Superstring theoryをめぐって(放談室)

http://cds.cern.ch/record/570429/files/0207130.pdf

The pre-big bang scenario in string cosmology

I review various aspects of the pre-big-bang scenario and of its main open problems, with emphasis on the role played by the dilaton Since the dilaton is a compelling consequence of string theory, tests of this scenario are direct tests of string theory and also, more generally, of Planck scale physics

Phenomenological aspects of the pre-big-bang scenario in string cosmology

Aspects of superstring cosmology are reviewed with an emphasis on the cosmological implications of duality symmetries in the theory The string effective actions are summarized and toroidal compactification to four dimensions reviewed Global symmetries that arise in the compactification are discussed and the duality relationships between the string effective actions are then highlighted Higher-dimensional Kasner cosmologies are presented and interpreted in both string and Einstein frames, and then given in dimensionally reduced forms String cosmologies containing both non-trivial Neveu-Schwarz/Neveu-Schwarz and Ramond-Ramond fields are derived by employing the global symmetries of the effective actions Anisotropic and inhomogeneous cosmologies in four-dimensions are also developed The review concludes with a detailed analysis of the pre-big bang inflationary scenario The generation of primordial spectra of cosmological perturbations in such a scenario is discussed Possible future directions offered in the Horava-Witten theory are outlined

Superstring Cosmology

The Calculus of many instantons

We consider M-theory on compact spaces of G2 holonomy constructed as orbifolds of the form (CY × S1)/2 with fixed point set Σ on the CY. This describes = 1 SU(2) gauge theories with b1(Σ) chiral multiplets in the adjoint. For b1 = 0, it generalizes to compact manifolds the study of the phase transition from the non-abelian to the confining phase through geometrical S3 flops. For b1 = 1, the non-abelian and Coulomb phases are realized, where the latter arises by desingularization of the fixed point set, while an S2 × S1 flop occurs. In addition, an extremal transition between G2 spaces can take place at conifold points of the CY moduli space where unoriented membranes wrapped on 1 and 2 become massless.

Phases of supersymmetric gauge theories from M theory on G(2) manifolds

We discuss higher derivative interactions in the type IIB superstring in ten dimensions. From the fundamental string point of view, the non-perturbative corrections are due to D-instantons. We argue that they can alternatively be understood as arising from $(p,q)$-strings. We derive a non-renormalization theorem for eight-derivative bosonic interactions, which states that terms involving either NS-NS or R-R fields occur at tree-level and one-loop only. By using the $SL(2, Z)$ symmetry of M-theory on $T^2$, we show that in order for the possible $R^{3m+1} (m=1,2,...)$ interactions in M-theory to have a consistent perturbative expansion in nine dimensions, $m$ must be odd. Thus, only $R^{6N+4} (N=0,1,...)$ terms can be present in M-theory and their string theory counterparts arise at $N$ and $2N+1$ loops. Finally, we treat an example of fermionic term.

D-Instanton Corrections as (p,q)-String Effects and Non-Renormalization Theorems

O(d, d) symmetry in quantum cosmology

Non-abelian duality for open strings

We consider M-theory on compact spaces of G_2 holonomy constructed as orbifolds of the form (CY x S^1)/Z_2 with fixed point set \Sigma on the CY. This describes N=1 SU(2) gauge theories with b_1(\Sigma) chiral multiplets in the adjoint. For b_1=0, it generalizes to compact manifolds the study of the phase transition from the non-Abelian to the confining phase through geometrical S^3 flops. For b_1=1, the non-Abelian and Coulomb phases are realized, where the latter arises by desingularization of the fixed point set, while an S^2 x S^1 flop occurs. In addition, an extremal transition between G_2 spaces can take place at conifold points of the CY moduli space where unoriented membranes wrapped on CP^1 and RP^2 become massless.

Alexandros A. Kehagias

Papers

Phases of supersymmetric gauge theories from M theory on G(2) manifolds

D-Instanton Corrections as (p,q)-String Effects and Non-Renormalization Theorems

O(d, d) symmetry in quantum cosmology

Non-abelian duality for open strings

Phases of supersymmetric gauge theories from M-theory on G_2 manifolds