Strings and branes with a modified measure

TL;DR

This paper explores a modified measure approach in string and brane theories, where the string tension emerges as an integration constant, allowing for variable tension and simplifying higher-dimensional brane formulations.

Contribution

It introduces a measure replacement in string actions leading to variable tension and extends the framework to higher-dimensional branes without fine-tuning cosmological terms.

Findings

String tension appears as an integration constant.

Tension can vary along the string due to gauge and point particle couplings.

Higher-dimensional branes do not require fine-tuned cosmological terms.

Abstract

In string theory, the consequences of replacing the measure of integration $\sqrt{-\gamma}d^2 x$ in the Polyakov's action by $\Phi d^2 x$ where $\Phi$ is a density built out of degrees of freedom independent of the metric $\gamma_{ab}$ defined in the string are studied. The string tension appears as an integration constant of the equations of motion. The string tension can change in different parts of the string due to the coupling of gauge fields and point particles living in the string. The generalization to higher dimensional extended objects is also studied. In this case there is no need of a fine tuned cosmological term, in sharp contrast to the standard formulation of the generalized Polyakov action for higher dimensional branes.