Università di Torino（都灵大学）；INFN Sezione di Torino（意大利国家核物理研究所都灵分部）；Institut de Physique Théorique CNRS, CEA, Université Paris-Saclay（巴黎萨克雷大学CNRS-CEA理论物理研究所）
Klaus Kaja, Carlo Maccaferri, Ulisses Portugal, Jakub Vošmera
Starting from the gauge invariant action for free string field theory with boundary recently constructed in 2506.05969, we define new gauge invariant observables which are analogous to the Brown-York charges of General Relativity. Just like the Brown-York charges, our observables originate from a boundary tadpole, and are associated to isometries of the SFT gauge group around a given background. The consistency of the construction requires the equation of motion of the background to be satisfied only at the boundary and therefore these observables can also be defined for backgrounds generated by sources in the bulk. As examples of our construction in open string field theory, we compute the flux through the boundary of constant electromagnetic field-strength solutions and the charge associated to the Coulomb solution. As a further example in closed string field theory, we characterize the infinite conserved charges associated to stringy-haired black-hole solutions in two-dimensional string theory. We also construct a generalization of these boundary observables to the full interacting string field theory.
The Presentation of the Quantum Algebra of Observables of the Closed Bosonic String in 1+3 Dimensions: The Presentation in Manifestly Lorentz Covariant Form
The Algebra of Observables of the Closed Bosonic Nambu-Goto-String: The Presentation of the Algebra of Classical Observables for Light-Like Energy-Momentum in 3+1 Dimensions
Using Maccaferri's formula, we derive new wedge based solutions of open string field theory. The solutions are gauge equivalent to the Takahashi-Tanimoto scalar solutions. The classical action and the gauge invariant overlap are evaluated analytically. We find a perturbative vacuum solution whose gauge invariant observables vanish. We also identify a tachyon vacuum solution whose gauge invariant observables are identical to those of the Erler-Schnabl solution.
We study profiles and gauge invariant observables of classical solutions corresponding to a constant magnetic field on a torus in open string field theory. We numerically find that the profile is not discontinuous on the torus, although the solution describes topologically nontrivial configurations in the context of low energy effective theory. From the gauge invariant observables, we show that the solution provide correct couplings of closed strings to a D-brane with constant magnetic field.
The Nambu-Goto Theory of Closed Bosonic Strings Moving in 1+3-Dimensional Minkowski Space: The Construction of the Quantum Algebra of Observables up to Degree Five
Abstract: We show that boundary string field theory realizes the minimal model of open string field theory. More precisely, we observe that the expansion of the (co)homological vector field, $Q$ of boundary string field theory in the cohomology of its linear part reproduces the S-matrices of perturbative string theory. In mathematical terms, boundary string field theory realizes the minimal model map of the cohomological perturbation lemma.
We make some remarks on possible definition of open string path integral in the presence of additional boundary couplings corresponding to the presence of masses at the ends of the string. These couplings are not conformally invariant implying that as in a non-critical string case one is to integrate over the 1d metric or reparametrizations of the boundary. We compute the partition function on the disc in the presence of an additional constant gauge field background and comment on the structure of the corresponding scattering amplitudes.
