formulation which would define the theory also in the regime of extreme quantum behavior such as at the beginning of our universe or deep within black holes.
One promising direction to address the second challenge is quantum field theoretic formulation of string theory that goes by the name of
String Field Theory. There are variants of this theory for open and closed strings and also for the simpler bosonic string and more realistic supersymmetric string. In some cases (notably closed superstring) even such a description is missing. The main goals of string field theory is to understand the classical backgrounds which present us with rather novel phenomena such as emergence of extended objects called D-branes or possibly non-smooth transitions in space-time geometry and/or topology.
Another fascinating feature of string theory which is believed to be present in any consistent quantum gravity theory is
holography. The holographic principle states roughly that the physics of quantum gravitational system can be described by degrees of freedom living on the boundary of the system only. Few explicit examples have been given and they also lead to non-perturbative definition of string theory in some regimes.
The string theory group works mostly on these two topics, but it plans to soon expand into other territories such as higher spin field theory.
Web page of the Prague string theory group:
http://www-hep2.fzu.cz/~schnabl/String_Theory_Prague.html
Important publications:
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A Simple Analytic Solution for Tachyon Condensation.
Theodore Erler, Martin Schnabl, (Prague, Inst. Phys. & Santa Barbara, KITP) . NSF-KITP-09-23, Jun 2009. 44pp.
Published in JHEP 0910:066,2009.
e-Print: arXiv:0906.0979 [hep-th]. Link
- Tachyon Vacuum in Cubic Superstring Field Theory.
Theodore Erler, (Harish-Chandra Res. Inst.) . Jul 2007. 16pp.
Published in JHEP 0801:013,2008.
e-Print: arXiv:0707.4591 [hep-th]. Link
- Proof of vanishing cohomology at the tachyon vacuum.
Ian Ellwood, (Wisconsin U., Madison) , Martin Schnabl, (CERN) . MAD-TH-06-6, CERN-PH-TH-2006-114, Jun 2006. 19pp.
Published in JHEP 0702:096,2007.
e-Print: hep-th/0606142. Link
- Analytic solution for tachyon condensation in open string field theory.
Martin Schnabl, (CERN) . CERN-PH-TH-2005-220, Nov 2005. 60pp.
Published in Adv.Theor.Math.Phys.10:433-501,2006.
e-Print: hep-th/0511286. Link
- Relating chronology protection and unitarity through holography.
Joris Raeymaekers, Dieter Van den Bleeken, Bert Vercnocke, . Nov 2009. 4pp. Temporary entry
e-Print: arXiv:0911.3893 [hep-th]. Link
- Godel space from wrapped M2-branes.
Thomas S. Levi, (British Columbia U.) , Joris Raeymaekers, (Prague, Inst. Phys.) , Dieter Van den Bleeken, (Rutgers U., Piscataway) , Walter Van Herck, (Leuven U.) , Bert Vercnocke, (Leuven U. & Harvard U., Phys. Dept.) . WITS-CTP-041, KUL-TF-09-20, Sep 2009. 37pp.
e-Print: arXiv:0909.4081 [hep-th]. Link
Researchers:
Martin Schnabl, Theodore Erler, Joris Raeymaekers, Dario Francia (from September 2010)
Student:
Matěj Kudrna
