相关论文: Cosmological unification of string theories

We derive a class of solutions to the string sigma-model equations for the closed bosonic string. The tachyon field is taken to form a constant condensate and the beta-function equations at one-loop level are solved for the evolution of the…

We propose a refinement of the physical picture describing different vacua in bosonic string theory. The vacua with closed strings and open strings are connected by the string field theory version of the Higgs mechanism, generalizing the…

Cosmic (super)strings offer promising ways to test ideas about the early universe and physics at high energies. While in field theory constructions their tension is usually assumed to be constant (or at most slowly-varying), this is often…

String theories with (N,N') local world-sheet supersymmetries are related to each other by marginal deformations. This connects N=1 and N=0 theories in which the target-spaces are interpreted as space-times, N=2 theories in which the target…

The intersection of string theory with cosmology is unavoidable in the early universe, and its exploration may shine light on both fields. In this thesis, three papers at this intersection are presented and reviewed, with the aim of…

We discuss some aspects of closed superstrings in Melvin-type magnetic backgrounds. A 2-parameter family of such NS-NS backgrounds are exactly solvable as weakly coupled string models with the spectrum containing tachyonic modes. Magnetic…

In this work we review Schnabl's construction of the tachyon vacuum solution to bosonic covariant open string field theory and the results that followed. We survey the state of the art of string field theory research preceding this…

We conjecture that the end point of bulk closed string tachyon decay at any non-zero coupling, is the annihilation of space time by Witten's bubble of nothing, resulting in a topological phase of the theory. In support of this we present a…

Special solutions of string theory in supercritical dimensions can interpolate in time between theories with different numbers of spacetime dimensions (via dimension quenching) and different amounts of worldsheet supersymmetry (via…

We discuss condensations of closed string tachyons localized in compact spaces. Time evolution of an on-shell condensation is naturally related to the worldsheet RG flow. Some explicit tachyonic compactifications of Type II string theory is…

In this thesis we investigate the microphysics of cosmic strings in non-minimal quantum field theories. In particular we consider theories in which fermion fields couple to the strings, and those with larger symmetry groups, such as grand…

We generalize recent results on tachyon condensation in boundary string field theory to the superstring.

We discuss tachyon configuration for the unoriented bosonic string theory which produces a bosonic string theory with SO(32) gauge symmetry in ten dimensions. It is closely related to the tachyon condensation scenario proposed by A. Sen. We…

We find solutions of supersymmetric string field theory that correspond to the photon marginal deformation in the boundary conformal field theory. We revisit the bosonic string marginal deformation and generate a real solution for it. We…

In some string theories, e.g. SO(32) heterotic string theory on Calabi-Yau manifolds, a massless field with a tree level potential can acquire a tachyonic mass at the one loop level, forcing us to quantize the theory around a new background…

Two of the important unresolved issues concerning fractional superstrings have been the appearance of new massive sectors whose spacetime statistics properties are unclear, and the appearance of new types of ``internal projections'' which…

The study of open string tachyon condensation in string field theory can be drastically simplified by making an appropriate choice of coordinates on the space of string fields. We show that a very natural coordinate system is suggested by…

We consider new cosmological solutions with a collapsing, an intermediate and an expanding phase. The boundary between the expanding (collapsing) phase and the intermediate phase is seen by comoving observers as a cosmological past (future)…

We study quantum corrections at the one loop level in open superstring tachyon condensation using the boundary string field theory (BSFT) method. We find that the tachyon field action has the same form as at the disc level, but with a…

In this letter we show that vacuum string field theory contains exact solutions that can be interpreted as macroscopic fundamental strings. They are formed by a condensate of infinitely many completely space-localized solutions (D0-branes).