Means and ends in string theory

The interplay between field and string theory is a powerful tool in modern theoretical research. Seminal examples are the CHY amplitudes and the double copy, which extended string features to scattering amplitudes to uncover some of their most fundamental structures.

This progress is essentially limited to massless theories (super Yang-Mills, gravity), leaving out a bulk of quantum field theories of interest, with increased phenomenological interest. At the same time, much is known about the structure of string scattering with massless external states. But when massive string resonances come to play, our knowledge is drastically reduced in terms of general properties of their scattering.

In this project the student will have direct contact with both field and string theory methods and their symbiosis. The goals are broad enough to adjust for individual preferences of the student. (1) to establish a robust framework for describing massive string states and their interactions in the context of modern field theory methods, in particular identifying their relevance towards a quantum theory of gravity. (2) to extract new practical tools from string theory and other string-like models to address realistic quantum field theories involving mass and higher spins.

References:

[1] M. Guillen, H. Johansson, R. Lipinski Jusinskas and O. Schlotterer, ``Scattering Massive String Resonances through Field-Theory Methods,'' Phys. Rev. Lett. 127 (2021) no.5, 051601 [arXiv:2104.03314 [hep-th]].
[2] H. Gomez and R. L. Jusinskas, ``Multiparticle Solutions to Einstein's Equations,'' Phys. Rev. Lett. 127 (2021) no.18, 181603 [arXiv:2106.12584 [hep-th]].
[3] R. Lipinski Jusinskas, ``Asymmetrically twisted strings,'' Phys. Lett. B 829 (2022), 137090 [arXiv:2108.13426 [hep-th]].
[4] N. Carabine and R. Lipinski Jusinskas, ``Massive strings from a haunted field theory,'' [arXiv:2312.04652 [hep-th]].