Solitons In String Theory Research Articles

The loop group ofE8andK-theory from 11d

We examine the conjecture that an 11d E_8 bundle, appearing in the calculation of phases in the M-Theory partition function, plays a physical role in M-Theory, focusing on consequences for the classification of string theory solitons. This leads for example to a classification of IIA solitons in terms of that of LE_8 bundles in 10d. Since K(Z,2) approximates LE_8 up to \pi_{14}, this reproduces the K-Theoretic classification of IIA D-branes while treating NSNS and RR solitons more symmetrically and providing a natural interpretation of G_0 as the central extension of LE_8.

Integrable many-body systems and gauge theories

The review studies connections between integrable many-body systems and gauge theories. It is shown how the degrees of freedom in integrable systems are related with topological degrees of freedom in gauge theories. The relations between families of integrable systems and N = 2 supersymmetric gauge theories are described. It is explained that the degrees of freedom in the many-body systems can be identified with collective coordinates of D-branes, solitons in string theory.

Microscopic recoil model for light-cone fluctuations in quantum gravity

We present a microscopic model for light-cone fluctuations in vacuo, which incorporates a treatment of quantum-gravitational recoil effects induced by energetic particles. Treating defects in space-time as solitons in string theory, we derive an energy-dependent refractive index and a stochastic spread in the arrival times of mono-energetic photons due to quantum diffusion through space-time foam, as found previously using an effective Born-Infeld action. Distant astrophysical sources provide sensitive tests of these possible quantum-gravitational phenomena.

Black holes and D-branes

Black holes have an entropy proportional to the area of the horizon. The microscopic degrees of freedom that give rise to the entropy are not visible in the classical theory. String theory, a quantum theory of gravity, provides a microscopic quantum description of the thermodynamic properties of some extremal and near extremal charged black holes. The description uses properties of some string theory solitons called D-branes. In this description, Hawking radiation emerges as a simple perturbative process. The low energy dynamics of particle absorption and emission agrees in detail with the semiclassical analysis in the thermodynamic limit. We describe here these results in some detail.

Introduction to D-Branes

D-branes are string theory solitons defined by boundary conditions on open strings that end on them. They play an important role in the non-perturbative dynamics of string theory and have found a wide range of applications. These lectures give a basic introduction to D-branes and their dynamics.

Are there topological black-hole solitons in string theory?

We point out that the celebrated Hawking effect of quantum instability of black holes seems to be a purely semiclassical but nonperturbative effect in string theory. Studying quantum dynamics of strings in the gravitational background of black holes we find classical instability due to emission of massless string excitations. The topology of a black hole seems to play a fundamental role in developing the string theory classical instability due to the effect of sigma model instantons. We argue that string theory allows for a qualitative description of black holes with very small masses and it predicts topological solitons with quantized spectrum of masses. These solitons would not decay into string massless excitations but could be pair-created and may annihilate also. Semiclassical mass quantization of topological solitons in string theory is based on the argument showing the existence of nontrivial zeros of the beta function of the renormalization group.