Spiky strings in de Sitter space

Abstract

We study semiclassical spiky strings in de Sitter space and the corresponding Regge trajectories, generalizing the analysis in anti-de Sitter space. In particular we demonstrate that each Regge trajectory has a maximum spin due to de Sitter acceleration, similarly to the folded string studied earlier. While this property is useful for the spectrum to satisfy the Higuchi bound, it makes a nontrivial question how to maintain mildness of high-energy string scattering which we are familiar with in flat space and anti-de Sitter space. Our analysis implies that in order to have infinitely many higher spin states, one needs to consider infinitely many Regge trajectories with an increasing folding number.

The gravitino and the swampland

“…More recently, obstructions to the limit of vanishing mass of various objects have been studied from different perspectives and related to the swampland program. For example, on backgrounds with positive energy, the consequences of the Higuchi bound [8] for integer higher spin particles and the string tower have been analysed in [9][10][11][12][13][14], while [15] proposes a general lower bound for the mass of any particle charged under an abelian symmetry. The specific case of massive spin-2 fields and of massive gravity has instead been considered in detail in [16].…”

“…Supersymmetry (SUSY) has been elusive so far. The LHC has probed energies up to 13 TeV and found no evidence of supersymmetric particles. At present, given the observed small value of the dark energy density, an estimation for the scale M SUSY at which we expect supersymmetry to be broken is given by the mass of the gravitino m 3/2 as…”

Finiteness and the Swampland

“…If the vacuum energy remains positive when approaching the infinite distance limit, the Higuchi bound implies that H < m tower (3.30) where H is the Hubble scale. Assuming the infinite tower becomes massless at an infinite distance (which is not obvious, due to effects of the dS curvature [60,61]), the Hubble scale must, therefore, go to zero (or to negative values) to satisfy (3.30). Furthermore, if the cosmological constant scales in Planck units with the mass of the tower as…”

String excitation by initial singularity of inflation

“…[9,10]. Recently, this analysis is revisited to see the consistency between the Higuchi bound and the modified Regge trajectory [11][12][13][14]. String propagation in an expanding universe has been studied in many contexts so far [15][16][17][18][19].…”