Cosmological evolution of Witten superconducting string networks (2304.00053v1)

Abstract: We consider the evolution of current-carrying cosmic string networks described by the charge-velocity-dependent one scale (CVOS) model beyond the linear equation of state regime, specifically focusing on the Witten superconducting model. We find that, generically, for almost chiral currents, the network evolution reduces dynamically to that of the linear case, which has been discussed in our previous work. However, the Witten model introduces a maximum critical current which constrains the network scaling behaviour during the radiation era when currents can grow and approach this limit. Unlike the linear model, only if the energy density in the critical current is comparable to the bare string tension will there be substantial backreaction on the network evolution, thus changing the observational predictions of superconducting strings from those expected from a Nambu-Goto network. During the matter era, if there are no external sources, then dynamical effects dilute these network currents and they disappear at late times.

• The paper uses the charge-velocity-dependent one scale (CVOS) model to analyze Witten superconducting string network evolution, incorporating critical current effects beyond linear models.
• Findings show network evolution deviates from linear predictions near critical current limits, forcing dynamics toward Nambu-Goto-like scaling during the radiation era.
• The research highlights the need for sophisticated simulations to validate model parameters and predict observational signatures, such as gravitational wave backgrounds.

Cosmological Evolution of Witten Superconducting String Networks

The paper under examination explores the intricate dynamics of Witten superconducting string networks, employing the charge-velocity-dependent one scale (CVOS) model to elucidate their evolution beyond linear equation of state constraints. This research builds upon previous work by extending analysis to incorporate the nonlinear complexities inherent in the Witten superconducting model, recognized for its critical current limitations which become particularly salient during the radiation era of the cosmos. The paper scrutinizes how these currents approach their critical limits and examines the significant implications for cosmic string network scaling behavior.

Key Findings

The paper establishes that for nearly chiral currents, the evolution of the string network simplifies to effectively mirror that of linear scenarios, a phenomenon reaffirmed by past investigations. However, the introduction of the Witten model indicates substantial deviations from linear predictions when critical current densities—comparable to the intrinsic bare string tension—are approached. Under these conditions, the resulting backreaction Consequently alters the predicted observational signatures of these strings relative to traditional Nambu-Goto networks.

Significantly, during the radiation era, the constraints imposed by critical currents lead to the suppression of large currents, effectively forcing the network dynamics toward a more Nambu-Goto-like scaling regime as these epochs evolve. Meanwhile, the matter-dominated period presents a dilutive effect on network currents, causing them to dissipate, which emphasizes the role of these cosmic strings as they integrate into the expanding universe.

Implications and Future Directions

The implications of this research are multifaceted, touching on both theoretical and observational fronts. Practically, it emphasizes the need for sophisticated simulations that can reliably capture the behaviors of superconducting string networks, as such data is crucial for validating the CVOS model parameters. These simulations are expected to shed light on the gravitational wave backgrounds generated by these networks, and the myriad of other cosmological signals they might produce.

Theoretically, the research opens several avenues for refining our understanding of cosmic string dynamics within field theory models, particularly those incorporating superconducting features. These considerations are essential as they point toward potential explanations for phenomena that existing standard cosmological models may leave unresolved.

Speculation about the future of AI and computational methods plays a role here as well. Sophisticated computational tools are required to accurately simulate the interactions and evolution of these networks over vast cosmic timescales. Increasingly powerful simulations, underpinned by advanced AI techniques, could offer new insights and more precise predictions about the universe's formative conditions and its eventual fate.

Conclusion

This paper presents a rigorous examination of the cosmological behavior of Witten superconducting string networks, revealing complexities not accounted for by previous linear models. By integrating considerations of critical current dynamics, the work significantly contributes to our foundational understanding of cosmic strings and their role in the broader tapestry of cosmic evolution. However, it also highlights the present gap in empirical network simulation data, a void that future research must aim to fill in order to fully leverage the predictive capabilities of models like CVOS.