[Seminar] "Solitons, Gravity, Gravitating Solitons and Holography" by Dr. Sven Bjarke Gudnason

Quantum Gravity Unit (Neiman Unit) would like to invite you to a seminar by Dr. Sven Bjarke Gudnason from Keio University

Title: "Solitons, Gravity, Gravitating Solitons and Holography"

Abstract:
This talk will take as a starting point the Skyrmions as baryons in large-N QCD. It is further assumed that at high density, the sextic term in derivatives becomes dominant at some large density. This assumption is based on the observation that the term behaves like a perfect fluid, which is welcome for nuclear matter at large density – an environment suitable for the studies of neutron stars. With very large masses and compact radii, neutron stars become the closes known stable objects to the critical line of gravitational collapse. With some phenomenological motivation in mind, we consider the possibilities of finding exact analytic solutions to a system which is approximated by the sextic derivative term and a potential; this system is called the BPS-Skyrme model. We find a condition for when the gravitating soliton equations can be solved exactly and deduce the phenomenological implications. We furthermore find that this system has the peculiarity of not having stable black holes, meaning that the soliton cannot become scalar hair of a black hole. This is somewhat surprising, because the Skyrme soliton with a fourth-order derivative term can become stable black hole hair. We write down a class of models with higher-order derivative terms and find 2 new models that can sustain stable hair and 2 new that cannot.

Finally, we consider the problem of the classical binding energies of the Skyrmions, which are far too large compared to nuclei and explain a solution to this problem based on holography. Interestingly the solution from holography relates the baryon to the instanton of a 5-dimensional theory and the moduli of the instanton become massive modes in the Skyrmion. These modes in addition to the zero modes of the Skyrmion are expected to describe the spectra of nuclei.

References:
S. B. Gudnason and M. Nitta, Higher-order Skyrme hair of black holes, JHEP 1805, 071 (2018).
S. B. Gudnason and M. Nitta, A higher-order Skyrme model, JHEP 1709, 028 (2017).
S. Baldino, S. Bolognesi, S. B. Gudnason and D. Koksal, Solitonic approach to holographic nuclear physics, Phys.Rev.D 96, no. 3, 034008 (2017).
S. B. Gudnason, M. Nitta and N. Sawado, Black hole Skyrmion in a generalized Skyrme model, JHEP 1609, 055 (2016).
S. B. Gudnason, M. Nitta and N. Sawado, Gravitating BPS Skyrmions,  JHEP 1512, 013 (2015).