Approaches to Quantum Gravity

226 W. Tayloror other 6D manifold. Quantum fluctuations should also allow the T 3 to containinflating regions where the energy of X is positive, and one could even imagineeternal inflation occurring in such a region, with bubbles of other vacua branchingoff to populate the string landscape. Or one could imagine some other dynamicsoccurring, demonstrating that the landscape picture is incorrect. It is impracticalwith our current understanding to implement such a computation, and presumablythe detailed physics of any inflating region of the universe would require a prohibitivenumber of degrees of freedom to describe. Nonetheless, if we can sensiblyquantize open superstring field theory, or a Closed String Field Theory, on T 9 oranother completely compact space, it may in some sense be the best-defined backgroundindependent formulation of string theory in which to grapple with issues ofcosmology.AcknowledgementsThis work was supported in part by the DOE under contract #DE-FC02-94ER40818, and in part by the Stanford Institute for Theoretical Physics (SITP).The author would also like to thank Harvard University for hospitality during partof this work. Thanks to Barton Zwiebach for helpful discussions and comments onan earlier version of this manuscript.References[1] I. Y. Arefeva, P. B. Medvedev & A. P. Zubarev, New representation for stringfield solves the consistence problem for open superstring field, Nucl. Phys.B 341 (1990) 464.[2] N. Berkovits, Review of open superstring field theory (2001) hep-th/0105230;[3] N. Berkovits, The Ramond sector of open superstring field theory, JHEP 0111(2001) 047, hep-th/0109100.[4] N. Berkovits, Y. Okawa & B. Zwiebach, WZW-like action for heterotic string fieldtheory, JHEP 0411 (2004) 038, hep-th/0409018.[5] E. Coletti, I. Sigalov & W. Taylor, Abelian and nonabelian vector field effectiveactions from string field theory, JHEP 0309 (2003) 050, hep-th/0306041.[6] E. Coletti, I. Sigalov & W. Taylor, Taming the tachyon in cubic string field theory,JHEP 0508 (2005) 104, hep-th/0505031.[7] E. Cremmer, A. Schwimmer & C. Thorn, The vertex function in Witten’sformulation of string field theory Phys. Lett. B179 (1986) 57.[8] I. Ellwood, B. Feng, Y. H. He & N. Moeller, The identity string field and thetachyon vacuum, JHEP 0107 (2001) 016, hep-th/0105024.[9] I. Ellwood, & W. Taylor, Open string field theory without open strings, Phys. Lett. B512 (2001) 181, hep-th/0103085.[10] I. Ellwood & W. Taylor, Gauge invariance and tachyon condensation in open stringfield theory (2001), hep-th/0105156.