Tachyon-massless couplings at order α′ in bosonic string theory
- 1Ferdowsi University of Mashhad
Abstract
Recently, it has been proposed that the classical effective action of bosonic string theory should contain only couplings with an even number of tachyon fields. We employ the T-duality procedure to derive such couplings at order α′ (four-derivative order) for the tachyon and massless fields. We first observe that, through higher-derivative field redefinitions of the tachyon potential term, one can choose a scheme in which — apart from the tachyon potential itself — all remaining couplings involve only covariant derivatives of the tachyon and the massless fields. We then construct a minimal basis of such couplings at four-derivative order, consisting of 14 independent terms. Imposing T-duality reduces this set to 6 nonzero couplings, expressed in terms of two unfixed parameters. One of these parameters is determined by matching to the known effective action in the zero-tachyon limit, while the other is fixed by comparison with the sphere-level S-matrix element of four tachyon vertex operators. This latter comparison also establishes that the coefficient of the T 4 term in the tachyon potential is positive. Remarkably, the tachyon mass term and this quartic term are consistent with a potential of the form (2/α′)(– 1 + cos T), which implies that the closed string tachyon condenses to the minimum of the potential at T = π, thereby generating an Anti-de Sitter spacetime with cosmological constant Λ = −4/α′.
Related
- Tachyon and massless sectors of the bosonic string effective action
- Calculating Axion-Matter Couplings in String Theory
- Bosonic String Amplitudes From Ribbon Graphs
- The spectrum of the bosonic ambitwistor string revisited
- On the analytic continuation and asymptotic behaviour of the two-point function in massless ϕ4-theory in Euclidean de Sitter space
BibTeX
@article{garousi2026tachyonmassless,
title = {{Tachyon-massless couplings at order α′ in bosonic string theory}},
author = {Mohammad R. Garousi},
journal = {Journal of High Energy Physics},
year = {2026},
month = oct,
doi = {10.1007/jhep10(2026)258},
url = {https://link.springer.com/article/10.1007/JHEP10(2026)258},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Tachyon-massless couplings at order α′ in bosonic string theory
AU - Mohammad R. Garousi
PY - 2026
DA - 2026/10/26
JO - Journal of High Energy Physics
DO - 10.1007/jhep10(2026)258
UR - https://link.springer.com/article/10.1007/JHEP10(2026)258
AB - Recently, it has been proposed that the classical effective action of bosonic string theory should contain only couplings with an even number of tachyon fields. We employ the T-duality procedure to derive such couplings at order α′ (four-derivative order) for the tachyon and massless fields. We first observe that, through higher-derivative field redefinitions of the tachyon potential term, one can choose a scheme in which — apart from the tachyon potential itself — all remaining couplings involve only covariant derivatives of the tachyon and the massless fields. We then construct a minimal basis of such couplings at four-derivative order, consisting of 14 independent terms. Imposing T-duality reduces this set to 6 nonzero couplings, expressed in terms of two unfixed parameters. One of these parameters is determined by matching to the known effective action in the zero-tachyon limit, while the other is fixed by comparison with the sphere-level S-matrix element of four tachyon vertex operators. This latter comparison also establishes that the coefficient of the T 4 term in the tachyon potential is positive. Remarkably, the tachyon mass term and this quartic term are consistent with a potential of the form (2/α′)(– 1 + cos T), which implies that the closed string tachyon condenses to the minimum of the potential at T = π, thereby generating an Anti-de Sitter spacetime with cosmological constant Λ = −4/α′.
SN - 1029-8479
ER -